---
tags:
  - authorship/other
  - destiny/fleeting
  - exclude-from-word-count
  - topic/construction/electrical
  - type/media/reference
title: Article 725 Class 1, Class 2, and Class 3 Remote-Control, Signaling, and Power-Limited Circuits
up: "[[nfpa-70_national-electric-code]]"
---
# NEC Chapter 3 Wiring Methods Articles Dump

# Article 320 Armored Cable: Type AC

## Part I. General

### 320.1 Scope.

This article covers the use, installation, and construction specifications for armored cable, Type AC.

### 320.2 Definition.

The definition in this section shall apply within this article and throughout the Code.

#### Armored Cable, Type AC.

A fabricated assembly of insulated conductors in a flexible interlocked metallic armor. See 320.100.

### 320.6 Listing Requirements.

Type AC cable and associated fittings shall be listed.

## Part II. Installation

### 320.10 Uses Permitted.

Type AC cable shall be permitted as follows:

* (1) For feeders and branch circuits in both exposed and concealed installations

* (2) In cable trays

* (3) In dry locations

* (4) Embedded in plaster finish on brick or other masonry, except in damp or wet locations

* (5) To be run or fished in the air voids of masonry block or tile walls where such walls are not exposed or subject to excessive moisture or dampness

> [!info] Informational Note:
> The “Uses Permitted” is not an all-inclusive list.

### 320.12 Uses Not Permitted.

Type AC cable shall not be used as follows:

* (1) Where subject to physical damage

* (2) In damp or wet locations

* (3) In air voids of masonry block or tile walls where such walls are exposed or subject to excessive moisture or dampness

* (4) Where exposed to corrosive conditions

* (5) Embedded in plaster finish on brick or other masonry in damp or wet locations

### 320.15 Exposed Work.

Exposed runs of cable, except as provided in 300.11(B), shall closely follow the surface of the building finish or of running boards.

Exposed runs shall also be permitted to be installed on the underside of joists where supported at each joist and located so as not to be subject to physical damage.

### 320.17 Through or Parallel to Framing Members.

Type AC cable shall be protected in accordance with 300.4(A), (C), and (D) where installed through or parallel to framing members.

### 320.23 In Accessible Attics.

Type AC cables in accessible attics or roof spaces shall be installed as specified in 320.23(A) and (B).

#### 320.23(A) Cables Run Across the Top of Floor Joists.

Where run across the top of floor joists, or within 2.1 m (7 ft) of the floor or floor joists across the face of rafters or studding, the cable shall be protected by guard strips that are at least as high as the cable. Where this space is not accessible by permanently installed stairs or ladders, protection shall only be required within 1.8 m (6 ft) of the nearest edge of the scuttle hole or attic entrance.

#### 320.23(B) Cable Installed Parallel to Framing Members.

Where the cable is installed parallel to the sides of rafters, studs, or ceiling or floor joists, neither guard strips nor running boards shall be required, and the installation shall also comply with 300.4(D).

### 320.24 Bending Radius.

Bends in Type AC cable shall be made such that the cable is not damaged. The radius of the curve of the inner edge of any bend shall not be less than five times the diameter of the Type AC cable.

### 320.30 Securing and Supporting.

#### 320.30(A) General.

Type AC cable shall be supported and secured by staples; cable ties listed and identified for securement and support; straps, hangers, or similar fittings; or other approved means designed and installed so as not to damage the cable.

#### 320.30(B) Securing.

Unless otherwise permitted, Type AC cable shall be secured within 300 mm (12 in.) of every outlet box, junction box, cabinet, or fitting and at intervals not exceeding 1.4 m (41⁄2 ft).

#### 320.30(C) Supporting.

Unless otherwise permitted, Type AC cable shall be supported at intervals not exceeding 1.4 m (41⁄2 ft).

Horizontal runs of Type AC cable installed in wooden or metal framing members or similar supporting means shall be considered supported and secured where such support does not exceed 1.4 m (41⁄2 ft) intervals.

#### 320.30(D) Unsupported Cables.

Type AC cable shall be permitted to be unsupported and unsecured where the cable complies with any of the following:

* (1) Is fished between access points through concealed spaces in finished buildings or structures and supporting is impracticable

* (2) Is not more than 600 mm (2 ft) in length at terminals where flexibility is necessary

* (3) Is not more than 1.8 m (6 ft) in length from the last point of cable support to the point of connection to a luminaire(s) or other electrical equipment and the cable and point of connection are within an accessible ceiling

For the purposes of this section, Type AC cable fittings shall be permitted as a means of cable support.

### 320.40 Boxes and Fittings.

At all points where the armor of AC cable terminates, a fitting shall be provided to protect wires from abrasion, unless the design of the outlet boxes or fittings is such as to afford equivalent protection, and, in addition, an insulating bushing or its equivalent protection shall be provided between the conductors and the armor. The connector or clamp by which the Type AC cable is fastened to boxes or cabinets shall be of such design that the insulating bushing or its equivalent will be visible for inspection. Where change is made from

Type AC cable to other cable or raceway wiring methods, a box, fitting, or conduit body shall be installed at junction points as required in 300.15.

### 320.80 Ampacity.

The ampacity shall be determined in accordance with 310.14.

#### 320.80(A) Thermal Insulation.

Armored cable installed in thermal insulation shall have conductors rated at 90°C (194°F). The ampacity of cable installed in these applications shall not exceed that of a 60°C (140°F) rated conductor. The 90°C (194°F) rating shall be permitted to be used for ampacity adjustment and correction calculations; however, the ampacity shall not exceed that of a 60°C (140°F) rated conductor.

Where more than two Type AC cables containing two or more current-carrying conductors in each cable are installed in contact with thermal insulation, caulk, or sealing foam without maintaining spacing between cables, the ampacity of each conductor shall be adjusted in accordance with Table 310.15(C)(1).

#### 320.80(B) Cable Tray.

The ampacity of Type AC cable installed in cable tray shall be determined in accordance with 392.80(A).

## Part III. Construction Specifications

### 320.100 Construction.

Type AC cable shall have an armor of flexible metal tape and shall have an internal bonding strip of copper or aluminum in intimate contact with the armor for its entire length.

### 320.104 Conductors.

Insulated conductors shall be of a type listed in Table 310.4(A) or those identified for use in this cable. In addition, the conductors shall have an overall moisture-resistant and fire-retardant fibrous covering. For Type ACT, a moisture-resistant fibrous covering shall be required only on the individual conductors.

### 320.108 Equipment Grounding Conductor.

Type AC cable shall provide an adequate path for fault current as required by 250.4(A)(5) or (B)(4) to act as an equipment grounding conductor.

### 320.120 Marking.

The cable shall be marked in accordance with 310.8, except that Type AC shall have ready identification of the manufacturer by distinctive external markings on the cable armor throughout its entire length.

# Article 322 Flat Cable Assemblies: Type FC

## Part I. General

### 322.1 Scope.

This article covers the use, installation, and construction specifications for flat cable assemblies, Type FC.

### 322.2 Definition.

The definition in this section shall apply within this article and throughout the Code.

#### Flat Cable Assembly, Type FC.

An assembly of parallel conductors formed integrally with an insulating material web specifically designed for field installation in surface metal raceway.

### 322.6 Listing Requirements.

Type FC and associated fittings shall be listed.

## Part II. Installation

### 322.10 Uses Permitted.

Flat cable assemblies shall be permitted only as follows:

* (1) As branch circuits to supply suitable tap devices for lighting, small appliances, or small power loads. The rating of the branch circuit shall not exceed 30 amperes.

* (2) Where installed for exposed work.

* (3) In locations where they will not be subjected to physical damage. Where a flat cable assembly is installed less than 2.5 m (8 ft) above the floor or fixed working platform, it shall be protected by a cover identified for the use.

* (4) In surface metal raceways identified for the use. The channel portion of the surface metal raceway systems shall be installed as complete systems before the flat cable assemblies are pulled into the raceways.

### 322.12 Uses Not Permitted.

Flat cable assemblies shall not be used as follows:

* (1) Where exposed to corrosive conditions, unless suitable for the application

* (2) In hoistways or on elevators or escalators

* (3) In any hazardous (classified) location, except as specifically permitted by other articles in this Code

* (4) Outdoors or in wet or damp locations unless identified for the use

### 322.30 Securing and Supporting.

The flat cable assemblies shall be supported by means of their special design features, within the surface metal raceways.

The surface metal raceways shall be supported as required for the specific raceway to be installed.

### 322.40 Boxes and Fittings.

#### 322.40(A) Dead Ends.

Each flat cable assembly dead end shall be terminated in an end-cap device identified for the use.

The dead-end fitting for the enclosing surface metal raceway shall be identified for the use.

#### 322.40(B) Luminaire Hangers.

Luminaire hangers installed with the flat cable assemblies shall be identified for the use.

#### 322.40(C) Fittings.

Fittings to be installed with flat cable assemblies shall be designed and installed to prevent physical damage to the cable assemblies.

#### 322.40(D) Extensions.

All extensions from flat cable assemblies shall be made by approved wiring methods, within the junction boxes, installed at either end of the flat cable assembly runs.

### 322.56 Splices and Taps.

#### 322.56(A) Splices.

Splices shall be made in listed junction boxes.

#### 322.56(B) Taps.

Taps shall be made between any phase conductor and the grounded conductor or any other phase conductor by means of devices and fittings identified for the use. Tap devices shall be rated at not less than 15 amperes, or more than 300 volts to ground, and shall be color-coded in accordance with the requirements of 322.120(C).

## Part III. Construction Specifications

### 322.100 Construction.

Flat cable assemblies shall consist of two, three, four, or five conductors.

### 322.104 Conductors.

Flat cable assemblies shall have conductors of 10 AWG special stranded copper wires.

### 322.112 Insulation.

The entire flat cable assembly shall be formed to provide a suitable insulation covering all the conductors and using one of the materials recognized in Table 310.4(A) for general branch-circuit wiring.

