From 9ffaa7c95d0e4334e8b8fda9a772edda2c5ba84f Mon Sep 17 00:00:00 2001 From: Zane Meyers Date: Mon, 1 Dec 2025 17:16:26 -0500 Subject: [PATCH] vault backup: 2025-12-01 17:16:25 --- .gitignore | 6 +- .obsidian/app.json | 2 +- .obsidian/plugins/obsidian-linter/data.json | 6 +- ...quirements-for-electrical-installations.md | 888 +++++- nfpa-70_210_branch-circuits.md | 784 +++++- nfpa-70_220_load-calculations.md | 660 ++++- nfpa-70_230_services.md | 1016 +++++++ nfpa-70_240_overcurrent-protection.md | 1351 +++++++++ nfpa-70_250_grounding-and-bonding.md | 13 +- nfpa-70_430_motors.md | 2406 ++++++++++++++++- nfpa-70_440_hvac-equipment.md | 486 ++++ nfpa-70_national-electric-code.md | 6 +- this-notebook.md | 1 + 13 files changed, 7508 insertions(+), 117 deletions(-) create mode 100644 nfpa-70_230_services.md create mode 100644 nfpa-70_240_overcurrent-protection.md create mode 100644 nfpa-70_440_hvac-equipment.md diff --git a/.gitignore b/.gitignore index eb99a8f..6802ded 100644 --- a/.gitignore +++ b/.gitignore @@ -1,4 +1,4 @@ -.obsidian/workspace.json -.obsidian/workspace-mobile.json -.obsidian/plugins/recent-files-obsidian/data.json +/.obsidian/workspace.json +/.obsidian/workspace-mobile.json +/.obsidian/plugins/recent-files-obsidian/data.json /.obsidian/plugins/novel-word-count/data.json \ No newline at end of file diff --git a/.obsidian/app.json b/.obsidian/app.json index 7897ec9..fc5142c 100644 --- a/.obsidian/app.json +++ b/.obsidian/app.json @@ -7,7 +7,7 @@ "autoPairMarkdown": false, "useTab": false, "alwaysUpdateLinks": true, - "tabSize": 2, + "tabSize": 4, "vimMode": true, "promptDelete": false, "focusNewTab": true, diff --git a/.obsidian/plugins/obsidian-linter/data.json b/.obsidian/plugins/obsidian-linter/data.json index f8c6aaa..50b217b 100644 --- a/.obsidian/plugins/obsidian-linter/data.json +++ b/.obsidian/plugins/obsidian-linter/data.json @@ -118,7 +118,7 @@ "extra-auto-correct-files": [] }, "blockquote-style": { - "enabled": false, + "enabled": true, "style": "space" }, "convert-bullet-list-markers": { @@ -258,13 +258,13 @@ "enabled": false }, "remove-hyphens-on-paste": { - "enabled": true + "enabled": false }, "remove-leading-or-trailing-whitespace-on-paste": { "enabled": false }, "remove-leftover-footnotes-from-quote-on-paste": { - "enabled": false + "enabled": true }, "remove-multiple-blank-lines-on-paste": { "enabled": true diff --git a/nfpa-70_110_requirements-for-electrical-installations.md b/nfpa-70_110_requirements-for-electrical-installations.md index 963b293..a293c14 100644 --- a/nfpa-70_110_requirements-for-electrical-installations.md +++ b/nfpa-70_110_requirements-for-electrical-installations.md @@ -26,7 +26,71 @@ and tunnel installations. > [!info] Informational Note: > See Informative Annex J for information regarding ADA accessibility design. - +### 110.2 Approval. + +The conductors and equipment required or permitted by this Code shall be acceptable only if approved. + +> [!info] Informational Note: +> See 90.7, Examination of Equipment for Safety, and 110.3, Examination, Identification, Installation, and Use of + +Equipment. See definitions of Approved, Identified, Labeled, and Listed. + +### 110.3 Examination, Identification, Installation, Use, and Listing (Product Certification) of Equipment. + +#### 110.3(A) Examination. + +In judging equipment, considerations such as the following shall be evaluated: + +* (1) Suitability for installation and use in conformity with this Code + +> [!info] Informational Note No. 1: +> Equipment may be new, reconditioned, refurbished, or remanufactured. + +> [!info] Informational Note No. 2: +> Suitability of equipment use may be identified by a description marked on or provided with a product to identify the suitability of the product for a specific purpose, environment, or application. Special conditions of use or other limitations and other pertinent information may be marked on the equipment, included in the product instructions, or included in the appropriate listing and labeling information. Suitability of equipment may be evidenced by listing or labeling. + +* (2) Mechanical strength and durability, including, for parts designed to enclose and protect other equipment, the adequacy of the protection thus provided + +* (3) Wire-bending and connection space + +* (4) Electrical insulation + +* (5) Heating effects under normal conditions of use and also under abnormal conditions likely to arise in service + +* (6) Arcing effects + +* (7) Classification by type, size, voltage, current capacity, and specific use + +* (8) Other factors that contribute to the practical safeguarding of persons using or likely to come in contact with the equipment + +#### 110.3(B) Installation and Use. + +Equipment that is listed, labeled, or both shall be installed and used in accordance with any instructions included in the listing or labeling. + +#### 110.3(C) Listing. + +Product testing, evaluation, and listing (product certification) shall be performed by recognized qualified electrical testing laboratories and shall be in accordance with applicable product standards recognized as achieving equivalent and effective safety for equipment installed to comply with this Code. + +> [!info] Informational Note: +> The Occupational Safety and Health Administration (OSHA) recognizes qualified electrical testing laboratories that perform evaluations, testing, and certification of certain products to ensure that they meet the requirements of both the construction and general industry OSHA electrical standards. If the listing (product certification) is done under a qualified electrical testing laboratory program, this listing mark signifies that the tested and certified product complies with the requirements of one or more appropriate product safety test standards. + +### 110.4 Voltages. + +Throughout this Code, the voltage considered shall be that at which the circuit operates. The voltage rating of electrical equipment shall not be less than the nominal voltage of a circuit to which it is connected. + +### 110.5 Conductors. + +Conductors used to carry current shall be of copper, aluminum, or copper-clad aluminum unless otherwise provided in this Code. + +Where the conductor material is not specified, the sizes given in this Code shall apply to copper conductors. Where other materials are used, the size shall be changed accordingly. + +### 110.6 Conductor Sizes. + +Conductor sizes are expressed in American Wire Gage (AWG) or in circular mils. + +### 110.7 Wiring Integrity. + +Completed wiring installations shall be free from short circuits, ground faults, or any connections to ground other than as required or permitted elsewhere in this Code. ### 110.8 Wiring Methods @@ -37,7 +101,83 @@ shall be permitted to be installed in any type of building or occupancy, except as otherwise provided in this Code. - +### 110.9 Interrupting Rating. + +Equipment intended to interrupt current at fault levels shall have an interrupting rating at nominal circuit voltage at least equal to the current that is available at the line terminals of the equipment. + +Equipment intended to interrupt current at other than fault levels shall have an interrupting rating at nominal circuit voltage at least equal to the current that must be interrupted. + +### 110.10 Circuit Impedance, Short-Circuit Current Ratings, and Other Characteristics. + +The overcurrent protective devices, the total impedance, the equipment short-circuit current ratings, and other characteristics of the circuit to be protected shall be selected and coordinated to permit the circuit protective devices used to clear a fault to do so without extensive damage to the electrical equipment of the circuit. This fault shall be assumed to be either between two or more of the circuit conductors or between any circuit conductor and the equipment grounding conductor(s) permitted in 250.118. Listed equipment applied in accordance with their listing shall be considered to meet the requirements of this section. + +### 110.11 Deteriorating Agents. + +Unless identified for use in the operating environment, no conductors or equipment shall be located in damp or wet locations; where exposed to gases, fumes, vapors, liquids, or other agents that have a deteriorating effect on the conductors or equipment; or where exposed to excessive temperatures. + +> [!info] Informational Note No. 1: +> See 300.6 for protection against corrosion. + +> [!info] Informational Note No. 2: +> Some cleaning and lubricating compounds can cause severe deterioration of many plastic materials used for insulating and structural applications in equipment. + +Equipment not identified for outdoor use and equipment identified only for indoor use, such as "dry locations," "indoor use only," "damp locations," or enclosure Types 1, 2, 5, 12, 12K, and/or 13, shall be protected against damage from the weather during construction. + +> [!info] Informational Note No. 3: +> See Table 110.28 for appropriate enclosure-type designations. + +> [!info] Informational Note No. 4: +> Minimum flood provisions are provided in NFPA 5000-2015 Building Construction and Safety Code, the + +International Building Code (IBC), and the International Residential Code for One- and Two-Family Dwellings (IRC). + +### 110.12 Mechanical Execution of Work. + +Electrical equipment shall be installed in a neat and workmanlike manner. + +> [!info] Informational Note: +> Accepted industry practices are described in ANSI/NECA 1-2015, Standard for Good Workmanship in Electrical + +Construction, and other ANSI-approved installation standards. + +#### 110.12(A) Unused Openings. + +Unused openings, other than those intended for the operation of equipment, those intended for mounting purposes, or those permitted as part of the design for listed equipment, shall be closed to afford protection substantially equivalent to the wall of the equipment. + +Where metallic plugs or plates are used with nonmetallic enclosures, they shall be recessed at least 6 mm (1/4 in.) from the outer surface of the enclosure. + +#### 110.12(B) Integrity of Electrical Equipment and Connections. + +Internal parts of electrical equipment, including busbars, wiring terminals, insulators, and other surfaces, shall not be damaged or contaminated by foreign materials such as paint, plaster, cleaners, abrasives, or corrosive residues. There shall be no damaged parts that may adversely affect safe operation or mechanical strength of the equipment such as parts that are broken; bent; cut; or deteriorated by corrosion, chemical action, or overheating. + +#### 110.12(C) Cables and Conductors. + +Cables and conductors installed exposed on the surfaces of ceilings and sidewalls shall be supported by the building structure in such a manner that the cables and conductors will not be damaged by normal building use. Such cables and conductors shall be secured by hardware including straps, staples, cable ties, hangers, or similar fittings designed and installed so as not to damage the cable. The installation shall also conform with 300.4 and 300.11. Nonmetallic cable ties and other nonmetallic cable accessories used to secure and support cables in other spaces used for environmental air (plenums) shall be listed as having low smoke and heat release properties. + +> [!info] Informational Note No. 1: +> Accepted industry practices are described in ANSI/ NECA/FOA 301-2009, Standard for Installing and Testing + +Fiber Optic Cables, and other ANSI-approved installation standards. + +> [!info] Informational Note No. 2: +> See 4.3.11.2.6.5 and 4.3.11.5.5.6 of NFPA 90A-2018, Standard for the Installation of Air-Conditioning and + +Ventilating Systems, for discrete combustible components installed in accordance with 300.22(C). + +> [!info] Informational Note No. 3: +> Paint, plaster, cleaners, abrasives, corrosive residues, or other contaminants may result in an undetermined alteration of optical fiber cable properties. + +### 110.13 Mounting and Cooling of Equipment. + +#### 110.13(A) Mounting. + +Electrical equipment shall be firmly secured to the surface on which it is mounted. Wooden plugs driven into holes in masonry, concrete, plaster, or similar materials shall not be used. + +#### 110.13(B) Cooling. + +Electrical equipment that depends on the natural circulation of air and convection principles for cooling of exposed surfaces shall be installed so that room airflow over such surfaces is not prevented by walls or by adjacent installed equipment. For equipment designed for floor mounting, clearance between top surfaces and adjacent surfaces shall be provided to dissipate rising warm air. + +Electrical equipment provided with ventilating openings shall be installed so that walls or other obstructions do not prevent the free circulation of air through the equipment. ### 110.14 Electrical Connections. @@ -135,7 +275,161 @@ Informational Note No. 3: Additional information for torquing threaded connections and terminations can be found in Section 8.11 of NFPA 70B-2019, Recommended Practice for Electrical Equipment Maintenance. - +### 110.15 High-Leg Marking. + +On a 4-wire, delta-connected system where the midpoint of one phase winding is grounded, only the conductor or busbar having the higher phase voltage to ground shall be durably and permanently marked by an outer finish that is orange in color or by other effective means. Such identification shall be placed at each point on the system where a connection is made if the grounded conductor is also present. + +### 110.16 Arc-Flash Hazard Warning. + +#### 110.16(A) General. + +Electrical equipment, such as switchboards, switchgear, panelboards, industrial control panels, meter socket enclosures, and motor control centers, that is in other than dwelling units, and is likely to require examination, adjustment, servicing, or maintenance while energized, shall be field or factory marked to warn qualified persons of potential electric arc flash hazards. The marking shall meet the requirements in 110.21(B) and shall be located so as to be clearly visible to qualified persons before examination, adjustment, servicing, or maintenance of the equipment. + +#### 110.16(B) Service Equipment. + +In other than dwelling units, in addition to the requirements in 110.16(A), a permanent label shall be field or factory applied to service equipment rated 1200 amps or more. The label shall meet the requirements of 110.21(B) and contain the following information: + +* (1) Nominal system voltage + +* (2) Available fault current at the service overcurrent protective devices + +* (3) The clearing time of service overcurrent protective devices based on the available fault current at the service equipment + +* (4) The date the label was applied + +> [!important] Exception: +> Service equipment labeling shall not be required if an arc flash label is applied in accordance with acceptable industry practice. + +> [!info] Informational Note No. 1: +> NFPA 70E-2018, Standard for Electrical Safety in the Workplace, provides guidance, such as determining severity of potential exposure, planning safe work practices, arc flash labeling, and selecting personal protective equipment. + +> [!info] Informational Note No. 2: +> ANSI Z535.4-2011, Product Safety Signs and Labels, provides guidelines for the design of safety signs and labels for application to products. + +> [!info] Informational Note No. 3: +> Acceptable industry practices for equipment labeling are described in NFPA 70E-2018, Standard for Electrical + +Safety in the Workplace. This standard provides specific criteria for developing arc-flash labels for equipment that provides nominal system voltage, incident energy levels, arc-flash boundaries, minimum required levels of personal protective equipment, and so forth. + +### 110.18 Arcing Parts. + +Parts of electrical equipment that in ordinary operation produce arcs, sparks, flames, or molten metal shall be enclosed or separated and isolated from all combustible material. + +> [!info] Informational Note: +> For hazardous (classified) locations, see Articles 500 through 517. For motors, see 430.14. + +### 110.19 Light and Power from Railway Conductors. + +Circuits for lighting and power shall not be connected to any system that contains trolley wires with a ground return. + +> [!important] Exception: +> Such circuit connections shall be permitted in car houses, power houses, or passenger and freight stations operated in connection with electric railways. + +### 110.21 Marking. + +#### 110.21(A) Equipment Markings. + +##### 110.21(A)(1) General. + +The manufacturer's name, trademark, or other descriptive marking by which the organization responsible for the product can be identified shall be placed on all electrical equipment. Other markings that indicate voltage, current, wattage, or other ratings shall be provided as specified elsewhere in this Code. The marking or label shall be of sufficient durability to withstand the environment involved. + +##### 110.21(A)(2) Reconditioned Equipment. + +Reconditioned equipment shall be marked with the name, trademark, or other descriptive marking by which the organization responsible for reconditioning the electrical equipment can be identified, along with the date of the reconditioning. + +Reconditioned equipment shall be identified as "reconditioned" and the original listing mark removed. Approval of the reconditioned equipment shall not be based solely on the equi pment's original listing. + +> [!important] Exception: +> In industrial occupancies, where conditions of maintenance and supervision ensure that only qualified persons service the equipment, the markings indicated in 110.21(A)(2) shall not be required for equipment that is reconditioned by the owner or operator as part of a regular equipment maintenance program. + +> [!info] Informational Note No. 1: +> Industry standards are available for application of reconditioned and refurbished equipment. + +> [!info] Informational Note No. 2: +> The term reconditioned may be interchangeable with the terms rebuilt, refurbished, or remanufactured. + +> [!info] Informational Note No. 3: +> The original listing mark may include the mark of the certifying body and not the entire equipment label. + +#### 110.21(B) Field-Applied Hazard Markings. + +Where caution, warning, or danger signs or labels are required by this Code, the labels shall meet the following requirements: + +* (1) The marking shall warn of the hazards using effective words, colors, symbols, or any combination thereof. + + > [!info] Informational Note: + > ANSI Z535.4-2011, Product Safety Signs and Labels, provides guidelines for suitable font sizes, words, colors, symbols, and location requirements for labels. + +* (2) The label shall be permanently affixed to the equipment or wiring method and shall not be handwritten. + + > [!important] Exception to (2): + > Portions of labels or markings that are variable, + > or that could be subject to changes, + > shall be permitted to be handwritten and shall be legible. + +* (3) The label shall be of sufficient durability to withstand the environment involved. + + > [!info] Informational Note: + > ANSI Z535.4-2011, Product Safety Signs and Labels, provides guidelines for the design and durability of safety signs and labels for application to electrical equipment. + +### 110.22 Identification of Disconnecting Means. + +#### 110.22(A) General. + +Each disconnecting means shall be legibly marked to indicate its purpose unless located and arranged so the purpose is evident. In other than one- or two-family dwellings, the marking shall include the identification of the circuit source that supplies the disconnecting means. The marking shall be of sufficient durability to withstand the environment involved. + +#### 110.22(B) Engineered Series Combination Systems. + +Equipment enclosures for circuit breakers or fuses applied in compliance with series combination ratings selected under engineering supervision in accordance with 240.86(A) shall be legibly marked in the field as directed by the engineer to indicate the equipment has been applied with a series combination rating. The marking shall meet the requirements in 110.21(B) and shall be readily visible and state the following: + +``` +CAUTION --- ENGINEERED SERIES COMBINATION SYSTEM RATED _______ AMPERES. +IDENTIFIED REPLACEMENT COMPONENTS REQUIRED. +``` + +#### 110.22(C) Tested Series Combination Systems. + +Equipment enclosures for circuit breakers or fuses applied in compliance with the series combination ratings marked on the equipment by the manufacturer in accordance with 240.86(B) shall be legibly marked in the field to indicate the equipment has been applied with a series combination rating. The marking shall meet the requirements in 110.21(B) and shall be readily visible and state the following: + +``` +CAUTION --- SERIES COMBINATION SYSTEM RATED ____ AMPERES. +IDENTIFIED REPLACEMENT COMPONENTS REQUIRED. +``` + +> [!info] Informational Note: +> See IEEE 3004.5-2014 Recommended Practice for the Application of Low-Voltage Circuit Breakers in Industrial and Commercial Power Systems, for further information on series tested systems. + +### 110.23 Current Transformers. + +Unused current transformers associated with potentially energized circuits shall be short-circuited. + +### 110.24 Available Fault Current. + +#### 110.24(A) Field Marking. + +Service equipment at other than dwelling units shall be legibly marked in the field with the available fault current. The field marking(s) shall include the date the fault-current calculation was performed and be of sufficient durability to withstand the environment involved. + +The calculation shall be documented and made available to those authorized to design, install, inspect, maintain, or operate the system. + +> [!info] Informational Note No. 1: +> The available fault-current marking(s) addressed in 110.24 is related to required short-circuit current and interrupting ratings of equipment. NFPA 70E-2018, Standard for Electrical Safety in the Workplace, provides assistance in determining the severity of potential exposure, planning safe work practices, and selecting personal protective equipment. + +> [!info] Informational Note No. 2: +> Values of available fault current for use in determining appropriate minimum short-circuit current and interrupting ratings of service equipment are available from electric utilities in published or other forms. + +#### 110.24(B) Modifications. + +When modifications to the electrical installation occur that affect the available fault current at the service, the available fault current shall be verified or recalculated as necessary to ensure the service equipment ratings are sufficient for the available fault current at the line terminals of the equipment. The required field marking(s) in 110.24(A) shall be adjusted to reflect the new level of available fault current. + +> [!important] Exception: +> The field marking requirements in 110.24(A) and 110.24(B) shall not be required in industrial installations where conditions of maintenance and supervision ensure that only qualified persons service the equipment. + +### 110.25 Lockable Disconnecting Means. + +If a disconnecting means is required to be lockable open elsewhere in this Code, it shall be capable of being locked in the open position. The provisions for locking shall remain in place with or without the lock installed. + +> [!important] Exception: +> Locking provisions for a cord-and-plug connection shall not be required to remain in place without the lock installed. ## Part II. 1000 Volts, Nominal, or Less @@ -177,16 +471,16 @@ Minimum Clear Distance Note: Where the conditions are as follows: -* Condition 1 -- Exposed live parts on one side of the working space +* Condition 1 --- Exposed live parts on one side of the working space and no live or grounded parts on the other side of the working space, or exposed live parts on both sides of the working space that are effectively guarded by insulating materials. -* Condition 2 -- Exposed live parts on one side of the working space +* Condition 2 --- Exposed live parts on one side of the working space and grounded parts on the other side of the working space. Concrete, brick, or tile walls shall be considered as grounded. -* Condition 3 -- Exposed live parts on both sides of the working space. +* Condition 3 --- Exposed live parts on both sides of the working space. (a) _Dead-Front Assemblies._ Working space shall not be required in the back or sides of assemblies, such as dead-front switchboards, switchgear, or motor control centers, where all connections and all renewable or adjustable parts, such as fuses or switches, are accessible from locations other than the back or sides. Where rear access is required to work on nonelectrical parts on the back of enclosed equipment, a minimum horizontal working space of 762 mm (30 in.) shall be provided. @@ -194,7 +488,70 @@ Working space shall not be required in the back or sides of assemblies, such as (b) _Low Voltage._ By special permission, smaller working spaces shall be permitted where all exposed live parts operate at not greater than 30 volts rms, 42 volts peak, or 60 volts dc. - +##### 110.26(A)(2) Width of Working Space. + +The width of the working space in front of the electrical equipment shall be the width of the equipment or 762 mm (30 in.), whichever is greater. In all cases, the work space shall permit at least a 90 degree opening of equipment doors or hinged panels. + +##### 110.26(A)(3) Height of Working Space. + +The work space shall be clear and extend from the grade, floor, or platform to a height of 2.0 m (61/2 ft) or the height of the equipment, whichever is greater. Within the height requirements of this section, other equipment or support structures, such as concrete pads, associated with the electrical installation and located above or below the electrical equipment shall be permitted to extend not more than 150 mm (6 in.) beyond the front of the electrical equipment. + +> [!important] Exception No. 1: +> On battery systems mounted on open racks, the top clearance shall comply with 480.10(D). + +> [!important] Exception No. 2: +> In existing dwelling units, service equipment or panelboards that do not exceed 200 amperes shall be permitted in spaces where the height of the working space is less than 2.0 m (61/2 ft). + +> [!important] Exception No. 3: +> Meters that are installed in meter sockets shall be permitted to extend beyond the other equipment. The meter socket shall be required to follow the rules of this section. + +##### 110.26(A)(4) Limited Access. + +Where equipment operating at 1000 volts, nominal, or less to ground and likely to require examination, adjustment, servicing, or maintenance while energized is required by installation instructions or function to be located in a space with limited access, all of the following shall apply: + +* (1) Where equipment is installed above a lay-in ceiling, + there shall be an opening not smaller than 559 mm × 559 mm (22 in. × 22 in.), + or in a crawl space, + there shall be an accessible opening not smaller than 559 mm × 762 mm (22 in. × 30 in.). + +* (2) The width of the working space + shall be the width of the equipment enclosure or a minimum of 762 mm (30 in.), + whichever is greater. + +* (3) All enclosure doors or hinged panels + shall be capable of opening a minimum of 90 degrees. + +* (4) The space in front of the enclosure shall comply with the depth requirements of Table 110.26(A)(1). The maximum height of the working space shall be the height necessary to install the equipment in the limited space. A horizontal ceiling structural member or access panel shall be permitted in this space. + +##### 110.26(A)(5) Separation from High-Voltage Equipment. + +Where switches, cutouts, or other equipment operating at 1000 volts, nominal, or less are installed in a vault, room, or enclosure where there are exposed live parts or exposed wiring operating over 1000 volts, nominal, the high-voltage equipment shall be effectively separated from the space occupied by the low-voltage equipment by a suitable partition, fence, or screen. + +#### 110.26(B) Clear Spaces. + +Working space required by this section shall not be used for storage. When normally enclosed live parts are exposed for inspection or servicing, the working space, if in a passageway or general open space, shall be suitably guarded. + +#### 110.26(C) Entrance to and Egress from Working Space. + +##### 110.26(C)(1) Minimum Required. + +At least one entrance of sufficient area shall be provided to give access to and egress from working space about electrical equipment. + +##### 110.26(C)(2) Large Equipment. + +For large equipment that contains overcurrent devices, switching devices, or control devices, there shall be one entrance to and egress from the required working space not less than 610 mm (24 in.) wide and 2.0 m (61/2 ft) high at each end of the working space. This requirement shall apply to either of the following conditions: + +* (1) For equipment rated 1200 amperes or more and over 1.8 m (6 ft) wide + +* (2) For service disconnecting means installed in accordance with 230.71 where the combined ampere rating is 1200 amperes or more and over 1.8 m (6 ft) wide + +Open equipment doors shall not impede the entry to or egress from the working space. + +A single entrance to and egress from the required working space shall be permitted where either of the conditions in 110.26(C)(2)(a) or (C)(2)(b) is met. + +* (a) Unobstructed Egress. Where the location permits a continuous and unobstructed way of egress travel, a single entrance to the working space shall be permitted. + +* (b) Extra Working Space. Where the depth of the working space is twice that required by 110.26(A)(1), a single entrance shall be permitted. It shall be located such that the distance from the equipment to the nearest edge of the entrance is not less than the minimum clear distance specified in Table 110.26(A)(1) for equipment operating at that voltage and in that condition. #### 110.26(C)(3) Personnel Doors. @@ -205,10 +562,10 @@ less than 7.6 m (25 ft) from the nearest edge of the working space, the door(s) shall open in the direction of egress and be equipped with listed panic hardware or listed fire exit hardware. -Informational Note: -For information on panic hardware, see UL 305, Standard For Safety For Panic Hardware. -For fire exit hardware, see UL 305, Standard For Panic Hardware, -and UL 10C, Standard for Safety for Positive Pressure Fire Tests of Door Assemblies. +> [!info] Informational Note: +> For information on panic hardware, see UL 305, Standard For Safety For Panic Hardware. +> For fire exit hardware, see UL 305, Standard For Panic Hardware, +> and UL 10C, Standard for Safety for Positive Pressure Fire Tests of Door Assemblies. #### 110.26(D) Illumination. @@ -278,3 +635,512 @@ Outdoor installations shall comply with 110.26(E)(2)(a) through (E)(2)(c). #### 110.26(F) Locked Electrical Equipment Rooms or Enclosures. Electrical equipment rooms or enclosures housing electrical apparatus that are controlled by a lock(s) shall be considered accessible to qualified persons. + +### 110.27 Guarding of Live Parts. + +#### 110.27(A) Live Parts Guarded Against Accidental Contact. + +Except as elsewhere required or permitted by this Code, live parts of electrical equipment operating at 50 to 1000 volts, nominal shall be guarded against accidental contact by approved enclosures or by any of the following means: + +* (1) By location in a room, vault, or similar enclosure that is accessible only to qualified persons. + +* (2) By permanent, substantial partitions or screens arranged so that only qualified persons have access to the space within reach of the live parts. Any openings in such partitions or screens shall be sized and located so that persons are not likely to come into accidental contact with the live parts or to bring conducting objects into contact with them. + +* (3) By location on a balcony, gallery, or platform elevated and arranged so as to exclude unqualified persons. + +* (4) By elevation above the floor or other working surface as follows: + * a. A minimum of 2.5 m (8 ft) for 50 volts to 300 volts between ungrounded conductors + * b. A minimum of 2.6 m (8 ft 6 in.) for 301 volts to 600 volts between ungrounded conductors + * c. A minimum of 2.62 m (8 ft 7 in.) for 601 volts to 1000 volts between ungrounded conductors + +#### 110.27(B) Prevent Physical Damage. + +In locations where electrical equipment is likely to be exposed to physical damage, enclosures or guards shall be so arranged and of such strength as to prevent such damage. + +#### 110.27(C) Warning Signs. + +Entrances to rooms and other guarded locations that contain exposed live parts shall be marked with conspicuous warning signs forbidding unqualified persons to enter. The marking shall meet the requirements in 110.21(B). + +> [!info] Informational Note: +> For motors, see 430.232 and 430.233. For over 1000 volts, see 110.34. + +### 110.28 Enclosure Types. + +Enclosures (other than surrounding fences or walls covered in 110.31) of switchboards, switchgear, panelboards, industrial control panels, motor control centers, meter sockets, enclosed switches, transfer switches, power outlets, circuit breakers, adjustable-speed drive systems, pullout switches, portable power distribution equipment, termination boxes, general-purpose transformers, fire pump controllers, fire pump motors, and motor controllers, rated not over 1000 volts nominal and intended for such locations, shall be marked with an enclosure-type number as shown in Table 110.28. + +Table 110.28 shall be used for selecting these enclosures for use in specific locations other than hazardous (classified) locations. The enclosures are not intended to protect against conditions such as condensation, icing, corrosion, or contamination that may occur within the enclosure or enter via the raceway or unsealed openings. + +#### Table 110.28 Enclosure Selection + +For Outdoor Use + +| Provides a Degree of Protection Against the Following Environmental Conditions | 3 | 3R | 3S | 3X | 3RX | 3SX | 4 | 4X | 6 | 6P | +| ------------------------------------------------------------------------------ | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | +| Incidental contact with the enclosed equipment | X | X | X | X | X | X | X | X | X | X | +| Rain, snow, and sleet | X | X | X | X | X | X | X | X | X | X | +| Sleet* | --- | --- | X | --- | --- | X | --- | --- | --- | --- | +| Windblown dust | X | --- | X | X | --- | X | X | X | X | X | +| Hosedown | --- | --- | --- | --- | --- | --- | X | X | X | X | +| Corrosive agents | --- | --- | --- | X | X | X | --- | X | --- | X | +| Temporary submersion | --- | --- | --- | --- | --- | --- | --- | --- | X | X | +| Prolonged submersion | --- | --- | --- | --- | --- | --- | --- | --- | --- | X | + +\*Mechanism shall be operable when ice covered. + +For Indoor Use + +| Provides a Degree of Protection Against the Following Environmental Conditions | 1 | 2 | 4 | 4X | 5 | 6 | 6P | 12 | 12K | 13 | +| ------------------------------------------------------------------------------ | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | +| Incidental contact with the enclosed equipment | X | X | X | X | X | X | X | X | X | X | +| Falling dirt | X | X | X | X | X | X | X | X | X | X | +| Falling liquids and light splashing | --- | X | X | X | X | X | X | X | X | X | +| Circulating dust, lint, fibers, and flyings | --- | --- | X | X | --- | X | X | X | X | X | +| Settling airborne dust, lint, fibers, and flyings | --- | --- | X | X | X | X | X | X | X | X | +| Hosedown and splashing water | --- | --- | X | X | --- | X | X | --- | --- | --- | +| Oil and coolant seepage | --- | --- | --- | --- | --- | --- | --- | X | X | X | +| Oil or coolant spraying and splashing | --- | --- | --- | --- | --- | --- | --- | --- | --- | X | +| Corrosive agents | --- | --- | --- | X | --- | --- | X | --- | --- | --- | +| Temporary submersion | --- | --- | --- | --- | --- | X | X | --- | --- | --- | +| Prolonged submersion | --- | --- | --- | --- | --- | --- | X | --- | --- | --- | + +> [!info] Informational Note No. 1: +> The term _raintight_ is typically used +> in conjunction with Enclosure Types 3, 3S, 3SX, 3X, 4, 4X, 6, and 6P. +> The term _rainproof_ is typically used +> in conjunction with Enclosure Types 3R and 3RX. +> The term _watertight_ is typically used +> in conjunction with Enclosure Types 4, 4X, 6, and 6P. +> The term _driptight_ is typically used +> in conjunction with Enclosure Types 2, 5, 12, 12K, and 13. +> The term _dusttight_ is typically used +> in conjunction with Enclosure Types 3, 3S, 3SX, 3X, 4, 4X, 5, 6, 6P, 12, 12K, and 13. + +> [!info] Informational Note No. 2: +> Ingress protection (IP) ratings may be found in ANSI/IEC 60529, +> Degrees of Protection Provided by Enclosures. +> IP ratings are not a substitute for Enclosure Type ratings. + +> [!info] Informational Note No. 3: +> Dusttight enclosures are suitable for use in hazardous locations +> in accordance with 502.10(B)(4), 503.10(A)(2), and 506.15(C)(9). + +> [!info] Informational Note No. 4: +> Dusttight enclosures are suitable for use in unclassified locations +> and in Class II, Division 2; Class III; +> and Zone 22 hazardous (classified) locations. + +## Part III. Over 1000 Volts, Nominal + +### 110.30 General. + +Conductors and equipment used on circuits over 1000 volts, nominal, shall comply with Part I of this article and with 110.30 through 110.41, which supplement or modify Part I. +In no case shall this part apply to equipment on the supply side of the service point. + +### 110.31 Enclosure for Electrical Installations. + +Electrical installations in a vault, room, or closet or in an area surrounded by a wall, screen, or fence, access to which is controlled by a lock(s) or other approved means, shall be considered to be accessible to qualified persons only. The type of enclosure used in a given case shall be designed and constructed according to the nature and degree of the hazard(s) associated with the installation. + +For installations other than equipment as described in 110.31(D), a wall, screen, or fence shall be used to enclose an outdoor electrical installation to deter access by persons who are not qualified. A fence shall not be less than 2.1 m (7 ft) in height or a combination of +1.8 m (6 ft) or more of fence fabric and a 300 mm (1 ft) or more extension utilizing three or more strands of barbed wire or equivalent. + +The distance from the fence to live parts shall be not less than given in Table 110.31. + +Table 110.31 Minimum Distance from Fence to Live Parts + +| Nominal Voltage | Minimum Distance to Live Parts | +|:---------------:|:------------------------------:| +| 1001--13,799 | 3.05 m (10 ft) | +| 13,800--230,000 | 4.57 m (15 ft) | +| Over 230,000 | 5.49 m (18 ft) | + +Note: For clearances of conductors for specific system voltages and typical BIL ratings, +see ANSI/IEEE C2-2017, National Electrical Safety Code. + +> [!info] Informational Note: +> See Article 450 for construction requirements for transformer vaults. + +#### 110.31(A) Electrical Vaults. + +Where an electrical vault is required or specified +for conductors and equipment +110.31(A)(1) to (A)(5) shall apply. + +##### 110.31(A)(1) Walls and Roof. + +The walls and roof shall be constructed of materials that have adequate structural strength for the conditions, with a minimum fire rating of 3 hours. For the purpose of this section, studs and wallboard construction shall not be permitted. + +##### 110.31(A)(2) Floors. + +The floors of vaults in contact with the earth shall be of concrete that is not less than 102 mm (4 in.) thick, but where the vault is constructed with a vacant space or other stories below it, the floor shall have adequate structural strength for the load imposed on it and a minimum fire resistance of 3 hours. + +##### 110.31(A)(3) Doors. + +Each doorway leading into a vault from the building interior +shall be provided with a tight-fitting door that has a minimum fire rating of 3 hours. +The authority having jurisdiction +shall be permitted to require such a door for an exterior wall opening where conditions warrant. + +> [!important] Exception to (1), (2), and (3): +> Where the vault is protected with automatic sprinkler, +> water spray, carbon dioxide, or halon, +> construction with a 1-hour rating shall be permitted. + +##### 110.31(A)(4) Locks. + +Doors shall be equipped with locks, and doors shall be kept locked, with access allowed only to qualified persons. Personnel doors shall open in the direction of egress and be equipped with listed panic hardware or listed fire exit hardware. + +##### 110.31(A)(5) Transformers. + +Where a transformer is installed in a vault as required by Article 450, the vault shall be constructed in accordance with the requirements of Part III of Article 450. + +> [!info] Informational Note No. 1: +> For additional information, see ANSI/ASTM E119-2018a, Method for Fire Tests of Building Construction and + +Materials, and NFPA 80-2019, Standard for Fire Doors and Other Opening Protectives. + +> [!info] Informational Note No. 2: +> A typical 3-hour construction is 150 mm (6 in.) thick reinforced concrete. + +#### 110.31(B) Indoor Installations. + +##### 110.31(B)(1) In Places Accessible to Unqualified Persons. + +Indoor electrical installations that are accessible to unqualified persons shall be made with metal-enclosed equipment. Switchgear, transformers, pull boxes, connection boxes, and other similar associated equipment shall be marked with appropriate caution signs. + +Openings in ventilated dry-type transformers or similar openings in other equipment shall be designed so that foreign objects inserted through these openings are deflected from energized parts. + +##### 110.31(B)(2) In Places Accessible to Qualified Persons Only. + +Indoor electrical installations considered accessible only to qualified persons in accordance with this section shall comply with 110.34, 110.36, and 490.24. + +#### 110.31(C) Outdoor Installations. + +##### 110.31(C)(1) In Places Accessible to Unqualified Persons. + +Outdoor electrical installations that are open to unqualified persons shall comply with Parts I, II, and III of Article 225. + +##### 110.31(C)(2) In Places Accessible to Qualified Persons Only. + +Outdoor electrical installations that have exposed live parts shall be accessible to qualified persons only in accordance with the first paragraph of this section and shall comply with 110.34, 110.36, and 490.24. + +#### 110.31(D) Enclosed Equipment Accessible to Unqualified Persons. + +Ventilating or similar openings in equipment shall be designed such that foreign objects inserted through these openings are deflected from energized parts. Where exposed to physical damage from vehicular traffic, suitable guards shall be provided. Equipment located outdoors and accessible to unqualified persons shall be designed such that exposed nuts or bolts cannot be readily removed, permitting access to live parts. Where equipment is accessible to unqualified persons and the bottom of the enclosure is less than +2.5 m (8 ft) above the floor or grade level, the enclosure door or hinged cover shall be kept locked. Doors and covers of enclosures used solely as pull boxes, splice boxes, or junction boxes shall be locked, bolted, or screwed on. Underground box covers that weigh over 45.4 kg (100 lb) shall be considered as meeting this requirement. + +### 110.32 Work Space About Equipment. + +Sufficient space shall be provided and maintained about electrical equipment to permit ready and safe operation and maintenance of such equipment. Where energized parts are exposed, the minimum clear work space shall be not less than 2.0 m (61/2 ft) high +(measured vertically from the floor or platform) and the width of the equipment or 914 mm (3 ft) wide (measured parallel to the equipment), whichever is greater. The depth shall be as required in 110.34(A). In all cases, the work space shall permit at least a 90degree opening of doors or hinged panels. Within the height requirements of this section, other equipment that is associated with the electrical installation and is located above or below the electrical equipment shall be permitted to extend not more than 150 mm (6 in.) beyond the front of the electrical equipment. Working space required by this section shall not be used for storage. When normally enclosed live parts are exposed for inspection or servicing, the working space, if in a passageway or general open space, shall be suitably guarded. + +### 110.33 Entrance to Enclosures and Access to Working Space. + +#### 110.33(A) Entrance. + +At least one entrance to enclosures for electrical installations as described in 110.31 +not less than 610 mm (24 in.) wide and 2.0 m (6 1/2 ft) high +shall be provided to give access to the working space about electrical equipment. + +##### 110.33(A)(1) Large Equipment. + +On switchgear and control panels exceeding 1.8 m (6 ft) in width, +there shall be one entrance at each end of the equipment. +A single entrance to the required working space +shall be permitted where either of the conditions in 110.33(A)(1)(a) or (A)(1)(b) is met. + +* (a) Unobstructed Exit. + Where the location permits a continuous and unobstructed way of exit travel, a single entrance to the working space shall be permitted. + +* (b) Extra Working Space. + Where the depth of the working space is twice that required by 110.34(A), + a single entrance shall be permitted. + It shall be located so that the distance from the equipment + to the nearest edge of the entrance + is not less than the minimum clear distance specified in Table 110.34(A) + for equipment operating at that voltage and in that condition. + +##### 110.33(A)(2) Guarding. + +Where bare energized parts at any voltage or insulated energized parts above 1000 volts, nominal, are located adjacent to such entrance, they shall be suitably guarded. + +##### 110.33(A)(3) Personnel Doors. + +Where there are personnel doors intended for entrance to and egress from the working space less than 7.6 m (25 ft) from the nearest edge of the working space, the doors shall open in the direction of egress and be equipped with listed panic hardware or listed fire exit hardware. + +#### 110.33(B) Access. + +Permanent ladders or stairways shall be provided to give safe access to the working space around electrical equipment installed on platforms, balconies, or mezzanine floors or in attic or roof rooms or spaces. + +### 110.34 Work Space and Guarding. + +#### 110.34(A) Working Space. + +Except as elsewhere required or permitted in this Code, equipment likely to require examination, adjustment, servicing, or maintenance while energized shall have clear working space in the direction of access to live parts of the electrical equipment and shall be not less than specified in Table 110.34(A). Distances shall be measured from the live parts, if such are exposed, or from the enclosure front or opening if such are enclosed. + +> [!important] Exception: +> Working space shall not be required in back of equipment such as switchgear or control assemblies where there are no renewable or adjustable parts (such as fuses or switches) on the back and where all connections are accessible from locations other than the back. Where rear access is required to work on nonelectrical parts on the back of enclosed equipment, a minimum working space of 762 mm (30 in.) horizontally shall be provided. + +##### Table 110.34(A) Minimum Depth of Clear Working Space at Electrical Equipment + +| Nominal Voltage to Ground | Condition | Minimum Clear Distance | +|:-------------------------:| ----------- |:----------------------:| +| 1001--2500 V | Condition 1 | 900 mm (3 ft) | +| 1001--2500 V | Condition 2 | 1.2 m (4 ft) | +| 1001--2500 V | Condition 3 | 1.5 m (5 ft) | +| 2501--9000 V | Condition 1 | 1.2 m (4 ft) | +| 2501--9000 V | Condition 2 | 1.5 m (5 ft) | +| 2501--9000 V | Condition 3 | 1.8 m (6 ft) | +| 9001--25,000 V | Condition 1 | 1.5 m (5 ft) | +| 9001--25,000 V | Condition 2 | 1.8 m (6 ft) | +| 9001--25,000 V | Condition 3 | 2.8 m (9 ft) | +| 25,001 V--75 kV | Condition 1 | 1.8 m (6 ft) | +| 25,001 V--75 kV | Condition 2 | 2.5 m (8 ft) | +| 25,001 V--75 kV | Condition 3 | 3.0 m (10 ft) | +| Above 75 kV | Condition 1 | 2.5 m (8 ft) | +| Above 75 kV | Condition 2 | 3.0 m (10 ft) | +| Above 75 kV | Condition 3 | 3.7 m (12 ft) | + +Note: +Where the conditions are as follows: + +* (1) **Condition 1** --- + Exposed live parts on one side of the working space and no live or grounded parts on the other side of the working space, or exposed live parts on both sides of the working space that are effectively guarded by insulating materials. + +* (2) **Condition 2** --- + Exposed live parts on one side of the working space and grounded parts on the other side of the working space. Concrete, brick, or tile walls shall be considered as grounded. + +* (3) **Condition 3** --- + Exposed live parts on both sides of the working space. + +#### 110.34(B) Separation from Low-Voltage Equipment. + +Where switches, cutouts, or other equipment operating at 1000 volts, nominal, or less are installed in a vault, room, or enclosure where there are exposed live parts or exposed wiring operating at over 1000 volts, nominal, the high-voltage equipment shall be effectively separated from the space occupied by the low-voltage equipment by a suitable partition, fence, or screen. + +> [!important] Exception: +> Switches or other equipment operating at 1000 volts, nominal, or less and serving only equipment within the high-voltage vault, room, or enclosure shall be permitted to be installed in the high-voltage vault, room, or enclosure without a partition, fence, or screen if accessible to qualified persons only. + +#### 110.34(C) Locked Rooms or Enclosures. + +The entrance to all buildings, vaults, rooms, or enclosures containing exposed live parts or exposed conductors operating at over +1000 volts, nominal, shall be kept locked unless such entrances are under the observation of a qualified person at all times. + +Permanent and conspicuous danger signs shall be provided. The danger sign shall meet the requirements in 110.21(B) and shall read as follows: + +DANGER --- HIGH VOLTAGE --- KEEP OUT + +#### 110.34(D) Illumination. + +Illumination shall be provided for all working spaces about electrical equipment. Control by automatic means only shall not be permitted. + +The lighting outlets shall be arranged so that persons changing lamps or making repairs on the lighting system are not endangered by live parts or other equipment. + +The points of control shall be located so that persons are not likely to come in contact with any live part or moving part of the equipment while turning on the lights. + +#### 110.34(E) Elevation of Unguarded Live Parts. + +Unguarded live parts above working space shall be maintained at elevations not less than required by Table 110.34(E). + +Table 110.34(E) Elevation of Unguarded Live Parts + +Above Working Space + +Nominal Voltage + +Between Phases + +Elevation m ft +1001--7500 V 2.7 9 +7501--35,000 V 2.9 9 ft 6 in. + +Over 35 kV Add 9.5 mm per kV above 35 kV + +Add 0.37 in. per kV above 35 kV + +#### 110.34(F) Protection of Service Equipment, Switchgear, and Industrial Control Assemblies. + +Pipes or ducts foreign to the electrical installation and requiring periodic maintenance or whose malfunction would endanger the operation of the electrical system shall not be located in the vicinity of the service equipment, switchgear, or industrial control assemblies. Protection shall be provided where necessary to avoid damage from condensation leaks and breaks in such foreign systems. Piping and other facilities shall not be considered foreign if provided for fire protection of the electrical installation. + +### 110.36 Circuit Conductors. + +Circuit conductors shall be permitted to be installed in raceways; in cable trays; as metal-clad cable Type MC; as bare wire, cable, and busbars; or as Type MV cables or conductors as provided in 300.37, 300.39, 300.40, and 300.50. Bare live conductors shall comply with 490.24. + +Insulators, together with their mounting and conductor attachments, where used as supports for wires, single-conductor cables, or busbars, shall be capable of safely withstanding the maximum magnetic forces that would prevail if two or more conductors of a circuit were subjected to short-circuit current. + +Exposed runs of insulated wires and cables that have a bare lead sheath or a braided outer covering shall be supported in a manner designed to prevent physical damage to the braid or sheath. Supports for lead-covered cables shall be designed to prevent electrolysis of the sheath. + +### 110.40 Temperature Limitations at Terminations. + +Conductors shall be permitted to be terminated based on the 90°C (194°F) temperature rating and ampacity as given in Table +311.60(C)(67) through Table 311.60(C)(86), unless otherwise identified. + +### 110.41 Inspections and Tests. + +#### 110.41(A) Pre-energization and Operating Tests. + +Where required elsewhere in this Code, the complete electrical system design, including settings for protective, switching, and control circuits, shall be prepared in advance and made available on request to the authority having jurisdiction and shall be tested when first installed on-site. + +#### 110.41(B) Test Report. + +A test report covering the results of the tests required in 110.41(A) shall be available to the authority having jurisdiction prior to energization and made available to those authorized to install, operate, test, and maintain the system. + +## Part IV. Tunnel Installations over 1000 Volts, Nominal + +### 110.51 General. + +#### 110.51(A) Covered. + +This part shall apply to the installation and use of high-voltage power distribution and utilization equipment that is portable, mobile, or both, such as substations, trailers, cars, mobile shovels, draglines, hoists, drills, dredges, compressors, pumps, conveyors, underground excavators, and the like. + +#### 110.51(B) Other Articles. + +The requirements of this part shall be additional to, or amendatory of, those prescribed in Articles 100 through 490 of this Code. + +#### 110.51(C) Protection Against Physical Damage. + +Conductors and cables in tunnels shall be located above the tunnel floor and so placed or guarded to protect them from physical damage. + +### 110.52 Overcurrent Protection. + +Motor-operated equipment shall be protected from overcurrent in accordance with Parts III, IV, and V of Article 430. Transformers shall be protected from overcurrent in accordance with 450.3. + +### 110.53 Conductors. + +High-voltage conductors in tunnels shall be installed in metal conduit or other metal raceway, Type MC cable, or other approved multiconductor cable. Multiconductor portable cable shall be permitted to supply mobile equipment. + +### 110.54 Bonding and Equipment Grounding Conductors. + +#### 110.54(A) Grounded and Bonded. + +All non--current-carrying metal parts of electrical equipment and all metal raceways and cable sheaths shall be solidly grounded and bonded to all metal pipes and rails at the portal and at intervals not exceeding 300 m (1000 ft) throughout the tunnel. + +#### 110.54(B) Equipment Grounding Conductors. + +An equipment grounding conductor shall be run with circuit conductors inside the metal raceway or inside the multiconductor cable jacket. The equipment grounding conductor shall be permitted to be insulated or bare. + +### 110.55 Transformers, Switches, and Electrical Equipment. + +All transformers, switches, motor controllers, motors, rectifiers, and other equipment installed belowground shall be protected from physical damage by location or guarding. + +### 110.56 Energized Parts. + +Bare terminals of transformers, switches, motor controllers, and other equipment shall be enclosed to prevent accidental contact with energized parts. + +### 110.57 Ventilation System Controls. + +Electrical controls for the ventilation system shall be arranged so that the airflow can be reversed. + +### 110.58 Disconnecting Means. + +A switch or circuit breaker that simultaneously opens all ungrounded conductors of the circuit shall be installed within sight of each transformer or motor location for disconnecting the transformer or motor. The switch or circuit breaker for a transformer shall have an ampere rating not less than the ampacity of the transformer supply conductors. The switch or circuit breaker for a motor shall comply with the applicable requirements of Article 430. + +### 110.59 Enclosures. + +Enclosures for use in tunnels shall be dripproof, weatherproof, or submersible as required by the environmental conditions. Switch or contactor enclosures shall not be used as junction boxes or as raceways for conductors feeding through or tapping off to other switches, unless the enclosures comply with 312.8. + +## Part V. Manholes and Other Electrical Enclosures Intended for Personnel Entry + +### 110.70 General. + +Electrical enclosures intended for personnel entry and specifically fabricated for this purpose shall be of sufficient size to provide safe work space about electrical equipment with live parts that is likely to require examination, adjustment, servicing, or maintenance while energized. Such enclosures shall have sufficient size to permit ready installation or withdrawal of the conductors employed without damage to the conductors or to their insulation. They shall comply with this part. + +> [!important] Exception: +> Where electrical enclosures covered by Part V of this article are part of an industrial wiring system operating under conditions of maintenance and supervision that ensure that only qualified persons monitor and supervise the system, they shall be permitted to be designed and installed in accordance with appropriate engineering practice. If required by the authority having jurisdiction, design documentation shall be provided. + +### 110.71 Strength. + +Manholes, vaults, and their means of access shall be designed under qualified engineering supervision and shall withstand all loads likely to be imposed on the structures. + +> [!info] Informational Note: +> See ANSI C2-2007, National Electrical Safety Code, for additional information on the loading that can be expected to bear on underground enclosures. + +### 110.72 Cabling Work Space. + +A clear work space not less than 900 mm (3 ft) wide shall be provided where cables are located on both sides, and not less than +750 mm (21/2 ft) where cables are only on one side. The vertical headroom shall be not less than 1.8 m (6 ft) unless the opening is within 300 mm (1 ft), measured horizontally, of the adjacent interior side wall of the enclosure. + +> [!important] Exception: +> A manhole containing only one or more of the following shall be permitted to have one of the horizontal work space dimensions reduced to 600 mm (2 ft) where the other horizontal clear work space is increased so the sum of the two dimensions is not less than 1.8 m (6 ft): + +* (1) Optical fiber cables as covered in Article 770 + +* (2) Power-limited fire alarm circuits supplied in accordance with 760.121 + +* (3) Class 2 or Class 3 remote-control and signaling circuits, or both, supplied in accordance with 725.121 + +### 110.73 Equipment Work Space. + +Where electrical equipment with live parts that is likely to require examination, adjustment, servicing, or maintenance while energized is installed in a manhole, vault, or other enclosure designed for personnel access, the work space and associated requirements in 110.26 shall be met for installations operating at 1000 volts or less. Where the installation is over 1000 volts, the work space and associated requirements in 110.34 shall be met. A manhole access cover that weighs over 45.4 kg (100 lb) shall be considered as meeting the requirements of 110.34(C). + +### 110.74 Conductor Installation. + +Conductors installed in manholes and other enclosures intended for personnel entry shall be cabled, racked up, or arranged in an approved manner that provides ready and safe access for persons to enter for installation and maintenance. The installation shall comply with 110.74(A) or 110.74(B), as applicable. + +#### 110.74(A) 1000 Volts, Nominal, or Less. + +Wire bending space for conductors operating at 1000 volts or less shall be provided in accordance with the requirements of 314.28. + +#### 110.74(B) Over 1000 Volts, Nominal. + +Conductors operating at over 1000 volts shall be provided with bending space in accordance with 314.71(A) and (B), as applicable. + +> [!important] Exception: +> Where 314.71(B) applies, each row or column of ducts on one wall of the enclosure shall be calculated individually, and the single row or column that provides the maximum distance shall be used. + +### 110.75 Access to Manholes. + +#### 110.75(A) Dimensions. + +Rectangular access openings shall not be less than 650 mm × 550 mm (26 in. × 22 in.). Round access openings in a manhole shall be not less than 650 mm (26 in.) in diameter. + +> [!important] Exception: +> A manhole that has a fixed ladder that does not obstruct the opening or that contains only one or more of the following shall be permitted to reduce the minimum cover diameter to 600 mm (2 ft): + +* (1) Optical fiber cables as covered in Article 770 + +* (2) Power-limited fire alarm circuits supplied in accordance with 760.121 + +* (3) Class 2 or Class 3 remote-control and signaling circuits, or both, supplied in accordance with 725.121 + +#### 110.75(B) Obstructions. + +Manhole openings shall be free of protrusions that could injure personnel or prevent ready egress. + +#### 110.75(C) Location. + +Manhole openings for personnel shall be located where they are not directly above electrical equipment or conductors in the enclosure. + +Where this is not practicable, either a protective barrier or a fixed ladder shall be provided. + +#### 110.75(D) Covers. + +Covers shall be over 45 kg (100 lb) or otherwise designed to require the use of tools to open. They shall be designed or restrained so they cannot fall into the manhole or protrude sufficiently to contact electrical conductors or equipment within the manhole. + +#### 110.75(E) Marking. + +Manhole covers shall have an identifying mark or logo that prominently indicates their function, such as "electric." + +### 110.76 Access to Vaults and Tunnels. + +#### 110.76(A) Location. + +Access openings for personnel shall be located where they are not directly above electrical equipment or conductors in the enclosure. + +Other openings shall be permitted over equipment to facilitate installation, maintenance, or replacement of equipment. + +#### 110.76(B) Locks. + +In addition to compliance with the requirements of 110.34, if applicable, access openings for personnel shall be arranged such that a person on the inside can exit when the access door is locked from the outside, or in the case of normally locking by padlock, the locking arrangement shall be such that the padlock can be closed on the locking system to prevent locking from the outside. + +### 110.77 Ventilation. + +Where manholes, tunnels, and vaults have communicating openings into enclosed areas used by the public, ventilation to open air shall be provided wherever practicable. + +### 110.78 Guarding. + +Where conductors or equipment, or both, could be contacted by objects falling or being pushed through a ventilating grating, both conductors and live parts shall be protected in accordance with the requirements of 110.27(A)(2) or 110.31(B)(1), depending on the voltage. + +### 110.79 Fixed Ladders. + +Fixed ladders shall be corrosion resistant. + +[^1]: diff --git a/nfpa-70_210_branch-circuits.md b/nfpa-70_210_branch-circuits.md index b64adab..448c573 100644 --- a/nfpa-70_210_branch-circuits.md +++ b/nfpa-70_210_branch-circuits.md @@ -19,7 +19,348 @@ title: Article 210 Branch Circuits This article provides the general requirements for branch circuits. - +### 210.3 Other Articles for Specific-Purpose Branch Circuits. + +Table 210.3 lists references for specific equipment and applications not located in Chapters 5, 6, and 7 that amend or supplement the requirements of this article. + +Table 210.3 Specific-Purpose Branch Circuits + +| Equipment | Article | Section | +| --------------------------------------------------------------------------- | ------- | --------------------- | +| Air-conditioning and refrigerating equipment | | 440.6, 440.31, 440.32 | +| Busways | | 368.17 | +| Central heating equipment other than fixed electric space-heating equipment | | 422.12 | +| Fixed electric heating equipment for pipelines and vessels | | 427.4 | +| Fixed electric space-heating equipment | | 424.3 | +| Fixed outdoor electrical deicing and snow-melting equipment | | 426.4 | +| Infrared lamp industrial heating equipment | | 422.48, 424.3 | +| Motors, motor circuits, and controllers | 430 | | +| Switchboards and panelboards | | 408.52 | + +### 210.4 Multiwire Branch Circuits. + +#### 210.4(A) General. + +Branch circuits recognized by this article shall be permitted as multiwire circuits. A multiwire circuit shall be permitted to be considered as multiple circuits. All conductors of a multiwire branch circuit shall originate from the same panelboard or similar distribution equipment. + +> [!info] Informational Note No. 1: +> A 3-phase, 4-wire, wye-connected power system used to supply power to nonlinear loads may necessitate that the power system design allow for the possibility of high harmonic currents on the neutral conductor. + +> [!info] Informational Note No. 2: +> See 300.13(B) for continuity of grounded conductors on multiwire circuits. + +#### 210.4(B) Disconnecting Means. + +Each multiwire branch circuit shall be provided with a means that will simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates. + +> [!info] Informational Note: +> See 240.15(B) for information on the use of single-pole circuit breakers as the disconnecting means. + +#### 210.4(C) Line-to-Neutral Loads. + +Multiwire branch circuits shall supply only line-to-neutral loads. + +> [!important] Exception No. 1: +> A multiwire branch circuit that supplies only one utilization equipment. + +> [!important] Exception No. 2: +> Where all ungrounded conductors of the multiwire branch circuit are opened simultaneously by the branch-circuit overcurrent device. + +#### 210.4(D) Grouping. + +The ungrounded and grounded circuit conductors of each multiwire branch circuit shall be grouped in accordance with 200.4(B). + +### 210.5 Identification for Branch Circuits. + +#### 210.5(A) Grounded Conductor. + +The grounded conductor of a branch circuit shall be identified in accordance with 200.6. + +#### 210.5(B) Equipment Grounding Conductor. + +The equipment grounding conductor shall be identified in accordance with 250.119. + +#### 210.5(C) Identification of Ungrounded Conductors. + +Ungrounded conductors shall be identified in accordance with 210.5(C)(1) or (2), as applicable. + +##### 210.5(C)(1) Branch Circuits Supplied from More Than One Nominal Voltage System. + +Where the premises wiring system has branch circuits supplied from more than one nominal voltage system, each ungrounded conductor of a branch circuit shall be identified by phase or line and by system voltage class at all termination, connection, and splice points in compliance with 210.5(C)(1)(a) and (b). Different systems within the same premises that have the same system voltage class shall be permitted to use the same identification. + +* (a) _Means of Identification._ + The means of identification shall be permitted to be by separate color coding, marking tape, tagging, or other approved means. + +* (b) _Posting of Identification Means._ + The method utilized for conductors originating within each branch-circuit panelboard or similar branch-circuit distribution equipment shall be documented in a manner that is readily available or shall be permanently posted at each branch-circuit panelboard or similar branch-circuit distribution equipment. The label shall be of sufficient durability to withstand the environment involved and shall not be handwritten. + +> [!important] Exception: +> In existing installations where a voltage system(s) already exists and a different voltage system is being added, it shall be permissible to mark only the new system voltage. Existing unidentified systems shall not be required to be identified at each termination, connection, and splice point in compliance with 210.5(C)(1)(a) and (b). Labeling shall be required at each voltage system distribution equipment to identify that only one voltage system has been marked for a new system(s). The new system label(s) shall include the words "other unidentified systems exist on the premises." + +##### 210.5(C)(2) Branch Circuits Supplied from Direct-Current Systems. + +Where a branch circuit is supplied from a dc system operating at more than 60 volts, each ungrounded conductor of 4 AWG or larger shall be identified by polarity at all termination, connection, and splice points by marking tape, tagging, or other approved means; each ungrounded conductor of 6 AWG or smaller shall be identified by polarity at all termination, connection, and splice points in compliance with 210.5(C) (2) (a) and (b). The identification methods utilized for conductors originating within each branch-circuit panelboard or similar branch-circuit distribution equipment shall be documented in a manner that is readily available or shall be permanently posted at each branch-circuit panelboard or similar branch-circuit distribution equipment. + +* (a) Positive Polarity, Sizes 6 AWG or Smaller. Where the positive polarity of a dc system does not serve as the connection point for the grounded conductor, each positive ungrounded conductor shall be identified by one of the following means: + +* (1) A continuous red outer finish + +* (2) A continuous red stripe durably marked along the conductor's entire length on insulation of a color other than green, white, gray, or black + +* (3) Imprinted plus signs (+) or the word POSITIVE or POS durably marked on insulation of a color other than green, white, gray, or black and repeated at intervals not exceeding 610 mm (24 in.) in accordance with 310.8(B) + +* (4) An approved permanent marking means such as sleeving or shrink-tubing that is suitable for the conductor size, at all termination, connection, and splice points, with imprinted plus signs (+) or the word POSITIVE or POS durably marked on insulation of a color other than green, white, gray, or black + +* (b) Negative Polarity, Sizes 6 AWG or Smaller. Where the negative polarity of a dc system does not serve as the connection point for the grounded conductor, each negative ungrounded conductor shall be identified by one of the following means: + +* (1) A continuous black outer finish + +* (2) A continuous black stripe durably marked along the conductor's entire length on insulation of a color other than green, white, gray, or red + +* (3) Imprinted minus signs (--) or the word NEGATIVE or NEG durably marked on insulation of a color other than green, white, gray, or red and repeated at intervals not exceeding 610 mm (24 in.) in accordance with 310.8(B) + +* (4) An approved permanent marking means such as sleeving or shrink-tubing that is suitable for the conductor size, at all termination, connection, and splice points, with imprinted minus signs (--) or the word NEGATIVE or NEG durably marked on insulation of a color other than green, white, gray, or red + +### 210.6 Branch-Circuit Voltage Limitations. + +The nominal voltage of branch circuits shall not exceed the values permitted by 210.6(A) through (E). + +#### 210.6(A) Occupancy Limitation. + +In dwelling units and guest rooms or guest suites of hotels, motels, and similar occupancies, the voltage shall not exceed 120 volts, nominal, between conductors that supply the terminals of the following: + +* (1) Luminaires + +* (2) Cord-and-plug-connected loads 1440 volt-amperes, nominal, + or less or less than 1/4 hp + +#### 210.6(B) 120 Volts Between Conductors. + +Circuits not exceeding 120 volts, nominal, between conductors shall be permitted to supply the following: + +* (1) The terminals of lampholders applied within their voltage ratings + +* (2) Auxiliary equipment of electric-discharge lamps + + > [!info] Informational Note: + > See 410.137 for auxiliary equipment limitations. + +* (3) Cord-and-plug-connected or permanently connected utilization equipment + +#### 210.6(C) 277 Volts to Ground. + +Circuits exceeding 120 volts, nominal, between conductors but not exceeding 277 volts, nominal, to ground shall be permitted to supply cord-and-plug-connected or permanently connected utilization equipment, or the following types of listed luminaires: + +* (1) Electric-discharge luminaires with integral ballasts + +* (2) LED luminaires with LED drivers between the branch circuit and the lampholders + +* (3) Incandescent or LED luminaires, equipped with medium-base or smaller screw shell lampholders, where the lampholders are supplied at 120 volts or less from the output of a stepdown autotransformer, LED driver, or other type of power supply that is an integral component of the luminaire + + > [!info] Informational Note: + > See 410.90 for requirements regarding the connection of screw shell lampholders to grounded conductors. + +* (4) Luminaires equipped with mogul-base screw shell lampholders + +* (5) Luminaires equipped with lampholders, other than the screw shell type, when used within their voltage ratings of their lampholders + +* (6) Luminaires without lampholders + + > [!info] Informational Note: + > Luminaires with nonserviceable LEDs are examples of luminaires without lampholders. + +* (7) Auxiliary equipment of electric-discharge or LED-type lamps + + > [!info] Informational Note: + > See 410.137 for auxiliary equipment limitations. + +* (8) Luminaires converted with listed retrofit kits incorporating integral LED light sources or accepting LED lamps that also conforms with 210.6(C)(1), (C)(2), (C)(3), (C)(4), or (C)(5) + +#### 210.6(D) 600 Volts Between Conductors. + +Circuits exceeding 277 volts, nominal, to ground and not exceeding 600 volts, nominal, between conductors shall be permitted to supply the following: + +* (1) The auxiliary equipment of electric-discharge lamps mounted in permanently installed luminaires where the luminaires are mounted in accordance with one of the following: + * a. Not less than a height of 6.7 m (22 ft) on poles or similar structures for the illumination of outdoor areas such as highways, roads, bridges, athletic fields, or parking lots + * b. Not less than a height of 5.5 m (18 ft) on other structures such as tunnels + +> [!info] Informational Note: +> See 410.137 for auxiliary equipment limitations. + +* (2) Cord-and-plug-connected or permanently connected utilization equipment other than luminaires + +* (3) Luminaires powered from direct-current systems where either of the following apply: + * a. The luminaire contains a listed, dc-rated ballast that provides isolation between the dc power source and the lamp circuit and protection from electric shock when changing lamps. + * b. The luminaire contains a listed, dc-rated ballast and has no provision for changing lamps. + +> [!important] Exception No. 1 to (B), (C), and (D): +> For lampholders of infrared industrial heating appliances as provided in 425.14. + +> [!important] Exception No. 2 to (B), (C), and (D): +> For railway properties as described in 110.19. + +#### 210.6(E) Over 600 Volts Between Conductors. + +Circuits exceeding 600 volts, nominal, between conductors shall be permitted to supply utilization equipment in installations where conditions of maintenance and supervision ensure that only qualified persons service the installation. + +### 210.7 Multiple Branch Circuits. + +Where two or more branch circuits supply devices or equipment on the same yoke or mounting strap, a means to simultaneously disconnect the ungrounded supply conductors shall be provided at the point at which the branch circuits originate. + +### 210.8 Ground-Fault Circuit-Interrupter Protection for Personnel. + +Ground-fault circuit-interrupter protection for personnel shall be provided as required in 210.8(A) through (F). The ground-fault circuit interrupter shall be installed in a readily accessible location. + +> [!info] Informational Note No. 1: +> See 215.9 for ground-fault circuit-interrupter protection for personnel on feeders. + +> [!info] Informational Note No. 2: +> See 422.5(A) for GFCI requirements for appliances. + +> [!info] Informational Note No. 3: +> See 555.9 for GFCI requirements for boat hoists. + +> [!info] Informational Note No. 4: +> Additional GFCI requirements for specific circuits and equipment are contained in Chapters 4, 5, and 6. + +For the purposes of this section, when determining the distance from receptacles the distance shall be measured as the shortest path the supply cord of an appliance connected to the receptacle would follow without piercing a floor, wall, ceiling, or fixed barrier, or the shortest path without passing through a window. + +#### 210.8(A) Dwelling Units. + +All 125-volt through 250-volt receptacles installed in the locations specified in 210.8(A)(1) through (A) (11) and supplied by single-phase branch circuits rated 150 volts or less to ground shall have ground-fault circuit-interrupter protection for personnel. + +* (1) Bathrooms + +* (2) Garages and also accessory buildings that have a floor located at or below grade level not intended as habitable rooms and limited to storage areas, work areas, and areas of similar use + +* (3) Outdoors + + > [!important] Exception to (3): + > Receptacles that are not readily accessible + > and are supplied by a branch circuit dedicated to electric snowmelting, + > deicing, or pipeline and vessel heating equipment + > shall be permitted to be installed in accordance with 426.28 or 427.22, as applicable. + +* (4) Crawl spaces --- at or below grade level + +* (5) Basements + + > [!important] Exception to (5): + > A receptacle supplying only a permanently installed fire alarm or burglar alarm system shall not be required to have ground-fault circuit-interrupter protection. + + > [!info] Informational Note: + > See 760.41(B) and 760.121(B) for power supply requirements for fire alarm systems. + +Receptacles installed under the exception to 210.8(A)(5) shall not be considered as meeting the requirements of 210.52(G). + +* (6) Kitchens --- where the receptacles are installed to serve the countertop surfaces + +* (7) Sinks --- where receptacles are installed within 1.8 m (6 ft) from the top inside edge of the bowl of the sink + +* (8) Boathouses + +* (9) Bathtubs or shower stalls --- where receptacles are installed within 1.8 m (6 ft) of the outside edge of the bathtub or shower stall + +* (10) Laundry areas + + > [!important] Exception to (1) through (3), (5) through (8), and (10): + > Listed locking support and mounting receptacles utilized in combination with compatible attachment fittings installed for the purpose of serving a ceiling luminaire or ceiling fan shall not be required to be ground-fault circuit-interrupter protected. If a general-purpose convenience receptacle is integral to the ceiling luminaire or ceiling fan, GFCI protection shall be provided. + +* (11) Indoor damp and wet locations + +#### 210.8(B) Other Than Dwelling Units. + +All 125-volt through 250-volt receptacles supplied by single-phase branch circuits rated 150 volts or less to ground, 50 amperes or less, and all receptacles supplied by three-phase branch circuits rated 150 volts or less to ground, 100 amperes or less, installed in the locations specified in 210.8(B)(1) through (B)(12) shall have ground-fault circuit-interrupter protection for personnel. + +* (1) Bathrooms + +* (2) Kitchens or areas with a sink and permanent provisions for either food preparation or cooking + +* (3) Rooftops + + > [!important] Exception: + > Receptacles on rooftops shall not be required to be readily accessible other than from the rooftop. + +* (4) Outdoors + +Exception No. 1 to (3) and (4): Receptacles that are not readily accessible and are supplied by a branch circuit dedicated to electric snow-melting, deicing, or pipeline and vessel heating equipment shall be permitted to be installed in accordance with +426.28 or 427.22, as applicable. + +Exception No. 2 to (4): In industrial establishments only, where the conditions of maintenance and supervision ensure that only qualified personnel are involved, an assured equipment grounding conductor program as specified in 590.6(B)(2) shall be permitted for only those receptacle outlets used to supply equipment that would create a greater hazard if power is interrupted or having a design that is not compatible with GFCI protection. + +* (5) Sinks --- where receptacles are installed within 1.8 m (6 ft) from the top inside edge of the bowl of the sink + +Exception No. 1 to (5): In industrial laboratories, receptacles used to supply equipment where removal of power would introduce a greater hazard shall be permitted to be installed without GFCI protection. + +Exception No. 2 to (5): Receptacles located in patient bed locations of Category 2 (general care) or Category 1 (critical care) spaces of health care facilities shall be permitted to comply with 517.21. + +* (6) Indoor damp and wet locations + +* (7) Locker rooms with associated showering facilities + +* (8) Garages, accessory buildings, service bays, and similar areas other than vehicle exhibition halls and showrooms + +* (9) Crawl spaces --- at or below grade level + +* (10) Unfinished areas of basements + +Exception to (1) through (5), (8), and (10): Listed locking support and mounting receptacles utilized in combination with compatible attachment fittings installed for the purpose of serving a ceiling luminaire or ceiling fan shall not be required to be ground-fault circuit-interrupter protected. If a general-purpose convenience receptacle is integral to the ceiling luminaire or ceiling fan, GFCI protection shall be provided. + +* (11) Laundry areas + +* (12) Bathtubs and shower stalls --- where receptacles are installed within 1.8 m (6 ft) of the outside edge of the bathtub or shower stall + +#### 210.8(C) Crawl Space Lighting Outlets. + +GFCI protection shall be provided for lighting outlets not exceeding 120 volts installed in crawl spaces. + +#### 210.8(D) Specific Appliances. + +Unless GFCI protection is provided in accordance with 422.5(B)(3) through (B)(5), the outlets supplying the appliances specified in +422.5(A) shall have GFCI protection in accordance with 422.5(B)(1) or (B)(2). + +Where the appliance is a vending machine as specified in 422.5(A)(5) and GFCI protection is not provided in accordance with 422.5(B) + +* (3) or (B)(4), branch circuits supplying vending machines shall have GFCI protection in accordance with 422.5(B)(1) or (B)(2). + +#### 210.8(E) Equipment Requiring Servicing. + +GFCI protection shall be provided for the receptacles required by 210.63. + +#### 210.8(F) Outdoor Outlets. + +All outdoor outlets for dwellings, other than those covered in 210.8(A)(3), Exception to (3), that are supplied by single-phase branch circuits rated 150 volts to ground or less, 50 amperes or less, shall have ground-fault circuit-interrupter protection for personnel. + +> [!important] Exception: +> Ground-fault circuit-interrupter protection shall not be required on lighting outlets other than those covered in 210.8(C). + +### 210.9 Circuits Derived from Autotransformers. + +Branch circuits shall not be derived from autotransformers unless the circuit supplied has a grounded conductor that is electrically connected to a grounded conductor of the system supplying the autotransformer. + +> [!important] Exception No. 1: +> An autotransformer shall be permitted without the connection to a grounded conductor where transforming from a nominal 208 volts to a nominal 240-volt supply or similarly from 240 volts to 208 volts. + +> [!important] Exception No. 2: +> In industrial occupancies, where conditions of maintenance and supervision ensure that only qualified persons service the installation, autotransformers shall be permitted to supply nominal 600-volt loads from nominal 480-volt systems, and 480-volt loads from nominal 600-volt systems, without the connection to a similar grounded conductor. + +### 210.10 Ungrounded Conductors Tapped from Grounded Systems. + +Two-wire dc circuits and ac circuits of two or more ungrounded conductors shall be permitted to be tapped from the ungrounded conductors of circuits that have a grounded neutral conductor. Switching devices in each tapped circuit shall have a pole in each ungrounded conductor. All poles of multipole switching devices shall manually switch together where such switching devices also serve as a disconnecting means as required by the following: + +* (1) 410.93 for double-pole switched lampholders + +* (2) 410.104(B) for electric-discharge lamp auxiliary equipment switching devices + +* (3) 422.31(B) for an appliance + +* (4) 424.20 for a fixed electric space-heating unit + +* (5) 426.51 for electric deicing and snow-melting equipment + +* (6) 430.85 for a motor controller + +* (7) 430.103 for a motor ### 210.11 Branch Circuits Required. @@ -72,10 +413,10 @@ to supply bathroom(s) receptacle outlet(s) required by 210.52(D) and any countertop and similar work surface receptacle outlets. Such circuits shall have no other outlets. -Exception: -Where the 20-ampere circuit supplies a single bathroom, -outlets for other equipment within the same bathroom -shall be permitted to be supplied in accordance with 210.23(A)(1) and (A)(2). +> [!important] Exception: +> Where the 20-ampere circuit supplies a single bathroom, +> outlets for other equipment within the same bathroom +> shall be permitted to be supplied in accordance with 210.23(A)(1) and (A)(2). ##### 210.11(C)(4) Garage Branch Circuits. @@ -85,11 +426,104 @@ to supply receptacle outlets required by 210.52(G)(1) for attached garages and in detached garages with electric power. This circuit shall have no other outlets. -Exception: -This circuit shall be permitted to supply -readily accessible outdoor receptacle outlets. +> [!important] Exception: +> This circuit shall be permitted to supply +> readily accessible outdoor receptacle outlets. - +### 210.12 Arc-Fault Circuit-Interrupter Protection. + +Arc-fault circuit-interrupter protection shall be provided as required in 210.12(A), (B), (C), and (D). The arc-fault circuit interrupter shall be installed in a readily accessible location. + +#### 210.12(A) Dwelling Units. + +All 120-volt, single-phase, 15- and 20-ampere branch circuits supplying outlets or devices installed in dwelling unit kitchens, family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, laundry areas, or similar rooms or areas shall be protected by any of the means described in 210.12(A)(1) through (6): + +* (1) A listed combination-type arc-fault circuit interrupter installed to provide protection of the entire branch circuit + +* (2) A listed branch/feeder-type AFCI installed at the origin of the branch-circuit in combination with a listed outlet branch-circuit-type arc-fault circuit interrupter installed at the first outlet box on the branch circuit. The first outlet box in the branch circuit shall be marked to indicate that it is the first outlet of the circuit. + +* (3) A listed supplemental arc protection circuit breaker installed at the origin of the branch circuit in combination with a listed outlet branch-circuit-type arc-fault circuit interrupter installed at the first outlet box on the branch circuit where all of the following conditions are met: + * a. The branch-circuit wiring shall be continuous from the branch-circuit overcurrent device to the outlet branch-circuit arcfault circuit interrupter. + * b. The maximum length of the branch-circuit wiring from the branch-circuit overcurrent device to the first outlet shall not exceed 15.2 m (50 ft) for a 14 AWG conductor or 21.3 m (70 ft) for a 12 AWG conductor. + * c. The first outlet box in the branch circuit shall be marked to indicate that it is the first outlet of the circuit. + +* (4) A listed outlet branch-circuit-type arc-fault circuit interrupter installed at the first outlet on the branch circuit in combination with a listed branch-circuit overcurrent protective device where all of the following conditions are met: + * a. The branch-circuit wiring shall be continuous from the branch-circuit overcurrent device to the outlet branch-circuit arcfault circuit interrupter. + * b. The maximum length of the branch-circuit wiring from the branch-circuit overcurrent device to the first outlet shall not exceed 15.2 m (50 ft) for a 14 AWG conductor or 21.3 m (70 ft) for a 12 AWG conductor. + * c. The first outlet box in the branch circuit shall be marked to indicate that it is the first outlet of the circuit. + * d. The combination of the branch-circuit overcurrent device and outlet branch-circuit AFCI shall be identified as meeting the requirements for a system combination-type AFCI and shall be listed as such. + +* (5) If metal raceway, metal wireways, metal auxiliary gutters, or Type MC, or Type AC cable meeting the applicable requirements of +250.118, with metal boxes, metal conduit bodies, and metal enclosures are installed for the portion of the branch circuit between the branch-circuit overcurrent device and the first outlet, it shall be permitted to install a listed outlet branch-circuit-type AFCI at the first outlet to provide protection for the remaining portion of the branch circuit. + +* (6) Where a listed metal or nonmetallic conduit or tubing or Type MC cable is encased in not less than 50 mm (2 in.) of concrete for the portion of the branch circuit between the branch-circuit overcurrent device and the first outlet, it shall be permitted to install a listed outlet branch-circuit-type AFCI at the first outlet to provide protection for the remaining portion of the branch circuit. + +> [!important] Exception: +> AFCI protection shall not be required for an individual branch circuit supplying a fire alarm system installed in accordance with 760.41(B) or 760.121(B). The branch circuit shall be installed in a metal raceway, metal auxiliary gutter, steel-armored cable, Type + +MC or Type AC, meeting the applicable requirements of 250.118, with metal boxes, conduit bodies, and enclosures. + +> [!info] Informational Note No. 1: +> For information on combination-type and branch/feeder-type arc-fault circuit interrupters, see UL 1699-2011, + +Standard for Arc-Fault Circuit Interrupters. For information on outlet branch-circuit type arc-fault circuit interrupters, see UL Subject +1699A, Outline of Investigation for Outlet Branch Circuit Arc-Fault Circuit-Interrupters. For information on system combination AFCIs, see UL Subject 1699C, Outline of Investigation for System Combination Arc-Fault Circuit Interrupters. + +> [!info] Informational Note No. 2: +> See 29.6.3(5) of NFPA 72-2013, National Fire Alarm and Signaling Code, for information related to secondary power-supply requirements for smoke alarms installed in dwelling units. + +> [!info] Informational Note No. 3: +> See 760.41(B) and 760.121(B) for power-supply requirements for fire alarm systems. + +#### 210.12(B) Dormitory Units. + +All 120-volt, single-phase, 15- and 20-ampere branch circuits supplying outlets and devices installed in dormitory unit bedrooms, living rooms, hallways, closets, bathrooms, and similar rooms shall be protected by any of the means described in 210.12(A)(1) through (6). +210.12(C) Guest Rooms, Guest Suites, and Patient Sleeping Rooms in Nursing Homes and Limited-Care + +Facilities. + +All 120-volt, single-phase, 15- and 20-ampere branch circuits supplying outlets and devices installed in guest rooms and guest suites of hotels and motels and patient sleeping rooms in nursing homes and limited-care facilities shall be protected by any of the means described in 210.12(A)(1) through (6). +210.12(D) Branch Circuit Extensions or Modifications --- Dwelling Units, Dormitory Units, and Guest + +Rooms and Guest Suites. + +Where branch circuit wiring for any of the areas specified in 210.12(A), (B), or (C) is modified, replaced, or extended, the branch circuit shall be protected by one of the following: + +* (1) By any of the means described in 210.12(A)(1) through (A)(6) + +* (2) A listed outlet branch-circuit-type AFCI located at the first receptacle outlet of the existing branch circuit + +> [!important] Exception: +> AFCI protection shall not be required where the extension of the existing branch circuit conductors is not more than 1.8 m +(6 ft) and does not include any additional outlets or devices, other than splicing devices. This measurement shall not include the conductors inside an enclosure, cabinet, or junction box. + +### 210.13 Ground-Fault Protection of Equipment. + +Each branch-circuit disconnect rated 1000 A or more and installed on solidly grounded wye electrical systems of more than 150 volts to ground, but not exceeding 600 volts phase-to-phase, shall be provided with ground-fault protection of equipment in accordance with +230.95. + +> [!info] Informational Note: +> For buildings that contain health care occupancies, see the requirements of 517.17. + +> [!important] Exception No. 1: +> This section shall not apply to a disconnecting means for a continuous industrial process where a nonorderly shutdown will introduce additional or increased hazards. + +> [!important] Exception No. 2: +> This section shall not apply if ground-fault protection of equipment is provided on the supply side of the branch circuit and on the load side of any transformer supplying the branch circuit. + +### 210.15 Reconditioned Equipment. + +The following shall not be reconditioned: + +* (1) Equipment that provides ground-fault circuit-interrupter protection for personnel + +* (2) Equipment that provides arc-fault circuit-interrupter protection + +* (3) Equipment that provides ground-fault protection of equipment + +### 210.17 Guest Rooms and Guest Suites. + +Guest rooms and guest suites that are provided with permanent provisions for cooking shall have branch circuits installed to meet the rules for dwelling units. ## Part II. Branch-Circuit Ratings @@ -110,9 +544,7 @@ shall determine the circuit rating. > where conditions of maintenance and supervision ensure > that only qualified persons service the equipment. -### 210.19 Conductors -- Minimum Ampacity and Size. - - +### 210.19 Conductors --- Minimum Ampacity and Size. #### 210.19(A) Branch Circuits Not More Than 600 Volts. @@ -137,13 +569,89 @@ for equipment terminations. or correction factors in accordance with [[nfpa-70_310_conductors_for_general_wiring#310.15 Ampacity Tables.|310.15]]. +> [!important] Exception No. 1 to (1)(a): +> If the assembly, including the overcurrent devices protecting the branch circuit(s), is listed for operation at +100 percent of its rating, the ampacity of the branch-circuit conductors shall be permitted to be not less than the sum of the continuous load plus the noncontinuous load in accordance with 110.14(C). + +> [!important] Exception No. 2 to (1)(a) and (1)(b): +> Where a portion of a branch circuit is connected at both its supply and load ends to separately installed pressure connections as covered in 110.14(C)(2), it shall be permitted to have an allowable ampacity, in accordance with 310.15, not less than the sum of the continuous load plus the noncontinuous load. No portion of a branch circuit installed under this exception shall extend into an enclosure containing either the branch-circuit supply or the branch-circuit load terminations. + ##### 210.19(A)(2) Branch Circuits with More than One Receptacle. Conductors of branch circuits supplying more than one receptacle for cord-and-plug-connected portable loads shall have an ampacity of not less than the rating of the branch circuit. - +##### 210.19(A)(3) Household Ranges and Cooking Appliances. + +Branch-circuit conductors supplying household ranges, wall-mounted ovens, counter-mounted cooking units, and other household cooking appliances shall have an ampacity not less than the rating of the branch circuit and not less than the maximum load to be served. For ranges of 8 3/4 kW or more rating, the minimum branch-circuit rating shall be 40 amperes. + +> [!important] Exception No. 1: +> Conductors tapped from a branch circuit not exceeding 50 amperes supplying electric ranges, wall-mounted electric ovens, and counter-mounted electric cooking units shall have an ampacity of not less than 20 amperes and shall be sufficient for the load to be served. These tap conductors include any conductors that are a part of the leads supplied with the appliance that are smaller than the branch-circuit conductors. The taps shall not be longer than necessary for servicing the appliance. + +> [!important] Exception No. 2: +> The neutral conductor of a 3-wire branch circuit supplying a household electric range, a wall-mounted oven, or a counter-mounted cooking unit shall be permitted to be smaller than the ungrounded conductors where the maximum demand of a range of 83/4 kW or more rating has been calculated according to Column C of Table 220.55, but such conductor shall have an ampacity of not less than 70 percent of the branch-circuit rating and shall not be smaller than 10 AWG. + +##### 210.19(A)(4) Other Loads. + +Branch-circuit conductors that supply loads other than those specified in 210.3 and other than cooking appliances as covered in +210.19(A)(3) shall have an ampacity sufficient for the loads served and shall not be smaller than 14 AWG. + +> [!important] Exception No. 1: +> Tap conductors shall have an ampacity sufficient for the load served. In addition, they shall have an ampacity of not less than 15 for circuits rated less than 40 amperes and not less than 20 for circuits rated at 40 or 50 amperes and only where these tap conductors supply any of the following loads: + +* (1) Individual lampholders or luminaires with taps extending not longer than 450 mm (18 in.) beyond any portion of the lampholder or luminaire + +* (2) A luminaire having tap conductors as provided in 410.117 + +* (3) Individual outlets, other than receptacle outlets, with taps not over 450 mm (18 in.) long + +* (4) Infrared lamp industrial heating appliances + +* (5) Nonheating leads of deicing and snow-melting cables and mats + +> [!important] Exception No. 2: +> Fixture wires and flexible cords shall be permitted to be smaller than 14 AWG as permitted by 240.5. + +#### 210.19(B) Branch Circuits Over 600 Volts. + +The ampacity of conductors shall be in accordance with 310.14 and 311.60, as applicable. Branch-circuit conductors over 600 volts shall be sized in accordance with 210.19(B)(1) or (B)(2). + +##### 210.19(B)(1) General. + +The ampacity of branch-circuit conductors shall not be less than 125 percent of the designed potential load of utilization equipment that will be operated simultaneously. + +##### 210.19(B)(2) Supervised Installations. + +For supervised installations, branch-circuit conductor sizing shall be permitted to be determined by qualified persons under engineering supervision. Supervised installations are defined as those portions of a facility where both of the following conditions are met: + +* (1) Conditions of design and installation are provided under engineering supervision. + +* (2) Qualified persons with documented training and experience in over 600-volt systems provide maintenance, monitoring, and servicing of the system. + +### 210.20 Overcurrent Protection. + +Branch-circuit conductors and equipment shall be protected by overcurrent protective devices that have a rating or setting that complies with 210.20(A) through (D). + +#### 210.20(A) Continuous and Noncontinuous Loads. + +Where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads, the rating of the overcurrent device shall not be less than the noncontinuous load plus 125 percent of the continuous load. + +> [!important] Exception: +> Where the assembly, including the overcurrent devices protecting the branch circuit(s), is listed for operation at 100 percent of its rating, the ampere rating of the overcurrent device shall be permitted to be not less than the sum of the continuous load plus the noncontinuous load. + +#### 210.20(B) Conductor Protection. + +Conductors shall be protected in accordance with 240.4. Flexible cords and fixture wires shall be protected in accordance with 240.5. + +#### 210.20(C) Equipment. + +The rating or setting of the overcurrent protective device shall not exceed that specified in the applicable articles referenced in Table +240.3 for equipment. + +#### 210.20(D) Outlet Devices. + +The rating or setting shall not exceed that specified in 210.21 for outlet devices. ### 210.21 Outlet Devices. @@ -292,7 +800,55 @@ or other utilization equipment. Branch circuits larger than 50 amperes shall supply only nonlighting outlet loads. - +### 210.24 Branch-Circuit Requirements --- Summary. + +The requirements for circuits that have two or more outlets or receptacles, other than the receptacle circuits of 210.11(C)(1), (C)(2), and +(C)(3), are summarized in Table 210.24. This table provides only a summary of minimum requirements. See 210.19, 210.20, and +210.21 for the specific requirements applying to branch circuits. + +Table 210.24 Summary of Branch-Circuit Requirements + +Circuit Rating 15 A 20 A 30 A 40 A 50 A + +Conductors (min. size): + +Circuit Rating 15 A 20 A 30 A 40 A 50 A + +Circuit wires 14 12 10 8 6 + +Taps 14 14 14 12 12 + +Fixture wires and cords +--- see 240.5 + +Overcurrent Protection 15 A 20 A 30 A 40 A 50 A + +Outlet devices: + +Lampholders permitted Any type Any type Heavy duty Heavy duty Heavy duty + +Receptacle rating 15 max. A 15 or 20 A 30 A 40 or 50 A 50 A + +Maximum Load 15 A 20 A 30 A 40 A 50 A + +Permissible load See 210.23(A) See 210.23(A) See 210.23(B) See 210.23(C) See 210.23(C) + +These gauges are for copper conductors. + +For receptacle rating of cord-connected electric-discharge luminaires, see 410.62(C). + +### 210.25 Branch Circuits in Buildings with More Than One Occupancy. + +#### 210.25(A) Dwelling Unit Branch Circuits. + +Branch circuits in each dwelling unit shall supply only loads within that dwelling unit or loads associated only with that dwelling unit. + +#### 210.25(B) Common Area Branch Circuits. + +Branch circuits installed for lighting, central alarm, signal, communications, or other purposes for public or common areas of a twofamily dwelling, a multifamily dwelling, or a multi-occupancy building shall not be supplied from equipment that supplies an individual dwelling unit or tenant space. + +> [!info] Informational Note: +> Examples of public or common areas include, but are not limited to, lobbies, corridors, stairways, laundry rooms, roofs, elevators, washrooms, store rooms, driveways (parking), and mechanical rooms. ## Part III. Required Outlets @@ -301,8 +857,8 @@ shall supply only nonlighting outlet loads. [[nfpa-70_100_definitions#Receptacle Outlet.|Receptacle outlets]] shall be installed as specified in 210.52 through 210.65. -Informational Note: -See Informative Annex J for information regarding ADA accessibility design. +> [!info] Informational Note: +> See Informative Annex J for information regarding ADA accessibility design. #### 210.50(A) Cord Pendants. @@ -329,14 +885,14 @@ This section provides requirements for 125-volt, 15- and 20-ampere receptacle ou The receptacles required by this section shall be in addition to any receptacle that is as follows: -1. Part of a luminaire or appliance, or +* (1) Part of a luminaire or appliance, or -2. Controlled by a listed wall-mounted control device - in accordance with 210.70(A)(1), Exception No. 1, or +* (2) Controlled by a listed wall-mounted control device + in accordance with 210.70(A)(1), Exception No. 1, or -3. Located within cabinets or cupboards, or +* (3) Located within cabinets or cupboards, or -4. Located more than 1.7 m (5 1⁄2 ft) above the floor +* (4) Located more than 1.7 m (5 1/2 ft) above the floor Permanently installed electric baseboard heaters equipped with factory-installed receptacle outlets @@ -345,9 +901,9 @@ shall be permitted as the required outlet or outlets for the wall space utilized by such permanently installed heaters. Such receptacle outlets shall not be connected to the heater circuits. -Informational Note: -Listed baseboard heaters include instructions -that may not permit their installation below receptacle outlets. +> [!info] Informational Note: +> Listed baseboard heaters include instructions +> that may not permit their installation below receptacle outlets. #### 210.52(A) General Provisions. @@ -369,15 +925,11 @@ is more than 1.8 m (6 ft) from a receptacle outlet. As used in this section, a wall space shall include the following: -1. Any space 600 mm (2 ft) or more in width - (including space measured around corners) - and unbroken along the floor line by doorways and similar openings, - fireplaces, and fixed cabinets that do not have countertops or similar work surfaces +* (1) Any space 600 mm (2 ft) or more in width (including space measured around corners) and unbroken along the floor line by doorways and similar openings, fireplaces, and fixed cabinets that do not have countertops or similar work surfaces -2. The space occupied by fixed panels in walls, excluding sliding panels +* (2) The space occupied by fixed panels in walls, excluding sliding panels -3. The space afforded by fixed room dividers, - such as freestanding bar-type counters or railings +* (3) The space afforded by fixed room dividers, such as freestanding bar-type counters or railings ##### 210.52(A)(3) Floor Receptacles. @@ -400,23 +952,27 @@ shall serve all wall and floor receptacle outlets covered by 210.52(A), all countertop outlets covered by 210.52(C), and receptacle outlets for refrigeration equipment. -Exception No. 1: In addition to the required receptacles specified by 210.52, -switched receptacles supplied from a general-purpose 15- or 20-ampere branch circuit -as required in 210.70(A)(1), Exception No. 1, shall be permitted. +> [!important] Exception No. 1: +> In addition to the required receptacles specified by 210.52, +> switched receptacles supplied from a general-purpose 15- or 20-ampere branch circuit +> as required in 210.70(A)(1), Exception No. 1, shall be permitted. -Exception No. 2: In addition to the required receptacles specified by 210.52, -a receptacle outlet to serve a specific appliance -shall be permitted to be supplied from an individual branch circuit rated 15 amperes or greater. +> [!important] Exception No. 2: +> In addition to the required receptacles specified by 210.52, +> a receptacle outlet to serve a specific appliance +> shall be permitted to be supplied from an individual branch circuit rated 15 amperes or greater. ##### 210.52(B)(2) No Other Outlets. The two or more small-appliance branch circuits specified in 210.52(B)(1) shall have no other outlets. -Exception No. 1: A receptacle installed solely for the electrical supply to and support -of an electric clock in any of the rooms specified in 210.52(B)(1). +> [!important] Exception No. 1: +> A receptacle installed solely for the electrical supply to and support +> of an electric clock in any of the rooms specified in 210.52(B)(1). -Exception No. 2: Receptacles installed to provide power for supplemental equipment and lighting -on gas-fired ranges, ovens, or counter-mounted cooking units. +> [!important] Exception No. 2: +> Receptacles installed to provide power for supplemental equipment and lighting +> on gas-fired ranges, ovens, or counter-mounted cooking units. ##### 210.52(B)(3) Kitchen Receptacle Requirements. @@ -447,12 +1003,10 @@ Receptacle outlets shall be installed so that no point along the wall line is more than 600 mm (24 in.) measured horizontally from a receptacle outlet in that space. -Exception: -Receptacle outlets shall not be required directly behind a range, -counter-mounted cooking unit, or sink -in the installation described in Figure 210.52(C)(1). - - ^210.52(C)(1), Exception +> [!important] Exception: ^52c1-ex +> Receptacle outlets shall not be required directly behind a range, +> counter-mounted cooking unit, or sink +> in the installation described in Figure 210.52(C)(1). ##### Figure 210.52(C)(1) Determination of Area Behind a Range, Counter-Mounted Cooking Unit, or Sink. @@ -502,14 +1056,14 @@ or rangetops as covered in 210.52(C)(1), Exception, or appliances occupying assigned spaces shall not be considered as these required outlets. -Informational Note No. 1: -See 406.5(E) and 406.5(G) for installation of receptacles in countertops -and 406.5(F) and 406.5(G) for installation of receptacles in work surfaces. -See 380.10 for installation of multioutlet assemblies. +> [!info] Informational Note No. 1: +> See 406.5(E) and 406.5(G) for installation of receptacles in countertops +> and 406.5(F) and 406.5(G) for installation of receptacles in work surfaces. +> See 380.10 for installation of multioutlet assemblies. -Informational Note No. 2: -See Annex J and ANSI/ICC A117.1-2009, -Standard on Accessible and Usable Buildings and Facilities. +> [!info] Informational Note No. 2: +> See Annex J and ANSI/ICC A117.1-2009, +> Standard on Accessible and Usable Buildings and Facilities. #### 210.52(D) Bathrooms. @@ -524,22 +1078,23 @@ below the top of the basin or basin countertop. Receptacle outlet assemblies listed for use in countertops shall be permitted to be installed in the countertop. -Informational Note: -See 406.5(E) and 406.5(G) for requirements for installation of receptacles in countertops. +> [!info] Informational Note: +> See 406.5(E) and 406.5(G) for requirements for installation of receptacles in countertops. #### 210.52(E) Outdoor Outlets. Outdoor receptacle outlets shall be installed in accordance with 210.52(E)(1) through (E)(3). -Informational Note: See 210.8(A)(3). +> [!info] Informational Note: +> See [[#210.8(A)(3) |210.8(A)(3)]]. ##### 210.52(E)(1) One-Family and Two-Family Dwellings. For a one-family dwelling and each unit of a two-family dwelling that is at grade level, at least one receptacle outlet readily accessible from grade -and not more than 2.0 m (6 1⁄2 ft) above grade level +and not more than 2.0 m (6 1/2 ft) above grade level shall be installed at the front and back of the dwelling. ##### 210.52(E)(2) Multifamily Dwellings. @@ -548,13 +1103,13 @@ For each dwelling unit of a multifamily dwelling where the dwelling unit is located at grade level and provided with individual exterior entrance/egress, at least one receptacle outlet readily accessible from grade -and not more than 2.0 m (6 1⁄2 ft) above grade level shall be installed. +and not more than 2.0 m (6 1/2 ft) above grade level shall be installed. ##### 210.52(E)(3) Balconies, Decks, and Porches. Balconies, decks, and porches that are within 102 mm (4 in.) horizontally of the dwelling unit shall have at least one receptacle outlet accessible from the balcony, deck, or porch. -The receptacle outlet shall not be located more than 2.0 m (6 1⁄2 ft) +The receptacle outlet shall not be located more than 2.0 m (6 1/2 ft) above the balcony, deck, or porch walking surface. #### 210.52(F) Laundry Areas. @@ -562,16 +1117,16 @@ above the balcony, deck, or porch walking surface. In dwelling units, at least one receptacle outlet shall be installed in areas designated for the installation of laundry equipment. -Exception No. 1: -A receptacle for laundry equipment -shall not be required in a dwelling unit of a multifamily building -where laundry facilities are provided on the premises -for use by all building occupants. +> [!important] Exception No. 1: +> A receptacle for laundry equipment +> shall not be required in a dwelling unit of a multifamily building +> where laundry facilities are provided on the premises +> for use by all building occupants. -Exception No. 2: -A receptacle for laundry equipment -shall not be required in other than one-family dwellings -where laundry facilities are not to be installed or permitted. +> [!important] Exception No. 2: +> A receptacle for laundry equipment +> shall not be required in other than one-family dwellings +> where laundry facilities are not to be installed or permitted. #### 210.52(G) Basements, Garages, and Accessory Buildings. @@ -584,11 +1139,11 @@ These receptacles shall be in addition to receptacles required for specific equi In each attached garage and in each detached garage with electric power, at least one receptacle outlet shall be installed in each vehicle bay -and not more than 1.7 m (5 1⁄2 ft) above the floor. +and not more than 1.7 m (5 1/2 ft) above the floor. -Exception: -Garage spaces not attached to an individual dwelling unit of a multifamily dwelling -shall not require a receptacle outlet in each vehicle bay. +> [!important] Exception: +> Garage spaces not attached to an individual dwelling unit of a multifamily dwelling +> shall not require a receptacle outlet in each vehicle bay. ##### 210.52(G)(2) Accessory Buildings. @@ -674,3 +1229,86 @@ requires dedicated equipment space as specified in [[nfpa-70_110_requirements-fo the required receptacle outlet shall be located within the same room or area as the electrical equipment and shall not be connected to the load side of the equipment's branch-circuit disconnecting means. + +### 210.65 Meeting Rooms. + +#### 210.65(A) General. + +Each meeting room of not more than 93 m (1000 ft ) in other than dwelling units shall have outlets for nonlocking-type, 125-volt, 15- or 20-ampere receptacles. The outlets shall be installed in accordance with 210.65(B). Where a room or space is provided with movable partition(s), each room size shall be determined with the partition in the position that results in the smallest size meeting room. + +> [!info] Informational Note No. 1: +> For the purposes of this section, meeting rooms are typically designed or intended for the gathering of seated occupants for such purposes as conferences, deliberations, or similar purposes, where portable electronic equipment such as computers, projectors, or similar equipment is likely to be used. + +> [!info] Informational Note No. 2: +> Examples of rooms that are not meeting rooms include auditoriums, schoolrooms, and coffee shops. + +#### 210.65(B) Receptacle Outlets Required. + +The total number of receptacle outlets, including floor outlets and receptacle outlets in fixed furniture, shall not be less than as determined in (1) and (2). + +##### 210.65(B)(1) Receptacle Outlets in Fixed Walls. + +The required number of receptacle outlets shall be determined in accordance with 210.52(A)(1) through (A)(4). These receptacle outlets shall be permitted to be located as determined by the installer, designer, or building owner. + +##### 210.65(B)(2) Floor Outlets. + +A meeting room with any floor dimension that is 3.7 m (12 ft) or greater in any direction and that has a floor area of at least 20 m +(215 ft ) shall have at least one floor receptacle outlet, or at least one floor outlet to serve receptacle(s), located at a distance not less than 1.8 m (6 ft) from any fixed wall for each 20 m (215 ft ) or major portion of floor space. + +> [!info] Informational Note No. 1: +> See 314.27(B) for floor boxes used for receptacles located in the floor. + +> [!info] Informational Note No. 2: +> See Article 518 for assembly occupancies designed for 100 or more persons. + +### 210.70 Lighting Outlets Required. + +Lighting outlets shall be installed where specified in 210.70(A), (B), and (C). + +#### 210.70(A) Dwelling Units. + +In dwelling units, lighting outlets shall be installed in accordance with 210.70(A)(1), (A)(2), and (A)(3). + +##### 210.70(A)(1) Habitable Rooms. + +At least one lighting outlet controlled by a listed wall-mounted control device shall be installed in every habitable room, kitchen, and bathroom. The wall-mounted control device shall be located near an entrance to the room on a wall. + +> [!important] Exception No. 1: +> In other than kitchens and bathrooms, one or more receptacles controlled by a listed wall-mounted control device shall be permitted in lieu of lighting outlets. + +> [!important] Exception No. 2: +> Lighting outlets shall be permitted to be controlled by occupancy sensors that are (1) in addition to listed wall-mounted control devices or (2) located at a customary wall switch location and equipped with a manual override that will allow the sensor to function as a wall switch. + +##### 210.70(A)(2) Additional Locations. + +Additional lighting outlets shall be installed in accordance with the following: + +* (1) At least one lighting outlet controlled by a listed wall-mounted control device shall be installed in hallways, stairways, attached garages, and detached garages with electric