### 322.120 Marking.

#### 322.120(A) Temperature Rating.

In addition to the provisions of 310.8, Type FC cable shall have the temperature rating durably marked on the surface at intervals not exceeding 600 mm (24 in.).

#### 322.120(B) Identification of Grounded Conductor.

The grounded conductor shall be identified throughout its length by means of a distinctive and durable white or gray marking.

> [!info] Informational Note:
> The color gray may have been used in the past as an ungrounded conductor. Care should be taken when working on existing systems.

#### 322.120(C) Terminal Block Identification.

Terminal blocks identified for the use shall have distinctive and durable markings for color or word coding. The grounded conductor section shall have a white marking or other suitable designation. The next adjacent section of the terminal block shall have a black marking or other suitable designation. The next section shall have a red marking or other suitable designation. The final or outer section, opposite the grounded conductor section of the terminal block, shall have a blue marking or other suitable designation.

# Article 324 Flat Conductor Cable: Type FCC

## Part I. General

### 324.1 Scope.

This article covers a field-installed wiring system for branch circuits incorporating Type FCC cable and associated accessories as defined by the article. The wiring system is designed for installation under carpet squares.

### 324.2 Definitions.

The definitions in this section shall apply only within this article.

#### Bottom Shield.

A protective layer that is installed between the floor and Type FCC flat conductor cable to protect the cable from physical damage and may or may not be incorporated as an integral part of the cable.

#### Cable Connector.

A connector designed to join Type FCC cables without using a junction box.

#### FCC System.

A complete wiring system for branch circuits that is designed for installation under carpet squares.

> [!info] Informational Note:
> The FCC system includes Type FCC cable and associated shielding, connectors, terminators, adapters, boxes, and receptacles.

#### Insulating End.

An insulator designed to electrically insulate the end of a Type FCC cable.

#### Metal Shield Connections.

Means of connection designed to electrically and mechanically connect a metal shield to another metal shield, to a receptacle housing or self-contained device, or to a transition assembly.

#### Top Shield.

A grounded metal shield covering under-carpet components of the FCC system for the purposes of providing protection against physical damage.

#### Transition Assembly.

An assembly to facilitate connection of the FCC system to other wiring systems, incorporating (1) a means of electrical interconnection and (2) a suitable box or covering for providing electrical safety and protection against physical damage.

#### Type FCC Cable.

Three or more flat copper conductors placed edge-to-edge and separated and enclosed within an insulating assembly.

### 324.6 Listing Requirements.

Type FCC cable and associated fittings shall be listed.

## Part II. Installation

### 324.10 Uses Permitted.

#### 324.10(A) Branch Circuits.

Use of FCC systems shall be permitted both for general-purpose and appliance branch circuits and for individual branch circuits.

#### 324.10(B) Branch-Circuit Ratings.

##### 324.10(B)(1) Voltage.

Voltage between ungrounded conductors shall not exceed 300 volts. Voltage between ungrounded conductors and the grounded conductor shall not exceed 150 volts.

##### 324.10(B)(2) Current.

General-purpose and appliance branch circuits shall have ratings not exceeding 20 amperes. Individual branch circuits shall have ratings not exceeding 30 amperes.

#### 324.10(C) Floors.

Use of FCC systems shall be permitted on hard, sound, smooth, continuous floor surfaces made of concrete, ceramic, or composition flooring, wood, and similar materials.

#### 324.10(D) Walls.

Use of FCC systems shall be permitted on wall surfaces in surface metal raceways.

#### 324.10(E) Damp Locations.

Use of FCC systems in damp locations shall be permitted.

#### 324.10(F) Heated Floors.

Materials used for floors heated in excess of 30°C (86°F) shall be identified as suitable for use at these temperatures.

#### 324.10(G) System Height.

Any portion of an FCC system with a height above floor level exceeding 2.3 mm (0.090 in.) shall be tapered or feathered at the edges to floor level.

### 324.12 Uses Not Permitted.

FCC systems shall not be used in the following locations:

* (1) Outdoors or in wet locations

* (2) Where subject to corrosive vapors

* (3) In any hazardous (classified) location

* (4) In residential buildings

* (5) In school and hospital buildings, other than administrative office areas

### 324.18 Crossings.

Crossings of more than two Type FCC cable runs shall not be permitted at any one point. Crossings of a Type FCC cable over or under a flat communications or signal cable shall be permitted. In each case, a grounded layer of metal shielding shall separate the two cables, and crossings of more than two flat cables shall not be permitted at any one point.

### 324.30 Securing and Supporting.

All FCC system components shall be firmly anchored to the floor or wall using an adhesive or mechanical anchoring system identified for this use. Floors shall be prepared to ensure adherence of the FCC system to the floor until the carpet squares are placed.

### 324.40 Boxes and Fittings.

#### 324.40(A) Cable Connections and Insulating Ends.

All Type FCC cable connections shall use connectors identified for their use, installed such that electrical continuity, insulation, and sealing against dampness and liquid spillage are provided. All bare cable ends shall be insulated and sealed against dampness and liquid spillage using listed insulating ends.

#### 324.40(B) Polarization of Connections.

All receptacles and connections shall be constructed and installed so as to maintain proper polarization of the system.

#### 324.40(C) Shields.

##### 324.40(C)(1) Top Shield.

A metal top shield shall be installed over all floor-mounted Type FCC cable, connectors, and insulating ends. The top shield shall completely cover all cable runs, corners, connectors, and ends.

##### 324.40(C)(2) Bottom Shield.

A bottom shield shall be installed beneath all Type FCC cable, connectors, and insulating ends.

#### 324.40(D) Connection to Other Systems.

Power feed, grounding connection, and shield system connection between the FCC system and other wiring systems shall be accomplished in a transition assembly identified for this use.

#### 324.40(E) Metal-Shield Connectors.

Metal shields shall be connected to each other and to boxes, receptacle housings, self-contained devices, and transition assemblies using metal-shield connectors.

### 324.41 Floor Coverings.

Floor-mounted Type FCC cable, cable connectors, and insulating ends shall be covered with carpet squares not larger than 1.0 m
(39.37 in.) square. Carpet squares that are adhered to the floor shall be attached with release-type adhesives.

### 324.42 Devices.

#### 324.42(A) Receptacles.

All receptacles, receptacle housings, and self-contained devices used with the FCC system shall be identified for this use and shall be connected to the Type FCC cable and metal shields. Connection from any equipment grounding conductor of the Type FCC cable shall be made to the shield system at each receptacle.

#### 324.42(B) Receptacles and Housings.

Receptacle housings and self-contained devices designed either for floor mounting or for in-wall or on-wall mounting shall be permitted for use with the FCC system. Receptacle housings and self-contained devices shall incorporate means for facilitating entry and termination of Type FCC cable and for electrically connecting the housing or device with the metal shield. Receptacles and selfcontained devices shall comply with 406.4. Power and communications outlets installed together in common housing shall be permitted in accordance with 805.133(A)(1)(c), Exception No. 2.

### 324.56 Splices and Taps.

#### 324.56(A) FCC Systems Alterations.

Alterations to FCC systems shall be permitted. New cable connectors shall be used at new connection points to make alterations. It shall be permitted to leave unused cable runs and associated cable connectors in place and energized. All cable ends shall be covered with insulating ends.

#### 324.56(B) Transition Assemblies.

All transition assemblies shall be identified for their use. Each assembly shall incorporate means for facilitating entry of the Type FCC cable into the assembly, for connecting the Type FCC cable to grounded conductors, and for electrically connecting the assembly to the metal cable shields and to equipment grounding conductors.

### 324.60 Grounding and Bonding.

All metal shields, boxes, receptacle housings, and self-contained devices shall be electrically continuous to the equipment grounding conductor of the supplying branch circuit. All such electrical connections shall be made with connectors identified for this use. The electrical resistivity of such shield system shall not be more than that of one conductor of the Type FCC cable used in the installation.

## Part III. Construction Specifications

### 324.100 Construction.

#### 324.100(A) Type FCC Cable.

Type FCC cable shall be listed for use with the FCC system and shall consist of three, four, or five flat copper conductors, one of which shall be an equipment grounding conductor.

#### 324.100(B) Shields.

##### 324.100(B)(1) Materials and Dimensions.

All top and bottom shields shall be of designs and materials identified for their use. Top shields shall be metal. Both metallic and nonmetallic materials shall be permitted for bottom shields.

##### 324.100(B)(2) Resistivity.

Metal shields shall have cross-sectional areas that provide for electrical resistivity of not more than that of one conductor of the Type

FCC cable used in the installation.

### 324.101 Corrosion Resistance.

Metal components of the system shall be either corrosion resistant, coated with corrosion-resistant materials, or insulated from contact with corrosive substances.

### 324.112 Insulation.

The insulating material of the cable shall be moisture resistant and flame retardant. All insulating materials in the FCC systems shall be identified for their use.

### 324.120 Markings.

#### 324.120(A) Cable Marking.

Type FCC cable shall be clearly and durably marked on both sides at intervals of not more than 610 mm (24 in.) with the information required by 310.8(A) and with the following additional information:

* (1) Material of conductors

* (2) Maximum temperature rating

* (3) Ampacity

#### 324.120(B) Conductor Identification.

Conductors shall be clearly and durably identified on both sides throughout their length as specified in 310.6.

# Article 326 Integrated Gas Spacer Cable: Type IGS

## Part I. General

### 326.1 Scope.

This article covers the use, installation, and construction specifications for integrated gas spacer cable, Type IGS.

### 326.2 Definition.

The definition in this section shall apply within this article and throughout the Code.

#### Integrated Gas Spacer Cable, Type IGS.

A factory assembly of one or more conductors, each individually insulated and enclosed in a loose fit, nonmetallic flexible conduit as an integrated gas spacer cable rated 0 volts through 600 volts.

## Part II. Installation

### 326.10 Uses Permitted.

Type IGS cable shall be permitted for use underground, including direct burial in the earth, as the following:

* (1) Service-entrance conductors

* (2) Feeder or branch-circuit conductors

* (3) Service conductors, underground

### 326.12 Uses Not Permitted.

Type IGS cable shall not be used as interior wiring or be exposed in contact with buildings.