power. + +* (2) For dwelling units, attached garages, and detached garages with electric power, at least one lighting outlet controlled by a listed wall-mounted control device shall be installed to provide illumination on the exterior side of outdoor entrances or exits with grade-level access. A vehicle door in a garage shall not be considered as an outdoor entrance or exit. +2 2 +2 +2 +2 2 + +* (3) Where one or more lighting outlet(s) are installed for interior stairways, there shall be a listed wall-mounted control device at each floor level and landing level that includes an entryway to control the lighting outlet(s) where the stairway between floor levels has six risers or more. + +Exception to (A)(2)(1), (A)(2)(2), and (A)(2)(3): In hallways, in stairways, and at outdoor entrances, remote, central, or automatic control of lighting shall be permitted. + +* (4) Lighting outlets controlled in accordance with 210.70(A)(2)(3) shall not be controlled by use of listed wall-mounted control devices unless they provide the full range of dimming control at each location. + +#### 210.70(B) Guest Rooms or Guest Suites. + +In hotels, motels, or similar occupancies, guest rooms or guest suites shall have at least one lighting outlet controlled by a listed wallmounted control device installed in every habitable room and bathroom. + +> [!important] Exception No. 1: +> In other than bathrooms and kitchens where provided, one or more receptacles controlled by a listed wall-mounted control device shall be permitted in lieu of lighting outlets. + +> [!important] Exception No. 2: +> Lighting outlets shall be permitted to be controlled by occupancy sensors that are (1) in addition to listed wall-mounted control devices or (2) located at a customary wall switch location and equipped with a manual override that allows the sensor to function as a wall switch. + +#### 210.70(C) All Occupancies. + +For attics and underfloor spaces, utility rooms, and basements, at least one lighting outlet containing a switch or controlled by a wall switch or listed wall-mounted control device shall be installed where these spaces are used for storage or contain equipment requiring servicing. A point of control shall be at each entry that permits access to the attic and underfloor space, utility room, or basement. + +Where a lighting outlet is installed for equipment requiring service, the lighting outlet shall be installed at or near the equipment. diff --git a/nfpa-70_220_load-calculations.md b/nfpa-70_220_load-calculations.md index e6a4500..241839b 100644 --- a/nfpa-70_220_load-calculations.md +++ b/nfpa-70_220_load-calculations.md @@ -24,30 +24,138 @@ Part II provides calculation methods for branch-circuit loads. Parts III and IV provide calculation methods for feeder and service loads. Part V provides calculation methods for farm loads. -Informational Note No. 1: -See examples in Informative Annex D. +> [!info] Informational Note No. 1: +> See examples in Informative Annex D. -Informational Note No. 2: -See Figure 220.1 for information on the organization of Article 220. +> [!info] Informational Note No. 2: +> See Figure 220.1 for information on the organization of Article 220. ### Figure 220.1 Branch-Circuit, Feeder, and Service Load Calculation Methods. - +### 220.3 Other Articles for Specific-Purpose Calculations. -### 220.14 Other Loads -- All Occupancies. +Table 220.3 shall provide references for specific-purpose calculation requirements not located in Chapters 5, 6, or 7 that amend or supplement the requirements of this article. + +Table 220.3 Specific-Purpose Calculation References + +| Calculation | Article | Section (or Part) | +| --------------------------------------------------------------------------------- | ------- | ----------------- | +| Air-conditioning and refrigerating equipment, branch-circuit conductor sizing | 440 | Part IV | +| Fixed electric heating equipment for pipelines and vessels, branch-circuit sizing | 427 | 427.4 | +| Fixed electric space-heating equipment, branch-circuit sizing | 424 | 424.3 | +| Fixed outdoor electric deicing and snow-melting equipment, branch-circuit sizing | 426 | 426.4 | +| Motors, feeder demand factor | 430 | 430.26 | +| Motors, multimotor and combination-load equipment | 430 | 430.25 | +| Motors, several motors or a motor(s) and other load(s) | 430 | 430.24 | +| Over 600-volt branch-circuit calculations | 210 | 210.19(B) | +| Over 600-volt feeder calculations | 215 | 215.2(B) | +| Phase converters, conductors | 455 | 455.6 | +| Storage-type water heaters | 422 | 422.11(E) | + +### 220.5 Calculations. + +#### 220.5(A) Voltages. + +Unless other voltages are specified, for purposes of calculating branch-circuit and feeder loads, nominal system voltages of 120, 120/240, 208Y/120, 240, 347, 480Y/277, 480, 600Y/347, and 600 volts shall be used. + +#### 220.5(B) Fractions of an Ampere. + +Calculations shall be permitted to be rounded to the nearest whole ampere, with decimal fractions smaller than 0.5 dropped. + +## Part II. Branch-Circuit Load Calculations + +### 220.10 General. + +Branch-circuit loads shall be calculated as shown in 220.12, 220.14, and 220.16. + +### 220.11 Floor Area. + +The floor area for each floor shall be calculated from the outside dimensions of the building, dwelling unit, or other area involved. For dwelling units, the calculated floor area shall not include open porches, garages, or unused or unfinished spaces not adaptable for future use. + +### 220.12 Lighting Load for Non-Dwelling Occupancies. + +#### 220.12(A) General. + +A unit load of not less than that specified in Table 220.12 for non-dwelling occupancies and the floor area determined in 220.11 shall be used to calculate the minimum lighting load. Motors rated less than 1/8 HP and connected to a lighting circuit shall be considered general lighting load. + +> [!info] Informational Note: +> The unit values of Table 220.12 are based on minimum load conditions and 100 percent power factor and may not provide sufficient capacity for the installation contemplated. + +#### 220.12(B) Energy Code. + +Where the building is designed and constructed to comply with an energy code adopted by the local authority, the lighting load shall be permitted to be calculated using the unit values specified in the energy code where the following conditions are met: + +* (1) A power monitoring system is installed that will provide continuous information regarding the total general lighting load of the building. + +* (2) The power monitoring system will be set with alarm values to alert the building owner or manager if the lighting load exceeds the values set by the energy code. Automatic means to take action to reduce the connected load shall be permitted. + +* (3) The demand factors specified in 220.42 are not applied to the general lighting load. + +* (4) The continuous load multiplier of 125 percent shall be applied. + +Table 220.12 General Lighting Loads by Non-Dwelling Occupancy + +| Type of Occupancy | Volt-amperes/m2 | Volt-amperes/ft2 | +| --------------------------------------------------------------------------------------------------- | -------------------------- | --------------------------- | +| Automotive facility | 16 | 1.5 | +| Convention center | 15 | 1.4 | +| Courthouse | 15 | 1.4 | +| Dormitory | 16 | 1.5 | +| Exercise center | 15 | 1.4 | +| Fire station | 14 | 1.3 | +| Gymnasiuma | 18 | 1.7 | +| Health care clinic | 17 | 1.6 | +| Hospital | 17 | 1.6 | +| Hotels and motels, including apartment houses without provisions for cooking by tenantsb | 18 | 1.7 | +| Library | 16 | 1.5 | +| Manufacturing facilityc | 24 | 2.2 | +| Motion picture theater | 17 | 1.6 | +| Museum | 17 | 1.6 | +| Officed | 14 | 1.3 | +| Parking garagee | 3 | 0.3 | +| Penitentiary | 13 | 1.2 | +| Performing arts theater | 16 | 1.5 | +| Police station | 14 | 1.3 | +| Post office | 17 | 1.6 | +| Religious facility | 24 | 2.2 | +| Restaurantf | 16 | 1.5 | +| Retailg,h | 20 | 1.9 | +| School/university | 33 | 3 | +| Sports arena | 33 | 3 | +| Town hall | 15 | 1.4 | +| Transportation | 13 | 1.2 | +| Warehouse | 13 | 1.2 | +| Workshop | 18 | 1.7 | + +Note: The 125 percent multiplier for a continuous load as specified in 210.20(A) is included when using the unit loads in this table for calculating the minimum lighting load for a specified occupancy. + +aArmories and auditoriums are considered gymnasium-type occupancies. + +bLodge rooms are similar to hotels and motels. + +cIndustrial commercial loft buildings are considered manufacturing-type occupancies. + +dBanks are office-type occupancies. + +eGarages --- commercial (storage) are considered parking garage occupancies. + +fClubs are considered restaurant occupancies. + +gBarber shops and beauty parlors are considered retail occupancies. + +hStores are considered retail occupancies. + +### 220.14 Other Loads --- All Occupancies. In all occupancies, the minimum load for each outlet for general-use receptacles and outlets not used for general illumination shall not be less than that calculated in 220.14(A) through (M), the loads shown being based on nominal branch-circuit voltages. -Exception: -The loads of outlets serving switchboards and switching frames in telephone exchanges -shall be waived from the calculations. - - +> [!important] Exception: +> The loads of outlets serving switchboards and switching frames in telephone exchanges shall be waived from the calculations. #### 220.14(A) Specific Appliances or Loads. @@ -125,13 +233,13 @@ and [[nfpa-70_210_branch-circuits#210.11(C)(2) Laundry Branch Circuits.|(C)(2)]] #### 220.14(J) Dwelling Units. In one-family, two-family, and multifamily dwellings, -the minimum unit load shall be not less than 33 volt-amperes/m$^2$ (3 volt-amperes/ft$^2$). +the minimum unit load shall be not less than 33 volt-amperes/m2 (3 volt-amperes/ft2). The lighting and receptacle outlets specified in 220.14(J)(1), (J)(2), and (J)(3) are included in the minimum unit load. No additional load calculations shall be required for such outlets. The minimum lighting load shall be determined using the minimum unit load and the floor area as determined in 220.11 for dwelling occupancies. -Motors rated less than 1⁄8 hp and connected to a lighting circuit +Motors rated less than 1/8 hp and connected to a lighting circuit shall be considered part of the minimum lighting load. * (1) All general-use receptacle outlets of 20-ampere rating or less, @@ -146,11 +254,533 @@ shall be calculated to be the larger of (1) or (2): * (1) The calculated load from 220.14(I) after all demand factors have been applied -* (2) 11 volt-amperes/m$^2$ or 1 volt-ampere/ft$^2$ +* (2) 11 volt-amperes/m2 or 1 volt-ampere/ft2 #### 220.14(L) Other Outlets. Other outlets not covered in 220.14(A) through (K) shall be calculated based on 180 volt-amperes per outlet. - +#### 220.14(M) Hotel and Motel Occupancies. + +In guest rooms or guest suites of hotels and motels, the lighting and receptacle outlets specified in 220.14(M)(1), (M)(2), and (M)(3) are included in the minimum unit load in Table 220.12. No additional load calculations shall be required for such outlets. The minimum lighting load shall be determined using the minimum unit load and the floor area as determined in 220.11 for hotel and motel occupancies. + +* (1) All general-use receptacle outlets of 20-ampere rating or less, including receptacles connected to the circuits in 210.11(C)(3) and 210.11(C)(4) + +* (2) The receptacle outlets specified in 210.52(E)(3) + +* (3) The lighting outlets specified in 210.70 + +### 220.16 Loads for Additions to Existing Installations. + +#### 220.16(A) Dwelling Units. + +Loads added to an existing dwelling unit(s) shall comply with the following as applicable: + +* (1) Loads for structural additions to an existing dwelling unit or for a previously unwired portion of an existing dwelling unit shall be calculated in accordance with 220.14. + +* (2) Loads for new circuits or extended circuits in previously wired dwelling units shall be calculated in accordance with 220.14. + +#### 220.16(B) Other Than Dwelling Units. + +Loads for new circuits or extended circuits in other than dwelling units shall be calculated in accordance with either 220.12 or 220.14, as applicable. + +### 220.18 Maximum Loads. + +The total load shall not exceed the rating of the branch circuit, and it shall not exceed the maximum loads specified in 220.18(A) through (C) under the conditions specified therein. + +#### 220.18(A) Motor-Operated and Combination Loads. + +Where a circuit supplies only motor-operated loads, Article 430 shall apply. Where a circuit supplies only air-conditioning equipment, refrigerating equipment, or both, Article 440 shall apply. For circuits supplying loads consisting of motor-operated utilization equipment that is fastened in place and has a motor larger than 1/8 hp in combination with other loads, the total calculated load shall be based on 125 percent of the largest motor load plus the sum of the other loads. + +#### 220.18(B) Inductive and LED Lighting Loads. + +For circuits supplying lighting units that have ballasts, transformers, autotransformers, or LED drivers, the calculated load shall be based on the total ampere ratings of such units and not on the total watts of the lamps. + +#### 220.18(C) Range Loads. + +It shall be permissible to apply demand factors for range loads in accordance with Table 220.55, including Note 4. + +## Part III. Feeder and Service Load Calculations + +### 220.40 General. + +The calculated load of a feeder or service shall not be less than the sum of the loads on the branch circuits supplied, as determined by Part II of this article, after any applicable demand factors permitted by Part III or IV or required by Part V have been applied. + +> [!info] Informational Note: +> See Examples D1(a) through D10 in Informative Annex D. See 220.18(B) for the maximum load in amperes permitted for lighting units operating at less than 100 percent power factor. + +### 220.42 General Lighting. + +The demand factors specified in Table 220.42 shall apply to that portion of the total branch-circuit load calculated for general illumination. They shall not be applied in determining the number of branch circuits for general illumination. + +#### Table 220.42 Lighting Load Demand Factors + +| Type of Occupancy | Portion of Lighting Load to Which Demand Factor Applies (Volt-Amperes) | Demand Factor (%) | +| --------------------------------------------------------------------------------------- | ---------------------------------------------------------------------- | ----------------- | +| Dwelling units | First 3000 at | 100 | +| ... | From 3001 to 120,000 at | 35 | +| ... | Remainder over 120,000 at | 25 | +| Hotels and motels, including apartment houses without provision for cooking by tenants* | First 20,000 or less at | 60 | +| ... | From 20,001 to 100,000 at | 50 | +| ... | Remainder over 100,000 at | 35 | +| Warehouses (storage) | First 12,500 or less at | 100 | +| ... | Remainder over 12,500 at | 50 | +| All others | Total volt-amperes | 100 | + +\*The demand factors of this table shall not apply to the calculated load of feeders or services supplying areas in hotels and motels where the entire lighting is likely to be used at one time, as in ballrooms or dining rooms. + +### 220.43 Show-Window and Track Lighting. + +#### 220.43(A) Show Windows. + +For show-window lighting, a load of not less than 660 volt-amperes/linear meter or 200 volt-amperes/linear foot shall be included for a show window, measured horizontally along its base. + +> [!info] Informational Note: +> See 220.14(G) for branch circuits supplying show windows. + +#### 220.43(B) Track Lighting. + +For track lighting in other than dwelling units or guest rooms or guest suites of hotels or motels, an additional load of 150 volt-amperes shall be included for every 600 mm (2 ft) of lighting track or fraction thereof. Where multicircuit track is installed, the load shall be considered to be divided equally between the track circuits. + +> [!important] Exception: +> If the track lighting is supplied through a device that limits the current to the track, the load shall be permitted to be calculated based on the rating of the device used to limit the current. + +### 220.44 Receptacle Loads --- Other Than Dwelling Units. + +Receptacle loads calculated in accordance with 220.14(H) and (I) shall be permitted to be made subject to the demand factors given in Table 220.42 or Table 220.44. + +#### Table 220.44 Demand Factors for Non-Dwelling Receptacle Loads + +| Portion of Receptacle Load to Which Demand Factor Applies (Volt-Amperes) | Demand Factor (%) | +| ------------------------------------------------------------------------ | ----------------- | +| First 10 kVA or less at | 100 | +| Remainder over 10 kVA at | 50 | + +### 220.50 Motors. + +Motor loads shall be calculated in accordance with 430.24, 430.25, and 430.26 and with 440.6 for hermetic refrigerant motor-compressors. + +### 220.51 Fixed Electric Space Heating. + +Fixed electric space-heating loads shall be calculated at 100 percent of the total connected load. However, in no case shall a feeder or service load current rating be less than the rating of the largest branch circuit supplied. + +> [!important] Exception: +> Where reduced loading of the conductors results from units operating on duty-cycle, intermittently, or from all units not operating at the same time, the authority having jurisdiction may grant permission for feeder and service conductors to have an ampacity less than 100 percent, provided the conductors have an ampacity for the load so determined. + +### 220.52 Small-Appliance and Laundry Loads --- Dwelling Unit. + +#### 220.52(A) Small-Appliance Circuit Load. + +In each dwelling unit, the load shall be calculated at 1500 volt-amperes for each 2-wire small-appliance branch circuit as covered by 210.11(C)(1). Where the load is subdivided through two or more feeders, the calculated load for each shall include not less than 1500 volt-amperes for each 2-wire small-appliance branch circuit. These loads shall be permitted to be included with the general lighting load and subjected to the demand factors provided in Table 220.42. + +> [!important] Exception: +> The individual branch circuit permitted by 210.52(B)(1), Exception No. 2, shall be permitted to be excluded from the calculation required by 220.52. + +#### 220.52(B) Laundry Circuit Load. + +A load of not less than 1500 volt-amperes shall be included for each 2-wire laundry branch circuit installed as covered by 210.11(C)(2). + +This load shall be permitted to be included with the general lighting load and shall be subjected to the demand factors provided in Table 220.42. + +### 220.53 Appliance Load --- Dwelling Unit(s). + +It shall be permissible to apply a demand factor of 75 percent to the nameplate rating load of four or more appliances rated 1/4 hp or greater, or 500 watts or greater, that are fastened in place, and that are served by the same feeder or service in a one-family, two-family, or multifamily dwelling. This demand factor shall not apply to: + +* (1) Household electric cooking equipment that is fastened in place + +* (2) Clothes dryers + +* (3) Space heating equipment + +* (4) Air-conditioning equipment + +### 220.54 Electric Clothes Dryers --- Dwelling Unit(s). + +The load for household electric clothes dryers in a dwelling unit(s) shall be either 5000 watts (volt-amperes) or the nameplate rating, whichever is larger, for each dryer served. The use of the demand factors in Table 220.54 shall be permitted. Where two or more single-phase dryers are supplied by a 3-phase, 4-wire feeder or service, the total load shall be calculated on the basis of twice the maximum number connected between any two phases. Kilovolt-amperes (kVA) shall be considered equivalent to kilowatts (kW) for loads calculated in this section. + +#### Table 220.54 Demand Factors for Household Electric Clothes Dryers + +| Number of Dryers | Demand Factor (%) | +| ---------------- | ------------------------------------------ | +| 1--4 | 100 | +| 5 | 85 | +| 6 | 75 | +| 7 | 65 | +| 8 | 60 | +| 9 | 55 | +| 10 | 50 | +| 11 | 47 | +| 12--23 | 47% minus 1% for each dryer exceeding 11 | +| 24--42 | 35% minus 0.5% for each dryer exceeding 23 | +| 43 and over | 25% | + +The load for household electric ranges, wall-mounted ovens, counter-mounted cooking units, and other household cooking appliances individually rated in excess of 13/4 kW shall be permitted to be calculated in accordance with Table 220.55. Kilovolt-amperes (kVA) shall be considered equivalent to kilowatts (kW) for loads calculated under this section. + +Where two or more single-phase ranges are supplied by a 3- phase, 4-wire feeder or service, the total load shall be calculated on the basis of twice the maximum number connected between any two phases. + +#### Table 220.55 Demand Factors and Loads for Household Electric Ranges, Wall-Mounted Ovens, Counter-Mounted Cooking Units, and Other Household Cooking Appliances over 1 3/4 kW Rating (Column C to be used in all cases except as otherwise permitted in Note 3.) + +| Number of Appliances | Demand Factor (%), Column A (Less than 3 1/2 kW Rating) | Demand Factor (%), Column B (3 1/2 kW through 8 3/4 kW Rating) | Column C Maximum Demand (kW) (Not over 12 kW Rating) | +|:--------------------:| -------------------------------------------------------:| --------------------------------------------------------------:| ---------------------------------------------------- | +| 1 | 80 | 80 | 8 | +| 2 | 75 | 65 | 11 | +| 3 | 70 | 55 | 14 | +| 4 | 66 | 50 | 17 | +| 5 | 62 | 45 | 20 | +| 6 | 59 | 43 | 21 | +| 7 | 56 | 40 | 22 | +| 8 | 53 | 36 | 23 | +| 9 | 51 | 35 | 24 | +| 10 | 49 | 34 | 25 | +| 11 | 47 | 32 | 26 | +| 12 | 45 | 32 | 27 | +| 13 | 43 | 32 | 28 | +| 14 | 41 | 32 | 29 | +| 15 | 40 | 32 | 30 | +| 16 | 39 | 28 | 31 | +| 17 | 38 | 28 | 32 | +| 18 | 37 | 28 | 33 | +| 19 | 36 | 28 | 34 | +| 20 | 35 | 28 | 35 | +| 21 | 34 | 26 | 36 | +| 22 | 33 | 26 | 37 | +| 23 | 32 | 26 | 38 | +| 24 | 31 | 26 | 39 | +| 25 | 30 | 26 | 40 | +| 26--30 | 30 | 24 | 15 kW + 1 kW for each range | +| 31--40 | 30 | 22 | | +| 41--50 | 30 | 20 | 25 kW + 3/4 kW for each range | +| 51--60 | 30 | 18 | | +| 61 and over | 30 | 16 | | + +Notes: + +1. Over 12 kW through 27 kW ranges all of same rating. For ranges individually rated more than 12 kW but not more than 27 kW, the maximum demand in Column C shall be increased 5 percent for each additional kilowatt of rating or major fraction thereof by which the rating of individual ranges exceeds 12 kW. + +2. Over 83/4 kW through 27 kW ranges of unequal ratings. For ranges individually rated more than 83/4 kW and of different ratings, but none exceeding 27 kW, an average value of rating shall be calculated by adding together the ratings of all ranges to obtain the total connected load (using 12 kW for any range rated less than 12 kW) and dividing by the total number of ranges. Then the maximum demand in Column C shall be increased 5 percent for each kilowatt or major fraction thereof by which this average value exceeds 12 kW. + +3. Over 13/4 kW through 83/4 kW. In lieu of the method provided in Column C, it shall be permissible to add the nameplate ratings of all household cooking appliances rated more than 13/4 kW but not more than 83/4 kW and multiply the sum by the demand factors specified in Column A or Column B for the given number of appliances. Where the rating of cooking appliances falls under both Column A and Column B, the demand factors for each column shall be applied to the appliances for that column, and the results added together. + +4. Branch-Circuit Load. It shall be permissible to calculate the branch-circuit load for one range in accordance with Table 220.55. The branch-circuit load for one wall-mounted oven or one counter-mounted cooking unit shall be the nameplate rating of the appliance. The branch-circuit load for a counter-mounted cooking unit and not more than two wall-mounted ovens, all supplied from a single branch circuit and located in the same room, shall be calculated by adding the nameplate rating of the individual appliances and treating this total as equivalent to one range. + +5. This table shall also apply to household cooking appliances rated over 1 3/4 kW and used in instructional programs. + +> [!info] Informational Note No. 1: +> See the examples in Informative Annex D. + +> [!info] Informational Note No. 2: +> See Table 220.56 for commercial cooking equipment. + +### 220.56 Kitchen Equipment --- Other Than Dwelling Unit(s). + +It shall be permissible to calculate the load for commercial electric cooking equipment, dishwasher booster heaters, water heaters, and other kitchen equipment in accordance with Table 220.56. These demand factors shall be applied to all equipment that has either thermostatic control or intermittent use as kitchen equipment. These demand factors shall not apply to space-heating, ventilating, or air-conditioning equipment. + +However, in no case shall the feeder or service calculated load be less than the sum of the largest two kitchen equipment loads. + +#### Table 220.56 Demand Factors for Kitchen Equipment --- Other Than Dwelling Unit(s) + +| Number of Units of Equipment | Demand Factor (%) | +| ---------------------------- | -----------------:| +| 1 | 100 | +| 2 | 100 | +| 3 | 90 | +| 4 | 80 | +| 5 | 70 | +| 6 and over | 65 | + +### 220.60 Noncoincident Loads. + +Where it is unlikely that two or more noncoincident loads will be in use simultaneously, it shall be permissible to use only the largest load(s) that will be used at one time for calculating the total load of a feeder or service. Where a motor is part of the noncoincident load and is not the largest of the noncoincident loads, 125 percent of the motor load shall be used in the calculation if it is the largest motor. + +### 220.61 Feeder or Service Neutral Load. + +#### 220.61(A) Basic Calculation. + +The feeder or service neutral load shall be the maximum unbalance of the load determined by this article. The maximum unbalanced load shall be the maximum net calculated load between the neutral conductor and any one ungrounded conductor. + +> [!important] Exception: +> For 3-wire, 2-phase or 5-wire, 2-phase systems, the maximum unbalanced load shall be the maximum net calculated load between the neutral conductor and any one ungrounded conductor multiplied by 140 percent. + +#### 220.61(B) Permitted Reductions. + +A service or feeder supplying the following loads shall be permitted to have an additional demand factor of 70 percent applied to the amount in 220.61(B)(1) or portion of the amount in 220.61(B)(2) determined by the following basic calculations: + +* (1) A feeder or service supplying household electric ranges, wall-mounted ovens, counter-mounted cooking units, and electric dryers, where the maximum unbalanced load has been determined in accordance with Table 220.55 for ranges and Table 220.54 for dryers + +* (2) That portion of the unbalanced load in excess of 200 amperes where the feeder or service is supplied from a 3-wire dc or single-phase ac system; or a 4-wire, 3-phase system; or a 3-wire, 2-phase system; or a 5-wire, 2-phase system + +> [!info] Informational Note: +> See Examples D1(a), D1(b), D2(b), D4(a), and D5(a) in Informative Annex D. + +#### 220.61(C) Prohibited Reductions. + +There shall be no reduction of the neutral or grounded conductor capacity applied to the amount in 220.61(C)(1), or portion of the amount in (C)(2), from that determined by the basic calculation: + +* (1) Any portion of a 3-wire circuit consisting of 2 ungrounded conductors and the neutral conductor of a 4-wire, 3-phase, wye-connected system + +* (2) That portion consisting of nonlinear loads supplied from a 4-wire, wye-connected, 3-phase system + +> [!info] Informational Note: +> A 3-phase, 4-wire, wye-connected power system used to supply power to nonlinear loads may necessitate that the power system design allow for the possibility of high harmonic neutral conductor currents. + +## Part IV. Optional Feeder and Service Load Calculations + +### 220.80 General. + +Optional feeder and service load calculations shall be permitted in accordance with Part IV. + +### 220.82 Dwelling Unit. + +#### 220.82(A) Feeder and Service Load. + +This section applies to a dwelling unit having the total connected load served by a single 120/240-volt or 208Y/120-volt set of 3-wire service or feeder conductors with an ampacity of 100 or greater. It shall be permissible to calculate the feeder and service loads in accordance with this section instead of the method specified in Part III of this article. The calculated load shall be the result of adding the loads from 220.82(B) and (C). Feeder and service-entrance conductors whose calculated load is determined by this optional calculation shall be permitted to have the neutral load determined by 220.61. + +#### 220.82(B) General Loads. + +The general calculated load shall be not less than 100 percent of the first 10 kVA plus 40 percent of the remainder of the following loads: + +* (1) 33 volt-amperes/m or 3 volt-amperes/ft for general lighting and general-use receptacles. The floor area for each floor shall be calculated from the outside dimensions of the dwelling unit. The calculated floor area shall not include open porches, garages, or unused or unfinished spaces not adaptable for future use. + +* (2) 1500 volt-amperes for each 2-wire, 20-ampere small-appliance branch circuit and each laundry branch circuit covered in 210.11(C)(1) and (C)(2). + +* (3) The nameplate rating of the following: + * a. All appliances that are fastened in place, permanently connected, or located to be on a specific circuit + * b. Ranges, wall-mounted ovens, counter-mounted cooking units + * c. Clothes dryers that are not connected to the laundry branch circuit specified in item (2) + * d. Water heaters + +* (4) The nameplate ampere or kVA rating of all permanently connected motors not included in item (3). + +#### 220.82(C) Heating and Air-Conditioning Load. + +The largest of the following six selections (load in kVA) shall be included: + +* (1) 100 percent of the nameplate rating(s) of the air conditioning and cooling. + +* (2) 100 percent of the nameplate rating(s) of the heat pump when the heat pump is used without any supplemental electric heating. + +* (3) 100 percent of the nameplate rating(s) of the heat pump compressor and 65 percent of the supplemental electric heating for central electric space-heating systems. If the heat pump compressor is prevented from operating at the same time as the supplementary heat, it does not need to be added to the supplementary heat for the total central space heating load. + +* (4) 65 percent of the nameplate rating(s) of electric space heating if less than four separately controlled units. + +* (5) 40 percent of the nameplate rating(s) of electric space heating if four or more separately controlled units. + +* (6) 100 percent of the nameplate ratings of electric thermal storage and other heating systems where the usual load is expected to be continuous at the full nameplate value. Systems qualifying under this selection shall not be calculated under any other selection in 220.82(C). + +### 220.83 Existing Dwelling Unit. + +This section shall be permitted to be used to determine if the existing service or feeder is of sufficient capacity to serve additional loads. + +Where the dwelling unit is served by a 120/240-volt or 208Y/120-volt, 3-wire service, it shall be permissible to calculate the total load in accordance with 220.83(A) or (B). + +### 220.83(A) Where Additional Air-Conditioning Equipment or Electric Space-Heating Equipment Is Not to Be Installed. + +The following percentages shall be used for existing and additional new loads. + +| Load (kVA) | Percent of Load | +| ---------------------- | ---------------:| +| First 8 kVA of load at | 100 | +| Remainder of load at | 40 | + +Load calculations shall include the following: + +* (1) General lighting and general-use receptacles at 33 volt-amperes/m or 3 volt-amperes/ft as determined by 220.12 + +* (2) 1500 volt-amperes for each 2-wire, 20-ampere small-appliance branch circuit and each laundry branch circuit covered in 210.11(C)(1) and (C)(2) + +* (3) The nameplate rating of the following: + * a. All appliances that are fastened in place, permanently connected, or located to be on a specific circuit + * b. Ranges, wall-mounted ovens, counter-mounted cooking units + * c. Clothes dryers that are not connected to the laundry branch circuit specified in item (2) + * d. Water heaters + +### 220.83(B) Where Additional Air-Conditioning Equipment or Electric Space-Heating Equipment Is to Be Installed. + +The following percentages shall be used for existing and additional new loads. The larger connected load of air conditioning or space heating, but not both, shall be used. + +| Load | Percent of Load | +| -------------------------------------------------------- | ---------------:| +| Air-conditioning equipment | 100 | +| Central electric space heating | 100 | +| Less than four separately controlled space-heating units | 100 | +| First 8 kVA of all other loads | 100 | +| Remainder of all other loads | 40 | + +Other loads shall include the following: + +* (1) General lighting and general-use receptacles at 33 volt-amperes/m or 3 volt-amperes/ft as determined by 220.12 + +* (2) 1500 volt-amperes for each 2-wire, 20-ampere small-appliance branch circuit and each laundry branch circuit covered in 210.11(C)(1) and (C)(2) + +* (3) The nameplate rating of the following: + * a. All appliances that are fastened in place, permanently connected, or located to be on a specific circuit + * b. Ranges, wall-mounted ovens, counter-mounted cooking units + * c. Clothes dryers that are not connected to the laundry branch circuit specified in item (2) + * d. Water heaters + +### 220.84 Multifamily Dwelling. + +#### 220.84(A) Feeder or Service Load. + +It shall be permissible to calculate the load of a feeder or service that supplies three or more dwelling units of a multifamily dwelling in accordance with Table 220.84 instead of Part III of this article if all the following conditions are met: + +* (1) No dwelling unit is supplied by more than one feeder. + +* (2) Each dwelling unit is equipped with electric cooking equipment + +> [!important] Exception: +> When the calculated load for multifamily dwellings without electric cooking in Part III of this article exceeds that calculated under Part IV for the identical load plus electric cooking (based on 8 kW per unit), the lesser of the two loads shall be permitted to be used. + +* (3) Each dwelling unit is equipped with either electric space heating or air conditioning, or both. Feeders and service conductors whose calculated load is determined by this optional calculation shall be permitted to have the neutral load determined by +220.61. + +#### 220.84(B) House Loads. + +House loads shall be calculated in accordance with Part III of this article and shall be in addition to the dwelling unit loads calculated in accordance with Table 220.84. + +##### Table 220.84 Optional Calculations --- Demand Factors for Three or More Multifamily Dwelling Units + +| Number of Dwelling Units | Demand Factor (%) | +|:------------------------:| -----------------:| +| 3--5 | 45 | +| 6--7 | 44 | +| 8--10 | 43 | +| 11 | 42 | +| 12--13 | 41 | +| 14--15 | 40 | +| 16--17 | 39 | +| 18--20 | 38 | +| 21 | 37 | +| 22--23 | 36 | +| 24--25 | 35 | +| 26--27 | 34 | +| 28--30 | 33 | +| 31 | 32 | +| 32--33 | 31 | +| 34--36 | 30 | +| 37--38 | 29 | +| 39--42 | 28 | +| 43--45 | 27 | +| 46--50 | 26 | +| 51--55 | 25 | +| 56--61 | 24 | +| 62 and over | 23 | + +#### 220.84(C) Calculated Loads. + +The calculated load to which the demand factors of Table 220.84 apply shall include the following: + +* (1) 33 volt-amperes/m or 3 volt-amperes/ft for general lighting and general-use receptacles + +* (2) 1500 volt-amperes for each 2-wire, 20-ampere small-appliance branch circuit and each laundry branch circuit covered in 210.11(C)(1) and (C)(2) + +* (3) The nameplate rating of the following: + * a. All appliances that are fastened in place, permanently connected, or located to be on a specific circui + * b. Ranges, wall-mounted ovens, counter-mounted cooking units + * c. Clothes dryers that are not connected to the laundry branch circuit specified in item (2) + * d. Water heaters + +* (4) The nameplate ampere or kVA rating of all permanently connected motors not included in item (3) + +* (5) The larger of the air-conditioning load or the fixed electric space-heating load + +### 220.85 Two Dwelling Units. + +Where two dwelling units are supplied by a single feeder and the calculated load under Part III of this article exceeds that for three identical units calculated under 220.84, the lesser of the two loads shall be permitted to be used. + +### 220.86 Schools. + +The calculation of a feeder or service load for schools shall be permitted in accordance with Table 220.86 in lieu of Part III of this article where equipped with electric space heating, air conditioning, or both. The connected load to which the demand factors of Table 220.86 apply shall include all of the interior and exterior lighting, power, water heating, cooking, other loads, and the larger of the air-conditioning load or space-heating load within the building or structure. + +Feeders and service conductors whose calculated load is determined by this optional calculation shall be permitted to have the neutral load determined by 220.61. Where the building or structure load is calculated by this optional method, feeders within the building or structure shall have ampacity as permitted in Part III of this article; however, the ampacity of an individual feeder shall not be required to be larger than the ampacity for the entire building. + +This section shall not apply to portable classroom buildings. + +#### Table 220.86 Optional Method --- Demand Factors for Feeders and Service Conductors for Schools + +| Connected Load | Demand Factor (Percent) | +| -------------------------------------------------------- | ----------------------- | +| First 33 VA/m2 Plus, (3 VA/ft2) at | 100 | +| Over 33 through 220 VA/m2 Plus, (3 through 20 VA/ft2) at | 75 | +| Remainder over 220 VA/m 2 (20 VA/ft2) at | 25 | + +### 220.87 Determining Existing Loads. + +The calculation of a feeder or service load for existing installations shall be permitted to use actual maximum demand to determine the existing load under all of the following conditions: + +* (1) The maximum demand data is available for a 1-year period. + +> [!important] Exception: +> If the maximum demand data for a 1-year period is not available, the calculated load shall be permitted to be based on the maximum demand (the highest average kilowatts reached and maintained for a 15-minute interval) continuously recorded over a minimum 30-day period using a recording ammeter or power meter connected to the highest loaded phase of the feeder or service, based on the initial loading at the start of the recording. The recording shall reflect the maximum demand of the feeder or service by being taken when the building or space is occupied and shall include by measurement or calculation the larger of the heating or cooling equipment load, and other loads that may be periodic in nature due to seasonal or similar conditions. + +* (2) The maximum demand at 125 percent plus the new load does not exceed the ampacity of the feeder or rating of the service. + +* (3) The feeder has overcurrent protection in accordance with 240.4, and the service has overload protection in accordance with 230.90. + +> [!important] Exception: +> If the feeder or service has any renewable energy system (i.e., solar photovoltaic systems or wind electric systems) or employs any form of peak load shaving, this calculation method shall not be permitted. + +### 220.88 New Restaurants. + +Calculation of a service or feeder load, where the feeder serves the total load, for a new restaurant shall be permitted in accordance with Table 220.88 in lieu of Part III of this article. + +The overload protection of the service conductors shall be in accordance with 230.90 and 240.4. + +Feeder conductors shall not be required to be of greater ampacity than the service conductors. + +Service or feeder conductors whose calculated load is determined by this optional calculation shall be permitted to have the neutral load determined by 220.61. + +#### Table 220.88 Optional Method --- Permitted Load Calculations for Service and Feeder Conductors for New Restaurants + +| Total Connected Load (kVA) | All Electric Restaurant Calculated Loads (kVA) | Not All Electric Restaurant Calculated Loads (kVA) | +|:--------------------------:| ---------------------------------------------- | -------------------------------------------------- | +| 0--200 | 80% | 100% | +| 201--325 | 10% (amount over 200) + 160.0 | 50% (amount over 200) + 200.0 | +| 326--800 | 50% (amount over 325) + 172.5 | 45% (amount over 325) + 262.5 | +| Over 800 | 50% (amount over 800) + 410.0 | 20% (amount over 800) + 476.3 | + +Note: Add all electrical loads, including both heating and cooling loads, to calculate the total connected load. Select the one demand factor that applies from the table, then multiply the total connected load by this single demand factor. + +## Part V. Farm Load Calculations + +### 220.100 General. + +Farm loads shall be calculated in accordance with Part V. + +### 220.102 Farm Loads --- Buildings and Other Loads. + +#### 220.102(A) Dwelling Unit. + +The feeder or service load of a farm dwelling unit shall be calculated in accordance with the provisions for dwellings in Part III or IV of this article. Where the dwelling has electric heat and the farm has electric grain-drying systems, Part IV of this article shall not be used to calculate the dwelling load where the dwelling and farm loads are supplied by a common service. + +#### 220.102(B) Other Than Dwelling Unit. + +Where a feeder or service supplies a farm building or other load having two or more separate branch circuits, the load for feeders, service conductors, and service equipment shall be calculated in accordance with demand factors not less than indicated in Table +220.102. + +#### Table 220.102 Method for Calculating Farm Loads for Other Than Dwelling Unit + +| Ampere Load at 240 Volts Maximum | Demand Factor (%) | +| ------------------------------------------------------------- | ----------------- | +| The greater of the following: | | +| All loads that are expected to operate simultaneously, or | 100 | +| 125 percent of the full load current of the largest motor, or | | +| First 60 amperes of the load | | +| Next 60 amperes of all other loads | 50 | +| Remainder of other loads | 25 | + +### 220.103 Farm Loads --- Total. + +Where supplied by a common service, the total load of the farm for service conductors and service equipment shall be calculated in accordance with the farm dwelling unit load and demand factors specified in Table 220.103. Where there is equipment in two or more farm equipment buildings or for loads having the same function, such loads shall be calculated in accordance with Table 220.102 and shall be permitted to be combined as a single load in Table 220.103 for calculating the total load. + +#### Table 220.103 Method for Calculating Total Farm Load + +| Individual Loads Calculated in Accordance with Table 220.102 | Demand Factor (%) | +| ------------------------------------------------------------ | ----------------- | +| Largest load | 100 | +| Second largest load | 75 | +| Third largest load | 65 | +| Remaining loads | 50 | + +Note: To this total load, add the load of the farm dwelling unit calculated in accordance with Part III or IV of this article. Where the dwelling has electric heat and the farm has electric grain-drying systems, Part IV of this article shall not be used to calculate the dwelling load. diff --git a/nfpa-70_230_services.md b/nfpa-70_230_services.md new file mode 100644 index 0000000..b32ebc0 --- /dev/null +++ b/nfpa-70_230_services.md @@ -0,0 +1,1016 @@ +--- +id: +aliases: + - nec-230 +tags: + - authorship/other + - destiny/uncertain + - exclude-from-word-count + - status/incomplete + - topic/construction/electrical + - type/media +title: Article 230 Services +--- +# Article 230 Services + +## 230.1 Scope. + +This article covers service conductors and equipment for control and protection of services and their installation requirements. + +> [!info] Informational Note: +> See Figure 230.1. + +### Figure 230.1 Services. + +%% TODO %% + +## Part I. General + +### 230.2 Number of Services. + +A building or other structure served shall be supplied by only one service unless permitted in 230.2(A) through (D). +For the purpose of [[#^40e2|230.40, Exception No. 2]] only, underground sets of conductors, 1/0 AWG and larger, running to the same location and connected together at their supply end but not connected together at their load end shall be considered to be supplying one service. + +#### 230.2(A) Special Conditions. + +Additional services shall be permitted to supply the following: + +* (1) Fire pumps + +* (2) Emergency systems + +* (3) Legally required standby systems + +* (4) Optional standby systems + +* (5) Parallel power production systems + +* (6) Systems designed for connection to multiple sources of supply + for the purpose of enhanced reliability + +#### 230.2(B) Special Occupancies. + +By special permission, additional services shall be permitted for either of the following: + +* (1) Multiple-occupancy buildings + where there is no available space for service equipment accessible to all occupants + +* (2) A single building or other structure + sufficiently large to make two or more services necessary + +#### 230.2(C) Capacity Requirements. + +Additional services shall be permitted under any of the following: + +* (1) Where the capacity requirements are in excess of 2000 amperes + at a supply voltage of 1000 volts or less + +* (2) Where the load requirements of a single-phase installation + are greater than the serving agency normally supplies through one service + +* (3) By special permission + +#### 230.2(D) Different Characteristics. + +Additional services shall be permitted for different voltages, frequencies, or phases, or for different uses, such as for different rate schedules. + +#### 230.2(E) Identification. + +Where a building or structure is supplied by more than one service, or any combination of branch circuits, feeders, and services, a permanent plaque or directory shall be installed at each service disconnect location denoting all other services, feeders, and branch circuits supplying that building or structure and the area served by each. See 225.37. + +### 230.3 One Building or Other Structure Not to Be Supplied Through Another. + +Service conductors supplying a building or other structure shall not pass through the interior of another building or other structure. + +### 230.6 Conductors Considered Outside the Building. + +Conductors shall be considered outside of a building or other structure under any of the following conditions: + +* (1) Where installed under not less than 50 mm (2 in.) of concrete beneath a building or other structure + +* (2) Where installed within a building or other structure in a raceway that is encased in concrete or brick not less than 50 mm (2 in.) thick + +* (3) Where installed in any vault that meets the construction requirements of Article 450, Part III + +* (4) Where installed in conduit and under not less than 450 mm (18 in.) of earth beneath a building or other structure + +* (5) Where installed within rigid metal conduit (Type RMC) or intermediate metal conduit (Type IMC) used to accommodate the clearance requirements in 230.24 and routed directly through an eave but not a wall of a building + +### 230.7 Other Conductors in Raceway or Cable. + +Conductors other than service conductors shall not be installed in the same service raceway or service cable in which the service conductors are installed. + +> [!important] Exception No. 1: +> Grounding electrode conductors or supply side bonding jumpers or conductors shall be permitted within service raceways. + +> [!important] Exception No. 2: +> Load management control conductors having overcurrent protection shall be permitted within service raceways. + +### 230.8 Raceway Seal. + +Where a service raceway enters a building or structure from an underground distribution system, it shall be sealed in accordance with +300.5(G). Spare or unused raceways shall also be sealed. Sealants shall be identified for use with the cable insulation, shield, or other components. + +### 230.9 Clearances on Buildings. + +Service conductors and final spans shall comply with 230.9(A), (B), and (C). + +#### 230.9(A) Clearances. + +Service conductors installed as open conductors or multiconductor cable without an overall outer jacket shall have a clearance of not less than 900 mm (3 ft) from windows that are designed to be opened, doors, porches, balconies, ladders, stairs, fire escapes, or similar locations. + +> [!important] Exception: +> Conductors run above the top level of a window shall be permitted to be less than the 900 mm (3 ft) requirement. + +#### 230.9(B) Vertical Clearance. + +The vertical clearance of final spans above, or within 900 mm (3 ft) measured horizontally of platforms, projections, or surfaces that will permit personal contact shall be maintained in accordance with 230.24(B). + +#### 230.9(C) Building Openings. + +Overhead service conductors shall not be installed beneath openings through which materials may be moved, such as openings in farm and commercial buildings, and shall not be installed where they obstruct entrance to these building openings. + +### 230.10 Vegetation as Support. + +Vegetation such as trees shall not be used for support of overhead service conductors or service equipment. + +## Part II. Overhead Service Conductors + +### 230.22 Insulation or Covering. + +Individual conductors shall be insulated or covered. + +> [!important] Exception: +> The grounded conductor of a multiconductor cable shall be permitted to be bare. + +### 230.23 Size and Ampacity. + +#### 230.23(A) General. + +Conductors shall have sufficient ampacity to carry the current for the load as calculated in accordance with Article 220 and shall have adequate mechanical strength. + +#### 230.23(B) Minimum Size. + +The conductors shall not be smaller than 8 AWG copper or 6 AWG aluminum or copper-clad aluminum. + +> [!important] Exception: +> Conductors supplying only limited loads of a single branch circuit --- such as small polyphase power, controlled water heaters, and similar loads --- shall not be smaller than 12 AWG hard-drawn copper or equivalent. + +#### 230.23(C) Grounded Conductors. + +The grounded conductor shall not be less than the minimum size as required by 250.24(C). + +### 230.24 Clearances. + +Overhead service conductors shall not be readily accessible and shall comply with 230.24(A) through (E) for services not over +1000 volts, nominal. + +#### 230.24(A) Above Roofs. + +Conductors shall have a vertical clearance of not less than 2.5 m (8 ft) above the roof surface. The vertical clearance above the roof level shall be maintained for a distance of not less than 900 mm (3 ft) in all directions from the edge of the roof. + +> [!important] Exception No. 1: +> The area above a roof surface subject to pedestrian or vehicular traffic shall have a vertical clearance from the roof surface in accordance with the clearance requirements of 230.24(B). + +> [!important] Exception No. 2: +> Where the voltage between conductors does not exceed 300 and the roof has a slope of 100 mm in 300 mm (4 in. in +12 in.) or greater, a reduction in clearance to 900 mm (3 ft) shall be permitted. + +> [!important] Exception No. 3: +> Where the voltage between conductors does not exceed 300, a reduction in clearance above only the overhanging portion of the roof to not less than 450 mm (18 in.) shall be permitted if (1) not more than 1.8 m (6 ft) of overhead service conductors, +1.2 m (4 ft) horizontally, pass above the roof overhang, and (2) they are terminated at a through-the-roof raceway or approved support. + +> [!info] Informational Note: +> See 230.28 for mast supports. + +> [!important] Exception No. 4: +> The requirement for maintaining the vertical clearance 900 mm (3 ft) from the edge of the roof shall not apply to the final conductor span where the service drop or overhead service conductors are attached to the side of a building. + +> [!important] Exception No. 5: +> Where the voltage between conductors does not exceed 300 and the roof area is guarded or isolated, a reduction in clearance to 900 mm (3 ft) shall be permitted. + +#### 230.24(B) Vertical Clearance for Overhead Service Conductors. + +Overhead service conductors, where not in excess of 1000 volts, nominal, shall have the following minimum clearance from final grade: + +* (1) 3.0 m (10 ft) --- at the electrical service entrance to buildings, also at the lowest point of the drip loop of the building electrical entrance, and above areas or sidewalks accessible only to pedestrians, measured from final grade or other accessible surface only for overhead service conductors supported on and cabled together with a grounded bare messenger where the voltage does not exceed 150 volts to ground + +* (2) 3.7 m (12 ft) --- over residential property and driveways, and those commercial areas not subject to truck traffic where the voltage does not exceed 300 volts to ground + +* (3) 4.5 m (15 ft) --- for those areas listed in the 3.7 m (12 ft) classification where the voltage exceeds 300 volts to ground + +* (4) 5.5 m (18 ft) --- over public streets, alleys, roads, parking areas subject to truck traffic, driveways on other than residential property, and other land such as cultivated, grazing, forest, and orchard + +* (5) 7.5 m (241/2 ft) over tracks of railroads + +#### 230.24(C) Clearance from Building Openings. + +See 230.9. + +#### 230.24(D) Clearance from Swimming Pools. + +See 680.9. + +#### 230.24(E) Clearance from Communication Wires and Cables. + +Clearance from communication wires and cables shall be in accordance with 800.44(A)(4). + +### 230.26 Point of Attachment. + +The point of attachment of the overhead service conductors to a building or other structure shall provide the minimum clearances as specified in 230.9 and 230.24. In no case shall this point of attachment be less than 3.0 m (10 ft) above finished grade. + +### 230.27 Means of Attachment. + +Multiconductor cables used for overhead service conductors shall be attached to buildings or other structures by fittings identified for use with service conductors. Open conductors shall be attached to fittings identified for use with service conductors or to noncombustible, nonabsorbent insulators securely attached to the building or other structure. + +### 230.28 Service Masts as Supports. + +Only power service-drop or overhead service conductors shall be permitted to be attached to a service mast. Service masts used for the support of service-drop or overhead service conductors shall be installed in accordance with 230.28(A) and (B). + +#### 230.28(A) Strength. + +The service mast shall be of adequate strength or be supported by braces or guy wires to withstand safely the strain imposed by the service-drop or overhead service conductors. Hubs intended for use with a conduit that serves as a service mast shall be identified for use with service-entrance equipment. + +#### 230.28(B) Attachment. + +Service-drop or overhead service conductors shall not be attached to a service mast between a weatherhead or the end of the conduit and a coupling, where the coupling is located above the last point of securement to the building or other structure or is located above the building or other structure. + +### 230.29 Supports over Buildings. + +Service conductors passing over a roof shall be securely supported by substantial structures. For a grounded system, where the substantial structure is metal, it shall be bonded by means of a bonding jumper and listed connector to the grounded overhead service conductor. Where practicable, such supports shall be independent of the building. + +## Part III. Underground Service Conductors + +### 230.30 Installation. + +#### 230.30(A) Insulation. + +Underground service conductors shall be insulated for the applied voltage. + +> [!important] Exception: +> A grounded conductor shall be permitted to be uninsulated as follows: + +* (1) Bare copper used in a raceway + +* (2) Bare copper for direct burial where bare copper is approved for the soil conditions + +* (3) Bare copper for direct burial without regard to soil conditions where part of a cable assembly identified for underground use + +* (4) Aluminum or copper-clad aluminum without individual insulation or covering where part of a cable assembly identified for underground use in a raceway or for direct burial + +#### 230.30(B) Wiring Methods. + +Underground service conductors shall be installed in accordance with the applicable requirements of this Code covering the type of wiring method used and shall be limited to the following methods: + +* (1) Type RMC conduit + +* (2) Type IMC conduit + +* (3) Type NUCC conduit + +* (4) Type HDPE conduit + +* (5) Type PVC conduit + +* (6) Type RTRC conduit + +* (7) Type IGS cable + +* (8) Type USE conductors or cables + +* (9) Type MV or Type MC cable identified for direct burial applications + +* (10) Type MI cable, where suitably protected against physical damage and corrosive conditions + +### 230.31 Size and Ampacity. + +#### 230.31(A) General. + +Underground service conductors shall have sufficient ampacity to carry the current for the load as calculated in accordance with Article +220 and shall have adequate mechanical strength. + +#### 230.31(B) Minimum Size. + +The conductors shall not be smaller than 8 AWG copper or 6 AWG aluminum or copper-clad aluminum. + +> [!important] Exception: +> Conductors supplying only limited loads of a single branch circuit --- such as small polyphase power, controlled water heaters, and similar loads --- shall not be smaller than 12 AWG copper or 10 AWG aluminum or copper-clad aluminum. + +#### 230.31(C) Grounded Conductors. + +The grounded conductor shall not be less than the minimum size required by 250.24(C). + +### 230.32 Protection