### 326.24 Bending Radius.

Where the coilable nonmetallic conduit and cable are bent for installation purposes or are flexed or bent during shipment or installation, the radius of the curve of the inner edge measured to the inside of the bend shall not be less than specified in Table 326.24.

Table 326.24 Minimum Radii of Bends

Conduit Size Minimum Radii

Metric Designator Trade Size mm in.

Conduit Size Minimum Radii

Metric Designator Trade Size mm in.
53 2 600 24
78 3 900 35
103 4 1150 45

### 326.26 Bends.

A run of Type IGS cable between pull boxes or terminations shall not contain more than the equivalent of four quarter bends (360 degrees total), including those bends located immediately at the pull box or terminations.

### 326.40 Fittings.

Terminations and splices for Type IGS cable shall be identified as a type that is suitable for maintaining the gas pressure within the conduit. A valve and cap shall be provided for each length of the cable and conduit to check the gas pressure or to inject gas into the conduit.

### 326.80 Ampacity.

The ampacity of Type IGS cable shall not exceed the values shown in Table 326.80.

Table 326.80 Ampacity of Type IGS Cable

Size (kcmil) Amperes Size (kcmil) Amperes
250 119 2500 376
500 168 3000 412
750 206 3250 429
1000 238 3500 445
1250 266 3750 461
1500 292 4000 476
1750 315 4250 491
2000 336 4500 505
2250 357 4750 519

## Part III. Construction Specifications

### 326.104 Conductors.

The conductors shall be solid aluminum rods, laid parallel, consisting of one to nineteen 12.7 mm (1⁄2 in.) diameter rods. The minimum conductor size shall be 250 kcmil, and the maximum size shall be 4750 kcmil.

### 326.112 Insulation.

The insulation shall be dry kraft paper tapes and a pressurized sulfur hexafluoride gas (SF ), both approved for electrical use. The nominal gas pressure shall be 138 kPa gauge (20 lb/in. gauge). The thickness of the paper spacer shall be as specified in Table
326.112.

Table 326.112 Paper

Spacer Thickness

Size (kcmil)

Thickness mm in.
250–1000 1.02 0.040
1250–4750 1.52 0.060

### 326.116 Conduit.

6
2

The conduit shall be a medium density polyethylene identified as suitable for use with natural gas rated pipe in metric designator 53, 78, or 103 (trade size 2, 3, or 4). The percent fill dimensions for the conduit are shown in Table 326.116.

The size of the conduit permitted for each conductor size shall be calculated for a percent fill not to exceed those found in Table 1,

Chapter 9.

Table 326.116 Conduit Dimensions

Conduit Size Actual Outside Diameter Actual Inside Diameter

Metric Designator Trade Size mm in. mm in.
53 2 60 2.375 49.46 1.947
78 3 89 3.500 73.30 2.886
103 4 114 4.500 94.23 3.710

### 326.120 Marking.

The cable shall be marked in accordance with 310.8(A), 310.8(B)(1), and 310.8(D).

# Article 336 Power and Control Tray Cable: Type TC

## Part I. General

### 336.1 Scope.

This article covers the use, installation, and construction specifications for power and control tray cable, Type TC.

### 336.2 Definition.

The definition in this section shall apply within this article and throughout this Code.

#### Power and Control Tray Cable, Type TC.

A factory assembly of two or more insulated conductors, with or without associated bare or covered equipment grounding conductors, under a nonmetallic jacket.

### 336.6 Listing Requirements.

Type TC cables and associated fittings shall be listed.

## Part II. Installation

### 336.10 Uses Permitted.

Type TC cable shall be permitted to be used as follows:

* (1) For power, lighting, control, and signal circuits.

* (2) In cable trays, including those with mechanically discontinuous segments up to 300 mm (1 ft).

* (3) In raceways.

* (4) In outdoor locations supported by a messenger wire.

* (5) For Class 1 circuits as permitted in Parts II and III of Article 725.

* (6) For non-power-limited fire alarm circuits if conductors comply with the requirements of 760.49.

* (7) Between a cable tray and the utilization equipment or device(s), provided all of the following apply:
    * a. The cable is Type TC-ER.
    * b. The cable is installed in industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons service the installation.
    * c. The cable is continuously supported and protected against physical damage using mechanical protection such as struts, angles, or channels.
    * d. The cable complies with the crush and impact requirements of Type MC cable and is identified with the marking “TC–

ER.”
    * e. The cable is secured at intervals not exceeding 1.8 m (6 ft).
    * f. Equipment grounding for the utilization equipment is provided by an equipment grounding conductor within the cable. In cables containing conductors sized 6 AWG or smaller, the equipment grounding conductor shall be provided within the cable or, at the time of installation, one or more insulated conductors shall be permanently identified as an equipment grounding conductor in accordance with 250.119(B).

Exception to (7): Where not subject to physical damage, Type TC-ER shall be permitted to transition between cable trays and between cable trays and equipment or devices for a distance not to exceed 1.8 m (6 ft) without continuous support. The cable shall be mechanically supported where exiting the cable tray to ensure that the minimum bending radius is not exceeded.

* (8) Type TC cable shall be resistant to moisture and corrosive agents where installed in wet locations.

* (9) In one- and two-family dwelling units, Type TC-ER-JP cable containing both power and control conductors shall be permitted for branch circuits and feeders. Type TC-ER-JP cable used as interior wiring shall be installed per the requirements of Part II of

Article 334 and where installed as exterior wiring shall be installed per the requirements of Part II of Article 340.

> [!important] Exception:
> Where used to connect a generator and associated equipment having terminals rated 75°C (140°F) or higher, the cable shall not be limited in ampacity by 334.80 or 340.80.

> [!info] Informational Note:
> See 725.136 for limitations on Class 2 or 3 circuits contained within the same cable with conductors of electric light, power, or Class 1 circuits.

* (10) Direct buried, where identified for such use.

* (11) In hazardous (classified) locations where specifically permitted by other articles in this Code.

> [!info] Informational Note:
> See 310.14(A)(3) for temperature limitation of conductors.

### 336.12 Uses Not Permitted.

Type TC tray cable shall not be installed or used as follows:

* (1) Installed where it will be exposed to physical damage

* (2) Installed outside a raceway or cable tray system, except as permitted in 336.10(4), 336.10(7), 336.10(9), and 336.10(10)

* (3) Used where exposed to direct rays of the sun, unless identified as sunlight resistant

### 336.24 Bending Radius.

Bends in Type TC cable shall be made so as not to damage the cable. For Type TC cable without metal shielding, the minimum bending radius shall be as follows:

* (1) Four times the overall diameter for cables 25 mm (1 in.) or less in diameter

* (2) Five times the overall diameter for cables larger than 25 mm (1 in.) but not more than 50 mm (2 in.) in diameter

* (3) Six times the overall diameter for cables larger than 50 mm (2 in.) in diameter

Type TC cables with metallic shielding shall have a minimum bending radius of not less than 12 times the cable overall diameter.

### 336.80 Ampacity.

The ampacity of Type TC tray cable shall be determined in accordance with 392.80(A) for 14 AWG and larger conductors, in accordance with 402.5 for 18 AWG through 16 AWG conductors where installed in cable trays, and in accordance with 310.14 where installed outside of cable trays, where permitted.

## Part III. Construction Specifications

### 336.100 Construction.

A metallic sheath or armor as defined in 330.116 shall not be permitted either under or over the nonmetallic jacket. Metallic shield(s) shall be permitted over groups of conductors, under the outer jacket, or both.

### 336.104 Conductors.

For ungrounded, grounded, and equipment grounding conductors, the conductor sizes shall be 14 AWG through 1000 kcmil copper, nickel, or nickel-coated copper and 12 AWG through 1000 kcmil aluminum or copper-clad aluminum. Insulation types shall be one of the types listed in Table 310.4(A) or Table 310.4(B) that is suitable for branch circuit and feeder circuits or one that is identified for such use.

For control and signal conductors, the minimum conductor sizes shall be 18 AWG copper, nickel, or nickel-coated copper, 14 AWG copper-clad aluminum, and 12 AWG aluminum.

#### 336.104(A) Fire Alarm Systems.

Where used for fire alarm systems, conductors shall also be in accordance with 760.49.

#### 336.104(B) Thermocouple Circuits.

Conductors in Type TC cable used for thermocouple circuits in accordance with Part III of Article 725 shall also be permitted to be any of the materials used for thermocouple extension wire.

#### 336.104(C) Class 1 Circuit Conductors.

Insulated conductors of 18 AWG and 16 AWG copper shall also be in accordance with 725.49.

### 336.116 Jacket.

The outer jacket shall be a flame-retardant, nonmetallic material.

### 336.120 Marking.

There shall be no voltage marking on a Type TC cable employing thermocouple extension wire.

### 336.130 Hazardous (Classified) Location Cable.

Cable listed and marked Type TC-ER-HL shall comply with the following:

* (1) The overall nonmetallic jacket shall be suitable for the environment.

* (2) The overall cable construction shall be essentially circular in cross-section.

* (3) The overall nonmetallic jacket shall be continuous and gas/vapor tight.

* (4) For construction greater than 25.4 mm (1 in.) in diameter, the following shall apply:
    * a. The equipment grounding conductor shall be bare.
    * b. A metallic shield shall be included over all conductors under the outer jacket.

# Article 337 Type P Cable

## Part I. General

### 337.1 Scope.

This article covers the use, installation, and construction specifications for up through 2000 volt Type P cable (armored and unarmored).

### 337.2 Definition.

The definition in this section shall apply within this article and throughout the Code.

#### Type P. Cable

A factory assembly of one or more insulated flexible tinned copper conductors, with associated equipment grounding conductor(s), with or without a braided metallic armor and with an overall nonmetallic jacket.

### 337.6 Listing Requirements.

Type P cables and associated fittings shall be listed.

## Part II. Installation

### 337.10 Uses Permitted.

Type P cable shall be permitted to be used:

* (1) Under engineering supervision in industrial installations where conditions of maintenance and supervision ensure that only qualified persons monitor and service the system.