Against Damage. + +Underground service conductors shall be protected against damage in accordance with 300.5. Service conductors entering a building or other structure shall be installed in accordance with 230.6 or protected by a raceway wiring method identified in 230.43. + +### 230.33 Spliced Conductors. + +Service conductors shall be permitted to be spliced or tapped in accordance with 110.14, 300.5(E), 300.13, and 300.15. + +## Part IV. Service-Entrance Conductors + +### 230.40 Number of Service-Entrance Conductor Sets. + +Each service drop, set of overhead service conductors, set of underground service conductors, or service lateral shall supply only one set of service-entrance conductors. + +> [!important] Exception No. 1: ^40e1 +> A building with more than one occupancy shall be permitted to have one set of service-entrance conductors for each service, as permitted in 230.2, run to each occupancy or group of occupancies. If the number of service disconnect locations for any given classification of service does not exceed six, the requirements of 230.2(E) shall apply at each location. If the number of service disconnect locations exceeds six for any given supply classification, all service disconnect locations for all supply characteristics, together with any branch circuit or feeder supply sources, if applicable, shall be clearly described using graphics or text, or both, on one or more plaques located in an approved, readily accessible location(s) on the building or structure served and as near as practicable to the point(s) of attachment or entry(ies) for each service drop or service lateral and for each set of overhead or underground service conductors. + +> [!important] Exception No. 2: ^40e2 +> Where two to six service disconnecting means in separate enclosures are grouped at one location and supply separate loads from one service drop, set of overhead service conductors, set of underground service conductors, or service lateral, one set of service-entrance conductors shall be permitted to supply each or several such service equipment enclosures. + +> [!important] Exception No. 3: ^40e3 +> A one-family dwelling unit and its accessory structures shall be permitted to have one set of service-entrance conductors run to each from a single service drop, set of overhead service conductors, set of underground service conductors, or service lateral. + +> [!important] Exception No. 4: ^40e4 +> Two-family dwellings, multifamily dwellings, and multiple occupancy buildings shall be permitted to have one set of service-entrance conductors installed to supply the circuits covered in 210.25. + +> [!important] Exception No. 5: ^40e5 +> One set of service-entrance conductors connected to the supply side of the normal service disconnecting means shall be permitted to supply each or several systems covered by 230.82(5) or 230.82(6). + +### 230.41 Insulation of Service-Entrance Conductors. + +Service-entrance conductors entering or on the exterior of buildings or other structures shall be insulated. + +> [!important] Exception: ^41e +> A grounded conductor shall be permitted to be uninsulated as follows: +> * (1) Bare copper used in a raceway or part of a service cable assembly +> * (2) Bare copper for direct burial where bare copper is approved for the soil conditions +> * (3) Bare copper for direct burial without regard to soil conditions where part of a cable assembly identified for underground use +> * (4) Aluminum or copper-clad aluminum without individual insulation or covering where part of a cable assembly or identified for underground use in a raceway, or for direct burial +> * (5) Bare conductors used in an auxiliary gutter + +### 230.42 Minimum Size and Ampacity. + +#### 230.42(A) General. + +Service-entrance conductors shall have an ampacity of not less than the maximum load to be served. Conductors shall be sized not less than the largest of 230.42(A)(1) or (A)(2). Loads shall be determined in accordance with Part III, IV, or V of Article 220, as applicable. Ampacity shall be determined from 310.14 and shall comply with 110.14(C). The maximum current of busways shall be that value for which the busway has been listed or labeled. + +> [!info] Informational Note: +> For information on busways, see UL 857, Standard for Safety for Busways. + +* (1) Where the service-entrance conductors supply continuous loads or any combination of noncontinuous and continuous loads, the minimum service-entrance conductor size shall have an ampacity not less than the sum of the noncontinuous loads plus 125 percent of continuous loads. + + > [!important] Exception No. 1: + > Grounded conductors that are not connected to an overcurrent device + > shall be permitted to be sized at 100 percent + > of the sum of the continuous and noncontinuous load. + + > [!important] Exception No. 2: + > The sum of the noncontinuous load and the continuous load if the service-entrance conductors terminate in an overcurrent device where both the overcurrent device and its assembly are listed for operation at 100 percent of their rating shall be permitted. + +* (2) The minimum service-entrance conductor size shall have an ampacity not less than the maximum load to be served after the application of any adjustment or correction factors. + +#### 230.42(B) Specific Installations. + +In addition to the requirements of 230.42(A), the minimum ampacity for ungrounded conductors for specific installations shall not be less than the rating of the service disconnecting means specified in 230.79(A) through (D). + +#### 230.42(C) Grounded Conductors. + +The grounded conductor shall not be smaller than the minimum size as required by 250.24(C). + +### 230.43 Wiring Methods for 1000 Volts, Nominal, or Less. + +Service-entrance conductors shall be installed in accordance with the applicable requirements of this Code covering the type of wiring method used and shall be limited to the following methods: + +* (1) Open wiring on insulators + +* (2) Type IGS cable + +* (3) Rigid metal conduit (RMC) + +* (4) Intermediate metal conduit (IMC) + +* (5) Electrical metallic tubing (EMT) + +* (6) Electrical nonmetallic tubing + +* (7) Service-entrance cables + +* (8) Wireways + +* (9) Busways + +* (10) Auxiliary gutters + +* (11) Rigid polyvinyl chloride conduit (PVC) + +* (12) Cablebus + +* (13) Type MC cable + +* (14) Mineral-insulated, metal-sheathed cable, Type MI + +* (15) Flexible metal conduit (FMC) not over 1.8 m (6 ft) long + or liquidtight flexible metal conduit (LFMC) not over 1.8 m (6 ft) long + between a raceway, or between a raceway and service equipment, + with a supply-side bonding jumper routed with the flexible metal conduit (FMC) + or the liquidtight flexible metal conduit (LFMC) + according to 250.102(A), (B), (C), and (E) + +* (16) Liquidtight flexible nonmetallic conduit (LFNC) + +* (17) High density polyethylene conduit (HDPE) + +* (18) Nonmetallic underground conduit with conductors (NUCC) + +* (19) Reinforced thermosetting resin conduit (RTRC) + +* (20) Type TC-ER cable + +### 230.44 Cable Trays. + +Cable tray systems shall be permitted to support service-entrance conductors. Cable trays used to support service-entrance conductors shall contain only service-entrance conductors and shall be limited to the following methods: + +* (1) Type SE cable + +* (2) Type MC cable + +* (3) Type MI cable + +* (4) Type IGS cable + +* (5) Single conductors 1/0 and larger that are listed for use in cable tray + +* (6) Type TC-ER cable + +Such cable trays shall be identified with permanently affixed labels with the wording "Service-Entrance Conductors." The labels shall be located so as to be visible after installation with a spacing not to exceed 3 m (10 ft) so that the service-entrance conductors are able to be readily traced through the entire length of the cable tray. + +> [!important] Exception: +> Conductors, other than service-entrance conductors, shall be permitted to be installed in a cable tray with service-entrance conductors, provided a solid fixed barrier of a material compatible with the cable tray is installed to separate the service-entrance conductors from other conductors installed in the cable tray. + +### 230.46 Spliced and Tapped Conductors. + +Service-entrance conductors shall be permitted to be spliced or tapped in accordance with 110.14, 300.5(E), 300.13, and 300.15. + +Power distribution blocks, pressure connectors, and devices for splices and taps shall be listed. Power distribution blocks installed on service conductors shall be marked "suitable for use on the line side of the service equipment" or equivalent. + +Effective January 1, 2023, pressure connectors and devices for splices and taps installed on service conductors shall be marked "suitable for use on the line side of the service equipment" or equivalent. + +### 230.50 Protection Against Physical Damage. + +#### 230.50(A) Underground Service-Entrance Conductors. + +Underground service-entrance conductors shall be protected against physical damage in accordance with 300.5. + +#### 230.50(B) All Other Service-Entrance Conductors. + +All other service-entrance conductors, other than underground service entrance conductors, shall be protected against physical damage as specified in 230.50(B)(1) or (B)(2). + +##### 230.50(B)(1) Service-Entrance Cables. + +Service-entrance cables, where subject to physical damage, shall be protected by any of the following: + +* (1) Rigid metal conduit (RMC) + +* (2) Intermediate metal conduit (IMC) + +* (3) Schedule 80 PVC conduit + +* (4) Electrical metallic tubing (EMT) + +* (5) Reinforced thermosetting resin conduit (RTRC) + +* (6) Other approved means + +##### 230.50(B)(2) Other Than Service-Entrance Cables. + +Individual open conductors and cables, other than service-entrance cables, shall not be installed within 3.0 m (10 ft) of grade level or where exposed to physical damage. + +> [!important] Exception: +> Type MI and Type MC cable shall be permitted within 3.0 m (10 ft) of grade level +> where not exposed to physical damage +> or where protected in accordance with 300.5(D). + +### 230.51 Mounting Supports. + +Service-entrance cables or individual open service-entrance conductors +shall be supported as specified in 230.51(A), (B), or (C). + +#### 230.51(A) Service-Entrance Cables. + +Service-entrance cables shall be supported by straps or other approved means within 300 mm (12 in.) of every service head, gooseneck, or connection to a raceway or enclosure and at intervals not exceeding 750 mm (30 in.). + +#### 230.51(B) Other Cables. + +Cables that are not approved for mounting in contact with a building or other structure shall be mounted on insulating supports installed at intervals not exceeding 4.5 m (15 ft) and in a manner that maintains a clearance of not less than 50 mm (2 in.) from the surface over which they pass. + +#### 230.51(C) Individual Open Conductors. + +Individual open conductors shall be installed in accordance with Table 230.51(C). Where exposed to the weather, the conductors shall be mounted on insulators or on insulating supports attached to racks, brackets, or other approved means. Where not exposed to the weather, the conductors shall be mounted on glass or porcelain knobs. + +##### Table 230.51(C) Supports + +| Maximum Volts | Maximum Distance Between Supports | Minimum Clearance Between Conductors | Minimum Clearance From Surface | +| ------------- | --------------------------------- | ------------------------------------ | ------------------------------ | +| 1000 | 2.7 m (9 ft) | 150 mm (6 in.) | 50 mm (2 in.) | +| 1000 | 4.5 m (15 ft) | 300 mm (12 in.) | 50 mm (2 in.) | +| 300 | 1.4 m (4 1/2 ft) | 75 mm (3 in.) | 50 mm (2 in.) | +| 1000* | 1.4 m (4 1/2 ft) | 65 mm (2 1/2 in.) | 25 mm (1 in.) | + +\*Where not exposed to weather. + +### 230.52 Individual Conductors Entering Buildings or Other Structures. + +Where individual open conductors enter a building or other structure, they shall enter through roof bushings or through the wall in an upward slant through individual, noncombustible, nonabsorbent insulating tubes. Drip loops shall be formed on the conductors before they enter the tubes. + +### 230.53 Raceways to Drain. + +Where exposed to the weather, raceways enclosing service-entrance conductors shall be listed or approved for use in wet locations and arranged to drain. Where embedded in masonry, raceways shall be arranged to drain. + +### 230.54 Overhead Service Locations. + +#### 230.54(A) Service Head. + +Service raceways shall be equipped with a service head at the point of connection to service-drop or overhead service conductors. The service head shall be listed for use in wet locations. + +#### 230.54(B) Service-Entrance Cables Equipped with Service Head or Gooseneck. + +Service-entrance cables shall be equipped with a service head. The service head shall be listed for use in wet locations. + +> [!important] Exception: +> Type SE cable shall be permitted to be formed in a gooseneck and taped with a self-sealing weather-resistant thermoplastic. + +#### 230.54(C) Service Heads and Goosenecks Above Service-Drop or Overhead Service Attachment. + +Service heads on raceways or service-entrance cables and goosenecks in service-entrance cables shall be located above the point of attachment of the service-drop or overhead service conductors to the building or other structure. + +> [!important] Exception: +> Where it is impracticable to locate the service head or gooseneck above the point of attachment, the service head or gooseneck location shall be permitted not farther than 600 mm (24 in.) from the point of attachment. + +#### 230.54(D) Secured. + +Service-entrance cables shall be held securely in place. + +#### 230.54(E) Separately Bushed Openings. + +Service heads shall have conductors of different potential brought out through separately bushed openings. + +> [!important] Exception: +> For jacketed multiconductor service-entrance cable without splice. + +#### 230.54(F) Drip Loops. + +Drip loops shall be formed on individual conductors. To prevent the entrance of moisture, service-entrance conductors shall be connected to the service-drop or overhead service conductors either (1) below the level of the service head or (2) below the level of the termination of the service-entrance cable sheath. + +#### 230.54(G) Arranged That Water Will Not Enter Service Raceway or Equipment. + +Service-entrance and overhead service conductors shall be arranged so that water will not enter service raceway or equipment. + +### 230.56 Service Conductor with the Higher Voltage to Ground. + +On a 4-wire, delta-connected service where the midpoint of one phase winding is grounded, the service conductor having the higher phase voltage to ground shall be durably and permanently marked by an outer finish that is orange in color, or by other effective means, at each termination or junction point. + +## Part V. Service Equipment --- General + +### 230.62 Service Equipment --- Enclosed or Guarded. + +Energized parts of service equipment shall be enclosed as specified in 230.62(A) or guarded as specified in 230.62(B). + +#### 230.62(A) Enclosed. + +Energized parts shall be enclosed so that they will not be exposed to accidental contact or shall be guarded as in 230.62(B). + +#### 230.62(B) Guarded. + +Energized parts that are not enclosed shall be installed on a switchboard, panelboard, or control board and guarded in accordance with +110.18 and 110.27. Where energized parts are guarded as provided in 110.27(A)(1) and (A) (2), a means for locking or sealing doors providing access to energized parts shall be provided. + +#### 230.62(C) Barriers. + +Barriers shall be placed in service equipment such that no uninsulated, ungrounded service busbar or service terminal is exposed to inadvertent contact by persons or maintenance equipment while servicing load terminations. + +### 230.66 Marking. + +#### 230.66(A) General. + +Service equipment rated at 1000 volts or less shall be marked to identify it as being suitable for use as service equipment. All service equipment shall be listed or field evaluated. + +#### 230.66(B) Meter Sockets. + +Meter sockets shall not be considered service equipment but shall be listed and rated for the voltage and current rating of the service. + +> [!important] Exception: +> Meter sockets supplied by and under the exclusive control of an electric utility shall not be required to be listed. + +### 230.67 Surge Protection. + +#### 230.67(A) Surge-Protective Device. + +All services supplying dwelling units shall be provided with a surge-protective device (SPD). + +#### 230.67(B) Location. + +The SPD shall be an integral part of the service equipment or shall be located immediately adjacent thereto. + +> [!important] Exception: +> The SPD shall not be required to be located in the service equipment as required in (B) if located at each next level distribution equipment downstream toward the load. + +#### 230.67(C) Type. + +The SPD shall be a Type 1 or Type 2 SPD. + +#### 230.67(D) Replacement. + +Where service equipment is replaced, all of the requirements of this section shall apply. + +## Part VI. Service Equipment --- Disconnecting Means + +### 230.70 General. + +Means shall be provided to disconnect all ungrounded conductors in a building or other structure from the service conductors. + +#### 230.70(A) Location. + +The service disconnecting means shall be instal led in accordance with 230.70(A)(1), (A)(2), and (A)(3). + +##### 230.70(A)(1) Readily Accessible Location. + +The service disconnecting means shall be installed at a readily accessible location either outside of a building or structure or inside nearest the point of entrance of the service conductors. + +##### 230.70(A)(2) Bathrooms. + +Service disconnecting means shall not be installed in bathrooms. + +##### 230.70(A)(3) Remote Control. + +Where a remote control device(s) is used to actuate the service disconnecting means, the service disconnecting means shall be located in accordance with 230.70(A) (1). + +#### 230.70(B) Marking. + +Each service disconnect shall be permanently marked to identify it as a service disconnect. + +#### 230.70(C) Suitable for Use. + +Each service disconnecting means shall be suitable for the prevailing conditions. Service equipment installed in hazardous (classified) locations shall comply with the requirements of Articles 500 through 517. + +### 230.71 Maximum Number of Disconnects. + +Each service shall have only one disconnecting means unless the requirements of 230.71(B) are met. + +#### 230.71(A) General. + +For the purpose of this section, disconnecting means installed as part of listed equipment and used solely for the following shall not be considered a service disconnecting means: + +* (1) Power monitoring equipment + +* (2) Surge-protective device(s) + +* (3) Control circuit of the ground-fault protection system + +* (4) Power-operable service disconnecting means + +#### 230.71(B) Two to Six Service Disconnecting Means. + +Two to six service disconnects shall be permitted for each service permitted by 230.2 or for each set of service-entrance conductors permitted by 230.40, Exception No. 1, 3, 4, or 5. The two to six service disconnecting means shall be permitted to consist of a combination of any of the following: + +* (1) Separate enclosures with a main service disconnecting means in each enclosure + +* (2) Panelboards with a main service disconnecting means in each panelboard enclosure + +* (3) Switchboard(s) where there is only one service disconnect in each separate vertical section where there are barriers separating each vertical section + +* (4) Service disconnects in switchgear or metering centers where each disconnect is located in a separate compartment + +> [!info] Informational Note No. 1: +> Metering centers are addressed in UL 67, Standard for Panelboards. + +> [!info] Informational Note No. 2: +> Examples of separate enclosures with a main service disconnecting means in each enclosure include but are not limited to motor control centers, fused disconnects, circuit breaker enclosures, and transfer switches that are suitable for use as service equipment. + +### 230.72 Grouping of Disconnects. + +#### 230.72(A) General. + +The two to six disconnects, if permitted in 230.71, shall be grouped. Each disconnect shall be marked to indicate the load served. + +> [!important] Exception: +> One of the two to six service disconnecting means permitted in 230.71, where used only for a water pump also intended to provide fire protection, shall be permitted to be located remote from the other disconnecting means. If remotely installed in accordance with this exception, a plaque shall be posted at the location of the remaining grouped disconnects denoting its location. + +#### 230.72(B) Additional Service Disconnecting Means. + +The one or more additional service disconnecting means for fire pumps, emergency systems, legally required standby, or optional standby services permitted by 230.2 shall be installed remote from the one to six service disconnecting means for normal service to minimize the possibility of simultaneous interruption of supply. + +#### 230.72(C) Access to Occupants. + +In a multiple-occupancy building, each occupant shall have access to the occupant's service disconnecting means. + +> [!important] Exception: +> In a multiple-occupancy building where electric service and electrical maintenance are provided by the building management and where these are under continuous building management supervision, the service disconnecting means supplying more than one occupancy shall be permitted to be accessible to authorized management personnel only. + +### 230.74 Simultaneous Opening of Poles. + +Each service disconnect shall simultaneously disconnect all ungrounded service conductors that it controls from the premises wiring system. + +### 230.75 Disconnection of Grounded Conductor. + +Where the service disconnecting means does not disconnect the grounded conductor from the premises wiring, other means shall be provided for this purpose in the service equipment. A terminal or bus to which all grounded conductors can be attached by means of pressure connectors shall be permitted for this purpose. In a multisection switchboard or switchgear, disconnects for the grounded conductor shall be permitted to be in any section of the switchboard or switchgear. + +> [!info] Informational Note: +> In switchgear or multisection switchboards, the disconnecting means provided for the grounded conductor is typically identified as a neutral disconnect link and is typically located in the bus to which the service grounded conductor is connected. + +### 230.76 Manually or Power Operable. + +The service disconnecting means for ungrounded service conductors shall consist of one of the following: + +* (1) A manually operable switch or circuit breaker equipped with a handle or other suitable operating means + +* (2) A power-operated switch or circuit breaker, provided the switch or circuit breaker can be opened by hand in the event of a power supply failure + +### 230.77 Indicating. + +The service disconnecting means shall plainly indicate whether it is in the open (off) or closed (on) position. + +### 230.79 Rating of Service Disconnecting Means. + +The service disconnecting means shall have a rating not less than the calculated load to be carried, determined in accordance with + +Part III, IV, or V of Article 220, as applicable. In no case shall the rating be lower than specified in 230.79(A), (B), (C), or (D). + +#### 230.79(A) One-Circuit Installations. + +For installations to supply only limited loads of a single branch circuit, the service disconnecting means shall have a rating of not less than 15 amperes. + +#### 230.79(B) Two-Circuit Installations. + +For installations consisting of not more than two 2-wire branch circuits, the service disconnecting means shall have a rating of not less than 30 amperes. + +#### 230.79(C) One-Family Dwellings. + +For a one-family dwelling, the service disconnecting means shall have a rating of not less than 100 amperes, 3-wire. + +#### 230.79(D) All Others. + +For all other installations, the service disconnecting means shall have a rating of not less than 60 amperes. + +### 230.80 Combined Rating of Disconnects. + +Where the service disconnecting means consists of more than one switch or circuit breaker, as permitted by 230.71, the combined ratings of all the switches or circuit breakers used shall not be less than the rating required by 230.79. + +### 230.81 Connection to Terminals. + +The service conductors shall be connected to the service disconnecting means by pressure connectors, clamps, or other approved means. Connections that depend on solder shall not be used. + +### 230.82 Equipment Connected to the Supply Side of Service Disconnect. + +Only the following equipment shall be permitted to be connected to the supply side of the service disconnecting means: + +* (1) Cable limiters. + +* (2) Meters and meter sockets nominally rated not in excess of 1000 volts, if all metal housings and service enclosures are grounded in accordance with Part VII and bonded in accordance with Part V of Article 250. + +* (3) Meter disconnect switches nominally rated not in excess of 1000 volts that have a short-circuit current rating equal to or greater than the available fault current, if all metal housings and service enclosures are grounded in accordance with Part VII and bonded in accordance with Part V of Article 250. A meter disconnect switch shall be capable of interrupting the load served. A meter disconnect shall be legibly field marked on its exterior in a manner suitable for the environment as follows: + + ``` + METER DISCONNECT + NOT SERVICE EQUIPMENT + ``` + +* (4) Instrument transformers (current and voltage), impedance shunts, load management devices, surge arresters, and Type 1 surge-protective devices. + +* (5) Conductors used to supply load management devices, circuits for standby power systems, fire pump equipment, and fire and sprinkler alarms, if provided with service equipment and installed in accordance with requirements for service-entrance conductors. + +* (6) Solar photovoltaic systems, fuel cell systems, wind electric systems, energy storage systems, or interconnected electric power production sources, if provided with a disconnecting means listed as suitable for use as service equipment, and overcurrent protection as specified in Part VII of Article 230. + +* (7) Control circuits for power-operable service disconnecting means, if suitable overcurrent protection and disconnecting means are provided. + +* (8) Ground-fault protection systems or Type 2 surge-protective devices, where installed as part of listed equipment, if suitable overcurrent protection and disconnecting means are provided. + +* (9) Connections used only to supply listed communications equipment under the exclusive control of the serving electric utility, if suitable overcurrent protection and disconnecting means are provided. For installations of equipment by the serving electric utility, a disconnecting means is not required if the supply is installed as part of a meter socket, such that access can only be gained with the meter removed. + +* (10) Emergency disconnects in accordance with 230.85, if all metal housings and service enclosures are grounded in accordance with Part VII and bonded in accordance with Part V of Article 250. + +* (11) Meter-mounted transfer switches nominally rated not in excess of 1000 volts that have a short-circuit current rating equal to or greater than the available fault current. A meter-mounted transfer switch shall be listed and be capable of transferring the load served. A meter-mounted transfer switch shall be marked on its exterior with both of the following: + * a. Meter-mounted transfer switch + * b. Not service equipment + +### 230.85 Emergency Disconnects. + +For one- and two-family dwelling units, all service conductors shall terminate in disconnecting means having a short-circuit current rating equal to or greater than the available fault current, installed in a readily accessible outdoor location. If more than one disconnect is provided, they shall be grouped. Each disconnect shall be one of the following: + +* (1) Service disconnects marked as follows: + + ``` + EMERGENCY DISCONNECT, + SERVICE DISCONNECT + ``` + +* (2) Meter disconnects installed per 230.82(3) and marked as follows: + + ``` + EMERGENCY DISCONNECT, + METER DISCONNECT, + NOT SERVICE EQUIPMENT + ``` + +* (3) Other listed disconnect switches or circuit breakers on the supply side of each service disconnect that are suitable for use as service equipment and marked as follows: + + ``` + EMERGENCY DISCONNECT, + NOT SERVICE EQUIPMENT + ``` + +Markings shall comply with 110.21(B). + +## Part VII. Service Equipment --- Overcurrent Protection + +### 230.90 Where Required. + +Each ungrounded service conductor shall have overload protection. + +#### 230.90(A) Ungrounded Conductor. + +Such protection shall be provided by an overcurrent device in series with each ungrounded service conductor that has a rating or setting not higher than the ampacity of the conductor. A set of fuses shall be considered all the fuses required to protect all the ungrounded conductors of a circuit. Single-pole circuit breakers, grouped in accordance with 230.71(B), shall be considered as one protective device. + +> [!important] Exception No. 1: +> For motor-starting currents, ratings that comply with 430.52, 430.62, and 430.63 shall be permitted. + +> [!important] Exception No. 2: +> Fuses and circuit breakers with a rating or setting that complies with 240.4(B) or (C) and 240.6 shall be permitted. + +> [!important] Exception No. 3: +> Two to six circuit breakers or sets of fuses shall be permitted as the overcurrent device to provide the overload protection. The sum of the ratings of the circuit breakers or fuses shall be permitted to exceed the ampacity of the service conductors, provided the calculated load does not exceed the ampacity of the service conductors. + +> [!important] Exception No. 4: +> Overload protection for fire pump supply conductors shall comply with 695.4(B)(2)(a). + +> [!important] Exception No. 5: +> Overload protection for 120/240-volt, 3-wire, single-phase dwelling services shall be permitted in accordance with the requirements of 310.12. + +#### 230.90(B) Not in Grounded Conductor. + +No overcurrent device shall be inserted in a grounded service conductor except a circuit breaker that simultaneously opens all conductors of the circuit. + +### 230.91 Location. + +The service overcurrent device shall be an integral part of the service disconnecting means or shall be located immediately adjacent thereto. Where fuses are used as the service overcurrent device, the disconnecting means shall be located ahead of the supply side of the fuses. + +### 230.92 Locked Service Overcurrent Devices. + +Where the service overcurrent devices are locked or sealed or are not readily accessible to the occupant, branch-circuit or feeder overcurrent devices shall be installed on the load side, shall be mounted in a readily accessible location, and shall be of lower ampere rating than the service overcurrent device. + +### 230.93 Protection of Specific Circuits. + +Where necessary to prevent tampering, an automatic overcurrent device that protects service conductors supplying only a specific load, such as a water heater, shall be permitted to be locked or sealed where located so as to be accessible. + +### 230.94 Relative Location of Overcurrent Device and Other Service Equipment. + +The overcurrent device shall protect all circuits and devices. + +> [!important] Exception No. 1: +> The service switch shall be permitted on the supply side. + +> [!important] Exception No. 2: +> High-impedance shunt circuits, surge arresters, Type 1 surge-protective devices, surge-protective capacitors, and instrument transformers (current and voltage) shall be permitted to be connected and installed on the supply side of the service disconnecting means as permitted by 230.82. + +> [!important] Exception No. 3: +> Circuits for load management devices shall be permitted to be connected on the supply side of the service overcurrent device where separately provided with overcurrent protection. + +> [!important] Exception No. 4: +> Circuits used only for the operation of fire alarm, other protective signaling systems, or the supply to fire pump equipment shall be permitted to be connected on the supply side of the service overcurrent device where separately provided with overcurrent protection. + +> [!important] Exception No. 5: +> Meters nominally rated not in excess of 600 volts shall be permitted, provided all metal housings and service enclosures are grounded. + +> [!important] Exception No. 6: +> Where service equipment is power operable, the control circuit shall be permitted to be connected ahead of the service equipment if suitable overcurrent protection and disconnecting means are provided. + +### 230.95 Ground-Fault Protection of Equipment. + +Ground-fault protection of equipment shall be provided for solidly grounded wye electric services of more than 150 volts to ground but not exceeding 1000 volts phase-to-phase for each service disconnect rated 1000 amperes or more. The grounded conductor for the solidly grounded wye system shall be connected directly to ground through a grounding electrode system, as specified in 250.50, without inserting any resistor or impedance device. + +The rating of the service disconnect shall be considered to be the rating of the largest fuse that can be installed or the highest continuous current trip setting for which the actual overcurrent device installed in a circuit breaker is rated or can be adjusted. + +> [!important] Exception: +> The ground-fault protection provisions of this section shall not apply to a service disconnect for a continuous industrial process where a nonorderly shutdown will introduce additional or increased hazards. + +#### 230.95(A) Setting. + +The ground-fault protection system shall operate to cause the service disconnect to open all ungrounded conductors of the faulted circuit. The maximum setting of the ground-fault protection shall be 1200 amperes, and the maximum time delay shall be one second for ground-fault currents equal to or greater than 3000 amperes. + +#### 230.95(B) Fuses. + +If a switch and fuse combination is used, the fuses employed shall be capable of interrupting any current higher than the interrupting capacity of the switch during a time that the ground-fault protective system will not cause the switch to open. + +#### 230.95(C) Performance Testing. + +The ground-fault protection system shall be performance tested when first installed on site. This testing shall be conducted by a qualified person(s) using a test process of primary current injection, in accordance with instructions that shall be provided with the equipment. A written record of this testing shall be made and shall be available to the authority having jurisdiction. + +> [!info] Informational Note No. 1: +> Ground-fault protection that functions to open the service disconnect affords no protection from faults on the line side of the protective element. It serves only to limit damage to conductors and equipment on the load side in the event of an arcing ground fault on the load side of the protective element. + +> [!info] Informational Note No. 2: +> This added protective equipment at the service equipment may make it necessary to review the overall wiring system for proper selective overcurrent protection coordination. Additional installations of ground-fault protective equipment may be needed on feeders and branch circuits where maximum continuity of electric service is necessary. + +> [!info] Informational Note No. 3: +> Where ground-fault protection is provided for the service disconnect and interconnection is made with another supply system by a transfer device, means or devices may be needed to ensure proper ground-fault sensing by the ground-fault protection equipment. + +> [!info] Informational Note No. 4: +> See 517.17(A) for information on where an additional step of ground-fault protection is required for hospitals and other buildings with critical areas or life support equipment. + +## Part VIII. Services Exceeding 1000 Volts, Nominal + +### 230.200 General. + +Service conductors and equipment used on circuits exceeding 1000 volts, nominal, shall comply with all the applicable preceding sections of this article and with the following sections that supplement or modify the preceding sections. In no case shall the provisions of Part VIII apply to equipment on the supply side of the service point. + +> [!info] Informational Note: +> For clearances of conductors of over 1000 volts, nominal, see ANSI/IEEE C2-2017, National Electrical Safety Code. + +### 230.202 Service-Entrance Conductors. + +Service-entrance conductors to buildings or enclosures shall be installed to conform to 230.202(A) and (B). + +#### 230.202(A) Conductor Size. + +Service-entrance conductors shall not be smaller than 6 AWG unless in multiconductor cable. Multiconductor cable shall not be smaller than 8 AWG. + +#### 230.202(B) Wiring Methods. + +Service-entrance conductors shall be installed by one of the wiring methods covered in 300.37 and 300.50. + +### 230.204 Isolating Switches. + +#### 230.204(A) Where Required. + +Where oil switches or air, oil, vacuum, or sulfur hexafluoride circuit breakers constitute the service disconnecting means, an isolating switch with visible break contacts shall be installed on the supply side of the disconnecting means and all associated service equipment. + +> [!important] Exception: +> An isolating switch shall not be required where the circuit breaker or switch is mounted on removable truck panels or switchgear units where both of the following conditions apply: + +* (1) Cannot be opened unless the circuit is disconnected + +* (2) Where all energized parts are automatically disconnected when the circuit breaker or switch is removed from the normal operating position + +#### 230.204(B) Fuses as Isolating Switch. + +Where fuses are of the type that can be operated as a disconnecting switch, a set of such fuses shall be permitted as the isolating switch. + +#### 230.204(C) Accessible to Qualified Persons Only. + +The isolating switch shall be accessible to qualified persons only. + +#### 230.204(D) Connection to Ground. + +Isolating switches shall be provided with a means for readily connecting the load side conductors to a grounding electrode system, equipment ground busbar, or grounded steel structure when disconnected from the source of supply. + +A means for grounding the load side conductors to a grounding electrode system, equipment grounding busbar, or grounded structural steel shall not be required for any duplicate isolating switch installed and maintained by the electric supply company. + +### 230.205 Disconnecting Means. + +#### 230.205(A) Location. + +The service disconnecting means shall be located in accordance with 230.70. + +For either overhead or underground primary distribution systems on private property, the service disconnect shall be permitted to be located in a location that is not readily accessible, if the disconnecting means can be operated by mechanical linkage from a readily accessible point, or electronically in accordance with 230.205(C), where applicable. + +#### 230.205(B) Type. + +Each service disconnect shall simultaneously disconnect all ungrounded service conductors that it controls and shall have a faultclosing rating that is not less than the available fault current at its supply terminals. + +Where fused switches or separately mounted fuses are instal led, the fuse characteristics shall be permitted to contribute to the faultclosing rating of the disconnecting means. + +#### 230.205(C) Remote Control. + +For multibuilding, industrial installations under single management, the service disconnecting means shall be permitted to be located at a separate building or structure. In such cases, the service disconnecting means shall be permitted to be electrically operated by a readily accessible, remote-control device. + +### 230.206 Overcurrent Devices as Disconnecting Means. + +Where the circuit breaker or alternative for it, as specified in 230.208 for service overcurrent devices, meets the requirements specified in 230.205, it shall constitute the service disconnecting means. + +### 230.208 Protection Requirements. + +A short-circuit protective device shall be provided on the load side of, or as an integral part of, the service disconnect, and shall protect all ungrounded conductors that it supplies. The protective device shall be capable of detecting and interrupting all values of current, in excess of its trip setting or melting point, that can occur at its location. A fuse rated in continuous amperes not to exceed three times the ampacity of the conductor, or a circuit breaker with a trip setting of not more than six times the ampacity of the conductors, shall be considered as providing the required short-circuit protection. + +> [!info] Informational Note: +> See Table 311.60(C)(67) through Table 311.60(C)(86) for ampacities of conductors rated 2001 volts to 35,000 volts. + +Overcurrent devices shall conform to 230.208(A) and (B). + +#### 230.208(A) Equipment Type. + +Equipment used to protect service-entrance conductors shall meet the requirements of Article 490, Part II. + +#### 230.208(B) Enclosed Overcurrent Devices. + +The restriction to 80 percent of the rating for an enclosed overcurrent device for continuous loads shall not apply to overcurrent devices instal led in systems operating at over 1000 volts. + +### 230.209 Surge Arresters. + +Surge arresters installed in accordance with the requirements of Article 242 shall be permitted on each ungrounded overhead service conductor. + +> [!info] Informational Note: +> Surge arresters may be referred to as lightning arresters in older documents. + +### 230.210 Service Equipment --- General Provisions. + +Service equipment, including instrument transformers, shall conform to Article 490, Part I. + +### 230.211 Switchgear. + +Switchgear shall consist of a substantial metal structure and a sheet metal enclosure. Where installed over a combustible floor, suitable protection thereto shall be provided. + +### 230.212 Over 35,000 Volts. + +Where the voltage exceeds 35,000 volts between conductors that enter a building, they shall terminate in a switchgear compartment or a vault conforming to the requirements of 450.41 through 450.48. diff --git a/nfpa-70_240_overcurrent-protection.md b/nfpa-70_240_overcurrent-protection.md new file mode 100644 index 0000000..0836caf --- /dev/null +++ b/nfpa-70_240_overcurrent-protection.md @@ -0,0 +1,1351 @@ +--- +id: +aliases: + - nec-240 +tags: + - authorship/other + - destiny/uncertain + - exclude-from-word-count + - status/incomplete + - topic/construction/electrical + - type/media +title: Article 240 Overcurrent Protection +--- +# Article 240 Overcurrent Protection + +## Part I. General + +### 240.1 Scope. + +Parts I through VII of this article +provide the general requirements for overcurrent protection +and overcurrent protective devices +not more than 1000 volts, nominal. +[[#Part VIII. Supervised Industrial Installations|Part VIII]] +covers overcurrent protection +for those portions of supervised industrial installations +operating at voltages of not more than 1000 volts, nominal. +[[#Part IX. Overcurrent Protection over 1000 Volts, Nominal|Part IX]] +covers overcurrent protection over 1000 volts, nominal. + +> [!info] Informational Note: +> Overcurrent protection for conductors and equipment +> is provided to open the circuit if the current reaches a value +> that will cause an excessive or dangerous temperature +> in conductors or conductor insulation. +> See also [[nfpa-70_110_requirements-for-electrical-installations#110.9 Interrupting Rating.|110.9]] +> for requirements for interrupting ratings +> and [[nfpa-70_110_requirements-for-electrical-installations#110.10 Circuit Impedance, Short-Circuit Current Ratings, and Other Characteristics.|110.10]] +> for requirements for protection against fault currents. + +### 240.2 Definitions. + +The definitions in this section shall apply only within this article. + +#### Current-Limiting Overcurrent Protective Device. + +A device that, when interrupting currents in its current-limiting range, +reduces the current flowing in the faulted circuit +to a magnitude substantially less than that obtainable in the same circuit +if the device were replaced with a solid conductor +having comparable impedance. + +#### Supervised Industrial Installation. + +For the purposes of Part VIII, +the industrial portions of a facility where all of the following conditions are met: + +* (1) Conditions of maintenance and engineering supervision + ensure that only qualified persons monitor and service the system. + +* (2) The premises wiring system has 2500 kVA or greater + of load used in industrial process(es), manufacturing activities, or both, + as calculated in accordance with [[nfpa-70_220_load-calculations|Article 220]]. + +* (3) The premises has at least one service or feeder + that is more than 150 volts to ground + and more than 300 volts phase-to-phase. + +This definition excludes installations in buildings used by the industrial facility +for offices, warehouses, garages, machine shops, and recreational facilities +that are not an integral part of the industrial plant, substation, or control center. + +#### Tap Conductor. + +A conductor, other than a service conductor, +that has overcurrent protection ahead of its point of supply +that exceeds the value permitted for similar conductors +that are protected as described elsewhere in +[[#240.4 Protection of Conductors.|240.4]]. + +### 240.3 Other Articles. + +Equipment shall be protected against overcurrent in accordance with the article in this Code that covers the type of equipment specified in Table 240.3. + +#### Table 240.3 Other Articles + +| Equipment | Article | +| ------------------------------------------------------------------------------------------- | ------- | +| Air-conditioning and refrigerating equipment | 440 | +| Appliances | 422 | +| Assembly occupancies | 518 | +| Audio signal processing, amplification, and reproduction equipment | 640 | +| Branch circuits | 210 | +| Busways | 368 | +| Capacitors | 460 | +| Class 1, Class 2, and Class 3 remote-control, signaling, and power-limited circuits | 725 | +| Cranes and hoists | 610 | +| Electric signs and outline lighting | 600 | +| Electric welders | 630 | +| Electrolytic cells | 668 | +| Elevators, dumbwaiters, escalators, moving walks, wheelchair lifts, and stairway chairlifts | 620 | +| Emergency systems | 700 | +| Fire alarm systems | 760 | +| Fire pumps | 695 | +| Fixed electric heating equipment for pipelines and vessels | 427 | +| Fixed electric space-heating equipment | 424 | +| Fixed outdoor electric deicing and snow-melting equipment | 426 | +| Generators | 445 | +| Health care facilities | 517 | +| Induction and dielectric heating equipment | 665 | +| Industrial machinery | 670 | +| Luminaires, lampholders, and lamps | 410 | +| Motion picture and television studios and similar locations | 530 | +| Motors, motor circuits, and controllers | 430 | +| Phase converters | 455 | +| Pipe organs | 650 | +| Receptacles | 406 | +| Services | 230 | +| Solar photovoltaic systems | 690 | +| Switchboards and panelboards | 408 | +| Theaters, audience areas of motion picture and television studios, and similar locations | 520 | +| Transformers and transformer vaults | 450 | +| X-ray equipment | 660 | + +### 240.4 Protection of Conductors. + +Conductors, +other than flexible cords, flexible cables, and fixture wires, +shall be protected against overcurrent in accordance with their ampacities specified in 310.14, +unless otherwise permitted or required in 240.4(A) through (G). + +> [!info] Informational Note: +> See ICEA P-32-382-2007 (R2013), Short Circuit Characteristics of Insulated Cables, +> for information on allowable short-circuit currents +> for insulated copper and aluminum conductors. + +#### 240.4(A) Power Loss Hazard. + +Conductor overload protection shall not be required +where the interruption of the circuit would create a hazard, +such as in a material-handling magnet circuit or fire pump circuit. +Short-circuit protection shall be provided. + +> [!info] Informational Note: +> See NFPA 20-2013, Standard for the Installation of Stationary Pumps for Fire Protection. + +#### 240.4(B) Overcurrent Devices Rated 800 Amperes or Less. + +The next higher standard overcurrent device rating (above the ampacity of the conductors being protected) shall be permitted to be used, provided all of the following conditions are met: + +* (1) The conductors being protected are not part of a branch circuit supplying more than one receptacle for cord-and-plug-connected portable loads. + +* (2) The ampacity of the conductors does not correspond with the standard ampere rating of a fuse or a circuit breaker without overload trip adjustments above its rating (but that shall be permitted to have other trip or rating adjustments). + +* (3) The next higher standard rating selected does not exceed 800 amperes. + +#### 240.4(C) Overcurrent Devices Rated over 800 Amperes. + +Where the overcurrent device is rated over 800 amperes, the ampacity of the conductors it protects shall be equal to or greater than the rating of the overcurrent device defined in 240.6. + +#### 240.4(D) Small Conductors. + +Unless specifically permitted in 240.4(E) or (G), the overcurrent protection shall not exceed that required by (D)(1) through (D)(7) after any correction factors for ambient temperature and number of conductors have been applied. + +##### 240.4(D)(1) 18 AWG Copper. + +7 amperes, provided all the following conditions are met: + +* (1) Continuous loads do not exceed 5.6 amperes. + +* (2) Overcurrent protection is provided by one of the following: + * a. Branch-circuit-rated circuit breakers listed and marked for use with 18 AWG copper wire + * b. Branch-circuit-rated fuses listed and marked for use with 18 AWG copper wire + * c. Class CC, Class J, or Class T fuses + +##### 240.4(D)(2) 16 AWG Copper. + +10 amperes, provided all the following conditions are met: + +* (1) Continuous loads do not exceed 8 amperes. + +* (2) Overcurrent protection is provided by one of the following: + * a. Branch-circuit-rated circuit breakers listed and marked for use with 16 AWG copper wire + * b. Branch-circuit-rated fuses listed and marked for use with 16 AWG copper wire + * c. Class CC, Class J, or Class T fuses + +##### 240.4(D)(3) 14 AWG Copper. + +15 amperes + +##### 240.4(D)(4) 12 AWG Aluminum and Copper-Clad Aluminum. + +15 amperes + +##### 240.4(D)(5) 12 AWG Copper. + +20 amperes + +##### 240.4(D)(6) 10 AWG Aluminum and Copper-Clad Aluminum. + +25 amperes + +##### 240.4(D)(7) 10 AWG Copper. + +30 amperes + +#### 240.4(E) Tap Conductors. + +Tap conductors shall be permitted to be protected against overcurrent in accordance with the following: + +* (1) [[nfpa-70_210_branch-circuits#210.19(A)(3) Household Ranges and Cooking Appliances.|210.19(A)(3)]] + and [[nfpa-70_210_branch-circuits#210.19(A)(4) Other Loads.|210.19(A)(4)]], + Household Ranges and Cooking Appliances and Other Loads + +* (2) [[#240.5(B)(2) Fixture Wire.|240.5(B)(2)]], + Fixture Wire + +* (3) [[#240.21 Location in Circuit.|240.21]], + Location in Circuit + +* (4) 368.17(B), + Reduction in Ampacity Size of Busway + +* (5) 368.17(C), + Feeder or Branch Circuits (busway taps) + +* (6) 430.53(D),[[nfpa-70_430_motors#430.5]] + Single Motor Taps + +#### 240.4(F) Transformer Secondary Conductors. + +Single-phase (other than 2-wire) and multiphase (other than delta-delta, 3-wire) transformer secondary conductors +shall not be considered to be protected by the primary overcurrent protective device. +Conductors supplied by the secondary side +of a single-phase transformer having a 2-wire (single-voltage) secondary, +or a three-phase, delta-delta connected transformer having a 3-wire (single-voltage) secondary, +shall be permitted to be protected by overcurrent protection provided on the primary (supply) side of the transformer, +provided this protection is in accordance with 450.3 +and does not exceed the value determined by multiplying the secondary conductor ampacity +by the secondary-to-primary transformer voltage ratio. + +#### 240.4(G) Overcurrent Protection for Specific Conductor Applications. + +Overcurrent protection for the specific conductors +shall be permitted to be provided as referenced in Table 240.4(G). + +Table 240.4(G) Specific Conductor Applications + +| Conductor | Article | Section | +| --------------------------------------------------------------- | ---------------------------------- | -------------------------------------------------------------- | +| Air-conditioning and refrigeration equipment circuit conductors | 440, Parts III, VI | | +| Capacitor circuit conductors | 460 | 460.8(B) and 460.25 | +| Control and instrumentation circuit conductors (Type ITC) | 727 | 727.9 | +| Electric welder circuit conductors | 630 | 630.12 and 630.32 | +| Fire alarm system circuit conductors | 760 | 760.43, 760.45, 760.121, and Chapter 9, Tables 12(A) and 12(B) | +| Motor-operated appliance circuit conductors | 422, Part II | | +| Motor and motor-control circuit conductors | 430, Parts II, III, IV, V, VI, VII | | +| Phase converter supply conductors | 455 | 455.7 | +| Remote-control, signaling, and power-limited circuit conductors | 725 | 725.43, 725.45, 725.121, and Chapter 9, Tables 11(A) and 11(B) | +| Secondary tie conductors | 450 | 450.6 | + +### 240.5 Protection of Flexible Cords, Flexible Cables, and Fixture Wires. + +Flexible cord and flexible cable, including tinsel cord and extension cords, and fixture wires shall be protected against overcurrent by either 240.5(A) or (B). + +#### 240.5(A) Ampacities. + +Flexible cord and flexible cable +shall be protected by an overcurrent device +in accordance with their ampacity +as specified in Table 400.5(A)(1) and Table 400.5(A) (2). +Fixture wire shall be protected against overcurrent +in accordance with its ampacity as specified in Table 402.5. +Supplementary overcurrent protection, as covered in 240.10, +shall be permitted to be an acceptable means for providing this protection. + +#### 240.5(B) Branch-Circuit Overcurrent Device. + +Flexible cord shall be protected, +where supplied by a branch circuit, +in accordance with one of the methods +described in 240.5(B)(1), +(B)(3), +or (B)(4). +Fixture wire shall be protected, +where supplied by a branch circuit, +in accordance with 240.5(B)(2). + +##### 240.5(B)(1) Supply Cord of Listed Appliance or Luminaire. + +Where flexible cord or tinsel cord is approved for and used with a specific listed appliance or luminaire, it shall be considered to be protected when applied within the appliance or luminaire listing requirements. For the purposes of this section, a luminaire may be either portable or permanent. + +##### 240.5(B)(2) Fixture Wire. + +Fixture wire shall be permitted to be tapped to the branch-circuit conductor of a branch circuit in accordance with the following: + +* (1) 15- or 20-ampere circuits --- 18 AWG, up to 15 m (50 ft) of run length +* (2) 15- or 20-ampere circuits --- 16 AWG, up to 30 m (100 ft) of run length +* (3) 20-ampere circuits --- 14 AWG and larger +* (4) 30-ampere circuits --- 14 AWG and larger +* (5) 40-ampere circuits --- 12 AWG and larger +* (6) 50-ampere circuits --- 12 AWG and larger + +##### 240.5(B)(3) Extension Cord Sets. + +Flexible cord used in listed extension cord sets shall be considered to be protected when applied within the extension cord listing requirements. + +##### 240.5(B)(4) Field Assembled Extension Cord Sets. + +Flexible cord used in extension cords made with separately listed and installed components shall be permitted to be supplied by a branch circuit in accordance with the following: +20-ampere circuits --- 16 AWG and larger + +### 240.6 Standard Ampere Ratings. + +#### 240.6(A) Fuses and Fixed-Trip Circuit Breakers. + +The standard ampere ratings +for fuses and inverse time circuit breakers +shall be considered as shown in Table 240.6(A). +Additional standard ampere ratings for fuses +shall be 1, 3, 6, 10, and 601. +The use of fuses and inverse time circuit breakers +with nonstandard ampere ratings shall be permitted. + +##### Table 240.6(A) Standard Ampere Ratings for Fuses and Inverse Time Circuit Breakers + +| Standard Ampere Ratings | +| ----------------------- | +| 15 | +| 20 | +| 25 | +| 30 | +| 35 | +| 40 | +| 45 | +| 50 | +| 60 | +| 70 | +| 80 | +| 90 | +| 100 | +| 110 | +| 125 | +| 150 | +| 175 | +| 200 | +| 225 | +| 250 | +| 300 | +| 350 | +| 400 | +| 450 | +| 500 | +| 600 | +| 700 | +| 800 | +| 1000 | +| 1200 | +| 1600 | +| 2000 | +| 2500 | +| 3000 | +| 4000 | +| 5000 | +| 6000 | + +#### 240.6(B) Adjustable-Trip Circuit Breakers. + +The rating of adjustable-trip circuit breakers +having external means for adjusting the current setting +(long-time pickup setting), +not meeting the requirements of 240.6(C), +shall be the maximum setting possible. + +#### 240.6(C) Restricted Access Adjustable-Trip Circuit Breakers. + +A circuit breaker(s) that has restricted access to the adjusting means shall be permitted to have an ampere rating(s) that is equal to the adjusted current setting (long-time pickup setting). Restricted access shall be achieved by one of the following methods: + +* (1) Located behind removable and sealable covers over the adjusting means +* (2) Located behind bolted equipment enclosure doors +* (3) Located behind locked doors accessible only to qualified personnel +* (4) Password protected, with password accessible only to qualified personnel + +### 240.8 Fuses or Circuit Breakers in Parallel. + +Fuses and circuit breakers +shall be permitted to be connected in parallel +where they are factory assembled in parallel +and listed as a unit. +Individual fuses, circuit breakers, +or combinations thereof +shall not otherwise be connected in parallel. + +### 240.9 Thermal Devices. + +Thermal relays and other devices not designed to open short circuits or ground faults +shall not be used for the protection of conductors +against overcurrent due to short circuits or ground faults, +but the use of such devices +shall be permitted to protect motor branch-circuit conductors +from overload if protected in accordance with 430.40. + +### 240.10 Supplementary Overcurrent Protection. + +Where supplementary overcurrent protection is used for luminaires, appliances, and other equipment or for internal circuits and components of equipment, it shall not be used as a substitute for required branch-circuit overcurrent devices or in place of the required branch-circuit protection. Supplementary overcurrent devices shall not be required to be readily accessible. + +### 240.12 Electrical System Coordination. + +Where an orderly shutdown is required to minimize the hazard(s) to personnel and equipment, a system of coordination based on the following two conditions shall be permitted: + +* (1) Coordinated short-circuit protection +* (2) Overload indication based on monitoring systems or devices + +> [!info] Informational Note: +> The monitoring system may cause the condition to go to alarm, allowing corrective action or an orderly shutdown, thereby minimizing personnel hazard and equipment damage. + +### 240.13 Ground-Fault Protection of Equipment. + +Ground-fault protection of equipment shall be provided in accordance with 230.95 for solidly grounded wye electrical systems of more than 150 volts to ground but not exceeding 1000 volts phase-to-phase for each individual device used as a building or structure main disconnecting means rated 1000 amperes or more. + +This section shall not apply to the disconnecting means for the following: + +* (1) Continuous industrial processes + where a nonorderly shutdown will introduce additional or increased hazard + +* (2) Installations where ground-fault protection + is provided by other requirements for services or feeders + +* (3) Fire pumps + +### 240.15 Ungrounded Conductors. + +#### 240.15(A) Overcurrent Device Required. + +A fuse or an overcurrent trip unit of a circuit breaker +shall be connected in series with each ungrounded conductor. +A combination of a current transformer and overcurrent relay +shall be considered equivalent to an overcurrent trip unit. + +> [!info] Informational Note: +> For motor circuits, see Parts III, IV, V, and XI of [[nfpa-70_430_motors|Article 430]]. + +#### 240.15(B) Circuit Breaker as Overcurrent Device. + +Circuit breakers shall open all ungrounded conductors of the circuit both manually and automatically unless otherwise permitted in +240.15(B)(1), (B)(2), (B)(3), and (B)(4). + +##### 240.15(B)(1) Multiwire Branch Circuits. + +Individual single-pole circuit breakers, with identified handle ties, shall be permitted as the protection for each ungrounded conductor of multiwire branch circuits that serve only single-phase line-to-neutral loads. + +##### 240.15(B)(2) Grounded Single-Phase Alternating-Current Circuits. + +In grounded systems, individual single-pole circuit breakers rated 120/240 volts ac, with identified handle ties, shall be permitted as the protection for each ungrounded conductor for line-to-line connected loads for single-phase circuits. + +##### 240.15(B)(3) 3-Phase and 2-Phase Systems. + +For line-to-line loads in 4-wire, 3-phase systems or 5-wire, 2-phase systems, individual single-pole circuit breakers rated 120/240 volts ac with identified handle ties shall be permitted as the protection for each ungrounded conductor, if the systems have a grounded neutral point and the voltage to ground does not exceed 120 volts. + +##### 240.15(B)(4) 3-Wire Direct-Current Circuits. + +Individual single-pole circuit breakers rated 125/250 volts dc with identified handle ties shall be permitted as the protection for each ungrounded conductor for line-to-line connected loads for 3-wire, direct-current circuits supplied from a system with a grounded neutral where the voltage to ground does not exceed 125 volts. + +## Part II. Location + +### 240.21 Location in Circuit. + +Overcurrent protection shall be provided in each ungrounded circuit conductor +and shall be located at the point where the conductors receive their supply +except as specified in 240.21(A) through (H). +Conductors supplied under 240.21(A) through (H) +shall not supply another conductor +except through an overcurrent protective device +meeting the requirements of [[#240.4 Protection of Conductors.|240.4]]. + +#### 240.21(A) Branch-Circuit Conductors. + +Branch-circuit tap conductors +meeting the requirements specified in 210.19 +shall be permitted to have overcurrent protection as specified in 210.20. + +#### 240.21(B) Feeder Taps. + +Conductors shall be permitted to be tapped, +without overcurrent protection at the tap, +to a feeder as specified in 240.21(B)(1) through (B)(5). +The tap shall be permitted at any point +on the load side of the feeder overcurrent protective device. +Section 240.4(B) shall not be permitted for tap conductors. + +##### 240.21(B)(1) Taps Not over 3 m (10 ft) Long. + +If the length of the tap conductors does not exceed 3 m (10 ft) +and the tap conductors comply with all of the following: + +* (1) The ampacity of the tap conductors is + * a. Not less than the combined calculated loads on the circuits supplied by the tap conductors + * b. Not less than the rating of the equipment containing an overcurrent device(s) supplied by the tap conductors + or not less than the rating of the overcurrent protective device at the termination of the tap conductors + + > [!important] Exception to b: + > Where listed equipment, such as a surge-protective device(s) \[SPD(s)\], + > is provided with specific instructions on minimum conductor sizing, + > the ampacity of the tap conductors supplying that equipment + > shall be permitted to be determined based on the manufacturer's instructions. + +* (2) The tap conductors do not extend beyond the switchboard, + switchgear, panelboard, disconnecting means, + or control devices they supply. + +* (3) Except at the point of connection to the feeder, + the tap conductors are enclosed in a raceway, + which extends from the tap to the enclosure of an enclosed switchboard, + switchgear, a panelboard, or control devices, + or to the back of an open switchboard. + +* (4) For field installations, + if the tap conductors leave the enclosure or vault in which the tap is made, + the ampacity of the tap conductors is not less than one-tenth of the rating + of the overcurrent device protecting the feeder conductors. + +> [!info] Informational Note: +> For overcurrent protection requirements for panelboards, see 408.36. + +##### 240.21(B)(2) Taps Not over 7.5 m (25 ft) Long. + +Where the length of the tap conductors does not exceed 7.5 m (25 ft) +and the tap conductors comply with all the following: + +* (1) The ampacity of the tap conductors is not less than one-third of the rating of the overcurrent device protecting the feeder conductors. + +* (2) The tap conductors terminate in a single circuit breaker or a single set of fuses + that limit the load to the ampacity of the tap conductors. + This device shall be permitted to supply any number of additional overcurrent devices on its load side. + +* (3) The tap conductors are protected from physical damage by being enclosed in an approved raceway or by other approved means. + +##### 240.21(B)(3) Taps Supplying a Transformer \[Primary Plus Secondary Not over 7.5 m (25 ft) Long\]. + +Where the tap conductors supply a transformer and comply with all the following conditions: + +* (1) The conductors supplying the primary of a transformer have an ampacity + at least one-third the rating of the overcurrent device + protecting the feeder conductors. + +* (2) The conductors supplied by the secondary of the transformer shall have an ampacity + that is not less than the value of the primary-to-secondary voltage ratio + multiplied by one-third of the rating of the overcurrent device + protecting the feeder conductors. + +* (3) The total length of one primary plus one secondary conductor, + excluding any portion of the primary conductor that is protected at its ampacity, + is not over 7.5 m (25 ft). + +* (4) The primary and secondary conductors are protected from physical damage + by being enclosed in an approved raceway or by other approved means. + +* (5) The secondary conductors terminate in a single circuit breaker or set of fuses + that limit the load current to not more than the conductor ampacity that is permitted by 310.14. + +##### 240.21(B)(4) Taps over 7.5 m (25 ft) Long. + +Where the feeder is in a high bay manufacturing building +over 11 m (35 ft) high at walls +and the installation complies with all the following conditions: + +* (1) Conditions of maintenance and supervision + ensure that only qualified persons service the systems. + +* (2) The tap conductors are not over 7.5 m (25 ft) long horizontally + and not over 30 m (100 ft) total length. + +* (3) The ampacity of the tap conductors + is not less than one-third the rating of the overcurrent device + protecting the feeder conductors. + +* (4) The tap conductors terminate at a single circuit breaker or a single set of fuses + that limit the load to the ampacity of the tap conductors. + This single overcurrent device + shall be permitted to supply any number of additional overcurrent devices + on its load side. + +* (5) The tap conductors are protected from physical damage + by being enclosed in an approved raceway or by other approved means. + +* (6) The tap conductors are continuous from end-to-end and contain no splices. + +* (7) The tap conductors are sized 6 AWG copper or 4 AWG aluminum or larger. + +* (8) The tap conductors do not penetrate walls, floors, or ceilings. + +* (9) The tap is made no less than 9 m (30 ft) from the floor. + +##### 240.21(B)(5) Outside Taps of Unlimited Length. + +Where the conductors are located outside of a building or structure, +except at the point of load termination, +and comply with all of the following conditions: + +* (1) The tap conductors are protected from physical damage in an approved manner. + +* (2) The tap conductors terminate at a single circuit breaker or a single set of fuses + that limits the load to the ampacity of the tap conductors. + This single overcurrent device + shall be permitted to supply any number of additional overcurrent devices + on its load side. + +* (3) The overcurrent device for the tap conductors + is an integral part of a disconnecting means + or shall be located immediately adjacent thereto. + +* (4) The disconnecting means for the tap conductors + is installed at a readily accessible location complying with one of the following: + + * a. Outside of a building or structure + * b. Inside, nearest the point of entrance of the tap conductors + * c. Where installed in accordance with 230.6, nearest the point of entrance of the tap conductors + +#### 240.21(C) Transformer Secondary Conductors. + +A set of conductors feeding a single load, or each set of conductors feeding separate loads, shall be permitted to be connected to a transformer secondary, without overcurrent protection at the secondary, as specified in 240.21(C)(1) through (C)(6). Section 240.4(B) shall not be permitted for transformer secondary conductors. + +> [!info] Informational Note: +> For overcurrent protection requirements for transformers, see 450.3. + +##### 240.21(C)(1) Protection by Primary Overcurrent Device. + +Conductors supplied by the secondary side +of a single-phase transformer having a 2-wire (single-voltage) secondary, +or a three-phase, delta-delta connected transformer having a 3-wire (single-voltage) secondary, +shall be permitted to be protected by overcurrent protection +provided on the primary (supply) side of the transformer, +provided this protection is in accordance with 450.3 +and does not exceed the value determined by multiplying the secondary conductor ampacity +by the secondary-to-primary transformer voltage ratio. + +Single-phase (other than 2-wire) and multiphase (other than delta-delta, 3-wire) transformer secondary conductors are not considered to be protected by the primary overcurrent protective device. + +##### 240.21(C)(2) Transformer Secondary Conductors Not over 3 m (10 ft) Long. + +If the length of secondary conductor does not exceed 3 m (10 ft) and complies with all of the following: + +* (1) The ampacity of the secondary conductors is + * a. Not less than the combined calculated loads on the circuits supplied by the secondary conductors, and + * b. Not less than the rating of the equipment containing an overcurrent device(s) supplied by the secondary conductors + or not less than the rating of the overcurrent protective device at the termination of the secondary conductors. + + > [!important] Exception: + > Where listed equipment, such as a surge protective device(s) \[SPD(s)\], + > is provided with specific instructions on minimum conductor sizing, + > the ampacity of the tap conductors supplying that equipment + > shall be permitted to be determined based on the manufacturer's instructions. + +* (2) The secondary conductors do not extend beyond the switchboard, switchgear, panelboard, disconnecting means, or control devices they supply. + +* (3) The secondary conductors are enclosed in a raceway, which shall extend from the transformer to the enclosure of an enclosed switchboard, switchgear, a panelboard, or control devices or to the back of an open switchboard. + +* (4) For field installations where the secondary conductors leave the enclosure or vault in which the supply connection is made, the rating of the overcurrent device protecting the primary of the transformer, multiplied by the primary to secondary transformer voltage ratio, shall not exceed 10 times the ampacity of the secondary conductor. + +> [!info] Informational Note: +> For overcurrent protection requirements for panelboards, see 408.36. + +##### 240.21(C)(3) Industrial Installation Secondary Conductors Not over 7.5 m (25 ft) Long. + +For the supply of switchgear or switchboards in industrial installations only, where the length of the secondary conductors does not exceed 7.5 m (25 ft) and complies with all of the following: + +* (1) Conditions of maintenance and supervision ensure that only qualified persons service the systems. + +* (2) The ampacity of the secondary conductors is not less than the secondary current rating of the transformer, and the sum of the ratings of the overcurrent devices does not exceed the ampacity of the secondary conductors. + +* (3) All overcurrent devices are grouped. + +* (4) The secondary conductors are protected from physical damage by being enclosed in an approved raceway or by other approved means. + +##### 240.21(C)(4) Outside Secondary Conductors. + +Where the conductors are located outside of a building or structure, except at the point of load termination, and comply with all of the following conditions: + +* (1) The conductors are protected from physical damage in an approved manner. + +* (2) The conductors terminate at a single circuit breaker or a single set of fuses that limit the load to the ampacity of the conductors. + +This single overcurrent device shall be permitted to supply any number of additional overcurrent devices on its load side. + +* (3) The overcurrent device for the conductors is an integral part of a disconnecting means or shall be located immediately adjacent thereto. + +* (4) The disconnecting means for the conductors is installed at a readily accessible location complying with one of the following: + * a. Outside of a building or structure + * b. Inside, nearest the point of entrance of the conductors + * c. Where installed in accordance with 230.6, nearest the point of entrance of the conductors + +##### 240.21(C)(5) Secondary Conductors from a Feeder Tapped Transformer. + +Transformer secondary conductors installed in accordance with 240.21(B)(3) shall be permitted to have overcurrent protection as specified in that section. + +##### 240.21(C)(6) Secondary Conductors Not over 7.5 m (25 ft) Long. + +Where the length of secondary conductor does not exceed 7.5 m (25 ft) and complies with all of the following: + +* (1) The secondary conductors shall have an ampacity that is not less than the value of the primary-to-secondary voltage ratio multiplied by one-third of the rating of the overcurrent device protecting the primary of the transformer. + +* (2) The secondary conductors terminate in a single circuit breaker or set of fuses that limit the load current to not more than the conductor ampacity that is permitted by 310.14. + +* (3) The secondary conductors are protected from physical damage by being enclosed in an approved raceway or by other approved means. + +#### 240.21(D) Service Conductors. + +Service conductors shall be permitted to be protected by overcurrent devices in accordance with 230.91. + +#### 240.21(E) Busway Taps. + +Busways and busway taps shall be permitted to be protected against overcurrent in accordance with 368.17. + +#### 240.21(F) Motor Circuit Taps. + +Motor-feeder and branch-circuit conductors shall be permitted to be protected against overcurrent in accordance with 430.28 and 430.53, respectively. + +#### 240.21(G) Conductors from Generator Terminals. + +Conductors from generator terminals that meet the size requirement in 445.13 shall be permitted to be protected against overload by the generator overload protective device(s) required by 445.12. + +#### 240.21(H) Battery Conductors. + +Overcurrent protection shall be permitted to be installed as close as practicable to the storage battery terminals in an unclassified location. Installation of the overcurrent protection within a hazardous (classified) location shall also be permitted. + +### 240.22 Grounded Conductor. + +No overcurrent device shall be connected in series with any conductor that is intentionally grounded, unless one of the following two conditions is met: + +* (1) The overcurrent device opens all conductors of the circuit, including the grounded conductor, and is designed so that no pole can operate independently. + +* (2) Where required by 430.36 or 430.37 for motor overload protection. + +### 240.24 Location in or on Premises. + +#### 240.24(A) Accessibility. + +Circuit breakers and switches containing fuses shall be readily accessible and installed so that the center of the grip of the operating handle of the switch or circuit breaker, when in its highest position, is not more than 2.0 m (6 ft 7 in.) above the floor or working platform, unless one of the following applies: + +* (1) For busways, as provided in 368.17(C). + +* (2) For supplementary overcurrent protection, as described in 240.10. + +* (3) For overcurrent devices, as described in 225.40 and 230.92. + +* (4) For overcurrent devices adjacent to utilization equipment that they supply, access shall be permitted to be by portable means. + +> [!important] Exception: +> The use of a tool shall be permitted to access overcurrent devices located within listed industrial control panels or similar enclosures. + +#### 240.24(B) Occupancy. + +Each occupant shall have ready access to all overcurrent devices protecting the conductors supplying that occupancy, unless otherwise permitted in 240.24(B)(1) and (B) (2). + +##### 240.24(B)(1) Service and Feeder Overcurrent Devices. + +Where electric service and electrical maintenance are provided by the building management and where these are under continuous building management supervision, the service overcurrent devices and feeder overcurrent devices supplying more than one occupancy shall be permitted to be accessible only to authorized management personnel in the following: + +* (1) Multiple-occupancy buildings +* (2) Guest rooms or guest suites + +##### 240.24(B)(2) Branch-Circuit Overcurrent Devices. + +Where electric service and electrical maintenance are provided by the building management and where these are under continuous building management supervision, the branch-circuit overcurrent devices supplying any guest rooms or guest suites without permanent provisions for cooking shall be permitted to be accessible only to authorized management personnel. + +#### 240.24(C) Not Exposed to Physical Damage. + +Overcurrent devices shall be located where they will not be exposed to physical damage. + +> [!info] Informational Note: +> See [[nfpa-70_110_requirements-for-electrical-installations#110.11 Deteriorating Agents.|110.11, Deteriorating Agents]] + +#### 240.24(D) Not in Vicinity of Easily Ignitible Material. + +Overcurrent devices shall not be located in the vicinity of easily ignitible material, such as in clothes closets. + +#### 240.24(E) Not Located in Bathrooms. + +In dwelling units, dormitory units, and guest rooms or guest suites, overcurrent devices, other than supplementary overcurrent protection, shall not be located in bathrooms. + +#### 240.24(F) Not Located over Steps. + +Overcurrent devices shall not be located over steps of a stairway. + +## Part III. Enclosures + +### 240.30 General. + +#### 240.30(A) Protection from Physical Damage. + +Overcurrent devices shall be protected from physical damage by one of the following: + +* (1) Installation in enclosures, cabinets, cutout boxes, or equipment assemblies + +* (2) Mounting on open-type switchboards, panelboards, or control boards that are in rooms or enclosures free from dampness and easily ignitible material and are accessible only to qualified personnel + +#### 240.30(B) Operating Handle. + +The operating handle of a circuit breaker shall be permitted to be accessible without opening a door or cover. + +### 240.32 Damp or Wet Locations. + +Enclosures for overcurrent devices in damp or wet locations shall comply with 312.2. + +### 240.33 Vertical Position. + +Enclosures for overcurrent devices shall be mounted in a vertical position. +Circuit breaker enclosures shall be permitted to be installed horizontally +where the circuit breaker is installed in accordance with 240.81. +Listed busway plug-in units shall be permitted to be mounted +in orientations corresponding to the busway mounting position. + +## Part IV. Disconnecting and Guarding + +### 240.40 Disconnecting Means for Fuses. + +Cartridge fuses in circuits of any voltage, +and all fuses in circuits over 150 volts to ground, +shall be provided with a disconnecting means on their supply side +so that each circuit containing fuses +can be independently disconnected from the source of power. +A cable limiter without a disconnecting means +shall be permitted on the supply side of the service disconnecting means +as permitted by 230.82. + +A single disconnecting means +shall be permitted on the supply side of more than one set of fuses +as permitted by 430.112, Exception, +for group operation of motors, 424.22(C) for fixed electric space-heating equipment, and 425.22(C) for fixed resistance and electrode industrial process heating equipment, or where specifically permitted elsewhere in this Code. + +### 240.41 Arcing or Suddenly Moving Parts. + +Arcing or suddenly moving parts shall comply with 240.41(A) and (B). + +#### 240.41(A) Location. + +Fuses and circuit breakers shall be located or shielded so that persons will not be burned or otherwise injured by their operation. + +#### 240.41(B) Suddenly Moving Parts. + +Handles or levers of circuit breakers, and similar parts that may move suddenly in such a way that persons in the vicinity are likely to be injured by being struck by them, shall be guarded or isolated. + +## Part V. Plug Fuses, Fuseholders, and Adapters + +### 240.50 General. + +#### 240.50(A) Maximum Voltage. + +Plug fuses shall be permitted to be used in the following circuits: + +* (1) Circuits not exceeding 125 volts between conductors + +* (2) Circuits supplied by a system having a grounded neutral point + where the line-to-neutral voltage does not exceed 150 volts + +#### 240.50(B) Marking. + +Each fuse, fuseholder, and adapter shall be marked with its ampere rating. + +#### 240.50(C) Hexagonal Configuration. + +Plug fuses of 15-ampere and lower rating shall be identified by a hexagonal configuration of the window, cap, or other prominent part to distinguish them from fuses of higher ampere ratings. + +#### 240.50(D) No Energized Parts. + +Plug fuses, fuseholders, and adapters shall have no exposed energized parts after fuses or fuses and adapters have been installed. + +#### 240.50(E) Screw Shell. + +The screw shell of a plug-type fuseholder shall be connected to the load side of the circuit. + +### 240.51 Edison-Base Fuses. + +#### 240.51(A) Classification. + +Plug fuses of the Edison-base type shall be classified at not over 125 volts and 30 amperes and below. + +#### 240.51(B) Replacement Only. + +Plug fuses of the Edison-base type shall be used only for replacements in existing installations where there is no evidence of overfusing or tampering. + +### 240.52 Edison-Base Fuseholders. + +Fuseholders of the Edison-base type shall be installed only where they are made to accept Type S fuses by the use of adapters. + +### 240.53 Type S Fuses. + +Type S fuses shall be of the plug type and shall comply with 240.53(A) and (B). + +#### 240.53(A) Classification. + +Type S fuses shall be classified at not over 125 volts and 0 to 15 amperes, 16 to 20 amperes, and 21 to 30 amperes. + +#### 240.53(B) Noninterchangeable. + +Type S fuses of an ampere classification as specified in 240.53(A) shall not be interchangeable with a lower ampere classification. They shall be designed so that they cannot be used in any fuseholder other than a Type S fuseholder or a fuseholder with a Type S adapter inserted. + +### 240.54 Type S Fuses, Adapters, and Fuseholders. + +#### 240.54(A) To Fit Edison-Base Fuseholders. + +Type S adapters shall fit Edison-base fuseholders. + +#### 240.54(B) To Fit Type S Fuses Only. + +Type S fuseholders and adapters shall be designed so that either the fuseholder itself or the fuseholder with a Type S adapter inserted cannot be used for any fuse other than a Type S fuse. + +#### 240.54(C) Nonremovable. + +Type S adapters shall be designed so that once inserted in a fuseholder, they cannot be removed. + +#### 240.54(D) Nontamperable. + +Type S fuses, fuseholders, and adapters shall be designed so that tampering or shunting (bridging) would be difficult. + +#### 240.54(E) Interchangeability. + +Dimensions of Type S fuses, fuseholders, and adapters shall be standardized to permit interchangeability regardless of the manufacturer. + +## Part VI. Cartridge Fuses and Fuseholders + +### 240.60 General. + +#### 240.60(A) Maximum Voltage --- 300-Volt Type. + +Cartridge fuses and fuseholders of the 300-volt type shall be permitted to be used in the following circuits: + +* (1) Circuits not exceeding 300 volts between conductors + +* (2) Single-phase line-to-neutral circuits + supplied from a 3-phase, 4-wire, solidly grounded neutral source + where the line-to-neutral voltage does not exceed 300 volts + +#### 240.60(B) Noninterchangeable --- 0--6000-Ampere Cartridge Fuseholders. + +Fuseholders shall be designed so that it will be difficult to put a fuse of any given class into a fuseholder that is designed for a current lower, or voltage higher, than that of the class to which the fuse belongs. Fuseholders for current-limiting fuses shall not permit insertion of fuses that are not current-limiting. + +#### 240.60(C) Marking. + +Fuses shall be plainly marked, either by printing on the fuse barrel or by a label attached to the barrel showing the following: + +* (1) Ampere rating +* (2) Voltage rating +* (3) Interrupting rating where other than 10,000 amperes +* (4) Current limiting where applicable +* (5) The name or trademark of the manufacturer + +The interrupting rating shall not be required to be marked on fuses used for supplementary protection. + +#### 240.60(D) Renewable Fuses. + +Class H cartridge fuses of the renewable type shall be permitted to be used only for replacement in existing installations where there is no evidence of overfusing or tampering. + +### 240.61 Classification. + +Cartridge fuses and fuseholders shall be classified according to voltage and amperage ranges. Fuses rated 1000 volts, nominal, or less shall be permitted to be used for voltages at or below their ratings. + +### 240.62 Reconditioned Equipment. + +Low-voltage fuseholders and low-voltage nonrenewable fuses shall not be permitted to be reconditioned. + +### 240.67 Arc Energy Reduction. + +Where fuses rated 1200 A or higher are installed, 240.67(A) and (B) shall apply. This requirement shall become effective January 1, + +#### 240.67(A) Documentation. + +Documentation shall be available to those authorized to design, install, operate, or inspect the installation as to the location of the fuses. + +Documentation shall also be provided to demonstrate that the method chosen to reduce clearing time is set to operate at a value below the available arcing current. + +#### 240.67(B) Method to Reduce Clearing Time. + +A fuse shall have a clearing time of 0.07 seconds or less at the available arcing current, or one of the following means shall be provided and shall be set to operate at less than the available arcing current: + +* (1) Differential relaying +* (2) Energy-reducing maintenance switching with local status indicator +* (3) Energy-reducing active arc-flash mitigation system +* (4) Current-limiting, electronically actuated fuses +* (5) An approved equivalent means + +> [!info] Informational Note No. 1: +> An energy-reducing maintenance switch +> allows a worker to set a disconnect switch +> to reduce the clearing time while the worker is working within an arc-flash boundary +> as defined in NFPA 70E-2018, Standard for Electrical Safety in the Workplace, +> and then to set the disconnect switch back to a normal setting +> after the potentially hazardous work is complete. + +> [!info] Informational Note No. 2: +> An energy-reducing active arc-flash mitigation system +> helps in reducing arcing duration in the electrical distribution system. +> No change in the disconnect switch or the settings of other devices +> is required during maintenance when a worker is working within an arc-flash boundary +> as defined in NFPA 70E-2018, Standard for Electrical Safety in the Workplace. + +> [!info] Informational Note No. 3: +> IEEE 1584-2002, IEEE Guide for Performing Arc Flash Hazard Calculations, +> is one of the available methods +> that provides guidance in determining arcing current. + +#### 240.67(C) Performance Testing. + +The arc energy reduction protection system +shall be performance tested by primary current injection testing +or another approved method when first installed on site. +This testing shall be conducted by a qualified person(s) +in accordance with the manufacturer's instructions. + +A written record of this testing +shall be made and shall be available to the authority having jurisdiction. + +> [!info] Informational Note: +> Some energy reduction protection systems cannot be tested +> using a test process of primary current injection +> due to either the protection method being damaged +> such as with the use of fuse technology +> or because current is not the primary method of arc detection. + +## Part VII. Circuit Breakers + +### 240.80 Method of Operation. + +Circuit breakers shall be trip free and capable of being closed and opened by manual operation. Their normal method of operation by other than manual means, such as electrical or pneumatic, shall be permitted if means for manual operation are also provided. + +### 240.81 Indicating. + +Circuit breakers shall clearly indicate whether they are in the open "off" or closed "on" position. + +Where circuit breaker handles are operated vertically rather than rotationally or horizontally, the "up" position of the handle shall be the "on" position. + +### 240.82 Nontamperable. + +A circuit breaker shall be of such design that any alteration of its trip point (calibration) or the time required for its operation requires dismantling of the device or breaking of a seal for other than intended adjustments. + +### 240.83 Marking. + +#### 240.83(A) Durable and Visible. + +Circuit breakers shall be marked with their ampere rating in a manner that will be durable and visible after installation. Such marking shall be permitted to be made visible by removal of a trim or cover. + +#### 240.83(B) Location. + +Circuit breakers rated at 100 amperes or less and 1000 volts or less shall have the ampere rating molded, stamped, etched, or similarly marked into their handles or escutcheon areas. + +#### 240.83(C) Interrupting Rating. + +Every circuit breaker having an interrupting rating other than 5000 amperes shall have its interrupting rating shown on the circuit breaker. The interrupting rating shall not be required to be marked on circuit breakers used for supplementary protection. + +#### 240.83(D) Used as Switches. + +Circuit breakers used as switches in 120- volt and 277-volt fluorescent lighting circuits shall be listed and shall be marked SWD or HID. + +Circuit breakers used as switches in high-intensity discharge lighting circuits shall be listed and shall be marked as HID. + +#### 240.83(E) Voltage Marking. + +Circuit breakers shall be marked with a voltage rating not less than the nominal system voltage that is indicative of their capability to interrupt fault currents between phases or phase to ground. + +### 240.85 Applications. + +A circuit breaker with a straight voltage rating, such as 240V or 480V, shall be permitted to be applied in a circuit in which the nominal voltage between any two conductors does not exceed the circuit breaker's voltage rating. A two-pole circuit breaker shall not be used for protecting a 3- phase, corner-grounded delta circuit unless the circuit breaker is marked 1φ--3φ to indicate such suitability. + +A circuit breaker with a slash rating, such as 120/240V or 480Y/277V, shall be permitted to be applied in a solidly grounded circuit where the nominal voltage of any conductor to ground does not exceed the lower of the two values of the circuit breaker's voltage rating and the nominal voltage between any two conductors does not exceed the higher value of the circuit breaker's voltage rating. + +> [!info] Informational Note: +> Proper application of molded case circuit breakers on 3-phase systems, other than solidly grounded wye, particularly on corner grounded delta systems, considers the circuit breakers' individual pole-interrupting capability. + +### 240.86 Series Ratings. + +Where a circuit breaker is used on a circuit having an available fault current higher than the marked interrupting rating by being connected on the load side of an approved overcurrent protective device having a higher rating, the circuit breaker shall meet the requirements specified in 240.86(A) or (B), and (C). + +#### 240.86(A) Selected Under Engineering Supervision in Existing Installations. + +The series rated combination devices shall be selected by a licensed professional engineer engaged primarily in the design or maintenance of electrical installations. The selection shall be documented and stamped by the professional engineer. This documentation shall be available to those authorized to design, install, inspect, maintain, and operate the system. This series combination rating, including identification of the upstream device, shall be field marked on the end use equipment. + +For calculated applications, the engineer shall ensure that the downstream circuit breaker(s) that are part of the series combination remain passive during the interruption period of the line side fully rated, current-limiting device. + +#### 240.86(B) Tested Combinations. + +The combination of line-side overcurrent device and load-side circuit breaker(s) is tested and marked on the end use equipment, such as switchboards and panelboards. + +Informational Note to (A) and (B): See 110.22 for marking of series combination systems. + +#### 240.86(C) Motor Contribution. + +Series ratings shall not be used where + +* (1) Motor circuits are connected between the higher-rated overcurrent device of a series-rated combination and on the lower-rated circuit breaker, and + +* (2) The sum of these motor full-load currents exceeds 1 percent of the interrupting rating of the lower-rated circuit breaker. + +### 240.87 Arc Energy Reduction. + +Where the highest continuous current trip setting for which the actual overcurrent device installed in a circuit breaker is rated or can be adjusted is 1200 A or higher, 240.87(A) and (B) shall apply. + +#### 240.87(A) Documentation. + +Documentation shall be available to those authorized to design, install, operate, or inspect the installation as to the location of the circuit breaker(s). Documentation shall also be provided to demonstrate that the method chosen to reduce clearing time is set to operate at a value below the available arcing current. + +#### 240.87(B) Method to Reduce Clearing Time. + +One of the following means shall be provided +and shall be set to operate at less than the available arcing current: + +* (1) Zone-selective interlocking + +* (2) Differential relaying + +* (3) Energy-reducing maintenance switching with local status indicator + +* (4) Energy-reducing active arc flash mitigation system + +* (5) An instantaneous trip setting. + Temporary adjustment of the instantaneous trip setting + to achieve arc energy reduction shall not be permitted. + +* (6) An instantaneous override + +* (7) An approved equivalent means + +> [!info] Informational Note No. 1: +> An energy-reducing maintenance switch allows a worker to set a circuit breaker trip unit to "no intentional delay" to reduce the clearing time while the worker is working within an arc-flash boundary as defined in NFPA 70E-2018, Standard for Electrical Safety in the Workplace, and then to set the trip unit back to a normal setting after the potentially hazardous work is complete. + +> [!info] Informational Note No. 2: +> An energy-reducing active arc-flash mitigation system helps in reducing arcing duration in the electrical distribution system. No change in the circuit breaker or the settings of other devices is required during maintenance when a worker is working within an arc-flash boundary as defined in NFPA 70E-2018, Standard for Electrical Safety in the Workplace. + +> [!info] Informational Note No. 3: +> An instantaneous trip is a function that causes a circuit breaker to trip with no intentional delay when currents exceed the instantaneous trip setting or current level. If arcing currents are above the instantaneous trip level, the circuit breaker will trip in the minimum possible time. + +> [!info] Informational Note No. 4: +> IEEE 1584-2002, IEEE Guide for Performing Arc Flash Hazard Calculations, is one of the available methods that provide guidance in determining arcing current. + +#### 240.87(C) Performance Testing. + +The arc energy reduction protection system shall be performance tested by primary current injection testing or another approved method when first installed on site. This testing shall be conducted by a qualified person(s) in accordance with the manufacturer's instructions. + +A written record of this testing shall be made and shall be available to the authority having jurisdiction. + +> [!info] Informational Note: +> Some energy reduction protection systems cannot be tested using a test process of primary current injection due to either the protection method being damaged such as with the use of fuse technology or because current is not the primary method of arc detection. + +### 240.88 Reconditioned Equipment. + +Reconditioned equipment shall be listed as "reconditioned" and the original listing mark removed. + +#### 240.88(A) Circuit Breakers. + +The use of reconditioned circuit breakers shall comply with (1) through (3): + +* (1) Molded-case circuit breakers shall not be permitted to be reconditioned. + +* (2) Low- and medium-voltage power circuit breakers shall be permitted to be reconditioned. + +* (3) High-voltage circuit breakers shall be permitted to be reconditioned. + +#### 240.88(B) Components. + +The use of reconditioned trip units, protective relays, and current transformers shall comply with (1) and (2): + +* (1) Low-voltage power circuit breaker electronic trip units shall not be permitted to be reconditioned. + +* (2) Electromechanical protective relays and current transformers shall be permitted to be reconditioned. + +## Part VIII. Supervised Industrial Installations + +### 240.90 General. + +Overcurrent protection in areas of supervised industrial installations shall comply with all of the other applicable provisions of this article, except as provided in Part VIII. Part VIII shall be permitted to apply only to those portions of the electrical system in the supervised industrial installation used exclusively for manufacturing or process control activities. + +### 240.91 Protection of Conductors. + +Conductors shall be protected in accordance with 240.91(A) or 240.91(B). + +#### 240.91(A) General. + +Conductors shall be protected in accordance with 240.4. + +#### 240.91(B) Devices Rated Over 800 Amperes. + +Where the overcurrent device is rated over 800 amperes, the ampacity of the conductors it protects shall be equal to or greater than +95 percent of the rating of the overcurrent device in accordance with the following: + +* (1) The conductors are protected within recognized time vs. current limits for short-circuit currents + +> [!info] Informational Note: +> Table 240.92(B) provides time vs. short-circuit current formulas to determine limits for copper and aluminum conductors. + +* (2) All equipment in which the conductors terminate is listed and marked for the application. + +### 240.92 Location in Circuit. + +An overcurrent device shall be connected in each ungrounded circuit conductor as required in 240.92(A) through (E). + +#### 240.92(A) Feeder and Branch-Circuit Conductors. + +Feeder and branch-circuit conductors shall be protected at the point the conductors receive their supply as permitted in 240.21 or as otherwise permitted in 240.92(B), (C), (D), or (E). + +#### 240.92(B) Feeder Taps. + +For feeder taps specified in 240.21(B)(2), (B)(3), and (B)(4), the tap conductors shall be permitted to be sized in accordance with Table +240.92(B). + +Table 240.92(B) Tap Conductor Short-Circuit Current Ratings + +Tap conductors are considered to be protected under short-circuit conditions when their short-circuit temperature limit is not exceeded. + +Conductor heating under short-circuit conditions is determined by (1) or (2): + +* (1) _Short-Circuit Formula for Copper Conductors_ + + $$ + (I^2|A^2)t = 0.0297 \log_{10} [(T_{2} + 234)/(T_{1} + 234)] + $$ + +* (2) _Short-Circuit Formula for Aluminum Conductor_ + + $$ + (I^2|A^2)t = 0.0125 \log_{10} [(T_{2} + 228)/(T_{1} + 228)] + $$ + +where: + +$I$ = short-circuit current in amperes + +$A$ = conductor area in circular mils + +$t$ = time of short circuit in seconds +(for times less than or equal to 10 seconds) + +$T_{1}$ = initial conductor temperature in degrees Celsius + +$T_{2}$ = final conductor temperature in degrees Celsius + +Copper conductor with paper, rubber, varnished cloth insulation, $T_{2}$ = 200 + +Copper conductor with thermoplastic insulation, $T_{2}$ = 150 + +Copper conductor with cross-linked polyethylene insulation, $T_{2}$ = 250 + +Copper conductor with ethylene propylene rubber insulation, $T_{2}$ = 250 + +Aluminum conductor with paper, rubber, varnished cloth insulation, $T_{2}$ = 200 + +Aluminum conductor with thermoplastic insulation, $T_{2}$ = 150 + +Aluminum conductor with cross-linked polyethylene insulation, $T_{2}$ = 250 + +Aluminum conductor with ethylene propylene rubber insulation, $T_{2}$ = 250 + +#### 240.92(C) Transformer Secondary Conductors of Separately Derived Systems. + +Conductors shall be permitted to be connected to a transformer secondary of a separately derived system, without overcurrent protection at the connection, where the conditions of 240.92(C)(1), (C)(2), and (C)(3) are met. + +##### 240.92(C)(1) Short-Circuit and Ground-Fault Protection. + +The conductors shall be protected from short-circuit and ground-fault conditions by complying with one of the following conditions: + +* (1) The length of the secondary conductors does not exceed 30 m (100 ft), and the transformer primary overcurrent device has a rating or setting that does not exceed 150 percent of the value determined by multiplying the secondary conductor ampacity by the secondary-to-primary transformer voltage ratio. + +* (2) The conductors are protected by a differential relay with a trip setting equal to or less than the conductor ampacity. + + > [!info] Informational Note: + > A differential relay is connected to be sensitive only to short-circuit or fault currents within the protected zone and is normally set much lower than the conductor ampacity. The differential relay is connected to trip protective devices that deenergize the protected conductors if a short-circuit condition occurs. + +* (3) The conductors shall be considered to be protected if calculations, made under engineering supervision, determine that the system overcurrent devices will protect the conductors within recognized time vs. current limits for all short-circuit and groundfault conditions. + +##### 240.92(C)(2) Overload Protection. + +The conductors shall be protected against overload conditions by complying with one of the following: + +* (1) The conductors terminate in a single overcurrent device that will limit the load to the conductor ampacity. + +* (2) The sum of the overcurrent devices at the conductor termination limits the load to the conductor ampacity. The overcurrent devices shall consist of not more than six circuit breakers or sets of fuses mounted in a single enclosure, in a group of separate enclosures, or in or on a switchboard or switchgear. There shall be no more than six overcurrent devices grouped in any one location. + +* (3) Overcurrent relaying is connected \[with a current transformer(s), if needed\] to sense all of the secondary conductor current and limit the load to the conductor ampacity by opening upstream or downstream devices. + +* (4) Conductors shall be considered to be protected if calculations, made under engineering supervision, determine that the system overcurrent devices will protect the conductors from overload conditions. + +##### 240.92(C)(3) Physical Protection. + +The secondary conductors are protected from physical damage by being enclosed in an approved raceway or by other approved means. + +#### 240.92(D) Outside Feeder Taps. + +Outside conductors shall be permitted to be tapped to a feeder or to be connected at a transformer secondary, without overcurrent protection at the tap or connection, where all the following conditions are met: + +* (1) The conductors are protected from physical damage in an approved manner. + +* (2) The sum of the overcurrent devices at the conductor termination limits the load to the conductor ampacity. The overcurrent devices shall consist of not more than six circuit breakers or sets of fuses mounted in a single enclosure, in a group of separate enclosures, or in or on a switchboard or switchgear. There shall be no more than six overcurrent devices grouped in any one location. + +* (3) The tap conductors are installed outdoors of a building or structure except at the point of load termination. + +* (4) The overcurrent device for the conductors is an integral part of a disconnecting means or is located immediately adjacent thereto. + +* (5) The disconnecting means for the conductors are installed at a readily accessible location complying with one of the following: + * a. Outside of a building or structure + * b. Inside, nearest the point of entrance of the conductors + * c. Where installed in accordance with 230.6, nearest the point of entrance of the conductors + +#### 240.92(E) Protection by Primary Overcurrent Device. + +Conductors supplied by the secondary side of a transformer shall be permitted to be protected by overcurrent protection provided on the primary (supply) side of the transformer, provided the primary device time--current protection characteristic, multiplied by the maximum effective primary-to-secondary transformer voltage ratio, effectively protects the secondary conductors. + +## Part IX. Overcurrent Protection over 1000 Volts, Nominal + +### 240.100 Feeders and Branch Circuits. + +#### 240.100(A) Location and Type of Protection. + +Feeder and branch-circuit conductors +shall have overcurrent protection in each ungrounded conductor +located at the point where the conductor receives its supply +or at an alternative location in the circuit +when designed under engineering supervision +that includes but is not limited to considering the appropriate fault studies and time--current coordination analysis of the protective devices and the conductor damage curves. +The overcurrent protection shall be permitted to be provided by either 240.100(A)(1) or (A)(2). + +##### 240.100(A)(1) Overcurrent Relays and Current Transformers. + +Circuit breakers used for overcurrent protection of 3-phase circuits shall have a minimum of three overcurrent relay elements operated from three current transformers. The separate overcurrent relay elements (or protective functions) shall be permitted to be part of a single electronic protective relay unit. + +On 3-phase, 3-wire circuits, an overcurrent relay element in the residual circuit of the current transformers shall be permitted to replace one of the phase relay elements. + +An overcurrent relay element, operated from a current transformer that links all phases of a 3-phase, 3-wire circuit, shall be permitted to replace the residual relay element and one of the phase-conductor current transformers. Where the neutral conductor is not regrounded on the load side of the circuit as permitted in 250.184(B), the current transformer shall be permitted to link all 3-phase conductors and the grounded circuit conductor (neutral). + +##### 240.100(A)(2) Fuses. + +A fuse shall be connected in series with each ungrounded conductor. + +#### 240.100(B) Protective Devices. + +The protective device(s) shall be capable of detecting and interrupting all values of current that can occur at their location in excess of their trip-setting or melting point. + +#### 240.100(C) Conductor Protection. + +The operating time of the protective device, the available short-circuit current, and the conductor used shall be coordinated to prevent damaging or dangerous temperatures in conductors or conductor insulation under short-circuit conditions. + +### 240.101 Additional Requirements for Feeders. + +#### 240.101(A) Rating or Setting of Overcurrent Protective Devices. + +The continuous ampere rating of a fuse shall not exceed three times the ampacity of the conductors. The long-time trip element setting of a breaker or the minimum trip setting of an electronically actuated fuse shall not exceed six times the ampacity of the conductor. For fire pumps, conductors shall be permitted to be protected for overcurrent in accordance with 695.4(B)(2). + +#### 240.101(B) Feeder Taps. + +Conductors tapped to a feeder shall be permitted to be protected by the feeder overcurrent device where that overcurrent device also protects the tap conductor. + +### 240.102 Reconditioned Equipment. + +Medium-voltage fuseholders and medium-voltage nonrenewable fuses shall not be permitted to be reconditioned. diff --git a/nfpa-70_250_grounding-and-bonding.md b/nfpa-70_250_grounding-and-bonding.md index 1081f3b..f4255e8 100644 --- a/nfpa-70_250_grounding-and-bonding.md +++ b/nfpa-70_250_grounding-and-bonding.md @@ -1770,9 +1770,12 @@ The structural metal frame of a building or structure shall not be used as an eq #### 250.122(A) General. -Copper, aluminum, or copper-clad aluminum equipment grounding conductors of the wire type shall not be smaller than shown in Table -250.122. The equipment grounding conductor shall not be required to be larger than the circuit conductors supplying the equipment. If a cable tray, a raceway, or a cable armor or sheath is used as the equipment grounding conductor, as provided in 250.118 and -250.134(1), it shall comply with 250.4(A)(5) or (B)(4). +Copper, aluminum, or copper-clad aluminum equipment grounding conductors of the wire type +shall not be smaller than shown in Table 250.122. +The equipment grounding conductor shall not be required +to be larger than the circuit conductors supplying the equipment. +If a cable tray, a raceway, or a cable armor or sheath is used as the equipment grounding conductor, +as provided in 250.118 and 250.134(1), it shall comply with 250.4(A)(5) or (B)(4). Equipment grounding conductors shall be permitted to be sectioned within a multiconductor cable, provided the combined circular mil area complies with Table 250.122. @@ -1807,9 +1810,7 @@ The equipment grounding conductor in a flexible cord with the largest circuit co #### 250.122(F) Conductors in Parallel. -For circuits of parallel conductors as permitted in 310.10(G), the equipment grounding conductor shall be installed in accordance with - -##### 250.122(F)(1) or (F) (2). +For circuits of parallel conductors as permitted in 310.10(G), the equipment grounding conductor shall be installed in accordance with 250.122(F)(1) or (F) (2). ##### 250.122(F)(1) Conductor Installations in Raceways, Auxiliary Gutters, or Cable Trays. diff --git a/nfpa-70_430_motors.md b/nfpa-70_430_motors.md index 2f220e8..d59f930 100644 --- a/nfpa-70_430_motors.md +++ b/nfpa-70_430_motors.md @@ -22,7 +22,432 @@ motor branch-circuit and feeder conductors and their protection, motor overload protection, motor control circuits, motor controllers, and motor control centers. - +### 430.2 Definitions. + +The definitions in this section shall apply only within this article. + +#### Controller. + +Any switch or device that is normally used to start and stop a motor by making and breaking the motor circuit current. + +#### Electronically Protected (as applied to motors). + +A motor that is provided with electronic control that is an integral part of the motor and protects the motor against dangerous overheating due to failure of the electronic control, overload and failure to start. + +#### Part-Winding Motors. + +A part-winding start induction or synchronous motor is one that is arranged for starting by first energizing part of its primary (armature) winding and, subsequently, energizing the remainder of this winding in one or more steps. A standard part-winding start induction motor is arranged so that one-half of its primary winding can be energized initially, and, subsequently, the remaining half can be energized, both halves then carrying equal current. + +> [!info] Informational Note: +> A hermetic refrigerant motor-compressor is not considered a standard part-winding start induction motor. + +#### System Isolation Equipment. + +A redundantly monitored, remotely operated contactor-isolating system, packaged to provide the disconnection/isolation function, capable of verifiable operation from multiple remote locations by means of lockout switches, each having the capability of being padlocked in the “off” (open) position. + +#### Valve Actuator Motor (VAM) Assemblies. + +A manufactured assembly, used to operate a valve, consisting of an actuator motor and other components such as controllers, torque switches, limit switches, and overload protection. + +> [!info] Informational Note: +> VAMs typically have short-time duty and high-torque characteristics. + +### 430.4 Part-Winding Motors. + +Where separate overload devices are used with a standard part-winding start induction motor, each half of the motor winding shall be individually protected in accordance with 430.32 and 430.37 with a trip current one-half that specified. + +Each motor-winding connection shall have branch-circuit short-circuit and ground-fault protection rated at not more than one-half that specified by 430.52. + +> [!important] Exception: +> A short-circuit and ground-fault protective device shall be permitted for both windings if the device will allow the motor to start. Where time-delay (dual-element) fuses are used, they shall be permitted to have a rating not exceeding 150 percent of the motor full-load current. + +### 430.5 Other Articles. + +Motors and controllers shall also comply with the applicable provisions of Table 430.5. + +#### Table 430.5 Other Articles + +| Equipment/Occupancy | Article | Section | +| -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------- | ----------------- | +| Air-conditioning and refrigerating equipment | 440 | | +| Capacitors 460.8, | | 460.9 | +| Commercial garages; aircraft hangars; motor fuel dispensing facilities; bulk storage plants; spray application, dipping, and coating processes; and inhalation anesthetizing locations | 511, 513, 514, 515, 516, and 517 Part IV | | +| Cranes and hoists | 610 | | +| Electrically driven or controlled irrigation machines | 675 | | +| Elevators, dumbwaiters, escalators, moving walks, wheelchair lifts, and stairway chair lifts | 620 | | +| Fire pumps | 695 | | +| Hazardous (classified) locations | 500–503, 505, and 506 | | +| Industrial machinery | 670 | | +| Motion picture projectors | | 540.11 and 540.20 | +| Motion picture and television studios and similar locations | 530 | | +| Resistors and reactors | 470 | | +| Theaters, audience areas of motion picture and television studios, and similar locations | | 520.48 | +| Transformers and transformer vaults | 450 | | + +### 430.6 Ampacity and Motor Rating Determination. + +The size of conductors supplying equipment covered by Article 430 shall be selected from the ampacity tables in accordance with 310.15 or shall be calculated in accordance with 310.14(B). Where flexible cord is used, the size of the conductor shall be selected in accordance with 400.5. The required ampacity and motor ratings shall be determined as specified in 430.6(A), (B), (C), and (D). + +#### 430.6(A) General Motor Applications. + +For general motor applications, current ratings shall be determined based on 430.6(A) (1) and (A)(2). + +##### 430.6(A)(1) Table Values. + +Other than for motors built for low speeds (less than 1200 RPM) or high torques, and for multispeed motors, the values given in Table 430.247, Table 430.248, Table 430.249, and Table 430.250 shall be used to determine the ampacity of conductors or ampere ratings of switches, branch-circuit short-circuit and ground-fault protection, instead of the actual current rating marked on the motor nameplate. + +Where a motor is marked in amperes, but not horsepower, the horsepower rating shall be assumed