* (2) In hazardous (classified) locations where specifically permitted by other articles in this Code.

### 337.12 Uses Not Permitted.

Type P cable shall not be installed or used:

* (1) Where it will be exposed to physical damage

* (2) Where not specifically permitted by other articles in the Code

### 337.24 Bending Radius.

The minimum bending radii during installations and handling in service shall be adequate to prevent damage to the cable.

### 337.30 Securing and Supporting.

Type P cable shall be supported and secured by cable ties listed and identified for securement and support; straps, hangers, or similar fittings; or other approved means designed and installed so as not to damage the cable.

### 337.31 Single Conductors.

Where single-conductor cables are used, the installation shall comply with 300.20.

### 337.80 Ampacity.

The ampacity of Type P cable shall be determined in accordance with 310.14(A) or 310.14(B) for 14 AWG and larger conductors. For
18 AWG and 16 AWG conductors the ampacities shall be determined in accordance with Table 402.5. When installed in cable tray, the ampacities shall be permitted to be determined in accordance with 392.80. The installation shall not exceed the temperature ratings of terminations and equipment.

## Part III. Construction Specifications

### 337.104 Conductors.

Conductors shall be of tinned copper. Conductors shall employ flexible stranding. The minimum conductor size shall be 18 AWG.

### 337.108 Equipment Grounding Conductor.

An equipment grounding conductor complying with 250.122 shall be provided within the cable.

### 337.112 Insulation.

Insulated conductors shall be a thermoset type identified for use in Type P cable. All conductors shall be suitable for wet locations. The minimum wall thickness shall be 0.76 mm (30 mils).

### 337.114 Shield.

Metallic shield(s) shall be permitted over a single conductor or groups of conductors.

### 337.115 Jacket.

Single conductor cables and multiconductor cables shall have an overall nonmetallic jacket that is impervious to moisture, corrosion resistant, and sunlight resistant.

### 337.116 Armor.

Armor shall be permitted over the jacket. If provided, the armor or metallic covering shall be a braided basket weave type consisting of wire laid closely together, flat and parallel, and forming a basket weave that shall firmly grip the cable. The wire shall be commercial bronze. The armor shall not be used as a current-carrying conductor or as an equipment grounding conductor. A nonmetallic jacket that conforms to 337.115 shall be provided over the armor.

### 337.120 Marking.

Type P cable shall be marked in accordance with 310.8. When an armor is provided, the cable shall be marked accordingly.

# Article 340 Underground Feeder and Branch-Circuit Cable: Type UF

## Part I. General

### 340.1 Scope.

This article covers the use, installation, and construction specifications for underground feeder and branch-circuit cable, Type UF.

### 340.2 Definition.

The definition in this section shall apply within this article and throughout the Code.

#### Underground Feeder and Branch-Circuit Cable, Type UF.

A factory assembly of one or more insulated conductors with an integral or an overall covering of nonmetallic material suitable for direct burial in the earth.

### 340.6 Listing Requirements.

Type UF cable and associated fittings shall be listed.

## Part II. Installation

### 340.10 Uses Permitted.

Type UF cable shall be permitted as follows:

* (1) For use underground, including direct burial in the earth.

* (2) As single-conductor cables. Where installed as single-conductor cables, all conductors of the feeder or branch circuit, including the grounded conductor and equipment grounding conductor, if any, shall be installed in accordance with 300.3.

* (3) For wiring in wet, dry, or corrosive locations.

* (4) Installed as nonmetallic-sheathed cable. Where so installed, the installation and conductor requirements shall comply with Parts

II and III of Article 334 and shall be of the multiconductor type.

* (5) As single-conductor cables as the nonheating leads for heating cables as provided in 424.43.

* (6) Supported by cable trays. Type UF cable supported by cable trays shall be of the multiconductor type.

> [!info] Informational Note:
> See 310.14(A)(3) for temperature limitation of conductors.

### 340.12 Uses Not Permitted.

Type UF cable shall not be used as follows:

* (1) As service-entrance cable

* (2) In commercial garages

* (3) In theaters and similar locations

* (4) In motion picture studios

* (5) In storage battery rooms

* (6) In hoistways or on elevators or escalators

* (7) In hazardous (classified) locations, except as specifically permitted by other articles in this Code

* (8) Embedded in poured cement, concrete, or aggregate, except where embedded in plaster as nonheating leads where permitted in 424.43

* (9) Where exposed to direct rays of the sun, unless identified as sunlight resistant

> [!info] Informational Note:
> The sunlight-resistant marking on the jacket does not apply to the individual conductors.

* (10) Where subject to physical damage

* (11) As overhead cable, except where installed as messenger-supported wiring in accordance with Part II of Article 396

### 340.24 Bending Radius.

Bends in Type UF cable shall be so made that the cable is not damaged. The radius of the curve of the inner edge of any bend shall not be less than five times the diameter of the cable.

### 340.80 Ampacity.

The ampacity of Type UF cable shall be that of 60°C (140°F) conductors in accordance with 310.14.

## Part III. Construction Specifications

### 340.104 Conductors.

The conductors shall be sizes 14 AWG copper or 12 AWG aluminum or copper-clad aluminum through 4/0 AWG.

### 340.108 Equipment Grounding Conductor.

In addition to the insulated conductors, the cable shall be permitted to have an insulated or bare equipment grounding conductor.

### 340.112 Insulation.

The conductors of Type UF shall be one of the moisture-resistant types listed in Table 310.4(A) that is suitable for branch-circuit wiring or one that is identified for such use. Where installed as a substitute wiring method for NM cable, the conductor insulation shall be rated
90°C (194°F).

### 340.116 Sheath.

The overall covering shall be flame retardant;
moisture, fungus, and corrosion resistant;
and suitable for direct burial in the earth.

# Article 354 Nonmetallic Underground Conduit with Conductors: Type NUCC

## Part I. General

### 354.1 Scope.

This article covers the use, installation, and construction specifications for nonmetallic underground conduit with conductors (NUCC).

### 354.2 Definition.

The definition in this section shall apply within this article and throughout the Code.

#### Nonmetallic Underground Conduit with Conductors (NUCC).

A factory assembly of conductors or cables inside a nonmetallic, smooth wall raceway with a circular cross section.

### 354.6 Listing Requirements.

NUCC and associated fittings shall be listed.

## Part II. Installation

### 354.10 Uses Permitted.

The use of NUCC and fittings shall be permitted in the following:

* (1) For direct burial underground installation (For minimum cover requirements, see Table 300.5 and Table 300.50 under Rigid

Nonmetallic Conduit.)

* (2) Encased or embedded in concrete

* (3) In cinder fill

* (4) In underground locations subject to severe corrosive influences as covered in 300.6 and where subject to chemicals for which the assembly is specifically approved

* (5) Aboveground, except as prohibited in 354.12, where encased in not less than 50 mm (2 in.) of concrete

### 354.12 Uses Not Permitted.

NUCC shall not be used in the following:

* (1) In exposed locations

* (2) Inside buildings

> [!important] Exception:
> The conductor or the cable portion of the assembly, where suitable, shall be permitted to extend within the building for termination purposes in accordance with 300.3.

* (3) In any hazardous (classified) location, except as permitted by other articles of this Code

### 354.20 Size.

#### 354.20(A) Minimum.

NUCC smaller than metric designator 16 (trade size 1⁄2) shall not be used.

#### 354.20(B) Maximum.

NUCC larger than metric designator 103 (trade size 4) shall not be used.

> [!info] Informational Note:
> See 300.1(C) for the metric designators and trade sizes. These are for identification purposes only and do not relate to actual dimensions.

### 354.22 Number of Conductors.

The number of conductors or cables shall not exceed that permitted by the percentage fill in Table 1, Chapter 9.

### 354.24 Bends — How Made.

Bends shall be manually made so that the conduit will not be damaged and the internal diameter of the conduit will not be effectively reduced. The radius of the curve of the centerline of such bends shall not be less than shown in Table 354.24.

Table 354.24 Minimum Bending Radius for Nonmetallic

Underground Conduit with Conductors (NUCC)

Conduit Size Minimum Bending Radius

Metric Designator Trade Size mm in.
16 1⁄2 250 10
21 3⁄4 300 12
27 1 350 14
35 11⁄4 450 18
41 11⁄2 500 20
53 2 650 26
63 21⁄2 900 36
78 3 1200 48
103 4 1500 60

### 354.26 Bends — Number in One Run.

There shall not be more than the equivalent of four quarter bends (360 degrees total) between termination points.

### 354.28 Trimming.

For termination, the conduit shall be trimmed away from the conductors or cables using an approved method that will not damage the conductor or cable insulation or jacket. All conduit ends shall be trimmed inside and out to remove rough edges.

### 354.46 Bushings.

Where the NUCC enters a box, fitting, or other enclosure, a bushing or adapter shall be provided to protect the conductor or cable from abrasion unless the design of the box, fitting, or enclosure provides equivalent protection.

> [!info] Informational Note:
> See 300.4(G) for the protection of conductors size 4 AWG or larger.

### 354.48 Joints.

All joints between conduit, fittings, and boxes shall be made by an approved method.

### 354.50 Conductor Terminations.

All terminations between the conductors or cables and equipment shall be made by an approved method for that type of conductor or cable.

### 354.56 Splices and Taps.

Splices and taps shall be made in junction boxes or other enclosures.

### 354.60 Grounding.

Where equipment grounding is required, an assembly containing a separate equipment grounding conductor shall be used.

## Part III. Construction Specifications

### 354.100 Construction.

#### 354.100(A) General.

NUCC is an assembly that is provided in continuous lengths shipped in a coil, reel, or carton.

#### 354.100(B) Nonmetallic Underground Conduit.

The nonmetallic underground conduit shall be listed and composed of a material that is resistant to moisture and corrosive agents. It shall also be capable of being supplied on reels without damage or distortion and shall be of sufficient strength to withstand abuse, such as impact or crushing, in handling and during installation without damage to conduit or conductors.

#### 354.100(C) Conductors and Cables.

Conductors and cables used in NUCC shall be listed and shall comply with 310.10(C). Conductors of different systems shall be installed in accordance with 300.3(C).

#### 354.100(D) Conductor Fill.

The maximum number of conductors or cables in NUCC shall not exceed that permitted by the percentage fill in Table 1, Chapter 9.

### 354.120 Marking.

NUCC shall be clearly and durably marked at least every 3.05 m (10 ft) as required by 110.21. The type of conduit material shall also be included in the marking.

Identification of conductors or cables used in the assembly shall be provided on a tag attached to each end of the assembly or to the side of a reel. Enclosed conductors or cables shall be marked in accordance with 310.8.

# Article 355 Reinforced Thermosetting Resin Conduit: Type RTRC

## Part I. General

### 355.1 Scope.

This article covers the use, installation, and construction specification for reinforced thermosetting resin conduit (RTRC) and associated fittings.

> [!info] Informational Note:
> Refer to Article 352 for Rigid Polyvinyl Chloride Conduit: Type PVC, and Article 353 for High Density Polyethylene Conduit: Type HDPE.

### 355.2 Definition.

The definition in this section shall apply within this article and throughout the Code.

#### Reinforced Thermosetting Resin Conduit (RTRC).

A rigid nonmetallic raceway of circular cross section, with integral or associated couplings, connectors, and fittings for the installation of electrical conductors and cables.

### 355.6 Listing Requirements.

RTRC, factory elbows, and associated fittings shall be listed.

## Part II. Installation

### 355.10 Uses Permitted.

The use of RTRC shall be permitted in accordance with 355.10(A) through (I).

#### 355.10(A) Concealed.

RTRC shall be permitted in walls, floors, and ceilings.

#### 355.10(B) Corrosive Influences.

RTRC shall be permitted in locations subject to severe corrosive influences as covered in 300.6 and where subject to chemicals for which the materials are specifically approved.

#### 355.10(C) Cinders.

RTRC shall be permitted in cinder fill.

#### 355.10(D) Wet Locations.

RTRC shall be permitted in portions of dairies, laundries, canneries, or other wet locations, and in locations where walls are frequently washed, the entire conduit system, including boxes and fittings used therewith, shall be installed and equipped so as to prevent water from entering the conduit. All supports, bolts, straps, screws, and so forth, shall be of corrosion-resistant materials or be protected against corrosion by approved corrosion-resistant materials.

#### 355.10(E) Dry and Damp Locations.

RTRC shall be permitted for use in dry and damp locations not prohibited by 355.12.

#### 355.10(F) Exposed.

RTRC shall be permitted for exposed work if identified for such use.

> [!info] Informational Note:
> RTRC, Type XW, is identified for areas of physical damage.

#### 355.10(G) Underground Installations.

For underground installations, see 300.5 and 300.50.

#### 355.10(H) Support of Conduit Bodies.

RTRC shall be permitted to support nonmetallic conduit bodies not larger than the largest trade size of an entering raceway. These conduit bodies shall not support luminaires or other equipment and shall not contain devices other than splicing devices as permitted by
110.14(B) and 314.16(C)(2).

#### 355.10(I) Insulation Temperature Limitations.

Conductors or cables rated at a temperature higher than the listed temperature rating of RTRC conduit shall be permitted to be installed in RTRC conduit, if the conductors or cables are not operated at a temperature higher than the listed temperature rating of the RTRC conduit.

### 355.12 Uses Not Permitted.

RTRC shall not be used under the following conditions.

#### 355.12(A) Hazardous (Classified) Locations.

* (1) In any hazardous (classified) location, except as permitted by other articles in this Code

* (2) In Class I, Division 2 locations, except as permitted in 501.10(B)(1)(6)

#### 355.12(B) Support of Luminaires.

For the support of luminaires or other equipment not described in 355.10(H).

#### 355.12(C) Physical Damage.

Where subject to physical damage unless identified for such use.

#### 355.12(D) Ambient Temperatures.

Where subject to ambient temperatures in excess of 50°C (122°F) unless listed otherwise.

#### 355.12(E) Theaters and Similar Locations.

In theaters and similar locations, except as provided in 518.4 and 520.5.

### 355.20 Size.

#### 355.20(A) Minimum.

RTRC smaller than metric designator 16 (trade size 1⁄2) shall not be used.

#### 355.20(B) Maximum.

RTRC larger than metric designator 155 (trade size 6) shall not be used.

> [!info] Informational Note:
> The trade sizes and metric designators are for identification purposes only and do not relate to actual dimensions.

See 300.1(C).

### 355.22 Number of Conductors.

The number of conductors shall not exceed that permitted by the percentage fill specified in Table 1, Chapter 9. Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9.

### 355.24 Bends — How Made.

Bends shall be so made that the conduit will not be damaged and the internal diameter of the conduit will not be effectively reduced.

Field bends shall be made only with identified bending equipment. The radius of the curve to the centerline of such bends shall not be less than shown in Table 2, Chapter 9.

### 355.26 Bends — Number in One Run.

There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, for example, conduit bodies and boxes.

### 355.28 Trimming.

All cut ends shall be trimmed inside and outside to remove rough edges.

### 355.30 Securing and Supporting.

RTRC shall be installed as a complete system in accordance with 300.18 and shall be securely fastened in place and supported in accordance with 355.30(A) and (B).

#### 355.30(A) Securely Fastened.

RTRC shall be securely fastened within 900 mm (3 ft) of each outlet box, junction box, device box, conduit body, or other conduit termination. Conduit listed for securing at other than 900 mm (3 ft) shall be permitted to be installed in accordance with the listing.

#### 355.30(B) Supports.

RTRC shall be supported as required in Table 355.30. Conduit listed for support at spacing other than as shown in Table 355.30 shall be permitted to be installed in accordance with the listing. Horizontal runs of RTRC supported by openings through framing members at intervals not exceeding those in Table 355.30 and securely fastened within 900 mm (3 ft) of termination points shall be permitted.

Table 355.30 Support of Reinforced Thermosetting Resin Conduit
(RTRC)

Conduit Size Maximum Spacing Between Supports

Metric Designator Trade Size mm or m ft
16–27 1⁄2–1 900 mm 3
35–53 11⁄4–2 1.5 m 5
63–78 21⁄2–3 1.8 m 6
91–129 31⁄2–5 2.1 m 7
155 6 2.5 m 8

### 355.44 Expansion Fittings.

Expansion fittings for RTRC shall be provided to compensate for thermal expansion and contraction where the length change, in accordance with Table 355.44, is expected to be 6 mm (1⁄4 in.) or greater in a straight run between securely mounted items such as boxes, cabinets, elbows, or other conduit terminations.

Table 355.44 Expansion Characteristics of Reinforced Thermosetting Resin Conduit (RTRC) Coefficient of Thermal Expansion = 2.7 × 10 mm/mm/°C (1.5 × 10 in./in./°F)

Temperature

Change (°C)

Length Change of

RTRC Conduit
(mm/m)

Temperature

Change (°F)

Length Change of

RTRC Conduit
(in./100 ft)

Temperature

Change (°F)

Length Change of RTRC

Conduit
(in./100 ft)
5 0.14 5 0.09 105 1.89
10 0.27 10 0.18 110 1.98
15 0.41 15 0.27 115 2.07
20 0.54 20 0.36 120 2.16
25 0.68 25 0.45 125 2.25
30 0.81 30 0.54 130 2.34
35 0.95 35 0.63 135 2.43
40 1.08 40 0.72 140 2.52
45 1.22 45 0.81 145 2.61
–5 –5

Temperature

Change (°C)

Length Change of

RTRC Conduit
(mm/m)

Temperature

Change (°F)

Length Change of

RTRC Conduit
(in./100 ft)

Temperature

Change (°F)

Length Change of RTRC

Conduit
(in./100 ft)
50 1.35 50 0.90 150 2.70
55 1.49 55 0.99 155 2.79
60 1.62 60 1.08 160 2.88
65 1.76 65 1.17 165 2.97
70 1.89 70 1.26 170 3.06
75 2.03 75 1.35 175 3.15
80 2.16 80 1.44 180 3.24
85 2.30 85 1.53 185 3.33
90 2.43 90 1.62 190 3.42
95 2.57 95 1.71 195 3.51
100 2.70 100 1.80 200 3.60

### 355.46 Bushings.

Where a conduit enters a box, fitting, or other enclosure, a bushing or adapter shall be provided to protect the wire from abrasion unless the box, fitting, or enclosure design provides equivalent protection.

> [!info] Informational Note:
> See 300.4(G) for the protection of conductors 4 AWG and larger at bushings.

### 355.48 Joints.

All joints between lengths of conduit, and between conduit and couplings, fitting, and boxes, shall be made by an approved method.

### 355.56 Splices and Taps.

Splices and taps shall be made in accordance with 300.15.

### 355.60 Grounding.

Where equipment grounding is required, a separate equipment grounding conductor shall be installed in the conduit.

> [!important] Exception No. 1:
> As permitted in 250.134, Exception No. 2, for dc circuits and 250.134, Exception No. 1, for separately run equipment grounding conductors.

> [!important] Exception No. 2:
> Where the grounded conductor is used to ground equipment as permitted in 250.142.

## Part III. Construction Specifications

### 355.100 Construction.

RTRC and fittings shall be composed of suitable nonmetallic material that is resistant to moisture and chemical atmospheres. For use aboveground, it shall also be flame retardant, resistant to impact and crushing, resistant to distortion from heat under conditions likely to be encountered in service, and resistant to low temperature and sunlight effects. For use underground, the material shall be acceptably resistant to moisture and corrosive agents and shall be of sufficient strength to withstand abuse, such as by impact and crushing, in handling and during installation. Where intended for direct burial, without encasement in concrete, the material shall also be capable of withstanding continued loading that is likely to be encountered after installation.