to be that corresponding to the value given in Table 430.247, Table 430.248, Table 430.249, and Table 430.250, interpolated if necessary. Motors built for low speeds +(less than 1200 RPM) or high torques may have higher full-load currents, and multispeed motors will have full-load current varying with speed, in which case the nameplate current ratings shall be used. + +> [!important] Exception No. 1: +> Multispeed motors shall be in accordance with 430.22(B) and 430.52. + +> [!important] Exception No. 2: +> For equipment that employs a shaded-pole or permanent-split capacitor-type fan or blower motor that is marked with the motor type, the full load current for such motor marked on the nameplate of the equipment in which the fan or blower motor is employed shall be used instead of the horsepower rating to determine the ampacity or rating of the disconnecting means, the branch-circuit conductors, the controller, the branch-circuit short-circuit and ground-fault protection, and the separate overload protection. This marking on the equipment nameplate shall not be less than the current marked on the fan or blower motor nameplate. + +> [!important] Exception No. 3: +> For a listed motor-operated appliance that is marked with both motor horsepower and full-load current, the motor fullload current marked on the nameplate of the appliance shall be used instead of the horsepower rating on the appliance nameplate to determine the ampacity or rating of the disconnecting means, the branch-circuit conductors, the controller, the branch-circuit short-circuit and ground-fault protection, and any separate overload protection. + +##### 430.6(A)(2) Nameplate Values. + +Separate motor overload protection shall be based on the motor nameplate current rating. + +#### 430.6(B) Torque Motors. + +For torque motors, the rated current shall be locked-rotor current, and this nameplate current shall be used to determine the ampacity of the branch-circuit conductors covered in 430.22 and 430.24, the ampere rating of the motor overload protection, and the ampere rating of motor branch-circuit short-circuit and ground-fault protection in accordance with 430.52(B). + +> [!info] Informational Note: +> For motor controllers and disconnecting means, see 430.83(D) and 430.110. + +#### 430.6(C) Alternating-Current Adjustable Voltage Motors. + +For motors used in alternating-current, adjustable voltage, variable torque drive systems, the ampacity of conductors, or ampere ratings of switches, branch-circuit short-circuit and ground-fault protection, and so forth, shall be based on the maximum operating current marked on the motor or control nameplate, or both. If the maximum operating current does not appear on the nameplate, the ampacity determination shall be based on 150 percent of the values given in Table 430.249 and Table 430.250. + +#### 430.6(D) Valve Actuator Motor Assemblies. + +For valve actuator motor assemblies (VAMs), the rated current shall be the nameplate full-load current, and this current shall be used to determine the maximum rating or setting of the motor branch-circuit short-circuit and ground-fault protective device and the ampacity of the conductors. + +### 430.7 Marking on Motors and Multimotor Equipment. + +#### 430.7(A) Usual Motor Applications. + +A motor shall be marked with the following information: + +* (1) Manufacturer’s name. + +* (2) Rated volts and full-load current. For a multispeed motor, full-load current for each speed, except shaded-pole and permanentsplit capacitor motors where amperes are required only for maximum speed. + +* (3) Rated frequency and number of phases if an ac motor. + +* (4) Rated full-load speed. + +* (5) Rated temperature rise or the insulation system class and rated ambient temperature. + +* (6) Time rating. The time rating shall be 5, 15, 30, or 60 minutes, or continuous. + +* (7) Rated horsepower if 1⁄8 hp or more. For a multispeed motor 1⁄8 hp or more, rated horsepower for each speed, except shadedpole and permanent-split capacitor motors 1⁄8 hp or more where rated horsepower is required only for maximum speed. Motors of arc welders are not required to be marked with the horsepower rating. + +* (8) Code letter or locked-rotor amperes if an alternating-current motor rated 1⁄2 hp or more. On polyphase wound-rotor motors, the code letter shall be omitted. + +> [!info] Informational Note: +> See 430.7(B). + +* (9) Design letter for design B, C, or D motors. + +> [!info] Informational Note: +> Motor design letter definitions are found in ANSI/NEMA MG 1-1993, Motors and Generators, Part 1, + +Definitions, and in IEEE 100-1996, Standard Dictionary of Electrical and Electronic Terms. + +* (10) Secondary volts and full-load current if a wound-rotor induction motor. + +* (11) Field current and voltage for dc excited synchronous motors. + +* (12) Winding — straight shunt, stabilized shunt, compound, or series, if a dc motor. Fractional horsepower dc motors 175 mm (7 in.) or less in diameter shall not be required to be marked. + +* (13) A motor provided with a thermal protector complying with 430.32(A)(2) or (B)(2) shall be marked “thermally protected.” + +Thermally protected motors rated 100 watts or less and complying with 430.32(B)(2) shall be permitted to use the abbreviated marking “T.P.” + +* (14) A motor complying with 430.32(B)(4) shall be marked “impedance protected.” Impedance-protected motors rated 100 watts or less and complying with 430.32(B)(4) shall be permitted to use the abbreviated marking “Z.P.” + +* (15) Motors equipped with electrically powered condensation prevention heaters shall be marked with the rated heater voltage, number of phases, and the rated power in watts. + +* (16) Motors that are electronically protected from overloads in accordance with 430.32(A)(2) and (B)(2) shall be marked “electronically protected” or “E.P.” + +#### 430.7(B) Locked-Rotor Indicating Code Letters. + +Code letters marked on motor nameplates to show motor input with locked rotor shall be in accordance with Table 430.7(B). + +The code letter indicating motor input with locked rotor shall be in an individual block on the nameplate, properly designated. + +##### Table 430.7(B) Locked-Rotor Indicating Code Letters + +| Code Letter | Kilovolt-Amperes per Horsepower with Locked Rotor | +| ----------- | ------------------------------------------------- | +| A | 0–3.14 | +| B | 3.15–3.54 | +| C | 3.55–3.99 | +| D | 4.0–4.49 | +| E | 4.5–4.99 | +| F | 5.0–5.59 | +| G | 5.6–6.29 | +| H | 6.3–7.09 | +| J | 7.1–7.99 | +| K | 8.0–8.99 | +| L | 9.0–9.99 | +| M | 10.0–11.19 | +| N | 11.2–12.49 | +| P | 12.5–13.99 | +| R | 14.0–15.99 | +| S | 16.0–17.99 | +| T | 18.0–19.99 | +| U | 20.0–22.39 | +| V | 22.4 and up | + +##### 430.7(B)(1) Multispeed Motors. + +Multispeed motors shall be marked with the code letter designating the locked-rotor kilovolt-ampere (kVA) per horsepower (hp) for the highest speed at which the motor can be started. + +> [!important] Exception: +> Constant horsepower multispeed motors shall be marked with the code letter giving the highest locked-rotor kilovolt-ampere (kVA) per horsepower (hp). + +##### 430.7(B)(2) Single-Speed Motors. + +Single-speed motors starting on wye connection and running on delta connections shall be marked with a code letter corresponding to the locked-rotor kilovolt-ampere (kVA) per horsepower (hp) for the wye connection. + +##### 430.7(B)(3) Dual-Voltage Motors. + +Dual-voltage motors that have a different locked-rotor kilovolt-ampere (kVA) per horsepower (hp) on the two voltages shall be marked with the code letter for the voltage giving the highest locked-rotor kilovolt-ampere (kVA) per horsepower (hp). + +##### 430.7(B)(4) 50/60 Hz Motors. + +Motors with 50- and 60-Hz ratings shall be marked with a code letter designating the locked-rotor kilovolt-ampere (kVA) per horsepower (hp) on 60 Hz. + +##### 430.7(B)(5) Part-Winding Motors. + +Part-winding start motors shall be marked with a code letter designating the locked-rotor kilovolt-ampere (kVA) per horsepower (hp) that is based on the locked-rotor current for the full winding of the motor. + +#### 430.7(C) Torque Motors. + +Torque motors are rated for operation at standstill and shall be marked in accordance with 430.7(A), except that locked-rotor torque shall replace horsepower. + +#### 430.7(D) Multimotor and Combination-Load Equipment. + +##### 430.7(D)(1) Factory-Wired. + +Multimotor and combination-load equipment shall be provided with a visible nameplate marked with the manufacturer’s name, the rating in volts, frequency, number of phases, minimum supply circuit conductor ampacity, and the maximum ampere rating of the circuit short-circuit and ground-fault protective device. The conductor ampacity shall be calculated in accordance with 430.24 and counting all of the motors and other loads that will be operated at the same time. The short-circuit and ground-fault protective device rating shall not exceed the value calculated in accordance with 430.53. Multimotor equipment for use on two or more circuits shall be marked with the preceding information for each circuit. + +##### 430.7(D)(2) Not Factory-Wired. + +Where the equipment is not factory-wired and the individual nameplates of motors and other loads are visible after assembly of the equipment, the individual nameplates shall be permitted to serve as the required marking. + +### 430.8 Marking on Controllers. + +A controller shall be marked with the manufacturer’s name or identification, the voltage, the current or horsepower rating, the short-circuit current rating, and other necessary data to properly indicate the applications for which it is suitable. + +> [!important] Exception No. 1: +> The short-circuit current rating is not required for controllers applied in accordance with 430.81(A) or (B). + +> [!important] Exception No. 2: +> The short-circuit rating is not required to be marked on the controller when the short-circuit current rating of the controller is marked elsewhere on the assembly. + +> [!important] Exception No. 3: +> The short-circuit rating is not required to be marked on the controller when the assembly into which it is installed has a marked short-circuit current rating. + +> [!important] Exception No. 4: +> Short-circuit ratings are not required for controllers rated less than 2 hp at 300 V or less and listed exclusively for general-purpose branch circuits. + +A controller that includes motor overload protection suitable for group motor application shall be marked with the motor overload protection and the maximum branch-circuit short-circuit and ground-fault protection for such applications. + +Combination controllers that employ adjustable instantaneous trip circuit breakers shall be clearly marked to indicate the ampere settings of the adjustable trip element. + +Where a controller is built in as an integral part of a motor or of a motor-generator set, individual marking of the controller shall not be required if the necessary data are on the nameplate. For controllers that are an integral part of equipment approved as a unit, the above marking shall be permitted on the equipment nameplate. + +> [!info] Informational Note: +> See 110.10 for information on circuit impedance and other characteristics. + +### 430.9 Terminals. + +#### 430.9(A) Markings. + +Terminals of motors and controllers shall be suitably marked or colored where necessary to indicate the proper connections. + +#### 430.9(B) Conductors. + +Motor controllers and terminals of control circuit devices shall be connected with copper conductors unless identified for use with a different conductor. + +#### 430.9(C) Torque Requirements. + +Control circuit devices with screw-type pressure terminals used with 14 AWG or smaller copper conductors shall be torqued to a minimum of 0.8 N·m (7 lb- in.) unless identified for a different torque value. + +### 430.10 Wiring Space in Enclosures. + +#### 430.10(A) General. + +Enclosures for motor controllers and disconnecting means shall not be used as junction boxes, auxiliary gutters, or raceways for conductors feeding through or tapping off to the other apparatus unless designs are employed that provide adequate space for this purpose. + +> [!info] Informational Note: +> See 312.8 for switch and overcurrent-device enclosures. + +#### 430.10(B) Wire-Bending Space in Enclosures. + +Minimum wire-bending space within the enclosures for motor controllers shall be in accordance with Table 430.10(B) where measured in a straight line from the end of the lug or wire connector (in the direction the wire leaves the terminal) to the wall or barrier. Where alternate wire termination means are substituted for that supplied by the manufacturer of the controller, they shall be of a type identified by the manufacturer for use with the controller and shall not reduce the minimum wire-bending space. + +Table 430.10(B) Minimum Wire-Bending Space at the Terminals of Enclosed Motor Controllers + +Size of Wire (AWG or kcmil) Wires per Terminal +1 2 +* mm in. mm in. + +Size of Wire (AWG or kcmil) Wires per Terminal +1 2 mm in. mm in. +10 and smaller Not specified — — +8–6 38 11⁄2 — — +4–3 50 2 — — +2 65 21⁄2 — — +1 75 3 — — +1/0 125 5 125 5 +2/0 150 6 150 6 +3/0–4/0 175 7 175 7 +250 200 8 200 8 +300 250 10 250 10 +350–500 300 12 300 12 +600–700 350 14 400 16 +750–900 450 18 475 19 + +Where provision for three or more wires per terminal exists, the minimum wire-bending space shall be in accordance with the requirements of Article 312. + +### 430.11 Protection Against Liquids. + +Suitable guards or enclosures shall be provided to protect exposed current-carrying parts of motors and the insulation of motor leads where instal led directly under equipment, or in other locations where dripping or spraying oil, water, or other liquid is capable of occurring, unless the motor is designed for the existing conditions. + +### 430.12 Motor Terminal Housings. + +#### 430.12(A) Material. + +Where motors are provided with terminal housings, the housings shall be of metal and of substantial construction. + +> [!important] Exception: +> In other than hazardous (classified) locations, substantial, nonmetallic, noncombustible housings shall be permitted, provided an internal grounding means between the motor frame and the equipment grounding connection is incorporated within the housing. + +#### 430.12(B) Dimensions and Space — Wire-to-Wire Connections. + +Where these terminal housings enclose wire-to-wire connections, they shall have minimum dimensions and usable volumes in accordance with Table 430.12(B). + +##### Table 430.12(B) Terminal Housings — Wire-to-Wire Connections + +Motors 275 mm (11 in.) in Diameter or Less + +| Horsepower | Cover Opening Minimum Dimension | Usable Volume Minimum | +| --------------------------- | ------------------------------- | ----------------------------------------- | +| 1 and smallera | 41 mm (1 5⁄8 in.) | 170 cm3 (10.5 in.3) | +| 1 1⁄2, 2, and 3b | 45 mm (1 3⁄4 in.) | 275 cm3 (16.8 in.3) | +| 5 and 7 1⁄2 | 50 mm (2 in.) | 365 cm3 (22.4 in.3) | +| 10 and 15 | 65 mm (2 1⁄2 in.) | 595 cm3 (36.4 in.3) | + +Motors Over 275 mm (11 in.) in Diameter — Alternating-Current Motors + +| Maximum Full Load Current for 3-Phase Motors with Maximum of 12 Leads (Amperes) | Terminal Box Cover Opening Minimum Dimension | Usable Volume Minimum | Typical Maximum Horsepower 3-Phase, 230 Volt | Typical Maximum Horsepower 3-Phase, 460 Volt | +| ------------------------------------------------------------------------------- | -------------------------------------------- |:------------------------------------------- |:-------------------------------------------- | -------------------------------------------- | +| 45 | 65 mm (2.5 in.) | 595 cm3 (36.4 in.3) | 15 | 30 | +| 70 | 84 mm (3.3 in.) | 1265 cm3 (77 in.3) | 25 | 50 | +| 110 | 100 mm (4.0 in.) | 2295 cm3 (140 in.3) | 40 | 75 | +| 160 | 125 mm (5.0 in.) | 4135 cm3 (252 in.3) | 60 | 125 | +| 250 | 150 mm (6.0 in.) | 7380 cm3 (450 in.3) | 100 | 200 | +| 400 | 175 mm (7.0 in.) | 13775 cm3 (840 in.3) | 150 | 300 | +| 600 | 200 mm (8.0 in.) | 25255 cm3 (1540 in.3) | 250 | 500 | + +Direct-Current Motors + +| Maximum Full-Load Current for Motors with Maximum of 6 Leads (Amperes) | Terminal Box Minimum Dimensions | Usable Volume Minimum | +| ---------------------------------------------------------------------- | ------------------------------- | -------------------------------------------:| +| 68 | 65 mm (2.5 in.) | 425 cm3 (26 in.3) | +| 105 | 84 mm (3.3 in.) | 900 cm3 (55 in.3) | +| 165 | 100 mm (4.0 in.) | 1640 cm3 (100 in.3) | +| 240 | 125 mm (5.0 in.) | 2950 cm3 (180 in.3) | +| 375 | 150 mm (6.0 in.) | 5410 cm3 (330 in.3) | +| 600 | 175 mm (7.0 in.) | 9840 cm3 (600 in.3) | +| 900 | 200 mm (8.0 in.) | 18040 cm3 (1100 in.3) | + +Note: Auxiliary leads for such items as brakes, thermostats, space heaters, and exciting fields shall be permitted to be neglected if their current-carrying area does not exceed 25 percent of the current-carrying area of the machine power leads. + +aFor motors rated 1 hp and smaller, and with the terminal housing partially or wholly integral with the frame or end shield, the volume of the terminal housing shall not be less than 18.0 cm (1.1 in. ) per wire-to-wire connection. The minimum cover opening dimension is not specified. + +bFor motors rated 1 1⁄2, 2, and 3 hp, and with the terminal housing partially or wholly integral with the frame or end shield, the volume of the terminal housing shall not be less than 23.0 cm (1.4 in. ) per wire-to-wire connection. The minimum cover opening dimension is not specified. + +#### 430.12(C) Dimensions and Space — Fixed Terminal Connections. + +Where these terminal housings enclose rigidly mounted motor terminals, the terminal housing shall be of sufficient size to provide minimum terminal spacings and usable volumes in accordance with Table 430.12(C)(1) and Table 430.12(C)(2). + +##### Table 430.12(C)(1) Terminal Spacings — Fixed Terminals + +| Nominal Volts | Minimum Spacing Between Line Terminals | Minimum Spacing Between Line Terminals and Other Uninsulated Metal Parts | +| --------------- | -------------------------------------- | ------------------------------------------------------------------------ | +| 250 or less | 6 mm (1⁄4 in.) | 6 mm (1⁄4 in.) | +| Over 250 – 1000 | 10 mm (3⁄8 in.) | 10 mm (3⁄8 in.) | + +Table 430.12(C)(2) Usable Volumes — Fixed Terminals + +| Power-Supply Conductor Size (AWG) | Minimum Usable Volume per Power-Supply Conductor | +| --------------------------------- | ------------------------------------------------ | +| 14 | 16 cm3 (1 in.3 | +| 12 and 10 | 20 cm3 (1 1⁄4 in.3 | +| 8 and 6 | 37 cm3 (2 1⁄4 in.3 | + +#### 430.12(D) Large Wire or Factory Connections. + +For motors with larger ratings, greater number of leads, or larger wire sizes, or where motors are installed as a part of factory-wired equipment, without additional connection being required at the motor terminal housing during equipment installation, the terminal housing shall be of ample size to make connections, but the foregoing provisions for the volumes of terminal housings shall not be considered applicable. + +#### 430.12(E) Equipment Grounding Connections. + +A means for attachment of an equipment grounding conductor termination in accordance with 250.8 shall be provided at motor terminal housings for wire-to-wire connections or fixed terminal connections. The means for such connections shall be permitted to be located either inside or outside the motor terminal housing. + +> [!important] Exception: +> Where a motor is installed as a part of factory-wired equipment that is required to be grounded and without additional connection being required at the motor terminal housing during equipment installation, a separate means for motor grounding at the motor terminal housing shall not be required. + +### 430.13 Bushing. + +Where wires pass through an opening in an enclosure, conduit box, or barrier, a bushing shall be used to protect the conductors from the edges of openings having sharp edges. The bushing shall have smooth, well-rounded surfaces where it may be in contact with the conductors. If used where oils, greases, or other contaminants may be present, the bushing shall be made of material not deleteriously affected. + +> [!info] Informational Note: +> For conductors exposed to deteriorating agents, see 310.10(F). + +### 430.14 Location of Motors. + +#### 430.14(A) Ventilation and Maintenance. + +Motors shall be located so that adequate ventilation is provided and so that maintenance, such as lubrication of bearings and replacing of brushes, can be readily accomplished. + +> [!important] Exception: +> Ventilation shall not be required for submersible types of motors. + +#### 430.14(B) Open Motors. + +Open motors that have commutators or collector rings shall be located or protected so that sparks cannot reach adjacent combustible material. + +> [!important] Exception: +> Installation of these motors on wooden floors or supports shall be permitted. + +### 430.16 Exposure to Dust Accumulations. + +In locations where dust or flying material collects on or in motors in such quantities as to seriously interfere with the ventilation or cooling of motors and thereby cause dangerous temperatures, suitable types of enclosed motors that do not overheat under the prevailing conditions shall be used. + +> [!info] Informational Note: +> Especially severe conditions may require the use of enclosed pipe-ventilated motors, or enclosure in separate dusttight rooms, properly ventilated from a source of clean air. + +### 430.17 Highest Rated or Smallest Rated Motor. + +In determining compliance with 430.24, 430.53(B), and 430.53(C), the highest rated or smallest rated motor shall be based on the rated full-load current as selected from Table 430.247, Table 430.248, Table 430.249, and Table 430.250. + +### 430.18 Nominal Voltage of Rectifier Systems. + +The nominal value of the ac voltage being rectified +shall be used to determine the voltage of a rectifier derived system. + +> [!important] Exception: +> The nominal dc voltage of the rectifier shall be used +> if it exceeds the peak value of the ac voltage being rectified. ## Part II. Motor Circuit Conductors @@ -54,4 +479,1981 @@ of the motor full-load current rating, as determined by 430.6(A)(1), or not less than specified in 430.22(A) through (G). - +#### 430.22(A) Direct-Current Motor-Rectifier Supplied. + +For dc motors operating from a rectified power supply, the conductor ampacity on the input of the rectifier shall not be less than +125 percent of the rated input current to the rectifier. For dc motors operating from a rectified single-phase power supply, the conductors between the field wiring output terminals of the rectifier and the motor shall have an ampacity of not less than the following percentages of the motor full-load current rating: + +* (1) Where a rectifier bridge of the single-phase, half-wave type is used, 190 percent. + +* (2) Where a rectifier bridge of the single-phase, full-wave type is used, 150 percent. + +#### 430.22(B) Multispeed Motor. + +For a multispeed motor, the selection of branch-circuit conductors on the line side of the controller shall be based on the highest of the full-load current ratings shown on the motor nameplate. The ampacity of the branch-circuit conductors between the controller and the motor shall not be less than 125 percent of the current rating of the winding(s) that the conductors energize. + +#### 430.22(C) Wye-Start, Delta-Run Motor. + +For a wye-start, delta-run connected motor, the ampacity of the branch-circuit conductors on the line side of the controller shall not be less than 125 percent of the motor full-load current as determined by 430.6(A)(1). The ampacity of the conductors between the controller and the motor shall not be less than 72 percent of the motor full-load current rating as determined by 430.6(A) (1). + +> [!info] Informational Note: +> The individual motor circuit conductors of a wye-start, delta-run connected motor carry 58 percent of the rated load current. The multiplier of 72 percent is obtained by multiplying 58 percent by 1.25. + +#### 430.22(D) Part-Winding Motor. + +For a part-winding connected motor, the ampacity of the branch-circuit conductors on the line side of the controller shall not be less than 125 percent of the motor full-load current as determined by 430.6(A)(1). The ampacity of the conductors between the controller and the motor shall not be less than 62.5 percent of the motor full-load current rating as determined by 430.6(A)(1). + +> [!info] Informational Note: +> The multiplier of 62.5 percent is obtained by multiplying 50 percent by 1.25. + +#### 430.22(E) Other Than Continuous Duty. + +Conductors for a motor used in a short-time, intermittent, periodic, or varying duty application shall have an ampacity of not less than the percentage of the motor nameplate current rating shown in Table 430.22(E), unless the authority having jurisdiction grants special permission for conductors of lower ampacity. + +Table 430.22(E) Duty-Cycle Service + +Classification of Service + +Nameplate Current Rating + +Percentages +5Minute + +Rated + +Motor +15MinuteRated + +Motor +30- & +60- + +Minute + +Rated + +Motor + +Continuous + +Rated + +Motor + +| Short-time duty operating valves, raising or lowering rolls, etc. | 110 | 120 | 150 | — | +| Intermittent duty freight and passenger elevators, tool heads, pumps, drawbridges, turntables, etc. (for arc welders, see 630.11) | 85 | 85 | 90 | 140 | +| Periodic duty rolls, ore- and coal-handling machines, etc. | 85 | 90 | 95 | 140 | +| Varying duty | 110 | 120 | 150 | 200 | + +Note: Any motor application shall be considered as continuous duty unless the nature of the apparatus it drives is such that the motor will not operate continuously with load under any condition of use. + +#### 430.22(F) Separate Terminal Enclosure. + +The conductors between a stationary motor rated 1 hp or less and the separate terminal enclosure permitted in 430.245(B) shall be permitted to be smaller than 14 AWG but not smaller than 18 AWG, provided they have an ampacity as specified in 430.22. + +#### 430.22(G) Conductors for Small Motors. + +Conductors for small motors shall not be smaller than 14 AWG unless otherwise permitted in 430.22(G)(1) or (G)(2). + +##### 430.22(G)(1) 18 AWG Copper. + +18 AWG individual copper conductors installed in a cabinet or enclosure, copper conductors that are part of a jacketed multiconductor cable assembly, or copper conductors in a flexible cord shall be permitted, under either of the following sets of conditions: + +* (1) The circuit supplies a motor with a full-load current rating, as determined by 430.6(A)(1), of greater than 3.5 amperes, and less than or equal to 5 amperes, and all the following conditions are met: + * a. The circuit is protected in accordance with 430.52. + * b. The circuit is provided with maximum Class 10 or Class 10A overload protection in accordance with 430.32. + * c. Overcurrent protection is provided in accordance with 240.4(D)(1)(2). + +* (2) The circuit supplies a motor with a full-load current rating, as determined by 430.6(A)(1), of 3.5 amperes or less, and all the following conditions are met: + * a. The circuit is protected in accordance with 430.52. + * b. The circuit is provided with maximum Class 20 overload protection in accordance with 430.32. + * c. Overcurrent protection is provided in accordance with 240.4(D)(1)(2). + +##### 430.22(G)(2) 16 AWG Copper. + +16 AWG individual copper conductors installed in a cabinet or enclosure, copper conductors that are part of a jacketed multiconductor cable assembly, or copper conductors in a flexible cord shall be permitted under either of the following sets of conditions: + +* (1) The circuit supplies a motor with a full-load current rating, as determined by 430.6(A)(1), of greater than 5.5 amperes, and less than or equal to 8 amperes, and all the following conditions are met: + * a. The circuit is protected in accordance with 430.52. + * b. The circuit is provided with maximum Class 10 or Class 10A overload protection in accordance with 430.32. + * c. Overcurrent protection is provided in accordance with 240.4(D)(2)(2). + +* (2) The circuit supplies a motor with a full-load current rating, as determined by 430.6(A)(1), of 5.5 amperes or less, and all the following conditions are met: + * a. The circuit is protected in accordance with 430.52. + * b. The circuit is provided with maximum Class 20 overload protection in accordance with 430.32. + * c. Overcurrent protection is provided in accordance with 240.4(D)(2)(2). + +### 430.23 Wound-Rotor Secondary. + +#### 430.23(A) Continuous Duty. + +For continuous duty, the conductors connecting the secondary of a wound-rotor ac motor to its controller shall have an ampacity not less than 125 percent of the full-load secondary current of the motor. + +#### 430.23(B) Other Than Continuous Duty. + +For other than continuous duty, these conductors shall have an ampacity, in percent of full-load secondary current, not less than that specified in Table 430.22(E). + +#### 430.23(C) Resistor Separate from Controller. + +Where the secondary resistor is separate from the controller, the ampacity of the conductors between controller and resistor shall not be less than that shown in Table 430.23(C). + +Table 430.23(C) Secondary Conductor + +| Resistor Duty Classification | Ampacity of Conductor in Percent of Full-Load Secondary Current | +|:---------------------------- | ---------------------------------------------------------------:| +| Light starting duty | 35 | +| Heavy starting duty | 45 | +| Extra-heavy starting duty | 55 | +| Light intermittent duty | 65 | +| Medium intermittent duty | 75 | +| Heavy intermittent duty | 85 | +| Continuous duty | 110 | + +### 430.24 Several Motors or a Motor(s) and Other Load(s). + +Conductors supplying several motors, or a motor(s) and other load(s), shall have an ampacity not less than the sum of each of the following: + +* (1) 125 percent of the full-load current rating of the highest rated motor, as determined by 430.6(A) + +* (2) Sum of the full-load current ratings of all the other motors in the group, as determined by 430.6(A) + +* (3) 100 percent of the noncontinuous non-motor load + +* (4) 125 percent of the continuous non-motor load. + +> [!info] Informational Note: +> See Informative Annex D, Example No. D8. + +> [!important] Exception No. 1: +> Where one or more of the motors of the group are used for short-time, intermittent, periodic, or varying duty, the ampere rating of such motors to be used in the summation shall be determined in accordance with 430.22(E). For the highest rated motor, the greater of either the ampere rating from 430.22(E) or the largest continuous duty motor full-load current multiplied by 1.25 shall be used in the summation. + +> [!important] Exception No. 2: +> The ampacity of conductors supplying motor-operated fixed electric space-heating equipment shall comply with 424.4(B). + +> [!important] Exception No. 3: +> Where the circuitry is interlocked so as to prevent simultaneous operation of selected motors or other loads, the conductor ampacity shall be permitted to be based on the summation of the currents of the motors and other loads to be operated simultaneously that results in the highest total current. + +### 430.25 Multimotor and Combination-Load Equipment. + +The ampacity of the conductors supplying multimotor and combination-load equipment shall not be less than the minimum circuit ampacity marked on the equipment in accordance with 430.7(D). Where the equipment is not factory-wired and the individual nameplates are visible in accordance with 430.7(D)(2), the conductor ampacity shall be determined in accordance with 430.24. + +### 430.26 Feeder Demand Factor. + +Where reduced heating of the conductors results from motors operating on duty-cycle, intermittently, or from all motors not operating at one time, the authority having jurisdiction may grant permission for feeder conductors to have an ampacity less than specified in +430.24, provided the conductors have sufficient ampacity for the maximum load determined in accordance with the sizes and number of motors supplied and the character of their loads and duties. + +> [!info] Informational Note: +> Demand factors determined in the design of new facilities can often be validated against actual historical experience from similar installations. + +### 430.27 Capacitors with Motors. + +Where capacitors are installed in motor circuits, conductors shall comply with 460.8 and 460.9. + +### 430.28 Feeder Taps. + +Feeder tap conductors shall have an ampacity not less than that required by Part II, shall terminate in a branch-circuit protective device, and, in addition, shall meet one of the following requirements: + +* (1) Be enclosed either by an enclosed controller or by a raceway, be not more than 3.0 m (10 ft) in length, and, for field installation, be protected by an overcurrent device on the line side of the tap conductor, the rating or setting of which shall not exceed +1000 percent of the tap conductor ampacity + +* (2) Have an ampacity of at least one-third that of the feeder conductors, be suitably protected from physical damage or enclosed in a raceway, and be not more than 7.5 m (25 ft) in length + +* (3) Have an ampacity not less than the feeder conductors + +> [!important] Exception: +> Feeder taps over 7.5 m (25 ft) long. In high-bay manufacturing buildings \[over 11 m (35 ft) high at walls\], where conditions of maintenance and supervision ensure that only qualified persons service the systems, conductors tapped to a feeder shall be permitted to be not over 7.5 m (25 ft) long horizontally and not over 30.0 m (100 ft) in total length where all of the following conditions are met: + +* (1) The ampacity of the tap conductors is not less than one-third that of the feeder conductors. + +* (2) The tap conductors terminate with a single circuit breaker or a single set of fuses complying with (1) Part IV, where the load-side conductors are a branch circuit, or (2) Part V, where the load-side conductors are a feeder. + +* (3) The tap conductors are suitably protected from physical damage and are installed in raceways. + +* (4) The tap conductors are continuous from end-to-end and contain no splices. + +* (5) The tap conductors shall be 6 AWG copper or 4 AWG aluminum or larger. + +* (6) The tap conductors shall not penetrate walls, floors, or ceilings. + +* (7) The tap shall not be made less than 9.0 m (30 ft) from the floor. + +### 430.29 Constant Voltage Direct-Current Motors — Power Resistors. + +Conductors connecting the motor controller to separately mounted power accelerating and dynamic braking resistors in the armature circuit shall have an ampacity not less than the value calculated from Table 430.29 using motor full-load current. If an armature shunt resistor is used, the power accelerating resistor conductor ampacity shall be calculated using the total of motor full-load current and armature shunt resistor current. + +Armature shunt resistor conductors shall have an ampacity of not less than that calculated from Table 430.29 using rated shunt resistor current as full-load current. + +#### Table 430.29 Conductor Rating Factors for Power Resistors + +Time in Seconds + +Ampacity of Conductor in Percent of Full-Load Current + +On Off +On 5, Off 75 | 35 +On 10, Off 70 | 45 +On 15, Off 75 | 55 +On 15, Off 45 | 65 +On 15, Off 30 | 75 +On 15, Off 15 | 85 + +Continuous Duty 110 + +## Part III. Motor and Branch-Circuit Overload Protection + +### 430.31 General. + +Part III specifies overload devices intended to protect motors, motor-control apparatus, and motor branch-circuit conductors against excessive heating due to motor overloads and failure to start. + +> [!info] Informational Note No. 1: +> See Informative Annex D, Example No. D8. + +> [!info] Informational Note No. 2: +> See the definition of Overload in Article 100. + +These provisions shall not require overload protection where a power loss would cause a hazard, such as in the case of fire pumps. + +> [!info] Informational Note: +> For protection of fire pump supply conductors, see 695.7. + +Part III shall not apply to motor circuits rated over 1000 volts, nominal. + +> [!info] Informational Note: +> For over 1000 volts, nominal, see Part XI. + +### 430.32 Continuous-Duty Motors. + +#### 430.32(A) More Than 1 Horsepower. + +Each motor used in a continuous duty application and rated more than 1 hp shall be protected against overload by one of the means in 430.32(A)(1) through (A)(4). + +##### 430.32(A)(1) Separate Overload Device. + +A separate overload device that is responsive to motor current. This device shall be selected to trip or shall be rated at no more than the following percent of the motor nameplate full-load current rating: + +Motors with a marked service factor 1.15 or greater 125% + +Motors with a marked temperature rise 40°C or less 125% + +All other motors 115% + +Modification of this value shall be permitted as provided in 430.32(C). For a multispeed motor, each winding connection shall be considered separately. + +Where a separate motor overload device is connected so that it does not carry the total current designated on the motor nameplate, such as for wye-delta starting, the proper percentage of nameplate current applying to the selection or setting of the overload device shall be clearly designated on the equipment, or the manufacturer’s selection table shall take this into account. + +> [!info] Informational Note: +> Where power factor correction capacitors are installed on the load side of the motor overload device, see 460.9. + +##### 430.32(A)(2) Thermal Protector or Electronically Protected. + +A thermal protector integral with the motor shall be approved for use with the motor it protects on the basis that it will prevent dangerous overheating of the motor due to overload and failure to start. An electronically protected motor shall be approved for use on the basis that it will prevent dangerous overheating due to the failure of the electronic control, overload, or failure to start the motor. The ultimate trip current of a thermally or electronically protected motor shall not exceed the following percentage of motor full-load current given in Table 430.248, Table 430.249, and Table 430.250: + +| | | +| -------------------------------------------------------------- | ---- | +| Motor full-load current 9 amperes or less | 170% | +| Motor full-load current from 9.1 to, and including, 20 amperes | 156% | +| Motor full-load current greater than 20 amperes | 140% | + +If the motor current-interrupting device is separate from the motor and its control circuit is operated by a protective device integral with the motor, it shall be arranged so that the opening of the control circuit will result in interruption of current to the motor. + +##### 430.32(A)(3) Integral with Motor. + +A protective device integral with a motor that will protect the motor against damage due to failure to start shall be permitted if the motor is part of an approved assembly that does not normally subject the motor to overloads. + +##### 430.32(A)(4) Larger Than 1500 Horsepower. + +For motors larger than 1500 hp, a protective device having embedded temperature detectors that cause current to the motor to be interrupted when the motor attains a temperature rise greater than marked on the nameplate in an ambient temperature of 40°C. + +#### 430.32(B) One Horsepower or Less, Automatically Started. + +Any motor of 1 hp or less that is started automatically shall be protected against overload by one of the following means. + +##### 430.32(B)(1) Separate Overload Device. + +By a separate overload device following the requirements of 430.32(A)(1). + +For a multispeed motor, each winding connection shall be considered separately. Modification of this value shall be permitted as provided in 430.32(C). + +##### 430.32(B)(2) Thermal Protector or Electronically Protected. + +A thermal protector integral with the motor shall be approved for use with the motor that it protects on the basis that it will prevent dangerous overheating of the motor due to overload and failure to start. An electronically protected motor shall be approved for use on the basis that it will prevent dangerous overheating due to the failure of the electronic control, overload, or failure to start the motor. + +Where the motor current-interrupting device is separate from the motor and its control circuit is operated by a protective device integral with the motor, it shall be arranged so that the opening of the control circuit results in interruption of current to the motor. + +##### 430.32(B)(3) Integral with Motor. + +A protective device integral with a motor that protects the motor against damage due to failure to start shall be permitted (1) if the motor is part of an approved assembly that does not subject the motor to overloads, or (2) if the assembly is also equipped with other safety controls (such as the safety combustion controls on a domestic oil burner) that protect the motor against damage due to failure to start. + +Where the assembly has safety controls that protect the motor, it shall be so indicated on the nameplate of the assembly where it will be visible after installation. + +##### 430.32(B)(4) Impedance-Protected. + +If the impedance of the motor windings is sufficient to prevent overheating due to failure to start, the motor shall be permitted to be protected as specified in 430.32(D)(2)(a) for manually started motors if the motor is part of an approved assembly in which the motor will limit itself so that it will not be dangerously overheated. + +> [!info] Informational Note: +> Many ac motors of less than 1⁄20 hp, such as clock motors, series motors, and so forth, and also some larger motors such as torque motors, come within this classification. It does not include split-phase motors having automatic switches that disconnect the starting windings. + +#### 430.32(C) Selection of Overload Device. + +Where the sensing element or setting or sizing of the overload device selected in accordance with 430.32(A)(1) and 430.32(B)(1) is not sufficient to start the motor or to carry the load, higher size sensing elements or incremental settings or sizing shall be permitted to be used, provided the trip current of the overload device does not exceed the following percentage of motor nameplate full-load current rating: + +| | | +| -------------------------------------------------- | ---- | +| Motors with marked service factor 1.15 or greater | 140% | +| Motors with a marked temperature rise 40°C or less | 140% | +| All other motors | 130% | + +If not shunted during the starting period of the motor as provided in 430.35, the overload device shall have sufficient time delay to permit the motor to start and accelerate its load. + +> [!info] Informational Note: +> A Class 20 overload relay will provide a longer motor acceleration time than a Class 10 or Class 10A overload relay. + +A Class 30 overload relay will provide a longer motor acceleration time than a Class 20 overload relay. Use of a higher class overload relay may preclude the need for selection of a higher trip current. + +#### 430.32(D) One Horsepower or Less, Nonautomatically Started. + +##### 430.32(D)(1) Permanently Installed. + +Overload protection shall be in accordance with 430.32(B). + +##### 430.32(D)(2) Not Permanently Installed. + +* (a) Within Sight from Controller. Overload protection shall be permitted to be furnished by the branch-circuit short-circuit and ground-fault protective device; such device, however, shall not be larger than that specified in Part IV of Article 430. + +> [!important] Exception: +> Any such motor shall be permitted on a nominal 120-volt branch circuit protected at not over 20 amperes. + +* (b) Not Within Sight from Controller. Overload protection shall be in accordance with 430.32(B). + +#### 430.32(E) Wound-Rotor Secondaries. + +The secondary circuits of wound-rotor ac motors, including conductors, controllers, resistors, and so forth, shall be permitted to be protected against overload by the motor-overload device. + +### 430.33 Intermittent and Similar Duty. + +A motor used for a condition of service that is inherently short-time, intermittent, periodic, or varying duty, as illustrated by Table +430.22(E), shall be permitted to be protected against overload by the branch-circuit short-circuit and ground-fault protective device, provided the protective device rating or setting does not exceed that specified in Table 430.52. + +Any motor application shall be considered to be for continuous duty unless the nature of the apparatus it drives is such that the motor cannot operate continuously with load under any condition of use. + +### 430.35 Shunting During Starting Period. + +#### 430.35(A) Nonautomatically Started. + +For a nonautomatically started motor, the overload protection shall be permitted to be shunted or cut out of the circuit during the starting period of the motor if the device by which the overload protection is shunted or cut out cannot be left in the starting position and if fuses or inverse time circuit breakers rated or set at not over 400 percent of the full-load current of the motor are located in the circuit so as to be operative during the starting period of the motor. + +#### 430.35(B) Automatically Started. + +The motor overload protection shall not be shunted or cut out during the starting period if the motor is automatically started. + +> [!important] Exception: +> The motor overload protection shall be permitted to be shunted or cut out during the starting period on an automatically started motor where the following apply: + +* (1) The motor starting period exceeds the time delay of available motor overload protective devices, and + +* (2) Listed means are provided to perform the following: + * a. Sense motor rotation and automatically prevent the shunting or cutout in the event that the motor fails to start, and + * b. Limit the time of overload protection shunting or cutout to less than the locked rotor time rating of the protected motor, and + * c. Provide for shutdown and manual restart if motor running condition is not reached. + +### 430.36 Fuses — In Which Conductor. + +Where fuses are used for motor overload protection, a fuse shall be inserted in each ungrounded conductor and also in the grounded conductor if the supply system is 3-wire, 3-phase ac with one conductor grounded. + +### 430.37 Devices Other Than Fuses — In Which Conductor. + +Where devices other than fuses are used for motor overload protection, Table 430.37 shall govern the minimum allowable number and location of overload units such as trip coils or relays. + +Table 430.37 Overload Units + +Kind of + +Motor Supply System + +Number and Location of Overload Units, Such as Trip + +Coils or Relays +1-phase ac or dc +2-wire, 1-phase ac or dc ungrounded 1 in either conductor +1-phase ac or dc +2-wire, 1-phase ac or dc, one conductor grounded +1 in ungrounded conductor +1-phase ac or dc +3-wire, 1-phase ac or dc, grounded neutral conductor +1 in either ungrounded conductor +1-phase ac Any 3-phase 1 in ungrounded conductor +2-phase ac 3-wire, 2-phase ac, ungrounded 2, one in each phase +2-phase ac 3-wire, 2-phase ac, one conductor grounded +2 in ungrounded conductors +2-phase ac 4-wire, 2-phase ac, grounded or ungrounded +2, one for each phase in ungrounded conductors +2-phase ac Grounded neutral or 5-wire, 2-phase ac, ungrounded +2, one for each phase in any ungrounded phase wire +3-phase ac Any 3-phase 3, one in each phase* +*Exception: An overload unit in each phase shall not be required where overload protection is provided by other approved means. + +### 430.38 Number of Conductors Opened by Overload Device. + +Motor overload devices, other than fuses or thermal protectors, shall simultaneously open a sufficient number of ungrounded conductors to interrupt current flow to the motor. + +### 430.39 Motor Controller as Overload Protection. + +A motor controller shall also be permitted to serve as an overload device if the number of overload units complies with Table 430.37 and if these units are operative in both the starting and running position in the case of a dc motor, and in the running position in the case of an ac motor. + +### 430.40 Overload Relays. + +Overload relays and other devices for motor overload protection that are not capable of opening short circuits or ground faults shall be protected by fuses or circuit breakers with ratings or settings in accordance with 430.52 or by a motor short-circuit protector in accordance with 430.52. + +> [!important] Exception: +> Where approved for group installation and marked to indicate the maximum size of fuse or inverse time circuit breaker by which they must be protected, the overload devices shall be protected in accordance with this marking. + +### 430.42 Motors on General-Purpose Branch Circuits. + +Overload protection for motors used on general-purpose branch circuits as permitted in Article 210 shall be provided as specified in +430.42(A), (B), (C), or (D). + +#### 430.42(A) Not over 1 Horsepower. + +One or more motors without individual overload protection shall be permitted to be connected to a general-purpose branch circuit only where the installation complies with the limiting conditions specified in 430.32(B) and 430.32(D) and 430.53(A)(1) and (A)(2). + +#### 430.42(B) Over 1 Horsepower. + +Motors of ratings larger than specified in 430.53(A) shall be permitted to be connected to general-purpose branch circuits only where each motor is protected by overload protection selected to protect the motor as specified in 430.32. Both the controller and the motor overload device shall be approved for group installation with the short-circuit and ground-fault protective device selected in accordance with 430.53. + +#### 430.42(C) Cord-and Plug-Connected. + +Where a motor is connected to a branch circuit by means of an attachment plug and a receptacle or a cord connector, and individual overload protection is omitted as provided in 430.42(A), the rating of the attachment plug and receptacle or cord connector shall not exceed 15 amperes at 125 volts or 250 volts. Where individual overload protection is required as provided in 430.42(B) for a motor or motor-operated appliance that is attached to the branch circuit through an attachment plug and a receptacle or a cord connector, the overload device shall be an integral part of the motor or of the appliance. The rating of the attachment plug and receptacle or the cord connector shall determine the rating of the circuit to which the motor may be connected, as provided in 210.21(B). + +#### 430.42(D) Time Delay. + +The branch-circuit short-circuit and ground-fault protective device protecting a circuit to which a motor or motor-operated appliance is connected shall have sufficient time delay to permit the motor to start and accelerate its load. + +### 430.43 Automatic Restarting. + +A motor overload device that can restart a motor automatically after overload tripping shall not be installed unless approved for use with the motor it protects. A motor overload device that can restart a motor automatically after overload tripping shall not be installed if automatic restarting of the motor can result in injury to persons. + +### 430.44 Orderly Shutdown. + +If immediate automatic shutdown of a motor by a motor overload protective device(s) would introduce additional or increased hazard(s) to a person(s) and continued motor operation is necessary for safe shutdown of equipment or process, a motor overload sensing device(s) complying with Part III of this article shall be permitted to be connected to a supervised alarm instead of causing immediate interruption of the motor circuit, so that corrective action or an orderly shutdown can be initiated. + +## Part IV. Motor Branch-Circuit Short-Circuit and Ground-Fault Protection + +### 430.51 General. + +Part IV specifies devices intended to protect the motor branch-circuit conductors, the motor control apparatus, and the motors against overcurrent due to short circuits or ground faults. These rules add to or amend Article 240. The devices specified in Part IV do not include the types of devices required by 210.8, 230.95, and 590.6. + +> [!info] Informational Note: +> See Informative Annex D, Example D8. + +Part IV shall not apply to motor circuits rated over 1000 volts, nominal. + +> [!info] Informational Note: +> For over 1000 volts, nominal, see Part XI. + +### 430.52 Rating or Setting for Individual Motor Circuit. + +#### 430.52(A) General. + +The motor branch-circuit short-circuit and ground-fault protective device shall comply with 430.52(B) and either 430.52(C) or (D), as applicable. + +#### 430.52(B) All Motors. + +The motor branch-circuit short-circuit and ground-fault protective device shall be capable of carrying the starting current of the motor. + +#### 430.52(C) Rating or Setting. + +##### 430.52(C)(1) In Accordance with Table 430.52. + +A protective device that has a rating or setting not exceeding the value calculated according to the values given in Table 430.52 shall be used. + +Table 430.52 Maximum Rating or Setting of Motor Branch-Circuit Short-Circuit and Ground-Fault + +Protective Devices + +Type of Motor + +Percentage of Full-Load Current + +Nontime + +Delay + +Fuse + +Dual Element +(Time-Delay) + +Fuse + +Instantaneous + +Trip + +Breaker + +Inverse + +Time + +Breaker + +Single-phase motors 300 175 800 250 + +AC polyphase motors other than wound-rotor 300 175 800 250 + +Squirrel cage — other than Design B energy-efficient 300 175 800 250 + +Design B energy-efficient 300 175 1100 250 + +Synchronous 300 175 800 250 + +Wound-rotor 150 150 800 150 + +DC (constant voltage) 150 150 250 150 + +Note: For certain exceptions to the values specified, see 430.54. + +The values in the Nontime Delay Fuse column apply to time-delay Class CC fuses. + +The values given in the last column also cover the ratings of nonadjustable inverse time types of circuit breakers that may be modified as in 430.52(C)(1), Exceptions No. 1 and No. 2. + +Synchronous motors of the low-torque, low-speed type (usually 450 rpm or lower), such as are used to drive reciprocating compressors, pumps, and so forth, that start unloaded, do not require a fuse rating or circuit-breaker setting in excess of 200 percent of full-load current. + +> [!important] Exception No. 1: +> Where the values for branch-circuit short-circuit and ground-fault protective devices determined by Table 430.52 do not correspond to the standard sizes or ratings of fuses, nonadjustable circuit breakers, thermal protective devices, or possible settings of adjustable circuit breakers, a higher size, rating, or possible setting that does not exceed the next higher standard ampere rating shall be permitted. + +> [!important] Exception No. 2: +> Where the rating specified in Table 430.52, or the rating modified by Exception No. 1, is not sufficient for the starting current of the motor: + +* (1) The rating of a nontime-delay fuse not exceeding 600 amperes or a time-delay Class CC fuse shall be permitted to be increased but shall in no case exceed 400 percent of the full-load current. + +* (2) The rating of a time-delay (dual-element) fuse shall be permitted to be increased but shall in no case exceed 225 percent of the full-load current. + +* (3) The rating of an inverse time circuit breaker shall be permitted to be increased but shall in no case exceed 400 percent for fullload currents of 100 amperes or less or 300 percent for full-load currents greater than 100 amperes. +1 1 2 +3 +1 +2 +3 + +* (4) The rating of a fuse of 601–6000 ampere classification shall be permitted to be increased but shall in no case exceed +300 percent of the full-load current. + +> [!info] Informational Note: +> See Informative Annex D, Example D8, and Figure 430.1. + +##### 430.52(C)(2) Overload Relay Table. + +Where maximum branch-circuit short-circuit and ground-fault protective device ratings are shown in the manufacturer’s overload relay table for use with a motor controller or are otherwise marked on the equipment, they shall not be exceeded even if higher values are allowed as shown above. + +##### 430.52(C)(3) Instantaneous Trip Circuit Breaker. + +An instantaneous trip circuit breaker shall be used only if adjustable and if part of a listed combination motor controller having coordinated motor overload and short-circuit and ground-fault protection in each conductor, and the setting is adjusted to no more than the value specified in Table 430.52. + +> [!info] Informational Note No. 1: +> Instantaneous trip circuit breakers are also known as motor-circuit protectors (MCPs). + +> [!info] Informational Note No. 2: +> For the purpose of this article, instantaneous trip circuit breakers may include a damping means to accommodate a transient motor inrush current without nuisance tripping of the circuit breaker. + +> [!important] Exception No. 1: +> Where the setting specified in Table 430.52 is not sufficient for the starting current of the motor, the setting of an instantaneous trip circuit breaker shall be permitted to be increased but shall in no case exceed 1300 percent of the motor full-load current for other than Design B energy-efficient motors and no more than 1700 percent of motor full-load current for Design B energyefficient motors. Trip settings above 800 percent for other than Design B energy-efficient motors and above 1100 percent for Design B energy-efficient motors shall be permitted where the need has been demonstrated by engineering evaluation. In such cases, it shall not be necessary to first apply an instantaneous-trip circuit breaker at 800 percent or 1100 percent. + +> [!info] Informational Note: +> For additional information on the requirements for a motor to be classified “energy efficient,” see NEMA MG 1-2016, + +Motors and Generators, Part 12.59. + +> [!important] Exception No. 2: +> Where the motor full-load current is 8 amperes or less, the setting of the instantaneous-trip circuit breaker with a continuous current rating of 15 amperes or less in a listed combination motor controller that provides coordinated motor branch-circuit overload and short-circuit and ground-fault protection shall be permitted to be increased to the value marked on the controller. + +##### 430.52(C)(4) Multispeed Motor. + +For