### 355.120 Marking.

Each length of RTRC shall be clearly and durably marked at least every 3 m (10 ft) as required in the first sentence of 110.21(A). The type of material shall also be included in the marking unless it is visually identifiable. For conduit recognized for use aboveground, these markings shall be permanent. For conduit limited to underground use only, these markings shall be sufficiently durable to remain legible until the material is installed. Conduit shall be permitted to be surface marked to indicate special characteristics of the material.

> [!info] Informational Note:
> Examples of these markings include but are not limited to “limited smoke” and “sunlight resistant.”

# Article 360 Flexible Metallic Tubing: Type FMT

## Part I. General

### 360.1 Scope.

This article covers the use, installation, and construction specifications for flexible metallic tubing (FMT) and associated fittings.

### 360.2 Definition.

The definition in this section shall apply within this article and throughout the Code.

#### Flexible Metallic Tubing (FMT).

A metal raceway that is circular in cross section, flexible, and liquidtight without a nonmetallic jacket.

### 360.6 Listing Requirements.

FMT and associated fittings shall be listed.

## Part II. Installation

### 360.10 Uses Permitted.

FMT shall be permitted to be used for branch circuits as follows:

* (1) In dry locations

* (2) Where concealed

* (3) In accessible locations

* (4) For system voltages of 1000 volts maximum

### 360.12 Uses Not Permitted.

FMT shall not be used as follows:

* (1) In hoistways

* (2) In storage battery rooms

* (3) In hazardous (classified) locations unless otherwise permitted under other articles in this Code

* (4) Underground for direct earth burial, or embedded in poured concrete or aggregate

* (5) Where subject to physical damage

* (6) In lengths over 1.8 m (6 ft)

### 360.20 Size.

#### 360.20(A) Minimum.

FMT smaller than metric designator 16 (trade size 1⁄2) shall not be used.

> [!important] Exception No. 1:
> FMT of metric designator 12 (trade size 3⁄8) shall be permitted to be installed in accordance with 300.22(B) and (C).

> [!important] Exception No. 2:
> FMT of metric designator 12 (trade size 3⁄8) shall be permitted in lengths not in excess of 1.8 m (6 ft) as part of a listed assembly or for luminaires. See 410.117(C).

#### 360.20(B) Maximum.

The maximum size of FMT shall be metric designator 21 (trade size 3⁄4).

> [!info] Informational Note:
> See 300.1(C) for the metric designators and trade sizes. These are for identification purposes only and do not relate to actual dimensions.

### 360.22 Number of Conductors.

#### 360.22(A) FMT — Metric Designators 16 and 21 (Trade Sizes 1⁄2 and 3⁄4).

The number of conductors in metric designators 16 (trade size 1⁄2) and 21 (trade size 3⁄4) shall not exceed that permitted by the percentage fill specified in Table 1, Chapter 9.

Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9.

#### 360.22(B) FMT — Metric Designator 12 (Trade Size 3⁄8).

The number of conductors in metric designator 12 (trade size 3⁄8) shall not exceed that permitted in Table 348.22.

### 360.24 Bends.

#### 360.24(A) Infrequent Flexing Use.

When FMT is infrequently flexed in service after installation, the radii of bends measured to the inside of the bend shall not be less than specified in Table 360.24(A).

Table 360.24(A) Minimum Radii for Flexing Use

Metric Designator

Minimum Radii for Flexing Use

Trade Size mm in.
12 3⁄8 254.0 10
16 1⁄2 317.5 121⁄2
21 3⁄4 444.5 171⁄2

#### 360.24(B) Fixed Bends.

Where FMT is bent for installation purposes and is not flexed or bent as required by use after installation, the radii of bends measured to the inside of the bend shall not be less than specified in Table 360.24(B).

Table 360.24(B) Minimum Radii for Fixed Bends

Metric Designator

Minimum Radii for

Fixed Bends

Trade Size mm in.
12 3⁄8 88.9 31⁄2
16 1⁄2 101.6 4
21 3⁄4 127.0 5

### 360.56 Splices and Taps.

Splices and taps shall be made in accordance with 300.15.

### 360.60 Grounding.

FMT shall be permitted as an equipment grounding conductor where installed in accordance with 250.118(7).

## Part III. Construction Specifications

### 360.120 Marking.

FMT shall be marked according to 110.21.

# Article 366 Auxiliary Gutters

## Part I. General

### 366.1 Scope.

This article covers the use, installation, and construction requirements of metal auxiliary gutters and nonmetallic auxiliary gutters and associated fittings.

### 366.2 Definitions.

The definitions in this section shall apply within this article and throughout the Code.

#### Metal Auxiliary Gutter.

A sheet metal enclosure used to supplement wiring spaces at meter centers, distribution centers, switchgear, switchboards, and similar points of wiring systems. The enclosure has hinged or removable covers for housing and protecting electrical wires, cable, and busbars.

The enclosure is designed for conductors to be laid or set in place after the enclosures have been installed as a complete system.

#### Nonmetallic Auxiliary Gutter.

A flame-retardant, nonmetallic enclosure used to supplement wiring spaces at meter centers, distribution centers, switchgear, switchboards, and similar points of wiring systems. The enclosure has hinged or removable covers for housing and protecting electrical wires, cable, and busbars. The enclosure is designed for conductors to be laid or set in place after the enclosures have been installed as a complete system.

### 366.6 Listing Requirements.

#### 366.6(A) Outdoors.

Nonmetallic auxiliary gutters installed outdoors shall be listed for all of the following conditions:

* (1) Exposure to sunlight

* (2) Use in wet locations

* (3) Maximum ambient temperature of the installation

#### 366.6(B) Indoors.

Nonmetallic auxiliary gutters installed indoors shall be listed for the maximum ambient temperature of the installation.

## Part II. Installation

### 366.10 Uses Permitted.

366.10(A)  Sheet Metal Auxiliary Gutters.

##### 366.10(A)(1) Indoor and Outdoor Use.

Sheet metal auxiliary gutters shall be permitted for indoor and outdoor use.

##### 366.10(A)(2) Wet Locations.

Sheet metal auxiliary gutters installed in wet locations shall be suitable for such locations.

#### 366.10(B) Nonmetallic Auxiliary Gutters.

Nonmetallic auxiliary gutters shall be listed for the maximum ambient temperature of the installation and marked for the installed conductor insulation temperature rating.

> [!info] Informational Note:
> Extreme cold may cause nonmetallic auxiliary gutters to become brittle and therefore more susceptible to damage from physical contact.

##### 366.10(B)(1) Outdoors.

Nonmetallic auxiliary gutters shall be permitted to be installed outdoors where listed and marked as suitable for the purpose.

##### 366.10(B)(2) Indoors.

Nonmetallic auxiliary gutters shall be permitted to be installed indoors.

### 366.12 Uses Not Permitted.

Auxiliary gutters shall not be used:

* (1) To enclose switches, overcurrent devices, appliances, or other similar equipment

* (2) To extend a greater distance than 9 m (30 ft) beyond the equipment that it supplements

> [!important] Exception:
> As permitted in 620.35 for elevators, an auxiliary gutter shall be permitted to extend a distance greater than 9 m (30 ft) beyond the equipment it supplements.

> [!info] Informational Note:
> For wireways, see Articles 376 and 378. For busways, see Article 368.

### 366.20 Conductors Connected in Parallel.

Where single conductor cables comprising each phase, neutral, or grounded conductor of an alternating-current circuit are connected in parallel as permitted in 310.10(G), the conductors shall be installed in groups consisting of not more than one conductor per phase, neutral, or grounded conductor to prevent current imbalance in the paralleled conductors due to inductive reactance.

### 366.22 Number of Conductors.

#### 366.22(A) Sheet Metal Auxiliary Gutters.

The sum of the cross-sectional areas of all contained conductors and cables at any cross section of a sheet metal auxiliary gutter shall not exceed 20 percent of the interior cross-sectional area of the sheet metal auxiliary gutter.

#### 366.22(B) Nonmetallic Auxiliary Gutters.

The sum of cross-sectional areas of all contained conductors and cables at any cross section of the nonmetallic auxiliary gutter shall not exceed 20 percent of the interior cross-sectional area of the nonmetallic auxiliary gutter.

### 366.23 Ampacity of Conductors.

#### 366.23(A) Sheet Metal Auxiliary Gutters.

The adjustment factors in 310.15(C)(1) shall be applied only where the number of current-carrying conductors, including neutral conductors clas sified as current-carrying under 310.15(E), exceeds 30 at any cross section of the sheet metal auxiliary gutter.

Conductors for signaling circuits or controller conductors between a motor and its starter and used only for starting duty shall not be considered as current-carrying conductors. The current carried continuously in bare copper bars in sheet metal auxiliary gutters shall not exceed 1.55 amperes/mm (1000 amperes/in. ) of cross section of the conductor. For aluminum bars, the current carried continuously shall not exceed 1.09 amperes/mm (700 amperes/in. ) of cross section of the conductor.

#### 366.23(B) Nonmetallic Auxiliary Gutters.

The adjustment factors specified in 310.15(C)(1) shall be applicable to the current-carrying conductors up to and including the 20 percent fill specified in 366.22(B).

### 366.30 Securing and Supporting.

#### 366.30(A) Sheet Metal Auxiliary Gutters.

Sheet metal auxiliary gutters shall be supported and secured throughout their entire length at intervals not exceeding 1.5 m (5 ft).

#### 366.30(B) Nonmetallic Auxiliary Gutters.

Nonmetallic auxiliary gutters shall be supported and secured at intervals not to exceed 900 mm (3 ft) and at each end or joint, unless listed for other support intervals. In no case shall the distance between supports exceed 3 m (10 ft).

### 366.44 Expansion Fittings.

Expansion fittings shall be installed where expected length change, due to expansion and contraction due to temperature change, is more than 6 mm (0.25 in.).

### 366.56 Splices and Taps.

Splices and taps shall comply with 366.56(A) through (D).

#### 366.56(A) Within Gutters.

Splices or taps shall be permitted within gutters where they are accessible by means of removable covers or doors. The conductors, including splices and taps, shall not fill the gutter to more than 75 percent of its area.

#### 366.56(B) Bare Conductors.

Taps from bare conductors shall leave the gutter opposite their terminal connections, and conductors shall not be brought in contact with uninsulated current-carrying parts of different voltages.

#### 366.56(C) Suitably Identified.

All taps shall be suitably identified at the gutter as to the circuit or equipment that they supply.

#### 366.56(D) Overcurrent Protection.

2 2
2 2

Tap connections from conductors in auxiliary gutters shall be provided with overcurrent protection as required in 240.21.

### 366.58 Insulated Conductors.

#### 366.58(A) Deflected Insulated Conductors.

Where insulated conductors are deflected within an auxiliary gutter, either at the ends or where conduits, fittings, or other raceways or cables enter or leave the gutter, or where the direction of the gutter is deflected greater than 30 degrees, dimensions corresponding to one wire per terminal in Table 312.6(A) shall apply.

#### 366.58(B) Auxiliary Gutters Used as Pull Boxes.

Where insulated conductors 4 AWG or larger are pulled through an auxiliary gutter, the distance between raceway and cable entries enclosing the same conductor shall not be less than that required in 314.28(A)(1) for straight pulls and 314.28(A)(2) for angle pulls.

### 366.60 Grounding.

Metal auxiliary gutters shall be connected to an equipment grounding conductor(s), to an equipment bonding jumper, or to the grounded conductor where permitted or required by 250.92(B)(1) or 250.142.

## Part III. Construction Specifications

### 366.100 Construction.

#### 366.100(A) Electrical and Mechanical Continuity.

Gutters shall be constructed and installed so that adequate electrical and mechanical continuity of the complete system is secured.

#### 366.100(B) Substantial Construction.

Gutters shall be of substantial construction and shall provide a complete enclosure for the contained conductors. All surfaces, both interior and exterior, shall be suitably protected from corrosion. Corner joints shall be made tight, and where the assembly is held together by rivets, bolts, or screws, such fasteners shall be spaced not more than 300 mm (12 in.) apart.

#### 366.100(C) Smooth Rounded Edges.

Suitable bushings, shields, or fittings having smooth, rounded edges shall be provided where conductors pass between gutters, through partitions, around bends, between gutters and cabinets or junction boxes, and at other locations where necessary to prevent abrasion of the insulation of the conductors.

#### 366.100(D) Covers.

Covers shall be securely fastened to the gutter.

#### 366.100(E) Clearance of Bare Live Parts.

Bare conductors shall be securely and rigidly supported so that the minimum clearance between bare current-carrying metal parts of different voltages mounted on the same surface will not be less than 50 mm (2 in.), nor less than 25 mm (1 in.) for parts that are held free in the air. A clearance not less than 25 mm (1 in.) shall be secured between bare current-carrying metal parts and any metal surface. Adequate provisions shall be made for the expansion and contraction of busbars.

### 366.120 Marking.

#### 366.120(A) Outdoors.

Nonmetallic auxiliary gutters installed outdoors shall have the following markings:

* (1) Suitable for exposure to sunlight

* (2) Suitable for use in wet locations

* (3) Installed conductor insulation temperature rating

#### 366.120(B) Indoors.

Nonmetallic auxiliary gutters installed indoors shall be marked with the installed conductor insulation temperature rating.

# Article 372 Cellular Concrete Floor Raceways

## Part I. General

### 372.1 Scope.

This article covers cellular concrete floor raceways, the hollow spaces in floors constructed of precast cellular concrete slabs, together with suitable metal fittings designed to provide access to the floor cells.

### 372.2 Definitions.

The definitions in this section shall apply only within this article.

#### Cell.

A single, enclosed tubular space in a floor made of precast cellular concrete slabs, the direction of the cell being parallel to the direction of the floor member.

#### Header.

Transverse metal raceways for electrical conductors, providing access to predetermined cells of a precast cellular concrete floor, thereby permitting the installation of electrical conductors from a distribution center to the floor cells.

## Part II. Installations

### 372.12 Uses Not Permitted.

Conductors shall not be installed in precast cellular concrete floor raceways as follows:

* (1) Where subject to corrosive vapor

* (2) In any hazardous (classified) location, except as permitted by other articles in this Code

* (3) In commercial garages, other than for supplying ceiling outlets or extensions to the area below the floor but not above

> [!info] Informational Note:
> See 300.8 for installation of conductors with other systems.

### 372.18 Cellular Concrete Floor Raceways Installation.

Installation of cellular concrete floor raceways shall comply with 372.18(A) through 372.18(E).

#### 372.18(A) Header.

The header shall be installed in a straight line at right angles to the cells. The header shall be mechanically secured to the top of the precast cellular concrete floor. The end joints shall be closed by a metal closure fitting and sealed against the entrance of concrete. The header shall be electrically continuous throughout its entire length and shall be electrically bonded to the enclosure of the distribution center.

#### 372.18(B) Connection to Cabinets and Other Enclosures.

Connections from headers to cabinets and other enclosures shall be made by means of listed metal raceways and listed fittings.

#### 372.18(C) Junction Boxes.

Junction boxes shall be leveled to the floor grade and sealed against the free entrance of water or concrete. Junction boxes shall be of metal and shall be mechanically and electrically continuous with the header.

#### 372.18(D) Inserts.

Inserts shall be leveled and sealed against the entrance of concrete. Inserts shall be of metal and shall be fitted with grounded-type receptacles. An equipment grounding conductor or bonding jumper shall connect the insert receptacles to a positive ground connection provided on the header. Where cutting through the cell wall for setting inserts or other purposes (such as providing access openings between header and cells), chips and other dirt shall not be allowed to remain in the raceway, and the tool used shall be designed so as to prevent the tool from entering the cell and damaging the conductors.

#### 372.18(E) Markers.

A suitable number of markers shall be installed for the future location of cells.

### 372.20 Size of Conductors.

No conductor larger than 1/0 AWG shall be installed, except by special permission.

### 372.22 Maximum Number of Conductors.

The combined cross-sectional area of all conductors or cables shall not exceed 40 percent of the cross-sectional area of the cell or header.

### 372.23 Ampacity of Conductors.

The ampacity adjustment factors as provided in 310.15(C) shall apply to conductors installed in cellular concrete floor raceways.

### 372.56 Splices and Taps.

Splices and taps shall be made only in header access units or junction boxes. A continuous unbroken conductor connecting the individual outlets is not a splice or tap.

### 372.58 Discontinued Outlets.

When an outlet is abandoned, discontinued, or removed, the sections of circuit conductors supplying the outlet shall be removed from the raceway. No splices or reinsulated conductors, such as would be the case of abandoned outlets on loop wiring, shall be allowed in raceways.

# Article 374 Cellular Metal Floor Raceways

## Part I. General

### 374.1 Scope.

This article covers the use and installation requirements for cellular metal floor raceways.

### 374.2 Definitions.

The definitions in this section shall apply within this article and throughout the Code.

#### Cellular Metal Floor Raceway.

The hollow spaces of cellular metal floors, together with suitable fittings, that may be approved as enclosed channel for electrical conductors.

#### Cell.

A single enclosed tubular space in a cellular metal floor member, the axis of the cell being parallel to the axis of the metal floor member.

#### Header.

A transverse raceway for electrical conductors, providing access to predetermined cells of a cellular metal floor, thereby permitting the installation of electrical conductors from a distribution center to the cells.

### 374.6 Listing Requirements.

Cellular metal floor raceways shall be listed.

## Part II. Installation

### 374.12 Uses Not Permitted.

Conductors shall not be installed in cellular metal floor raceways as follows:

* (1) Where subject to corrosive vapor

* (2) In any hazardous (classified) location, except as permitted by other articles in this Code

* (3) In commercial garages, other than for supplying ceiling outlets or extensions to the area below the floor but not above

> [!info] Informational Note:
> See 300.8 for installation of conductors with other systems.

### 374.18 Cellular Metal Floor Raceways Installations.

Installation of cellular metal floor raceways shall comply with 374.18(A) through 374.18(D).

#### 374.18(A) Connection to Cabinets and Extensions from Cells.

Connections between raceways and distribution centers and wall outlets shall be made by means of liquidtight flexible metal conduit, flexible metal conduit where not installed in concrete, rigid metal conduit, intermediate metal conduit, electrical metallic tubing, or approved fittings. Where there are provisions for the termination of an equipment grounding conductor, rigid polyvinyl chloride conduit, reinforced thermosetting resin conduit, electrical nonmetallic tubing, or liquidtight flexible nonmetallic conduit shall be permitted. Where installed in concrete, liquidtight flexible metal conduit and liquidtight flexible nonmetallic conduit shall be listed and marked for direct burial.

#### 374.18(B) Junction Boxes.

Junction boxes shall be leveled to the floor grade and sealed against the free entrance of water or concrete. Junction boxes used with these raceways shall be of metal and shall be electrically continuous with the raceway.

#### 374.18(C) Inserts.

Inserts shall be leveled to the floor grade and sealed against the entrance of concrete. Inserts shall be of metal and shall be electrically continuous with the raceway. In cutting through the cell wall and setting inserts, chips and other dirt shall not be allowed to remain in the raceway, and tools shall be used that are designed to prevent the tool from entering the cell and damaging the conductors.

#### 374.18(D) Markers.

A suitable number of markers shall be installed for locating cells in the future.

### 374.20 Size of Conductors.

No conductor larger than 1/0 AWG shall be installed, except by special permission.

### 374.22 Maximum Number of Conductors in Raceway.

The combined cross-sectional area of all conductors or cables shall not exceed 40 percent of the interior cross-sectional area of the cell or header.

### 374.23 Ampacity of Conductors.

The ampacity adjustment factors in 310.15(C) shall apply to conductors installed in cellular metal floor raceways.

### 374.56 Splices and Taps.

Splices and taps shall be made only in header access units or junction boxes.

For the purposes of this section, so-called loop wiring (continuous unbroken conductor connecting the individual outlets) shall not be considered to be a splice or tap.

### 374.58 Discontinued Outlets.

When an outlet is abandoned, discontinued, or removed, the sections of circuit conductors supplying the outlet shall be removed from the raceway. No splices or reinsulated conductors, such as would be the case with abandoned outlets on loop wiring, shall be allowed in raceways.