a multispeed motor, a single short-circuit and ground-fault protective device shall be permitted for two or more windings of the motor, provided the rating of the protective device does not exceed the above applicable percentage of the nameplate rating of the smallest winding protected. + +> [!important] Exception: +> For a multispeed motor, a single short-circuit and ground-fault protective device shall be permitted to be used and sized according to the full-load current of the highest current winding, where all of the following conditions are met: + +* (1) Each winding is equipped with individual overload protection sized according to its full-load current. + +* (2) The branch-circuit conductors supplying each winding are sized according to the full-load current of the highest full-load current winding. + +* (3) The controller for each winding has a horsepower rating not less than that required for the winding having the highest horsepower rating. + +##### 430.52(C)(5) Power Electronic Devices. + +Semiconductor fuses intended for the protection of electronic devices shall be permitted in lieu of devices listed in Table 430.52 for power electronic devices, associated electromechanical devices (such as bypass contactors and isolation contactors), and conductors in a solid-state motor controller system, provided that the marking for replacement fuses is provided adjacent to the fuses. + +##### 430.52(C)(6) Self-Protected Combination Controller. + +A listed self-protected combination controller shall be permitted in lieu of the devices specified in Table 430.52. Adjustable instantaneous-trip settings shall not exceed 1300 percent of full-load motor current for other than Design B energy-efficient motors and not more than 1700 percent of full-load motor current for Design B energy-efficient motors. + +> [!info] Informational Note: +> Proper application of self-protected combination controllers on 3-phase systems, other than solidly grounded wye, particularly on corner grounded delta systems, considers the self-protected combination controllers' individual pole-interrupting capability. + +##### 430.52(C)(7) Motor Short-Circuit Protector. + +A motor short-circuit protector shall be permitted in lieu of devices listed in Table 430.52 if the motor short-circuit protector is part of a listed combination motor controller having coordinated motor overload protection and short-circuit and ground-fault protection in each conductor and it will open the circuit at currents exceeding 1300 percent of motor full-load current for other than Design B energyefficient motors and 1700 percent of motor full-load motor current for Design B energy-efficient motors. + +> [!info] Informational Note: +> A motor short-circuit protector, as used in this section, is a fused device and is not an instantaneous trip circuit breaker. + +#### 430.52(D) Torque Motors. + +Torque motor branch circuits shall be protected at the motor nameplate current rating in accordance with 240.4(B). + +### 430.53 Several Motors or Loads on One Branch Circuit. + +Two or more motors or one or more motors and other loads shall be permitted to be connected to the same branch circuit under conditions specified in 430.53(D) and in 430.53(A), (B), or (C). The branch-circuit protective device shall be fuses or inverse time circuit breakers. + +#### 430.53(A) Not Over 1 Horsepower. + +Several motors, each not exceeding 1 hp in rating, shall be permitted on a nominal 120-volt branch circuit protected at not over 20 amperes or a branch circuit of 1000 volts, nominal, or less, protected at not over 15 amperes, if all of the following conditions are met: + +* (1) The full-load rating of each motor does not exceed 6 amperes. + +* (2) The rating of the branch-circuit short-circuit and ground-fault protective device marked on any of the controllers is not exceeded. + +* (3) Individual overload protection conforms to 430.32. + +#### 430.53(B) If Smallest Rated Motor Protected. + +If the branch-circuit short-circuit and ground-fault protective device is selected not to exceed that allowed by 430.52 for the smallest rated motor, two or more motors or one or more motors and other load(s), with each motor having individual overload protection, shall be permitted to be connected to a branch circuit where it can be determined that the branch-circuit short-circuit and ground-fault protective device will not open under the most severe normal conditions of service that might be encountered. + +#### 430.53(C) Other Group Installations. + +Two or more motors of any rating or one or more motors and other load(s), with each motor having individual overload protection, shall be permitted to be connected to one branch circuit where the motor controller(s) and overload device(s) are (1) installed as a listed factory assembly and the motor branch-circuit short-circuit and ground-fault protective device either is provided as part of the assembly or is specified by a marking on the assembly, or (2) the motor branch-circuit short-circuit and ground-fault protective device, the motor controller(s), and overload device(s) are field-installed as separate assemblies listed for such use and provided with manufacturers’ instructions for use with each other, and (3) all of the following conditions are complied with: + +* (1) Each motor overload device is either (a) listed for group installation with a specified maximum rating of fuse, inverse time circuit breaker, or both, or (b) selected such that the ampere rating of the motor-branch short-circuit and ground-fault protective device does not exceed that permitted by 430.52 for that individual motor overload device and corresponding motor load. + +* (2) Each motor controller is either (a) listed for group installation with a specified maximum rating of fuse, circuit breaker, or both, or + +* (b) selected such that the ampere rating of the motor-branch short-circuit and ground-fault protective device does not exceed that permitted by 430.52 for that individual controller and corresponding motor load. + +* (3) Each circuit breaker is listed and is of the inverse time type. + +* (4) The branch circuit shall be protected by fuses or inverse time circuit breakers having a rating not exceeding that specified in +430.52 for the highest rated motor connected to the branch circuit plus an amount equal to the sum of the full-load current ratings of all other motors and the ratings of other loads connected to the circuit. Where this calculation results in a rating less than the ampacity of the branch-circuit conductors, it shall be permitted to increase the maximum rating of the fuses or circuit breaker to a value not exceeding that permitted by 240.4(B). + +* (5) The branch-circuit fuses or inverse time circuit breakers are not larger than allowed by 430.40 for the overload relay protecting the smallest rated motor of the group. + +* (6) Overcurrent protection for loads other than motor loads shall be in accordance with Parts I through VII of Article 240. + +> [!info] Informational Note: +> See 110.10 for circuit impedance and other characteristics. + +#### 430.53(D) Single Motor Taps. + +For group installations described above, the conductors of any tap supplying a single motor shall not be required to have an individual branch-circuit short-circuit and ground-fault protective device, provided they comply with one of the following: + +* (1) No conductor to the motor shall have an ampacity less than that of the branch-circuit conductors. + +* (2) No conductor to the motor shall have an ampacity less than one-third that of the branch-circuit conductors, with a minimum in accordance with 430.22. The conductors from the point of the tap to the motor overload device shall be not more than 7.5 m +(25 ft) long and be protected from physical damage by being enclosed in an approved raceway or by use of other approved means. + +* (3) Conductors from the point of the tap from the branch circuit to a listed manual motor controller additionally marked “Suitable for + +Tap Conductor Protection in Group Installations,” or to a branch-circuit protective device, shall be permitted to have an ampacity not less than one-tenth the rating or setting of the branch-circuit short-circuit and ground-fault protective device. The conductors from the controller to the motor shall have an ampacity in accordance with 430.22. The conductors from the point of the tap to the controller(s) shall (1) be suitably protected from physical damage and enclosed either by an enclosed controller or by a raceway and be not more than 3 m (10 ft) long or (2) have an ampacity not less than that of the branch-circuit conductors. + +* (4) Conductors from the point of the tap from the branch circuit to a listed manual motor controller additionally marked “Suitable for + +Tap Conductor Protection in Group Installations,” or to a branch-circuit protective device, shall be permitted to have an ampacity not less than one-third that of the branch-circuit conductors. The conductors from the controller to the motor shall have an ampacity in accordance with 430.22. The conductors from the point of the tap to the controller(s) shall (1) be suitably protected from physical damage and enclosed either by an enclosed controller or by a raceway and be not more than 7.5 m (25 ft) long or + +* (2) have an ampacity not less than that of the branch-circuit conductors. + +### 430.54 Multimotor and Combination-Load Equipment. + +The rating of the branch-circuit short-circuit and ground-fault protective device for multimotor and combination-load equipment shall not exceed the rating marked on the equipment in accordance with 430.7(D). + +### 430.55 Combined Overcurrent Protection. + +Motor branch-circuit short-circuit and ground-fault protection and motor overload protection shall be permitted to be combined in a single protective device where the rating or setting of the device provides the overload protection specified in 430.32. + +### 430.56 Branch-Circuit Protective Devices — In Which Conductor. + +Branch-circuit protective devices shall comply with 240.15. + +### 430.57 Size of Fuseholder. + +Where fuses are used for motor branch-circuit short-circuit and ground-fault protection, the fuseholders shall not be of a smaller size than required to accommodate the fuses specified by Table 430.52. + +> [!important] Exception: +> Where fuses having time delay appropriate for the starting characteristics of the motor are used, it shall be permitted to use fuseholders sized to fit the fuses that are used. + +### 430.58 Rating of Circuit Breaker. + +A circuit breaker for motor branch-circuit short-circuit and ground-fault protection shall have a current rating in accordance with 430.52 and 430.110. + +## Part V. Motor Feeder Short-Circuit and Ground-Fault Protection + +### 430.61 General. + +Part V specifies protective devices intended to protect feeder conductors supplying motors against overcurrents due to short circuits or grounds. + +> [!info] Informational Note: +> See Informative Annex D, Example D8. + +### 430.62 Rating or Setting — Motor Load. + +#### 430.62(A) Specific Load. + +A feeder supplying a specific fixed motor load(s) and consisting of conductor sizes based on 430.24 shall be provided with a protective device having a rating or setting not greater than the largest rating or setting of the branch-circuit short-circuit and ground-fault protective device for any motor supplied by the feeder \[based on the maximum permitted value for the specific type of a protective device in accordance with 430.52, or 440.22(A) for hermetic refrigerant motor-compressors\], plus the sum of the full-load currents of the other motors of the group. + +Where the same rating or setting of the branch-circuit short-circuit and ground-fault protective device is used on two or more of the branch circuits supplied by the feeder, one of the protective devices shall be considered the largest for the above calculations. + +> [!important] Exception No. 1: +> Where one or more instantaneous trip circuit breakers or motor short-circuit protectors are used for motor branch-circuit short-circuit and ground-fault protection as permitted in 430.52(C), the procedure provided above for determining the maximum rating of the feeder protective device shall apply with the following provision: For the purpose of the calculation, each instantaneous trip circuit breaker or motor short-circuit protector shall be assumed to have a rating not exceeding the maximum percentage of motor fullload current permitted by Table 430.52 for the type of feeder protective device employed. + +> [!important] Exception No. 2: +> Where the feeder overcurrent protective device also provides overcurrent protection for a motor control center, the provisions of 430.94 shall apply. + +> [!info] Informational Note: +> See Informative Annex D, Example D8. + +#### 430.62(B) Other Installations. + +Where feeder conductors have an ampacity greater than required by 430.24, the rating or setting of the feeder overcurrent protective device shall be permitted to be based on the ampacity of the feeder conductors. + +### 430.63 Rating or Setting — Motor Load and Other Load(s). + +Where a feeder supplies a motor load and other load(s), the feeder protective device shall have a rating not less than that required for the sum of the other load(s) plus the following: + +* (1) For a single motor, the rating permitted by 430.52 + +* (2) For a single hermetic refrigerant motor-compressor, the rating permitted by 440.22 + +* (3) For two or more motors, the rating permitted by 430.62 + +> [!important] Exception: +> Where the feeder overcurrent device provides the overcurrent protection for a motor control center, the provisions of 430.94 shall apply. + +## Part VI. Motor Control Circuits + +### 430.71 General. + +Part VI contains modifications of the general requirements and applies to the particular conditions of motor control circuits. + +### 430.72 Overcurrent Protection. + +#### 430.72(A) General. + +A motor control circuit tapped from the load side of a motor branch-circuit short-circuit and ground-fault protective device(s) and functioning to control the motor(s) connected to that branch circuit shall be protected against overcurrent in accordance with 430.72. + +Such a tapped control circuit shall not be considered to be a branch circuit and shall be permitted to be protected by either a supplementary or branch-circuit overcurrent protective device(s). A motor control circuit other than such a tapped control circuit shall be protected against overcurrent in accordance with 725.43 or the notes to Table 11(A) and Table 11(B) in Chapter 9, as applicable. + +#### 430.72(B) Conductor Protection. + +The overcurrent protection for conductors shall be provided as specified in 430.72(B)(1) or (B)(2). + +> [!important] Exception No. 1: +> Where the opening of the control circuit would create a hazard as, for example, the control circuit of a fire pump motor, and the like, conductors of control circuits shall require only short-circuit and ground-fault protection and shall be permitted to be protected by the motor branch-circuit short-circuit and ground-fault protective device(s). + +> [!important] Exception No. 2: +> Conductors supplied by the secondary side of a single-phase transformer having only a two-wire (single-voltage) secondary shall be permitted to be protected by overcurrent protection provided on the primary (supply) side of the transformer, provided this protection does not exceed the value determined by multiplying the appropriate maximum rating of the overcurrent device for the secondary conductor from Table 430.72(B) by the secondary-to-primary voltage ratio. Transformer secondary conductors (other than two-wire) shall not be considered to be protected by the primary overcurrent protection. + +##### 430.72(B)(1) Separate Overcurrent Protection. + +Where the motor branch-circuit short-circuit and ground-fault protective device does not provide protection in accordance with +430.72(B)(2), separate overcurrent protection shall be provided. The overcurrent protection shall not exceed the values specified in + +Column A of Table 430.72(B). + +##### 430.72(B)(2) Branch-Circuit Overcurrent Protective Device. + +Conductors shall be permitted to be protected by the motor branch-circuit short-circuit and ground-fault protective device and shall require only short-circuit and ground-fault protection. Where the conductors do not extend beyond the motor control equipment enclosure, the rating of the protective device(s) shall not exceed the value specified in Column B of Table 430.72(B). Where the conductors extend beyond the motor control equipment enclosure, the rating of the protective device(s) shall not exceed the value specified in Column C of Table 430.72(B). + +Table 430.72(B) Maximum Rating of Overcurrent Protective Device in Amperes + +Column A + +Separate Protection + +Protection Provided by Motor Branch-Circuit + +Protective Device(s) + +Provided + +Column B + +Conductors Within + +Enclosure + +Column C + +Conductors Extend + +Beyond + +Enclosure + +Control Circuit + +Conductor Size +(AWG) Copper + +Aluminum or + +Copper-Clad + +Aluminum Copper + +Aluminum or + +Copper-Clad + +Aluminum Copper + +Aluminum or + +Copper-Clad + +Aluminum + +Column A + +Separate Protection + +Provided + +Protection Provided by Motor Branch-Circuit + +Protective Device(s) + +Column B + +Conductors Within + +Enclosure + +Column C + +Conductors Extend + +Beyond + +Enclosure + +Control Circuit + +Conductor Size +(AWG) Copper + +Aluminum or + +Copper-Clad + +Aluminum Copper + +Aluminum or + +Copper-Clad + +Aluminum Copper + +Aluminum or + +Copper-Clad + +Aluminum +18 7 — 25 — 7 — +16 10 — 40 — 10 — +14 (Note 1) — 100 — 45 — +12 (Note 1) (Note 1) 120 100 60 45 +10 (Note 1) (Note 1) 160 140 90 75 + +Larger than 10 (Note 1) (Note 1) (Note 2) (Note 2) (Note 3) (Note 3) + +Notes: +1. Value specified in 310.15 as applicable. +2. 400 percent of value specified in Table 310.17 for 60°C conductors. +3. 300 percent of value specified in Table 310.16 for 60°C conductors. + +#### 430.72(C) Control Circuit Transformer. + +Where a motor control circuit transformer is provided, the transformer shall be protected in accordance with 430.72(C)(1), (C)(2), (C)(3), +(C)(4), or (C)(5). + +> [!important] Exception: +> Overcurrent protection shall be omitted where the opening of the control circuit would create a hazard as, for example, the control circuit of a fire pump motor and the like. + +##### 430.72(C)(1) Compliance with Article 725. + +Where the transformer supplies a Class 1 power-limited circuit, Class 2, or Class 3 remote-control circuit complying with the requirements of Article 725, protection shall comply with Article 725. + +##### 430.72(C)(2) Compliance with Article 450. + +Protection shall be permitted to be provided in accordance with 450.3. + +##### 430.72(C)(3) Less Than 50 Volt-Amperes. + +Control circuit transformers rated less than 50 volt-amperes (VA) and that are an integral part of the motor controller and located within the motor controller enclosure shall be permitted to be protected by primary overcurrent devices, impedance limiting means, or other inherent protective means. + +##### 430.72(C)(4) Primary Less Than 2 Amperes. + +Where the control circuit transformer rated primary current is less than 2 amperes, an overcurrent device rated or set at not more than +500 percent of the rated primary current shall be permitted in the primary circuit. + +##### 430.72(C)(5) Other Means. + +Protection shall be permitted to be provided by other approved means. + +### 430.73 Protection of Conductors from Physical Damage. + +Where damage to a motor control circuit would constitute a hazard, all conductors of such a remote motor control circuit that are outside the control device itself shall be installed in a raceway or be otherwise protected from physical damage. + +### 430.74 Electrical Arrangement of Control Circuits. + +Where one conductor of the motor control circuit is grounded, the motor control circuit shall be arranged so that a ground fault in the control circuit remote from the motor controller will (1) not start the motor and (2) not bypass manually operated shutdown devices or automatic safety shutdown devices. + +### 430.75 Disconnection. + +#### 430.75(A) General. + +Motor control circuits shall be arranged so that they will be disconnected from all sources of supply when the disconnecting means is in the open position. The disconnecting means shall be permitted to consist of two or more separate devices, one of which disconnects the motor and the controller from the source(s) of power supply for the motor, and the other(s), the motor control circuit(s) from its power supply. Where separate devices are used, they shall be located immediately adjacent to each other. + +> [!important] Exception No. 1: +> Where more than 12 motor control circuit conductors are required to be disconnected, the disconnecting means shall be permitted to be located other than immediately adjacent to each other where all of the following conditions are complied with: + +* (1) Access to energized parts is limited to qualified persons in accordance with Part XII of this article. + +* (2) A warning sign is permanently located on the outside of each equipment enclosure door or cover permitting access to the live parts in the motor control circuit(s), warning that motor control circuit disconnecting means are remotely located and specifying the location and identification of each disconnect. Where energized parts are not in an equipment enclosure as permitted by +430.232 and 430.233, an additional warning sign(s) shall be located where visible to persons who may be working in the area of the energized parts. + +> [!important] Exception No. 2: +> The motor control circuit disconnecting means shall be permitted to be remote from the motor controller power supply disconnecting means where the opening of one or more motor control circuit disconnecting means is capable of resulting in potentially unsafe conditions for personnel or property and the conditions of items (1) and (2) of Exception No. 1 are complied with. + +#### 430.75(B) Control Transformer in Controller Enclosure. + +Where a transformer or other device is used to obtain a reduced voltage for the motor control circuit and is located in the controller enclosure, such transformer or other device shall be connected to the load side of the disconnecting means for the motor control circuit. + +## Part VII. Motor Controllers + +### 430.81 General. + +Part VII is intended to require suitable controllers for all motors. + +#### 430.81(A) Stationary Motor of 1⁄8 Horsepower or Less. + +For a stationary motor rated at 1⁄8 hp or less that is normally left running and is constructed so that it cannot be damaged by overload or failure to start, such as clock motors and the like, the branch-circuit disconnecting means shall be permitted to serve as the controller. + +#### 430.81(B) Portable Motor of 1⁄3 Horsepower or Less. + +For a portable motor rated at 1⁄3 hp or less, the controller shall be permitted to be an attachment plug and receptacle or cord connector. + +### 430.82 Controller Design. + +#### 430.82(A) Starting and Stopping. + +Each controller shall be capable of starting and stopping the motor it controls and shall be capable of interrupting the locked-rotor current of the motor. + +#### 430.82(B) Autotransformer. + +An autotransformer starter shall provide an “off” position, a running position, and at least one starting position. It shall be designed so that it cannot rest in the starting position or in any position that will render the overload device in the circuit inoperative. + +#### 430.82(C) Rheostats. + +Rheostats shall be in compliance with the following: + +* (1) Motor-starting rheostats shall be designed so that the contact arm cannot be left on intermediate segments. The point or plate on which the arm rests when in the starting position shall have no electrical connection with the resistor. + +* (2) Motor-starting rheostats for dc motors operated from a constant voltage supply shall be equipped with automatic devices that will interrupt the supply before the speed of the motor has fallen to less than one-third its normal rate. + +### 430.83 Ratings. + +The controller shall have a rating as specified in 430.83(A), unless otherwise permitted in 430.83(B) or (C), or as specified in (D), under the conditions specified. + +#### 430.83(A) General. + +##### 430.83(A)(1) Horsepower Ratings. + +Controllers, other than inverse time circuit breakers and molded case switches, shall have horsepower ratings at the application voltage not lower than the horsepower rating of the motor. + +##### 430.83(A)(2) Circuit Breaker. + +A branch-circuit inverse time circuit breaker rated in amperes shall be permitted as a controller for all motors. Where this circuit breaker is also used for overload protection, it shall conform to the appropriate provisions of this article governing overload protection. + +##### 430.83(A)(3) Molded Case Switch. + +A molded case switch rated in amperes shall be permitted as a controller for all motors. + +#### 430.83(B) Small Motors. + +Devices as specified in 430.81(A) and (B) shall be permitted as a controller. + +#### 430.83(C) Stationary Motors of 2 Horsepower or Less. + +For stationary motors rated at 2 hp or less and 300 volts or less, the controller shall be permitted to be either of the following: + +* (1) A general-use switch having an ampere rating not less than twice the full-load current rating of the motor + +* (2) On ac circuits, a general-use snap switch suitable only for use on ac (not general-use ac–dc snap switches) where the motor full-load current rating is not more than 80 percent of the ampere rating of the switch + +#### 430.83(D) Torque Motors. + +For torque motors, the controller shall have a continuous-duty, full-load current rating not less than the nameplate current rating of the motor. For a motor controller rated in horsepower but not marked with the foregoing current rating, the equivalent current rating shall be determined from the horsepower rating by using Table 430.247, Table 430.248, Table 430.249, or Table 430.250. + +#### 430.83(E) Voltage Rating. + +A controller with a straight voltage rating, for example, 240 volts or 480 volts, shall be permitted to be applied in a circuit in which the nominal voltage between any two conductors does not exceed the controller’s voltage rating. A controller with a slash rating, for example, 120/240 volts or 480Y/277 volts, shall only be applied in a solidly grounded circuit in which the nominal voltage to ground from any conductor does not exceed the lower of the two values of the controller’s voltage rating and the nominal voltage between any two conductors does not exceed the higher value of the controller’s voltage rating. + +### 430.84 Need Not Open All Conductors. + +The controller shall not be required to open all conductors to the motor. + +> [!important] Exception: +> Where the controller serves also as a disconnecting means, it shall open all ungrounded conductors to the motor as provided in 430.111. + +### 430.85 In Grounded Conductors. + +One pole of the controller shall be permitted to be placed in a permanently grounded conductor, provided the controller is designed so that the pole in the grounded conductor cannot be opened without simultaneously opening all conductors of the circuit. + +### 430.87 Number of Motors Served by Each Controller. + +Each motor shall be provided with an individual controller. + +> [!important] Exception No. 1: +> For motors rated 1000 volts or less, a single controller rated at not less than the equivalent horsepower, as determined in accordance with 430.110(C)(1), of all the motors in the group shall be permitted to serve the group under any of the following conditions: + +* (1) Where a number of motors drive several parts of a single machine or piece of apparatus, such as metal and woodworking machines, cranes, hoists, and similar apparatus + +* (2) Where a group of motors is under the protection of one overcurrent device as permitted in 430.53(A) + +* (3) Where a group of motors is located in a single room within sight from the controller location + +> [!important] Exception No. 2: +> A branch-circuit disconnecting means serving as the controller as allowed in 430.81(A) shall be permitted to serve more than one motor. + +### 430.88 Adjustable-Speed Motors. + +Adjustable-speed motors that are controlled by means of field regulation shall be equip ped and connected so that they cannot be started under a weakened field. + +> [!important] Exception: +> Starting under a weakened field shall be permitted where the motor is designed for such starting. + +### 430.89 Speed Limitation. + +Machines of the following types shall be provided with speed-limiting devices or other speed-limiting means: + +* (1) Separately excited dc motors + +* (2) Series motors + +* (3) Motor-generators and converters that can be driven at excessive speed from the dc end, as by a reversal of current or decrease in load + +> [!important] Exception: +> Separate speed-limiting devices or means shall not be required under either of the following conditions: + +* (1) Where the inherent characteristics of the machines, the system, or the load and the mechanical connection thereto are such as to safely limit the speed + +* (2) Where the machine is always under the manual control of a qualified operator + +### 430.90 Combination Fuseholder and Switch as Controller. + +The rating of a combination fuseholder and switch used as a motor controller shall be such that the fuseholder will accommodate the size of the fuse specified in Part III of this article for motor overload protection. + +> [!important] Exception: +> Where fuses having time delay appropriate for the starting characteristics of the motor are used, fuseholders of smaller size than specified in Part III of this article shall be permitted. + +## Part VIII. Motor Control Centers + +### 430.92 General. + +Part VIII covers motor control centers instal led for the control of motors, lighting, and power circuits. + +### 430.94 Overcurrent Protection. + +Motor control centers shall be provided with overcurrent protection in accordance with Parts I, II, and VIII of Article 240. The ampere rating or setting of the overcurrent protective device shall not exceed the rating of the common power bus. This protection shall be provided by (1) an overcurrent protective device located ahead of the motor control center or (2) a main overcurrent protective device located within the motor control center. + +### 430.95 Service Equipment. + +Where used as service equipment, each motor control center shall be provided with a single main disconnecting means to disconnect all ungrounded service conductors. + +> [!important] Exception: +> A second service disconnect shall be permitted to supply additional equipment. + +Where a grounded conductor is provided, the motor control center shall be provided with a main bonding jumper, sized in accordance with 250.28(D), within one of the sections for connecting the grounded conductor, on its supply side, to the motor control center equipment ground bus. + +> [!important] Exception: +> High-impedance grounded neutral systems shall be permitted to be connected as provided in 250.36. + +### 430.96 Grounding. + +Multisection motor control centers shall be connected together with an equipment grounding conductor or an equivalent equipment grounding bus sized in accordance with Table 250.122. Equipment grounding conductors shall be connected to this equipment grounding bus or to a grounding termination point provided in a single-section motor control center. + +### 430.97 Busbars and Conductors. + +#### 430.97(A) Support and Arrangement. + +Busbars shall be protected from physical damage and be held firmly in place. Other than for required interconnections and control wiring, only those conductors that are intended for termination in a vertical section shall be located in that section. + +> [!important] Exception: +> Conductors shall be permitted to travel horizontally through vertical sections where such conductors are isolated from the busbars by a barrier. + +#### 430.97(B) Phase Arrangement. + +The phase arrangement on 3-phase horizontal common power and vertical buses shall be A, B, C from front to back, top to bottom, or left to right, as viewed from the front of the motor control center. The B phase shall be that phase having the higher voltage to ground on 3-phase, 4-wire, delta-connected systems. Other busbar arrangements shall be permitted for additions to existing installations and shall be marked. + +> [!important] Exception: +> Rear-mounted units connected to a vertical bus that is common to front-mounted units shall be permitted to have a C, B, A phase arrangement where properly identified. + +#### 430.97(C) Minimum Wire-Bending Space. + +The minimum wire-bending space at the motor control center terminals and minimum gutter space shall be as required in Article 312. + +#### 430.97(D) Spacings. + +Spacings between motor control center bus terminals and other bare metal parts shall not be less than specified in Table 430.97(D). + +#### 430.97(E) Barriers. + +Barriers shall be placed in all service-entrance motor control centers to isolate service busbars and terminals from the remainder of the motor control center. + +Table 430.97(D) Minimum Spacing Between Bare Metal Parts + +Nominal + +Voltage + +Opposite Polarity Where Mounted on the Same Surface + +Opposite Polarity Where + +Held Free in Air + +Live Parts to + +Ground mm in. mm in. mm in. + +Not over 125 volts, nominal +19.1 3⁄4 12.7 1⁄2 12.7 1⁄2 + +Not over 250 volts, nominal +31.8 11⁄4 19.1 3⁄4 12.7 1⁄2 + +Not over 600 volts, nominal +50.8 2 25.4 1 25.4 1 + +### 430.98 Marking. + +#### 430.98(A) Motor Control Centers. + +Motor control centers shall be marked according to 110.21, and the marking shall be plainly visible after installation. Marking shall also include common power bus current rating and motor control center short-circuit current rating. + +#### 430.98(B) Motor Control Units. + +Motor control units in a motor control center shall comply with 430.8. + +### 430.99 Available Fault Current. + +The available fault current at the motor control center and the date the available fault current calculation was performed shall be documented and made available to those authorized to inspect, install, or maintain the installation. + +## Part IX. Disconnecting Means + +### 430.101 General. + +Part IX is intended to require disconnecting means capable of disconnecting motors and controllers from the circuit. + +### 430.102 Location. + +#### 430.102(A) Controller. + +An individual disconnecting means shall be provided for each controller and shall disconnect the controller. The disconnecting means shall be located in sight from the controller location. + +> [!important] Exception No. 1: +> For motor circuits over 1000 volts, nominal, a controller disconnecting means lockable in accordance with 110.25 shall be permitted to be out of sight of the controller, provided that the controller is marked with a warning label giving the location of the disconnecting means. + +> [!important] Exception No. 2: +> A single disconnecting means shall be permitted for a group of coordinated controllers that drive several parts of a single machine or piece of apparatus. The disconnecting means shall be located in sight from the controllers, and both the disconnecting means and the controllers shall be located in sight from the machine or apparatus. + +> [!important] Exception No. 3: +> The disconnecting means shall not be required to be in sight from valve actuator motor (VAM) assemblies containing the controller where such a location introduces additional or increased hazards to persons or property and conditions (1) and (2) are met. + +* (1) The valve actuator motor assembly is marked with a warning label giving the location of the disconnecting means. + +* (2) The disconnecting means is lockable in accordance with 110.25. + +#### 430.102(B) Motor. + +A disconnecting means shall be provided for a motor in accordance with 430.102(B)(1) or (B)(2). + +##### 430.102(B)(1) Separate Motor Disconnect. + +A disconnecting means for the motor shall be located in sight from the motor location and the driven machinery location. + +##### 430.102(B)(2) Controller Disconnect. + +The controller disconnecting means required in accordance with 430.102(A) shall be permitted to serve as the disconnecting means for the motor if it is in sight from the motor location and the driven machinery location. + +Exception to (1) and (2): The disconnecting means for the motor shall not be required under either condition (1) or condition (2), which follow, provided that the controller disconnecting means required in 430.102(A) is lockable in accordance with 110.25. + +* (1) Where such a location of the disconnecting means for the motor is impracticable or introduces additional or increased hazards to persons or property + +> [!info] Informational Note: +> Some examples of increased or additional hazards include, but are not limited to, motors rated in excess of +100 hp, multimotor equipment, submersible motors, motors associated with adjustable speed drives, and motors located in hazardous (classified) locations. + +* (2) In industrial installations, with written safety procedures, where conditions of maintenance and supervision ensure that only qualified persons service the equipment + +> [!info] Informational Note: +> For information on lockout/tagout procedures, see NFPA 70E-2015, Standard for Electrical Safety in the Workplace. + +### 430.103 Operation. + +The disconnecting means shall open all ungrounded supply conductors and shall be designed so that no pole can be operated independently. The disconnecting means shall be permitted in the same enclosure with the controller. The disconnecting means shall be designed so that it cannot be closed automatically. + +> [!info] Informational Note: +> See 430.113 for equipment receiving energy from more than one source. + +### 430.104 To Be Indicating. + +The disconnecting means shall plainly indicate whether it is in the open (off) or closed (on) position. + +### 430.105 Grounded Conductors. + +One pole of the disconnecting means shall be permitted to disconnect a permanently grounded conductor, provided the disconnecting means is designed so that the pole in the grounded conductor cannot be opened without simultaneously disconnecting all conductors of the circuit. + +### 430.107 Readily Accessible. + +At least one of the disconnecting means shall be readily accessible. + +### 430.108 Every Disconnecting Means. + +Every disconnecting means in the motor circuit between the point of attachment to the feeder or branch circuit and the point of connection to the motor shall comply with the requirements of 430.109 and 430.110. + +### 430.109 Type. + +The disconnecting means shall be a type specified in 430.109(A), unless otherwise permitted in 430.109(B) through (G), under the conditions specified. + +#### 430.109(A) General. + +##### 430.109(A)(1) Motor Circuit Switch. + +A listed motor-circuit switch rated in horsepower. + +##### 430.109(A)(2) Molded Case Circuit Breaker. + +A listed molded case circuit breaker. + +##### 430.109(A)(3) Molded Case Switch. + +A listed molded case switch. + +##### 430.109(A)(4) Instantaneous Trip Circuit Breaker. + +An instantaneous trip circuit breaker that is part of a listed combination motor controller. + +##### 430.109(A)(5) Self-Protected Combination Controller. + +Listed self-protected combination controller. + +##### 430.109(A)(6) Manual Motor Controller. + +Listed manual motor controllers additionally marked “Suitable as Motor Disconnect” shall be permitted as a disconnecting means where installed between the final motor branch-circuit short-circuit protective device and the motor. Listed manual motor controllers additionally marked “Suitable as Motor Disconnect” shall be permitted as disconnecting means on the line side of the fuses permitted in +430.52(C)(5). In this case, the fuses permitted in 430.52(C)(5) shall be considered supplementary fuses, and suitable branch-circuit short-circuit and ground-fault protective devices shall be installed on the line side of the manual motor controller additionally marked +“Suitable as Motor Disconnect.” + +##### 430.109(A)(7) System Isolation Equipment. + +System isolation equipment shall be listed for disconnection purposes. System isolation equipment shall be installed on the load side of the overcurrent protection and its disconnecting means. The disconnecting means shall be one of the types permitted by 430.109(A)(1) through (A)(3). + +#### 430.109(B) Stationary Motors of 1⁄8 Horsepower or Less. + +For stationary motors of 1⁄8 hp or less, the branch-circuit overcurrent device shall be permitted to serve as the disconnecting means. + +#### 430.109(C) Stationary Motors of 2 Horsepower or Less. + +For stationary motors rated at 2 hp or less and 300 volts or less, the disconnecting means shall be permitted to be one of the devices specified in (1), (2), or (3): + +* (1) A general-use switch having an ampere rating not less than twice the full-load current rating of the motor + +* (2) On ac circuits, a general-use snap switch suitable only for use on ac (not general-use ac–dc snap switches) where the motor full-load current rating is not more than 80 percent of the ampere rating of the switch + +* (3) A listed manual motor controller having a horsepower rating not less than the rating of the motor and marked “Suitable as Motor + +Disconnect” + +#### 430.109(D) Autotransformer-Type Controlled Motors. + +For motors of over 2 hp to and including 100 hp, the separate disconnecting means required for a motor with an autotransformer-type controller shall be permitted to be a general-use switch where all of the following provisions are met: + +* (1) The motor drives a generator that is provided with overload protection. + +* (2) The controller is capable of interrupting the locked-rotor current of the motors, is provided with a no voltage release, and is provided with running overload protection not exceeding 125 percent of the motor full-load current rating. + +* (3) Separate fuses or an inverse time circuit breaker rated or set at not more than 150 percent of the motor full-load current is provided in the motor branch circuit. + +#### 430.109(E) Isolating Switches. + +For stationary motors rated at more than 40 hp dc or 100 hp ac, the disconnecting means shall be permitted to be a general-use or isolating switch where plainly marked “Do not operate under load.” + +#### 430.109(F) Cord-and-Plug-Connected Motors. + +For a cord-and-plug-connected motor, a horsepower-rated attachment plug and receptacle, flanged surface inlet and cord connector, or attachment plug and cord connector having ratings no less than the motor ratings shall be permitted to serve as the disconnecting means. Horsepower-rated attachment plugs, flanged surface inlets, receptacles, or cord connectors shall not be required for cord-andplug-connected appliances in accordance with 422.33, room air conditioners in accordance with 440.63, or portable motors rated 1⁄3 hp or less. + +#### 430.109(G) Torque Motors. + +For torque motors, the disconnecting means shall be permitted to be a general-use switch. + +### 430.110 Ampere Rating and Interrupting Capacity. + +#### 430.110(A) General. + +The disconnecting means for motor circuits rated 1000 volts, nominal, or less shall have an ampere rating not less than 115 percent of the full-load current rating of the motor. + +> [!important] Exception: +> A listed unfused motor-circuit switch having a horsepower rating not less than the motor horsepower shall be permitted to have an ampere rating less than 115 percent of the full-load current rating of the motor. + +#### 430.110(B) For Torque Motors. + +Disconnecting means for a torque motor shall have an ampere rating of at least 115 percent of the motor nameplate current. + +#### 430.110(C) For Combination Loads. + +Where two or more motors are used together or where one or more motors are used in combination with other loads, such as resistance heaters, and where the combined load may be simultaneous on a single disconnecting means, the ampere and horsepower ratings of the combined load shall be determined as follows. + +##### 430.110(C)(1) Horsepower Rating. + +The rating of the disconnecting means shall be determined from the sum of all currents, including resistance loads, at the full-load condition and also at the locked-rotor condition. The combined full-load current and the combined locked-rotor current so obtained shall be considered as a single motor for the purpose of this requirement as follows. + +The full-load current equivalent to the horsepower rating of each motor shall be selected from Table 430.247, Table 430.248, Table +430.249, or Table 430.250. These full-load currents shall be added to the rating in amperes of other loads to obtain an equivalent fullload current for the combined load. + +The locked-rotor current equivalent to the horsepower rating of each motor shall be selected from Table 430.251(A) or Table +430.251(B). The locked-rotor currents shall be added to the rating in amperes of other loads to obtain an equivalent locked-rotor current for the combined load. Where two or more motors or other loads cannot be started simultaneously, the largest sum of locked-rotor currents of a motor or group of motors that can be started simultaneously and the full-load currents of other concurrent loads shall be permitted to be used to determine the equivalent locked-rotor current for the simultaneous combined loads. In cases where different current ratings are obtained when applying these tables, the largest value obtained shall be used. + +> [!important] Exception: +> Where part of the concurrent load is resistance load, and where the disconnecting means is a switch rated in horsepower and amperes, the switch used shall be permitted to have a horsepower rating that is not less than the combined load of the motor(s), if the ampere rating of the switch is not less than the locked-rotor current of the motor(s) plus the resistance load. + +##### 430.110(C)(2) Ampere Rating. + +The ampere rating of the disconnecting means shall not be less than 115 percent of the sum of all currents at the full-load condition determined in accordance with 430.110(C)(1). + +> [!important] Exception: +> A listed nonfused motor-circuit switch having a horsepower rating equal to or greater than the equivalent horsepower of the combined loads, determined in accordance with 430.110(C)(1), shall be permitted to have an ampere rating less than 115 percent of the sum of all currents at the full-load condition. + +##### 430.110(C)(3) Small Motors. + +For small motors not covered by Table 430.247, Table 430.248, Table 430.249, or Table 430.250, the locked-rotor current shall be assumed to be six times the full-load current. + +### 430.111 Switch or Circuit Breaker as Both Controller and Disconnecting Means. + +A switch or circuit breaker shall be permitted to be used as both the controller and disconnecting means if it complies with 430.111(A) and is one of the types specified in 430.111(B). + +#### 430.111(A) General. + +The switch or circuit breaker complies with the requirements for controllers specified in 430.83, opens all ungrounded conductors to the motor, and is protected by an overcurrent device in each ungrounded conductor (which shall be permitted to be the branch-circuit fuses). The overcurrent device protecting the controller shall be permitted to be part of the controller assembly or shall be permitted to be separate. An autotransformer-type controller shall be provided with a separate disconnecting means. + +#### 430.111(B) Type. + +The device shall be one of the types specified in 430.111(B)(1), (B)(2), or (B)(3). + +##### 430.111(B)(1) Air-Break Switch. + +An air-break switch, operable directly by applying the hand to a lever or handle. + +##### 430.111(B)(2) Inverse Time Circuit Breaker. + +An inverse time circuit breaker operable directly by applying the hand to a lever or handle. The circuit breaker shall be permitted to be both power and manually operable. + +##### 430.111(B)(3) Oil Switch. + +An oil switch used on a circuit whose rating does not exceed 1000 volts or 100 amperes, or by special permission on a circuit exceeding this capacity where under expert supervision. The oil switch shall be permitted to be both power and manually operable. + +### 430.112 Motors Served by Single Disconnecting Means. + +Each motor shall be provided with an individual disconnecting means. + +> [!important] Exception: +> A single disconnecting means shall be permitted to serve a group of motors under any one of the conditions of (1), (2), and +(3). The single disconnecting means shall be rated in accordance with 430.110(C). + +* (1) Where a number of motors drive several parts of a single machine or piece of apparatus, such as metal- and woodworking machines, cranes, and hoists. + +* (2) Where a group of motors is under the protection of one set of branch-circuit protective devices as permitted by 430.53(A). + +* (3) Where a group of motors is in a single room within sight from the location of the disconnecting means. + +### 430.113 Energy from More Than One Source. + +Motor and motor-operated equipment receiving electric energy from more than one source shall be provided with disconnecting means from each source of electric energy immediately adjacent to the equipment served. Each source shall be permitted to have a separate disconnecting means. Where multiple disconnecting means are provided, a permanent warning sign shall be provided on or adjacent to each disconnecting means. + +> [!important] Exception No. 1: +> Where a motor receives electric energy from more than one source, the disconnecting means for the main power supply to the motor shall not be required to be immediately adjacent to the motor, provided that the controller disconnecting means is lockable in accordance with 110.25. + +> [!important] Exception No. 2: +> A separate disconnecting means shall not be required for a Class 2 remote-control circuit conforming with Article 725, rated not more than 30 volts, and isolated and ungrounded. + +## Part X. Adjustable-Speed Drive Systems + +### 430.120 General. + +The installation provisions of Part I through Part IX are applicable unless modified or supplemented by Part X. + +### 430.122 Conductors — Minimum Size and Ampacity. + +#### 430.122(A) Branch/Feeder Circuit Conductors. + +Circuit conductors supplying power conversion equipment included as part of an adjustable-speed drive system shall have an ampacity not less than 125 percent of the rated input current to the power conversion equipment. + +> [!info] Informational Note No. 1: +> Power conversion equipment can have multiple power ratings and corresponding input currents. + +> [!info] Informational Note No. 2: +> Circuit conductors on the output of an adjustable-speed drive system are susceptible to breakdown under certain conditions due to the characteristics of the output waveform of the drive. Factors affecting the conductors include but are not limited to the output voltage, frequency, and current, the length of the conductors, the spacing between the conductors, and the dielectric strength of the conductor insulation. Methods to mitigate breakdown include consideration of one or more of these factors. + +#### 430.122(B) Output Conductors. + +The conductors between the power conversion equipment and the motor shall have an ampacity equal to or larger than 125 percent of the motor full-load current as determined by 430.6(A) or (B). + +> [!important] Exception: +> If the power conversion equipment is listed and marked as “Suitable for Output Motor Conductor Protection,” the conductor between the power conversion equipment and the motor shall have an ampacity equal to or greater than the larger of: + +* (1) 125 percent of the motor full load current as determined by 430.6(A) or (B) + +* (2) The ampacity of the minimum conductor size marked on the power conversion equipment + +> [!info] Informational Note: +> The minimum ampacity required of output conductors is often different than that of the conductors supplying the power conversion equipment. See 430.130 and 430.131 for branch circuit protection requirements. + +#### 430.122(C) Bypass Device. + +For an adjustable-speed drive system that utilizes a bypass device, the conductor ampacity shall not be less than required by 430.6. + +The ampacity of circuit conductors supplying power conversion equipment included as part of an adjustable-speed drive system that utilizes a bypass device shall be the larger of either of the following: + +* (1) 125 percent of the rated input current to the power conversion equipment + +* (2) 125 percent of the motor full-load current rating as determined by 430.6 + +#### 430.122(D) Several Motors or a Motor and Other Loads. + +Conductors supplying several motors or a motor and other loads, including power conversion equipment, shall have ampacity in accordance with 430.24, using the rated input current of the power conversion equipment for purposes of calculating ampacity. + +### 430.124 Overload Protection. + +Overload protection of the motor shall be provided. + +#### 430.124(A) Included in Power Conversion Equipment. + +Where the power conversion equipment is marked to indicate that motor overload protection is included, additional overload protection shall not be required. + +#### 430.124(B) Bypass Circuits. + +For adjustable-speed drive systems that utilize a bypass device to allow motor operation at rated full-load speed, motor overload protection as described in Article 430, Part III, shall be provided in the bypass circuit. + +#### 430.124(C) Multiple Motor Applications. + +For multiple motor application, individual motor overload protection shall be provided in accordance with Article 430, Part III. + +### 430.126 Motor Overtemperature Protection. + +#### 430.126(A) General. + +Adjustable-speed drive systems shall protect against motor overtemperature conditions where the motor is not rated to operate at the nameplate rated current over the speed range required by the application. This protection shall be provided in addition to the conductor protection required in 430.32. Protection shall be provided by one of the following means. + +* (1) Motor thermal protector in accordance with 430.32 + +* (2) Adjustable-speed drive system with load and speed-sensitive overload protection and thermal memory retention upon shutdown or power loss + +Exception to (2): Thermal memory retention upon shutdown or power loss is not required for continuous duty loads. + +* (3) Overtemperature protection relay utilizing thermal sensors embedded in the motor and meeting the requirements of 430.126(A) +(2) + +* (4) Thermal sensor embedded in the motor whose communications are received and acted upon by an adjustable-speed drive system + +> [!info] Informational Note: +> The relationship between motor current and motor temperature changes when the motor is operated by an adjustable-speed drive. In certain applications, overheating of motors can occur when operated at reduced speed, even at current levels less than a motor’s rated full-load current. The overheating can be the result of reduced motor cooling when its shaft-mounted fan is operating less than rated nameplate RPM. As part of the analysis to determine whether overheating will occur, it is necessary to consider the continuous torque capability curves for the motor given the application requirements. This will assist in determining whether the motor overload protection will be able, on its own, to provide protection against overheating. These overheating protection requirements are only intended to apply to applications where an adjustable-speed drive, as defined in Article 100, is used. + +For motors that utilize external forced air or liquid cooling systems, overtemperature can occur if the cooling system is not operating. + +Although this issue is not unique to adjustable speed applications, externally cooled motors are most often encountered with such applications. In these instances, overtemperature protection using direct temperature sensing is recommended \[i.e., 430.126(A)(1), (A) +(3), or (A)(4)\], or additional means should be provided to ensure that the cooling system is operating (flow or pressure sensing, interlocking of adjustable-speed drive system and cooling system, etc.). + +#### 430.126(B) Multiple Motor Applications. + +For multiple motor applications, individual motor overtemperature protection shall be provided as required in 430.126(A). + +#### 430.126(C) Automatic Restarting and Orderly Shutdown. + +430.43 and 430.44 shall apply to the motor overtemperature protection means. + +### 430.128 Disconnecting Means. + +The disconnecting means shall be permitted to be in the incoming line to the conversion equipment and shall have a rating not less than 115 percent of the rated input current of the conversion unit. +430.130 Branch-Circuit Short-Circuit and Ground-Fault Protection for Single Motor Circuits Containing + +Power Conversion Equipment. + +#### 430.130(A) Circuits Containing Power Conversion Equipment. + +Circuits containing power conversion equipment shall be protected by a branch circuit short-circuit and ground-fault protective device in accordance with all of the following: + +* (1) The rating and type of protection shall be determined by 430.52(C)(1), (C)(3), (C)(5), or (C)(6), using the full-load current rating of the motor load as determined by 430.6(A) or (B). + +Exception to 1: The rating and type of protection shall be permitted to be determined by Table 430.52 using the power conversion equipment’s rated input current where the power conversion equipment is listed and marked “Suitable for Output + +Motor Conductor Protection.” + +> [!info] Informational Note No. 1: +> Motor conductor branch circuit short-circuit and ground-fault protection from the power conversion equipment to the motor is provided by power conversion equipment that is listed and marked “Suitable for Output Motor + +Conductor Protection.” + +> [!info] Informational Note No. 2: +> A motor branch circuit using power conversion equipment, including equipment listed and marked +“Suitable for Output Motor Conductor Protection,” includes the input circuit to the power conversion equipment. + +* (2) Where maximum branch circuit short-circuit and ground-fault protective ratings are stipulated for specific device types in the manufacturer's instructions for the power conversion equipment or are otherwise marked on the equipment, they shall not be exceeded even if higher values are permitted by 430.130(A)(1). + +* (3) A self-protected combination controller shall only be permitted where specifically identified in the manufacturer’s instructions for the power conversion equipment or if otherwise marked on the equipment. + +> [!info] Informational Note: +> The type of protective device, its rating, and its setting are often marked on or provided with the power conversion equipment. + +* (4) Where an instantaneous trip circuit breaker or semiconductor fuses are permitted in accordance with the drive manufacturer’s instructions for use as the branch circuit short-circuit and ground-fault protective device for listed power conversion equipment, they shall be provided as an integral part of a single listed assembly incorporating both the protective device and power conversion equipment. + +#### 430.130(B) Bypass Circuit/Device. + +Branch-circuit short-circuit and ground-fault protection shall also be provided for a bypass circuit/device(s). Where a single branch-circuit short-circuit and ground-fault protective device is provided for circuits containing both power conversion equipment and a bypass circuit, the branch-circuit protective device type and its rating or setting shall be in accordance with those determined for the power conversion equipment and for the bypass circuit/device(s) equipment. + +### 430.131 Several Motors or Loads on One Branch Circuit Including Power Conversion Equipment. + +For installations meeting all the requirements of 430.53 that include one or more power converters, the branch-circuit short-circuit and ground-fault protective fuses or inverse time circuit breakers shall be of a type and rating or setting permitted for use with the power conversion equipment using the full-load current rating of the connected motor load in accordance with 430.53. For the purposes of +430.53 and 430.131, power conversion equipment shall be considered to be a motor controller. + +## Part XI. Over 1000 Volts, Nominal + +### 430.221 General. + +Part XI recognizes the additional hazard due to the use of higher voltages. It adds to or amends the other provisions of this article. + +### 430.222 Marking on Controllers. + +In addition to the marking required by 430.8, a controller shall be marked with the control voltage. + +### 430.223 Raceway Connection to Motors. + +Flexible metal conduit or liquidtight flexible metal conduit not exceeding 1.8 m (6 ft) in length shall be permitted to be employed for raceway connection to a motor terminal enclosure. + +### 430.224 Size of Conductors. + +Conductors supplying motors shall have an ampacity not less than the current at which the motor overload protective device(s) is selected to trip. + +### 430.225 Motor-Circuit Overcurrent Protection. + +#### 430.225(A) General. + +Each motor circuit shall include coordinated protection to automatically interrupt overload and fault currents in the motor, the motorcircuit conductors, and the motor control apparatus. + +> [!important] Exception: +> Where a motor is critical to an operation and the motor should operate to failure if necessary to prevent a greater hazard to persons, the sensing device(s) shall be permitted to be connected to a supervised annunciator or alarm instead of interrupting the motor circuit. + +#### 430.225(B) Overload Protection. + +##### 430.225(B)(1) Type of Overload Device. + +Each motor shall be protected against dangerous heating due to motor overloads and failure to start by a thermal protector integral with the motor or external current-sensing devices, or both. Protective device settings for each motor circuit shall be determined under engineering supervision. + +##### 430.225(B)(2) Wound-Rotor Alternating-Current Motors. + +The secondary circuits of wound-rotor ac motors, including conductors, controllers, and resistors rated for the application, shall be considered as protected against overcurrent by the motor overload protection means. + +##### 430.225(B)(3) Operation. + +Operation of the overload interrupting device shall simultaneously disconnect all ungrounded conductors. + +##### 430.225(B)(4) Automatic Reset. + +Overload sensing devices shall not automatically reset after trip unless resetting of the overload sensing device does not cause automatic restarting of the motor or there is no hazard to persons created by automatic restarting of the motor and its connected machinery. + +#### 430.225(C) Fault-Current Protection. + +##### 430.225(C)(1) Type of Protection. + +Fault-current protection shall be provided in each motor circuit as specified by either 430.225(C) (1) (a) or (C)(1)(b). + +* (a) A circuit breaker of suitable type and rating arranged so that it can be serviced without hazard. The circuit breaker shall simultaneously disconnect all ungrounded conductors. The circuit breaker shall be permitted to sense the fault current by means of integral or external sensing elements. + +* (b) Fuses of a suitable type and rating placed in each ungrounded conductor. Fuses shall be used with suitable disconnecting means, or they shall be of a type that can also serve as the disconnecting means. They shall be arranged so that they cannot be serviced while they are energized. + +##### 430.225(C)(2) Reclosing. + +Fault-current interrupting devices shall not automatically reclose the circuit. + +> [!important] Exception: +> Automatic reclosing of a circuit shall be permitted where the circuit is exposed to transient faults and where such automatic reclosing does not create a hazard to persons. + +##### 430.225(C)(3) Combination Protection. + +Overload protection and fault-current protection shall be permitted to be provided by the same device. + +### 430.226 Rating of Motor Control Apparatus. + +The ultimate trip current of overcurrent (overload) relays or other motor-protective devices used shall not exceed 115 percent of the controller’s continuous current rating. Where the motor branch-circuit disconnecting means is separate from the controller, the disconnecting means current rating shall not be less than the ultimate trip setting of the overcurrent relays in the circuit. + +### 430.227 Disconnecting Means. + +The controller disconnecting means shall be lockable in accordance with 110.25. + +## Part XII. Protection of Live Parts — All Voltages + +### 430.231 General. + +Part XII specifies that live parts shall be protected in an approved manner for the hazard involved. + +### 430.232 Where Required. + +Exposed live parts of motors and controllers operating at 50 volts or more between terminals shall be guarded against accidental contact by enclosure or by location as follows: + +* (1) By installation in a room or enclosure that is accessible only to qualified persons + +* (2) By installation on a suitable balcony, gallery, or platform, elevated and arranged so as to exclude unqualified persons + +* (3) By elevation 2.5 m (8 ft) or more above the floor + +> [!important] Exception: +> Live parts of motors operating at more than 50 volts between terminals shall not require additional guarding for stationary motors that have commutators, collectors, and brush rigging located inside of motor-end brackets and not conductively connected to supply circuits operating at more than 150 volts to ground. + +### 430.233 Guards for Attendants. + +Where live parts of motors or controllers operating at over 50 volts to ground are guarded against accidental contact only by location as specified in 430.232, and where adjustment or other attendance may be necessary during the operation of the apparatus, suitable insulating mats or platforms shall be provided so that the attendant cannot readily touch live parts unless standing on the mats or platforms. + +> [!info] Informational Note: +> For working space, see 110.26 and 110.34. + +## Part XIII. Grounding — All Voltages + +### 430.241 General. + +Part XIII specifies the grounding of exposed non–current-carrying metal parts, likely to become energized, of motor and controller frames to prevent a voltage aboveground in the event of accidental contact between energized parts and frames. Insulation, isolation, or guarding are suitable alternatives to grounding of motors under certain conditions. + +### 430.242 Stationary Motors. + +The frames of stationary motors shall be grounded under any of the following conditions: + +* (1) Where supplied by metal-enclosed wiring + +* (2) Where in a wet location and not isolated or guarded + +* (3) If in a hazardous (classified) location + +* (4) If the motor operates with any terminal at over 150 volts to ground + +Where the frame of the motor is not grounded, it shall be permanently and effectively insulated from the ground. + +### 430.243 Portable Motors. + +The frames of portable motors that operate over 150 volts to ground shall be guarded or grounded. + +> [!info] Informational Note No. 1: +> See 250.114(4) for grounding of portable appliances in other than residential occupancies. + +> [!info] Informational Note No. 2: +> See 250.119(C) for color of equipment grounding conductor. + +> [!important] Exception No. 1: +> Listed motor-operated tools, listed motor-operated appliances, and listed motor-operated equipment shall not be required to be grounded where protected by a system of double insulation or its equivalent. Double-insulated equipment shall be distinctively marked. + +> [!important] Exception No. 2: +> Listed motor-operated tools, listed motor-operated appliances, and listed motor-operated equipment connected by a cord and attachment plug other than those required to be grounded in accordance with 250.114. + +### 430.244 Controllers. + +Controller enclosures shall be connected to the equipment grounding conductor regardless of voltage. Controller enclosures shall have means for attachment of an equipment grounding conductor termination in accordance with 250.8. + +> [!important] Exception: +> Enclosures attached to ungrounded portable equipment shall not be required to be grounded. + +### 430.245 Method of Grounding. + +Connection to the equipment grounding conductor shall be done in the manner specified in Part VI of Article 250. + +#### 430.245(A) Grounding Through Terminal Housings. + +Where the wiring to motors is metal-enclosed cable or in metal raceways, junction boxes to house motor terminals shall be provided, and the armor of the cable or the metal raceways shall be connected to them in the manner specified in 250.96(A) and 250.97. + +#### 430.245(B) Separation of Junction Box from Motor. + +The junction box required by 430.245(A) shall be permitted to be separated from the motor by not more than 1.8 m (6 ft), provided the leads to the motor are stranded conductors within Type AC cable, interlocked metal tape Type MC cable where listed and identified in accordance with 250.118(10)(a), or armored cord or are stranded leads enclosed in liquidtight flexible metal conduit, flexible metal conduit, intermediate metal conduit, rigid metal conduit, or electrical metallic tubing not smaller than metric designator 12 (trade size +3⁄8), the armor or raceway being connected both to the motor and to the box. + +Liquidtight flexible nonmetallic conduit and rigid nonmetallic conduit shall be permitted to enclose the leads to the motor, provided the leads are stranded and the required equipment grounding conductor is connected to both the motor and to the box. + +Where stranded leads are used, protected as specified above, each strand within the conductor shall be not larger than 10 AWG and shall comply with other requirements of this Code for conductors to be used in raceways. + +#### 430.245(C) Grounding of Controller-Mounted Devices. + +Instrument transformer secondaries and exposed non–current-carrying metal or other conductive parts or cases of instrument transformers, meters, instruments, and relays shall be grounded as specified in 250.170 through 250.178. + +## Part XIV. Tables + +Table 430.247 Full-Load Current in Amperes, Direct-Current Motors + +The following values of full-load currents* are for motors running at base speed. + +Horsepower + +Armature Voltage Rating* +90 Volts 120 Volts 180 Volts 240 Volts 500 Volts 550 Volts +1⁄4 4.0 3.1 2.0 1.6 — — +1⁄3 5.2 4.1 2.6 2.0 — — +1⁄2 6.8 5.4 3.4 2.7 — — +3⁄4 9.6 7.6 4.8 3.8 — — +1 12.2 9.5 6.1 4.7 — — +11⁄2 — 13.2 8.3 6.6 — — +2 — 17 10.8 8.5 — — +3 — 25 16 12.2 — — +5 — 40 27 20 — — +71⁄2 — 58 — 29 13.6 12.2 +10 — 76 — 38 18 16 +15 — — — 55 27 24 +20 — — — 72 34 31 +25 — — — 89 43 38 +30 — — — 106 51 46 +40 — — — 140 67 61 +50 — — — 173 83 75 +60 — — — 206 99 90 +75 — — — 255 123 111 +100 — — — 341 164 148 +125 — — — 425 205 185 +150 — — — 506 246 222 +200 — — — 675 330 294 +*These are average dc quantities. + +Table 430.248 Full-Load Currents in + +Amperes, Single-Phase AlternatingCurrent Motors + +The following values of full-load currents are for motors running at usual speeds and motors with normal torque characteristics. The voltages listed are rated motor voltages. The currents listed shall be permitted for system voltage ranges of 110 to 120 and 220 to 240 volts. + +Horsepower +115 + +Volts +200 + +Volts +208 + +Volts +230 + +Volts +1⁄6 4.4 2.5 2.4 2.2 +1⁄4 5.8 3.3 3.2 2.9 +1⁄3 7.2 4.1 4.0 3.6 +1⁄2 9.8 5.6 5.4 4.9 +3⁄4 13.8 7.9 7.6 6.9 +1 16 9.2 8.8 8.0 +11⁄2 20 11.5 11.0 10 +2 24 13.8 13.2 12 +3 34 19.6 18.7 17 +5 56 32.2 30.8 28 +71⁄2 80 46.0 44.0 40 +10 100 57.5 55.0 50 + +Table 430.249 Full-Load Current, Two-Phase + +Alternating-Current Motors (4-Wire) + +The following values of full-load current are for motors running at speeds usual for belted motors and motors with normal torque characteristics. Current in the common conductor of a 2-phase, 3-wire system will be +1.41 times the value given. The voltages listed are rated motor voltages. The currents listed shall be permitted for system voltage ranges of +110 to 120, 220 to 240, 440 to 480, and 550 to +600 volts. + +Horsepower + +Induction-Type Squirrel Cage and + +Wound Rotor (Amperes) +115 + +Volts +230 + +Volts +460 + +Volts +575 + +Volts +2300 + +Volts +1⁄2 4.0 2.0 1.0 0.8 — +3⁄4 4.8 2.4 1.2 1.0 — +1 6.4 3.2 1.6 1.3 — +11⁄2 9.0 4.5 2.3 1.8 — +2 11.8 5.9 3.0 2.4 — +3 — 8.3 4.2 3.3 — +5 — 13.2 6.6 5.3 — + +Horsepower + +Induction-Type Squirrel Cage and + +Wound Rotor (Amperes) +115 + +Volts +230 + +Volts +460 + +Volts +575 + +Volts +2300 + +Volts +71⁄2 — 19 9.0 8.0 — +10 — 24 12 10 — +15 — 36 18 14 — +20 — 47 23 19 — +25 — 59 29 24 — +30 — 69 35 28 — +40 — 90 45 36 — +50 — 113 56 45 — +60 — 133 67 53 14 +75 — 166 83 66 18 +100 — 218 109 87 23 +125 — 270 135 108 28 +150 — 312 156 125 32 +200 — 416 208 167 43 + +Table 430.250 Full-Load Current, Three-Phase Alternating-Current Motors + +The following values of full-load currents are typical for motors running at speeds usual for belted motors torque characteristics. The voltages listed are rated motor voltages. The currents listed shall be permitted ranges of 110 to 120, 220 to 240, 440 to 480, and 550 to 600 volts. + +Horsepower + +Induction-Type Squirrel Cage and Wound Rotor (Amperes) + +Synchronou + +Facto +115 Volts 200 Volts 208 Volts 230 Volts 460 Volts 575 Volts 2300 Volts 230 Volts 460 Vo +1⁄2 4.4 2.5 2.4 2.2 1.1 0.9 — — — +3⁄4 6.4 3.7 3.5 3.2 1.6 1.3 — — — +1 8.4 4.8 4.6 4.2 2.1 1.7 — — — +11⁄2 12.0 6.9 6.6 6.0 3.0 2.4 — — — +2 13.6 7.8 7.5 6.8 3.4 2.7 — — — +3 — 11.0 10.6 9.6 4.8 3.9 — — — +5 — 17.5 16.7 15.2 7.6 6.1 — — — +71⁄2 — 25.3 24.2 22 11 9 — — — +10 — 32.2 30.8 28 14 11 — — — +15 — 48.3 46.2 42 21 17 — — — +20 — 62.1 59.4 54 27 22 — — — +25 — 78.2 74.8 68 34 27 — 53 26 +30 — 92 88 80 40 32 — 63 32 +40 — 120 114 104 52 41 — 83 41 +50 — 150 143 130 65 52 — 104 52 +60 — 177 169 154 77 62 16 123 61 +75 — 221 211 192 96 77 20 155 78 +*For 90 and 80 percent power factor, the figures shall be multiplied by 1.1 and 1.25, respectively. + +Table 430.251(A) Conversion Table of SinglePhase + +Locked-Rotor Currents for Selection of + +Disconnecting Means and Controllers as + +Determined from Horsepower and Voltage Rating + +For use only with 430.110, 440.12, 440.41, and +455.8(C). + +Rated + +Horsepower + +Maximum Locked-Rotor Current in + +Amperes, Single Phase +115 Volts 208 Volts 230 Volts +½ 58.8 32.5 29.4 +¾ 82.8 45.8 41.4 +1 96 53 48 +1½ 120 66 60 +2 144 80 72 +3 204 113 102 +5 336 186 168 +7½ 480 265 240 +10 1000 332 300 + +Table 430.251(B) Conversion Table of Polyphase Design B, C, and D Maximum Locked-Rotor Currents for + +Selection of Disconnecting Means and Controllers as Determined from Horsepower and Voltage Rating and Design Letter + +For use only with 430.110, 440.12, 440.41, and 455.8(C). + +Rated + +Horsepower + +Maximum Motor Locked-Rotor Current in Amperes, Two- and Three-Phase, Design B, C, and D* +115 Volts 200 Volts 208 Volts 230 Volts 460 Volts 575 Volts + +B, C, D B, C, D B, C, D B, C, D B, C, D B, C, D +1⁄2 40 23 22.1 20 10 8 + +Horsepower + +Induction-Type Squirrel Cage and Wound Rotor (Amperes) + +Synchronou + +Facto +115 Volts 200 Volts 208 Volts 230 Volts 460 Volts 575 Volts 2300 Volts 230 Volts 460 Vo +100 — 285 273 248 124 99 26 202 101 +125 — 359 343 312 156 125 31 253 126 +150 — 414 396 360 180 144 37 302 151 +200 552 528 480 240 192 49 400 201 +250 — — — — 302 242 60 — — +300 — — — — 361 289 72 — — +350 — — — — 414 336 83 — — +400 — — — — 477 382 95 — — +450 — — — — 515 412 103 — — +500 — — — — 590 472 118 — — + +Rated + +Horsepower + +Maximum Motor Locked-Rotor Current in Amperes, Two- and Three-Phase, Design B, C, and D* +115 Volts 200 Volts 208 Volts 230 Volts 460 Volts 575 Volts + +B, C, D B, C, D B, C, D B, C, D B, C, D B, C, D +3⁄4 50 28.8 27.6 25 12.5 10 +1 60 34.5 33 30 15 12 +11⁄2 80 46 44 40 20 16 +2 100 57.5 55 50 25 20 +3 — 73.6 71 64 32 25.6 +5 — 105.8 102 92 46 36.8 +71⁄2 — 146 140 127 63.5 50.8 +10 — 186.3 179 162 81 64.8 +15 — 267 257 232 116 93 +20 — 334 321 290 145 116 +25 — 420 404 365 183 146 +30 — 500 481 435 218 174 +40 — 667 641 580 290 232 +50 — 834 802 725 363 290 +60 — 1001 962 870 435 348 +75 — 1248 1200 1085 543 434 +100 — 1668 1603 1450 725 580 +125 — 2087 2007 1815 908 726 +150 — 2496 2400 2170 1085 868 +200 — 3335 3207 2900 1450 1160 +250 — — — — 1825 1460 +300 — — — — 2200 1760 +350 — — — — 2550 2040 +400 — — — — 2900 2320 +450 — — — — 3250 2600 +500 — — — — 3625 2900 +*Design A motors are not limited to a maximum starting current or locked rotor current. diff --git a/nfpa-70_440_hvac-equipment.md b/nfpa-70_440_hvac-equipment.md new file mode 100644 index 0000000..70adff2 --- /dev/null +++ b/nfpa-70_440_hvac-equipment.md @@ -0,0 +1,486 @@ +--- +id: +aliases: + - nec-440 +tags: + - authorship/other + - destiny/uncertain + - exclude-from-word-count + - status/incomplete + - topic/construction/electrical + - type/media +title: Article 440 Air-Conditioning and Refrigerating Equipment +--- +# Article 440 Air-Conditioning and Refrigerating Equipment + +## Part I. General + +### 440.1 Scope. + +This article applies to electric motor-driven air-conditioning and refrigerating equipment and to the branch circuits and controllers for such equipment. It provides for the special considerations necessary for circuits supplying hermetic refrigerant motor-compressors and for any air-conditioning or refrigerating equipment that is supplied from a branch circuit that supplies a hermetic refrigerant motor-compressor. + +#### 440.2 Definitions. + +The definitions in this section shall apply only within this article. + +##### Branch-Circuit Selection Current. + +The value in amperes to be used instead of the rated-load current in determining the ratings of motor branch-circuit conductors, disconnecting means, controllers, and branch-circuit short-circuit and ground-fault protective devices wherever the running overload protective device permits a sustained current greater than the specified percentage of the rated-load current. The value of branch-circuit selection current will always be equal to or greater than the marked rated-load current. + +##### Leakage-Current Detector-Interrupter (LCDI). + +A device provided in a power supply cord or cord set that senses leakage current flowing between or from the cord conductors and interrupts the circuit at a predetermined level of leakage current. + +##### Rated-Load Current. + +The current of a hermetic refrigerant motor-compressor resulting when it is operated at the rated load, rated voltage, and rated frequency of the equipment it serves. + +### 440.3 Other Articles. + +#### 440.3(A) Article 430. + +These provisions are in addition to, or amendatory of, +the provisions of Article 430 and other articles in this Code, +which apply except as modified in this article. + +#### 440.3(B) Articles 422, 424, or 430. + +The rules of Articles 422, 424, or 430, as applicable, +shall apply to air-conditioning and refrigerating equipment +that does not incorporate a hermetic refrigerant motor-compressor. +This equipment includes devices +that employ refrigeration compressors driven by conventional motors, +furnaces with air-conditioning evaporator coils installed, +fan-coil units, remote forced air-cooled condensers, +remote commercial refrigerators, and so forth. + +#### 440.3(C) Article 422. + +Equipment such as room air conditioners, +household refrigerators and freezers, +drinking water coolers, and beverage dispensers +shall be considered appliances, +and Article 422 shall also apply. + +#### 440.3(D) Other Applicable Articles. + +Hermetic refrigerant motor-compressors, +circuits, controllers, and equipment +shall also comply with the applicable provisions of Table 440.3(D). + +##### Table 440.3(D) Other Articles + +| Equipment/Occupancy | Article | Section | +| -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------- | ------- | +| Capacitors | | 460.9 | +| Commercial garages, aircraft hangars, motor fuel dispensing facilities, bulk storage plants, spray application, dipping, and coating processes, and inhalation anesthetizing locations | 511, 513, 514, 515, 516, and 517 Part IV | | +| Hazardous (classified) locations | 500--503, 505, and 506 | | +| Motion picture and television studios and similar locations | 530 | | +| Resistors and reactors | 470 | | + +### 440.4 Marking on Hermetic Refrigerant Motor-Compressors and Equipment. + +#### 440.4(A) Hermetic Refrigerant Motor-Compressor Nameplate. + +A hermetic refrigerant motor-compressor shall be provided with a nameplate that shall indicate the manufacturer's name, trademark, or symbol; identifying designation; phase; voltage; and frequency. +The rated-load current in amperes of the motor-compressor shall be marked by the equipment manufacturer on either or both the motor-compressor nameplate and the nameplate of the equipment in which the motor-compressor is used. +The locked-rotor current of each single-phase motor-compressor having a rated-load current of more than 9 amperes at 115 volts, or more than 4.5 amperes at 230 volts, and each polyphase motor-compressor shall be marked on the motor-compressor nameplate. +Where a thermal protector complying with 440.52(A)(2) and (B)(2) is used, +the motor-compressor nameplate or the equipment nameplate +shall be marked with the words "thermally protected." +Where a protective system complying with 440.52(A)(4) and (B)(4) +is used and is furnished with the equipment, +the equipment nameplate shall be marked with the words, +"thermally protected system." +Where a protective system complying with 440.52(A) (4) and (B)(4) is specified, +the equipment nameplate shall be appropriately marked. + +#### 440.4(B) Multimotor and Combination-Load Equipment. + +Multimotor and combination-load equipment shall be provided with a visible nameplate marked with the maker's name, the rating in volts, frequency and number of phases, minimum supply circuit conductor ampacity, the maximum rating of the branch-circuit short-circuit and ground-fault protective device, and the short-circuit current rating of the motor controllers or industrial control panel. The ampacity shall be calculated by using Part IV and counting all the motors and other loads that will be operated at the same time. The branch-circuit short-circuit and ground-fault protective device rating shall not exceed the value calculated by using Part III. Multimotor or combination-load equipment for use on two or more circuits shall be marked with the above information for each circuit. + +> [!important] Exception No. 1: +> Multimotor and combination-load equipment that is suitable under the provisions of this article for connection to a single 15- or 20-ampere, 120-volt, or a 15-ampere, 208- or 240-volt, single-phase branch circuit shall be permitted to be marked as a single load. + +> [!important] Exception No. 2: +> The minimum supply circuit conductor ampacity and the maximum rating of the branch-circuit short-circuit and groundfault protective device shall not be required to be marked on a room air conditioner complying with 440.62(A). + +> [!important] Exception No. 3: +> Multimotor and combination-load equipment used in one- and two-family dwellings or cord-and-attachment-plugconnected equipment shall not be required to be marked with a short-circuit current rating. + +#### 440.4(C) Branch-Circuit Selection Current. + +A hermetic refrigerant motor-compressor, or equipment containing such a compressor, having a protection system that is approved for use with the motor-compressor that it protects and that permits continuous current in excess of the specified percentage of nameplate rated-load current given in 440.52(B)(2) or (B)(4) shall also be marked with a branch-circuit selection current that complies with +440.52(B)(2) or (B)(4). This marking shall be provided by the equipment manufacturer and shall be on the nameplate(s) where the rated-load current(s) appears. + +### 440.5 Marking on Controllers. + +A controller shall be marked with the manufacturer's name, trademark, or symbol; identifying designation; voltage; phase; full-load and locked-rotor current (or horsepower) rating; and other data as may be needed to properly indicate the motor-compressor for which it is suitable. + +### 440.6 Ampacity and Rating. + +The size of conductors for equipment covered by this article shall be selected from Table 310.16 through Table 310.19 or calculated in accordance with 310.14 as applicable. The required ampacity of conductors and rating of equipment shall be determined according to +440.6(A) and 440.6(B). + +#### 440.6(A) Hermetic Refrigerant Motor-Compressor. + +For a hermetic refrigerant motor-compressor, the rated-load current marked on the nameplate of the equipment in which the motorcompressor is employed shall be used in determining the rating or ampacity of the disconnecting means, the branch-circuit conductors, the controller, the branch-circuit short-circuit and ground-fault protection, and the separate motor overload protection. Where no ratedload current is shown on the equipment nameplate, the rated-load current shown on the compressor nameplate shall be used. + +> [!important] Exception No. 1: +> Where so marked, the branch-circuit selection current shall be used instead of the rated-load current to determine the rating or ampacity of the disconnecting means, the branch-circuit conductors, the controller, and the branch-circuit short-circuit and ground-fault protection. + +> [!important] Exception No. 2: +> For cord-and-plug-connected equipment, the nameplate marking shall be used in accordance with 440.22(B), Exception No. 2. + +#### 440.6(B) Multimotor Equipment. + +For multimotor equipment employing a shaded-pole or permanent split-capacitor-type fan or blower motor, the full-load current for such motor marked on the nameplate of the equipment in which the fan or blower motor is employed shall be used instead of the horsepower rating to determine the ampacity or rating of the disconnecting means, the branch-circuit conductors, the controller, the branch-circuit short-circuit and ground-fault protection, and the separate overload protection. This marking on the equipment nameplate shall not be less than the current marked on the fan or blower motor nameplate. + +### 440.7 Highest Rated (Largest) Motor. + +In determining compliance with this article and with 430.24, 430.53(B) and 430.53(C), and 430.62(A), the highest rated (largest) motor shall be considered to be the motor that has the highest rated-load current. Where two or more motors have the same highest ratedload current, only one of them shall be considered as the highest rated (largest) motor. For other than hermetic refrigerant motorcompressors, and fan or blower motors as covered in 440.6(B), the full-load current used to determine the highest rated motor shall be the equivalent value corresponding to the motor horsepower rating selected from Table 430.248, Table 430.249, or Table 430.250. + +> [!important] Exception: +> Where so marked, the branch-circuit selection current shall be used instead of the rated-load current in determining the highest rated (largest) motor-compressor. + +### 440.8 Single Machine. + +An air-conditioning or refrigerating system shall be considered to be a single machine under the provisions of 430.87, Exception No. 1, and 430.112, Exception. The motors shall be permitted to be located remotely from each other. + +### 440.9 Grounding and Bonding. + +Where equipment is installed outdoors on a roof, an equipment grounding conductor of the wire type shall be installed in outdoor portions of metallic raceway systems that use compression-type fittings. + +### 440.10 Short-Circuit Current Rating. + +#### 440.10(A) Installation. + +Motor controllers or industrial control panels of multimotor and combination-load equipment shall not be installed where the available fault current exceeds its short-circuit current rating as marked in accordance with 440.4(B). + +#### 440.10(B) Documentation. + +When motor controllers or industrial control panels of multimotor and combination-load equipment are required to be marked with a short circuit current rating, the available fault current and the date the available fault current calculation was performed shall be documented and made available to those authorized to inspect, install, or maintain the installation. + +## Part II. Disconnecting Means + +### 440.11 General. + +Part II is intended to require disconnecting means capable of disconnecting air-conditioning and refrigerating equipment, including motor-compressors and controllers from the circuit conductors. + +### 440.12 Rating and Interrupting Capacity. + +#### 440.12(A) Hermetic Refrigerant Motor-Compressor. + +A disconnecting means serving a hermetic refrigerant motor-compressor shall be selected on the basis of the nameplate rated-load current or branch-circuit selection current, whichever is greater, and locked-rotor current, respectively, of the motor-compressor as follows. + +##### 440.12(A)(1) Ampere Rating. + +The ampere rating shall be at least 115 percent of the nameplate rated-load current or branch-circuit selection current, whichever is greater. + +> [!important] Exception: +> A listed unfused motor circuit switch, without fuseholders, having a horsepower rating not less than the equivalent horsepower determined in accordance with 440.12(A)(2) shall be permitted to have an ampere rating less than 115 percent of the specified current. + +##### 440.12(A)(2) Equivalent Horsepower. + +To determine the equivalent horsepower in complying with the requirements of 430.109, the horsepower rating shall be selected from + +Table 430.248, Table 430.249, or Table 430.250 corresponding to the rated-load current or branch-circuit selection current, whichever is greater, and also the horsepower rating from Table 430.251(A) or Table 430.251(B) corresponding to the locked-rotor current. In case the nameplate rated-load current or branch-circuit selection current and locked-rotor current do not correspond to the currents shown in + +Table 430.248, Table 430.249, Table 430.250, Table 430.251(A), or Table 430.251(B), the horsepower rating corresponding to the next higher value shall be selected. In case different horsepower ratings are obtained when applying these tables, a horsepower rating at least equal to the larger of the values obtained shall be selected. + +#### 440.12(B) Combination Loads. + +Where the combined load of two or more hermetic refrigerant motor-compressors or one or more hermetic refrigerant motorcompressor with other motors or loads may be simultaneous on a single disconnecting means, the rating for the disconnecting means shall be determined in accordance with 440.12(B)(1) and (B)(2). + +##### 440.12(B)(1) Horsepower Rating. + +The horsepower rating of the disconnecting means shall be determined from the sum of all currents, including resistance loads, at the rated-load condition and also at the locked-rotor condition. The combined rated-load current and the combined locked-rotor current so obtained shall be considered as a single motor for the purpose of this requirement as required by 440.12(B)(1)(a) and (B) (1) (b). + +* (a) The full-load current equivalent to the horsepower rating of each motor, other than a hermetic refrigerant motor-compressor, and fan or blower motors as covered in 440.6(B) shall be selected from Table 430.248, Table 430.249, or Table 430.250. These fullload currents shall be added to the motor-compressor rated-load current(s) or branch-circuit selection current(s), whichever is greater, and to the rating in amperes of other loads to obtain an equivalent full-load current for the combined load. + +* (b) The locked-rotor current equivalent to the horsepower rating of each motor, other than a hermetic refrigerant motor-compressor, shall be selected from Table 430.251(A) or Table 430.251(B), and, for fan and blower motors of the shaded-pole or permanent split-capacitor type marked with the locked-rotor current, the marked value shall be used. The locked-rotor currents shall be added to the motor-compressor locked-rotor current(s) and to the rating in amperes of other loads to obtain an equivalent locked-rotor current for the combined load. Where two or more motors or other loads such as resistance heaters, or both, cannot be started simultaneously, appropriate combinations of locked-rotor and rated-load current or branch-circuit selection current, whichever is greater, shall be an acceptable means of determining the equivalent locked-rotor current for the simultaneous combined load. + +> [!important] Exception: +> Where part of the concurrent load is a resistance load and the disconnecting means is a switch rated in horsepower and amperes, the switch used shall be permitted to have a horsepower rating not less than the combined load to the motor-compressor(s) and other motor(s) at the locked-rotor condition, if the ampere rating of the switch is not less than this locked-rotor load plus the resistance load. + +##### 440.12(B)(2) Full-Load Current Equivalent. + +The ampere rating of the disconnecting means shall be at least 115 percent of the sum of all currents at the rated-load condition determined in accordance with 440.12(B)(1). + +> [!important] Exception: +> A listed unfused motor circuit switch, without fuseholders, having a horsepower rating not less than the equivalent horsepower determined by 440.12(B)(1) shall be permitted to have an ampere rating less than 115 percent of the sum of all currents. + +#### 440.12(C) Small Motor-Compressors. + +For small motor-compressors not having the locked-rotor current marked on the nameplate, or for small motors not covered by Table +430.247, Table 430.248, Table 430.249, or Table 430.250, the locked-rotor current shall be assumed to be six times the rated-load current. + +#### 440.12(D) Disconnecting Means. + +Every disconnecting means in the refrigerant motor-compressor circuit between the point of attachment to the feeder and the point of connection to the refrigerant motor-compressor shall comply with the requirements of 440.12. + +#### 440.12(E) Disconnecting Means Rated in Excess of 100 Horsepower. + +Where the rated-load or locked-rotor current as determined above would indicate a disconnecting means rated in excess of 100 hp, +430.109(E) shall apply. + +### 440.13 Cord-Connected Equipment. + +For cord-connected equipment such as room air conditioners, household refrigerators and freezers, drinking water coolers, and beverage dispensers, a separable connector or an attachment plug and receptacle shall be permitted to serve as the disconnecting means. + +> [!info] Informational Note: +> For room air conditioners, see 440.63. + +### 440.14 Location. + +Disconnecting means shall be located within sight from, and readily accessible from the air-conditioning or refrigerating equipment. The disconnecting means shall be permitted to be installed on or within the air-conditioning or refrigerating equipment. + +The disconnecting means shall not be located on panels that are designed to allow access to the air-conditioning or refrigeration equipment or to obscure the equipment nameplate(s). + +> [!important] Exception No. 1: +> Where the disconnecting means provided in accordance with 430.102(A) is lockable in accordance with 110.25 and the refrigerating or air-conditioning equipment is essential to an industrial process in a facility with written safety procedures, and where the conditions of maintenance and supervision ensure that only qualified persons service the equipment, a disconnecting means within sight from the equipment shall not be required. + +> [!important] Exception No. 2: +> Where an attachment plug and receptacle serve as the disconnecting means in accordance with 440.13, their location shall be accessible but shall not be required to be readily accessible. + +> [!info] Informational Note No. 1: +> See Parts VII and IX of Article 430 for additional requirements. + +> [!info] Informational Note No. 2: +> See 110.26. + +## Part III. Branch-Circuit Short-Circuit and Ground-Fault Protection + +### 440.21 General. + +Part III specifies devices intended to protect the branch-circuit conductors, control apparatus, and motors in circuits supplying hermetic refrigerant motor-compressors against overcurrent due to short circuits and ground faults. They are in addition to or amendatory of + +Article 240. + +### 440.22 Application and Selection. + +#### 440.22(A) Rating or Setting for Individual Motor-Compressor. + +The motor-compressor branch-circuit short-circuit and ground-fault protective device shall be capable of carrying the starting current of the motor. A protective device having a rating or setting not exceeding 175 percent of the motor-compressor rated-load current or branch-circuit selection current, whichever is greater, shall be permitted, provided that, where the protection specified is not sufficient for the starting current of the motor, the rating or setting shall be permitted to be increased but shall not exceed 225 percent of the motor rated-load current or branch-circuit selection current, whichever is greater. + +> [!important] Exception: +> The rating of the branch-circuit short-circuit and ground-fault protective device shall not be required to be less than 15 amperes. + +#### 440.22(B) Rating or Setting for Equipment. + +The equipment branch-circuit short-circuit and ground-fault protective device shall be capable of carrying the starting current of the equipment. Where the hermetic refrigerant motor-compressor is the only load on the circuit, the protection shall comply with 440.22(A). + +Where the equipment incorporates more than one hermetic refrigerant motor-compressor or a hermetic refrigerant motor-compressor and other motors or other loads, the equipment short-circuit and ground-fault protection shall comply with 430.53 and 440.22(B)(1) and +(B)(2). + +##### 440.22(B)(1) Motor-Compressor Largest Load. + +Where a hermetic refrigerant motor-compressor is the largest load connected to the circuit, the rating or setting of the branch-circuit short-circuit and ground-fault protective device shall not exceed the value specified in 440.22(A) for the largest motor-compressor plus the sum of the rated-load current or branch-circuit selection current, whichever is greater, of the other motor-compressor(s) and the ratings of the other loads supplied. + +##### 440.22(B)(2) Motor-Compressor Not Largest Load. + +Where a hermetic refrigerant motor-compressor is not the largest load connected to the circuit, the rating or setting of the branch-circuit short-circuit and ground-fault protective device shall not exceed a value equal to the sum of the rated-load current or branch-circuit selection current, whichever is greater, rating(s) for the motor-compressor(s) plus the value specified in 430.53(C)(4) where other motor loads are supplied, or the value specified in 240.4 where only nonmotor loads are supplied in addition to the motor-compressor(s). + +> [!important] Exception No. 1: +> Equipment that starts and operates on a 15- or 20-ampere 120-volt, or 15-ampere 208- or 240-volt single-phase branch circuit, shall be permitted to be protected by the 15- or 20-ampere overcurrent device protecting the branch circuit, but if the maximum branch-circuit short-circuit and ground-fault protective device rating marked on the equipment is less than these values, the circuit protective device shall not exceed the value marked on the equipment nameplate. + +> [!important] Exception No. 2: +> The nameplate marking of cord-and-plug-connected equipment rated not greater than 250 volts, single-phase, such as household refrigerators and freezers, drinking water coolers, and beverage dispensers, shall be used in determining the branch-circuit requirements, and each unit shall be considered as a single motor unless the nameplate is marked otherwise. + +#### 440.22(C) Protective Device Rating Not to Exceed the Manufacturer's Values. + +Where maximum protective device ratings shown on a manufacturer's overload relay table for use with a motor controller are less than the rating or setting selected in accordance with 440.22(A) and (B), the protective device rating shall not exceed the manufacturer's values marked on the equipment. + +## Part IV. Branch-Circuit Conductors + +### 440.31 General. + +Part IV and Article 310 specify ampacities of conductors required to carry the motor current without overheating under the conditions specified, except as modified in 440.6(A), Exception No. 1. + +These articles shall not apply to integral conductors of motors, to motor controllers and the like, or to conductors that form an integral part of approved equipment. + +### 440.32 Single Motor-Compressor. + +Branch-circuit conductors supplying a single motor-compressor shall have an ampacity not less than the greater of: + +* (1) 125 percent of the motor-compressor rated-load current + +* (2) 125 percent of the branch-circuit selection current + +For a wye-start, delta-run connected motor-compressor, the selection of branch-circuit conductors between the controller and the motor-compressor shall be permitted to be based on 72 percent of either the motor-compressor rated-load current or the branch-circuit selection current, whichever is greater. + +> [!info] Informational Note: +> The individual motor circuit conductors of wye-start, delta-run connected motor-compressors carry 58 percent of the rated load current. The multiplier of 72 percent is obtained by multiplying 58 percent by 1.25. + +### 440.33 Motor-Compressor(s) With or Without Additional Motor Loads. + +Conductors supplying one or more motor-compressor(s) with or without an additional motor load(s) shall have an ampacity not less than the sum of each of the following: + +* (1) The sum of the rated-load or branch-circuit selection current, whichever is greater, of all motor-compressor(s) + +* (2) The sum of the full-load current rating of all other motors + +* (3) 25 percent of the highest motor-compressor or motor full load current in the group + +> [!important] Exception No. 1: +> Where the circuitry is interlocked so as to prevent the starting and running of a second motor-compressor or group of motor-compressors, the conductor size shall be determined from the largest motor-compressor or group of motor-compressors that is to be operated at a given time. + +> [!important] Exception No. 2: +> The branch-circuit conductors for room air conditioners shall be in accordance with Part VII of Article 440. + +### 440.34 Combination Load. + +Conductors supplying a motor-compressor load in addition to other load(s) as calculated from Article 220 and other applicable articles shall have an ampacity sufficient for the other load(s) plus the required ampacity for the motor-compressor load determined in accordance with 440.33 or, for a single motor-compressor, in accordance with 440.32. + +> [!important] Exception: +> Where the circuitry is interlocked so as to prevent simultaneous operation of the motor-compressor(s) and all other loads connected, the conductor size shall be determined from the largest size required for the motor-compressor(s) and other loads to be operated at a given time. + +### 440.35 Multimotor and Combination-Load Equipment. + +The ampacity of the conductors supplying multimotor and combination-load equipment shall not be less than the minimum circuit ampacity marked on the equipment in accordance with 440.4(B). + +## Part V. Controllers for Motor-Compressors + +### 440.41 Rating. + +#### 440.41(A) Motor-Compressor Controller. + +A motor-compressor controller shall have both a continuous-duty full-load current rating and a locked-rotor current rating not less than the nameplate rated-load current or branch-circuit selection current, whichever is greater, and locked-rotor current, respectively, of the compressor. In case the motor controller is rated in horsepower but is without one or both of the foregoing current ratings, equivalent currents shall be determined from the ratings as follows. Table 430.248, Table 430.249, and Table 430.250 shall be used to determine the equivalent full-load current rating. Table 430.251(A) and Table 430.251(B) shall be used to determine the equivalent locked-rotor current ratings. + +#### 440.41(B) Controller Serving More Than One Load. + +A controller serving more than one motor-compressor or a motor-compressor and other loads shall have a continuous-duty full-load current rating and a locked-rotor current rating not less than the combined load as determined in accordance with 440.12(B). + +## Part VI. Motor-Compressor and Branch-Circuit Overload Protection + +### 440.51 General. + +Part VI specifies devices intended to protect the motor-compressor, the motor-control apparatus, and the branch-circuit conductors against excessive heating due to motor overload and failure to start. + +> [!info] Informational Note: +> See 240.4(G) for application of Parts III and VI of Article 440. + +### 440.52 Application and Selection. + +#### 440.52(A) Protection of Motor-Compressor. + +Each motor-compressor shall be protected against overload and failure to start by one of the following means: + +* (1) A separate overload relay that is responsive to motor-compressor current. This device shall be selected to trip at not more than +140 percent of the motor-compressor rated-load current. + +* (2) A thermal protector integral with the motor-compressor, approved for use with the motor-compressor that it protects on the basis that it will prevent dangerous overheating of the motor-compressor due to overload and failure to start. If the current-interrupting device is separate from the motor-compressor and its control circuit is operated by a protective device integral with the motorcompressor, it shall be arranged so that the opening of the control circuit will result in interruption of current to the motorcompressor.(3) A fuse or inverse time circuit breaker responsive to motor current, which shall also be permitted to serve as the branch-circuit short-circuit and ground-fault protective device. This device shall be rated at not more than 125 percent of the motor-compressor rated-load current. It shall have sufficient time delay to permit the motor-compressor to start and accelerate its load. The equipment or the motor-compressor shall be marked with this maximum branch-circuit fuse or inverse time circuit breaker rating. + +* (4) A protective system, furnished or specified and approved for use with the motor-compressor that it protects on the basis that it will prevent dangerous overheating of the motor-compressor due to overload and failure to start. If the current-interrupting device is separate from the motor-compressor and its control circuit is operated by a protective device that is not integral with the current-interrupting device, it shall be arranged so that the opening of the control circuit will result in interruption of current to the motor-compressor. + +#### 440.52(B) Protection of Motor-Compressor Control Apparatus and Branch-Circuit Conductors. + +The motor-compressor controller(s), the disconnecting means, and the branch-circuit conductors shall be protected against overcurrent due to motor overload and failure to start by one of the following means, which shall be permitted to be the same device or system protecting the motor-compressor in accordance with 440.52(A): + +> [!important] Exception: +> Overload protection of motor-compressors and equipment on 15- and 20-ampere, single-phase, branch circuits shall be permitted to be in accordance with 440.54 and 440.55. + +* (1) An overload relay selected in accordance with 440.52(A) (1) + +* (2) A thermal protector applied in accordance with 440.52(A)(2), that will not permit a continuous current in excess of 156 percent of the marked rated-load current or branch-circuit selection current + +* (3) A fuse or inverse time circuit breaker selected in accordance with 440.52(A)(3) + +* (4) A protective system, in accordance with 440.52(A)(4), that will not permit a continuous current in excess of 156 percent of the marked rated-load current or branch-circuit selection current + +### 440.53 Overload Relays. + +Overload relays and other devices for motor overload protection that are not capable of opening short circuits shall be protected by fuses or inverse time circuit breakers with ratings or settings in accordance with Part III unless identified for group installation or for partwinding motors and marked to indicate the maximum size of fuse or inverse time circuit breaker by which they shall be protected. + +> [!important] Exception: +> The fuse or inverse time circuit breaker size marking shall be permitted on the nameplate of the equipment in which the overload relay or other overload device is used. +440.54 Motor-Compressors and Equipment on 15- or 20-Ampere Branch Circuits --- Not Cord- and + +Attachment-Plug-Connected. + +Overload protection for motor-compressors and equipment used on 15- or 20-ampere 120-volt, or 15-ampere 208- or 240-volt singlephase branch circuits as permitted in Article 210 shall be permitted as indicated in 440.54(A) and 440.54(B). + +#### 440.54(A) Overload Protection. + +The motor-compressor shall be provided with overload protection selected as specified in 440.52(A). Both the controller and motor overload protective device shall be identified for installation with the short-circuit and ground-fault protective device for the branch circuit to which the equipment is connected. + +#### 440.54(B) Time Delay. + +The short-circuit and ground-fault protective device protecting the branch circuit shall have sufficient time delay to permit the motorcompressor and other motors to start and accelerate their loads. +440.55 Cord- and Attachment-Plug-Connected Motor-Compressors and Equipment on 15- or 20-Ampere + +Branch Circuits. + +Overload protection for motor-compressors and equipment that are cord- and attachment-plug-connected and used on 15- or 20ampere +120-volt, or 15-ampere 208- or 240-volt, single-phase branch circuits as permitted in Article 210 shall be permitted as indicated in 440.55(A), (B), and (C). + +#### 440.55(A) Overload Protection. + +The motor-compressor shall be provided with overload protection as specified in 440.52(A). Both the controller and the motor overload protective device shall be identified for installation with the short-circuit and ground-fault protective device for the branch circuit to which the equipment is connected. + +#### 440.55(B) Attachment Plug and Receptacle or Cord Connector Rating. + +The rating of the attachment plug and receptacle or cord connector shall not exceed 20 amperes at 125 volts or 15 amperes at +250 volts. + +#### 440.55(C) Time Delay. + +The short-circuit and ground-fault protective device protecting the branch circuit shall have sufficient time delay to permit the motorcompressor and other motors to start and accelerate their loads. + +## Part VII. Provisions for Room Air Conditioners + +### 440.60 General. + +Part VII shall apply to electrically energized room air conditioners that control temperature and humidity. For the purpose of Part VII, a room air conditioner (with or without provisions for heating) shall be considered as an ac appliance of the air-cooled window, console, or in-wall type that is installed in the conditioned room and that incorporates a hermetic refrigerant motor-compressor(s). Part VII covers equipment rated not over 250 volts, single phase, and the equipment shall be permitted to be cord- and attachment-plug-connected. + +A room air conditioner that is rated 3-phase or rated over 250 volts shall be directly connected to a wiring method recognized in + +Chapter 3, and Part VII shall not apply. + +### 440.61 Grounding. + +The enclosures of room air conditioners shall be connected to the equipment grounding conductor in accordance with 250.110, +250.112, and 250.114. + +### 440.62 Branch-Circuit Requirements. + +#### 440.62(A) Room Air Conditioner as a Single Motor Unit. + +A room air conditioner shall be considered as a single motor unit in determining its branch-circuit requirements where all the following conditions are met: + +* (1) It is cord- and attachment-plug-connected. + +* (2) Its rating is not more than 40 amperes and 250 volts, single phase. + +* (3) Total rated-load current is shown on the room air-conditioner nameplate rather than individual motor currents. + +* (4) The rating of the branch-circuit short-circuit and ground-fault protective device does not exceed the ampacity of the branchcircuit conductors or the rating of the receptacle, whichever is less. + +#### 440.62(B) Where No Other Loads Are Supplied. + +The total marked rating of a cord- and attachment-plug-connected room air conditioner shall not exceed 80 percent of the rating of a branch circuit where no other loads are supplied. + +#### 440.62(C) Where Lighting Units or Other Appliances Are Also Supplied. + +The total marked rating of a cord- and attachment-plug-connected room air conditioner shall not exceed 50 percent of the rating of a branch circuit where lighting outlets, other appliances, or general-use receptacles are also supplied. Where the circuitry is interlocked to prevent simultaneous operation of the room air conditioner and energization of other outlets on the same branch circuit, a cord- and attachment-plug-connected room air conditioner shall not exceed 80 percent of the branch-circuit rating. + +### 440.63 Disconnecting Means. + +An attachment plug and receptacle or cord connector shall be permitted to serve as the disconnecting means for a single-phase room air conditioner rated 250 volts or less if (1) the manual controls on the room air conditioner are readily accessible and located within +1.8 m (6 ft) of the floor, or (2) an approved manually operable disconnecting means is installed in a readily accessible location within sight from the room air conditioner. + +### 440.64 Supply Cords. + +Where a flexible cord is used to supply a room air conditioner, the length of such cord shall not exceed 3.0 m (10 ft) for a nominal, 120volt rating or 1.8 m (6 ft) for a nominal, 208- or 240-volt rating. + +### 440.65 Protection Devices. + +Single-phase cord- and plug-connected room air conditioners shall be provided with one of the following factory-installed devices: + +* (1) Leakage-current detector-interrupter (LCDI) + +* (2) Arc-fault circuit interrupter (AFCI) + +* (3) Heat detecting circuit interrupter (HDCI) + +The protection device shall be an integral part of the attachment plug or be located in the power supply cord within 300 mm (12 in.) of the attachment plug. diff --git a/nfpa-70_national-electric-code.md b/nfpa-70_national-electric-code.md index 68bae21..e3faabf 100644 --- a/nfpa-70_national-electric-code.md +++ b/nfpa-70_national-electric-code.md @@ -28,8 +28,8 @@ title: "NFPA 70: National Electric Code" * [[nfpa-70_215_feeders|215 Feeders]] * [[nfpa-70_220_load-calculations|220 Branch-Circuit, Feeder, and Service Load Calculations]] * [[nfpa-70_225|225 Outside Branch Circuits and Feeders]] -* [[nfpa-70_230|230 Services]] -* [[nfpa-70_240|240 Overcurrent Protection]] +* [[nfpa-70_230_services|230 Services]] +* [[nfpa-70_240_overcurrent-protection|240 Overcurrent Protection]] * [[nfpa-70_242|242 Overvoltage Protection]] * [[nfpa-70_250_grounding-and-bonding|250 Grounding and Bonding]] @@ -99,7 +99,7 @@ title: "NFPA 70: National Electric Code" * [[nfpa-70_426|426 Fixed Outdoor Electric Deicing and Snow-Melting Equipment]] * [[nfpa-70_427|427 Fixed Electric Heating Equipment for Pipelines and Vessels]] * [[nfpa-70_430_motors|430 Motors, Motor Circuits, and Controllers]] -* [[nfpa-70_440|440 Air-Conditioning and Refrigerating Equipment]] +* [[nfpa-70_440_hvac-equipment|440 Air-Conditioning and Refrigerating Equipment]] * [[nfpa-70_445|445 Generators]] * [[nfpa-70_450_transformers|450 Transformers and Transformer Vaults (Including Secondary Ties)]] * [[nfpa-70_455|455 Phase Converters]] diff --git a/this-notebook.md b/this-notebook.md index f4823d9..304fdb7 100644 --- a/this-notebook.md +++ b/this-notebook.md @@ -67,6 +67,7 @@ but this notebook uses [[semantic-line-breaks]] for text wrapping. I shoot for less than 90 columns. +This line of text (which is precisely 90 characters) is the maximum length for prose here. ## Licensing