## Part III. Construction Specifications

### 374.100 General.

Cellular metal floor raceways shall be constructed so that adequate electrical and mechanical continuity of the complete system will be secured. They shall provide a complete enclosure for the conductors. The interior surfaces shall be free from burrs and sharp edges, and surfaces over which conductors are drawn shall be smooth. Suitable bushings or fittings having smooth rounded edges shall be provided where conductors pass.

# Article 376 Metal Wireways

## Part I. General

### 376.1 Scope.

This article covers the use, installation, and construction specifications for metal wireways and associated fittings.

### 376.2 Definition.

The definition in this section shall apply within this article and throughout the Code.

#### Metal Wireways.

Sheet metal troughs with hinged or removable covers for housing and protecting electrical wires and cable and in which conductors are laid in place after the raceway has been installed as a complete system.

## Part II. Installation

### 376.10 Uses Permitted.

The use of metal wireways shall be permitted as follows:

* (1) For exposed work.

* (2) In any hazardous (classified) location, as permitted by other articles in this Code.

* (3) In wet locations where wireways are listed for the purpose.

* (4) In concealed spaces as an extension that passes transversely through walls, if the length passing through the wall is unbroken.

Access to the conductors shall be maintained on both sides of the wall.

### 376.12 Uses Not Permitted.

Metal wireways shall not be used in the following:

* (1) Where subject to severe physical damage

* (2) Where subject to severe corrosive environments

### 376.20 Conductors Connected in Parallel.

Where single conductor cables comprising each phase, neutral, or grounded conductor of an alternating-current circuit are connected in parallel as permitted in 310.10(G), the conductors shall be installed in groups consisting of not more than one conductor per phase, neutral, or grounded conductor.

> [!info] Informational Note:
> The purpose of having all parallel conductor sets within the same group is to prevent current imbalance in the paralleled conductors due to inductive reactance.

### 376.21 Size of Conductors.

No conductor larger than that for which the wireway is designed shall be installed in any wireway.

### 376.22 Number of Conductors and Ampacity.

The number of conductors or cables and their ampacity shall comply with 376.22(A) and (B).

#### 376.22(A) Cross-Sectional Areas of Wireway.

The sum of the cross-sectional areas of all contained conductors and cables at any cross section of a wireway shall not exceed
20 percent of the interior cross-sectional area of the wireway.

#### 376.22(B) Adjustment Factors.

The adjustment factors in 310.15(C) (1) shall be applied only where the number of current-carrying conductors, including neutral conductors classified as current-carrying under 310.15(E), exceeds 30 at any cross section of the wireway. Conductors for signaling circuits or controller conductors between a motor and its starter and used only for starting duty shall not be considered as currentcarrying conductors.

### 376.23 Insulated Conductors.

Insulated conductors installed in a metal wireway shall comply with 376.23(A) and (B).

#### 376.23(A) Deflected Insulated Conductors.

Where insulated conductors are deflected within a metal wireway, either at the ends or where conduits, fittings, or other raceways or cables enter or leave the metal wireway, or where the direction of the metal wireway is deflected greater than 30 degrees, dimensions corresponding to one wire per terminal in Table 312.6(A) shall apply.

#### 376.23(B) Metal Wireways Used as Pull Boxes.

Where insulated conductors 4 AWG or larger are pulled through a wireway, the distance between raceway and cable entries enclosing the same conductor shall not be less than that required by 314.28(A)(1) for straight pulls and 314.28(A)(2) for angle pulls. When transposing cable size into raceway size, the minimum metric designator (trade size) raceway required for the number and size of conductors in the cable shall be used.

### 376.30 Securing and Supporting.

Metal wireways shall be supported in accordance with 376.30(A) and (B).

#### 376.30(A) Horizontal Support.

Wireways shall be supported where run horizontally at each end and at intervals not to exceed 1.5 m (5 ft) or for individual lengths longer than 1.5 m (5 ft) at each end or joint, unless listed for other support intervals. The distance between supports shall not exceed
3 m (10 ft).

#### 376.30(B) Vertical Support.

Vertical runs of wireways shall be securely supported at intervals not exceeding 4.5 m (15 ft) and shall not have more than one joint between supports. Adjoining wireway sections shall be securely fastened together to provide a rigid joint.

### 376.56 Splices, Taps, and Power Distribution Blocks.

#### 376.56(A) Splices and Taps.

Splices and taps shall be permitted within a wireway, provided they are accessible. The conductors, including splices and taps, shall not fill the wireway to more than 75 percent of its area at that point.

#### 376.56(B) Power Distribution Blocks.

##### 376.56(B)(1) Installation.

Power distribution blocks installed in metal wireways shall be listed. Power distribution blocks installed on the line side of the service equipment shall be marked “suitable for use on the line side of service equipment” or equivalent.

##### 376.56(B)(2) Size of Enclosure.

In addition to the wiring space requirement in 376.56(A), the power distribution block shall be installed in a wireway with dimensions not smaller than specified in the installation instructions of the power distribution block.

##### 376.56(B)(3) Wire Bending Space.

Wire bending space at the terminals of power distribution blocks shall comply with 312.6(B).

##### 376.56(B)(4) Live Parts.

Power distribution blocks shall not have uninsulated live parts exposed within a wireway, whether or not the wireway cover is installed.

##### 376.56(B)(5) Conductors.

Conductors shall be arranged so the power distribution block terminals are unobstructed following installation.

### 376.58 Dead Ends.

Dead ends of metal wireways shall be closed.

### 376.70 Extensions from Metal Wireways.

Extensions from wireways shall be made with cord pendants installed in accordance with 400.14 or with any wiring method in Chapter 3 that includes a means for equipment grounding. Where a separate equipment grounding conductor is employed, connection of the equipment grounding conductors in the wiring method to the wireway shall comply with 250.8 and 250.12.

## Part III. Construction Specifications

### 376.100 Construction.

#### 376.100(A) Electrical and Mechanical Continuity.

Wireways shall be constructed and installed so that electrical and mechanical continuity of the complete system are assured.

#### 376.100(B) Substantial Construction.

Wireways shall be of substantial construction and shall provide a complete enclosure for the contained conductors. All surfaces, both interior and exterior, shall be suitably protected from corrosion. Corner joints shall be made tight, and where the assembly is held together by rivets, bolts, or screws, such fasteners shall be spaced not more than 300 mm (12 in.) apart.

#### 376.100(C) Smooth Rounded Edges.

Suitable bushings, shields, or fittings having smooth, rounded edges shall be provided where conductors pass between wireways, through partitions, around bends, between wireways and cabinets or junction boxes, and at other locations where necessary to prevent abrasion of the insulation of the conductors.

#### 376.100(D) Covers.

Covers shall be securely fastened to the wireway.

### 376.120 Marking.

Metal wireways shall be so marked that their manufacturer’s name or trademark will be visible after installation.

# Article 378 Nonmetallic Wireways

## Part I. General

### 378.1 Scope.

This article covers the use, installation, and construction specifications for nonmetallic wireways and associated fittings.

### 378.2 Definition.

The definition in this section shall apply within this article and throughout the Code.

#### Nonmetallic Wireways.

Flame-retardant, nonmetallic troughs with removable covers for housing and protecting electrical wires and cables in which conductors are laid in place after the raceway has been installed as a complete system.

### 378.6 Listing Requirements.

Nonmetallic wireways and associated fittings shall be listed.

## Part II. Installation

### 378.10 Uses Permitted.

The use of nonmetallic wireways shall be permitted in the following:

* (1) Only for exposed work, except as permitted in 378.10(4).

* (2) Where subject to corrosive environments where identified for the use.

* (3) In wet locations where listed for the purpose.

> [!info] Informational Note:
> Extreme cold may cause nonmetallic wireways to become brittle and therefore more susceptible to damage from physical contact.

* (4) As extensions to pass transversely through walls if the length passing through the wall is unbroken. Access to the conductors shall be maintained on both sides of the wall.

### 378.12 Uses Not Permitted.

Nonmetallic wireways shall not be used in the following:

* (1) Where subject to physical damage

* (2) In any hazardous (classified) location, except as permitted by other articles in this Code

* (3) Where exposed to sunlight unless listed and marked as suitable for the purpose

* (4) Where subject to ambient temperatures other than those for which nonmetallic wireway is listed

* (5) For conductors whose insulation temperature limitations would exceed those for which the nonmetallic wireway is listed

### 378.20 Conductors Connected in Parallel.

Where single conductor cables comprising each phase, neutral, or grounded conductor of an alternating-current circuit are connected in parallel as permitted in 310.10(G), the conductors shall be installed in groups consisting of not more than one conductor per phase, neutral, or grounded conductor to prevent current imbalance in the paralleled conductors due to inductive reactance.

### 378.21 Size of Conductors.

No conductor larger than that for which the nonmetallic wireway is designed shall be installed in any nonmetallic wireway.

### 378.22 Number of Conductors.

The sum of cross-sectional areas of all contained conductors or cables at any cross section of the nonmetallic wireway shall not exceed
20 percent of the interior cross-sectional area of the nonmetallic wireway. Conductors for signaling circuits or controller conductors between a motor and its starter and used only for starting duty shall not be considered as current-carrying conductors.

The adjustment factors specified in 310.15(C)(1) shall be applicable to the current-carrying conductors up to and including the
20 percent fill specified in the first paragraph of this section.

### 378.23 Insulated Conductors.

Insulated conductors installed in a nonmetallic wireway shall comply with 378.23(A) and (B).

#### 378.23(A) Deflected Insulated Conductors.

Where insulated conductors are deflected within a nonmetallic wireway, either at the ends or where conduits, fittings, or other raceways or cables enter or leave the nonmetallic wireway, or where the direction of the nonmetallic wireway is deflected greater than 30 degrees, dimensions corresponding to one wire per terminal in Table 312.6(A) shall apply.

#### 378.23(B) Nonmetallic Wireways Used as Pull Boxes.

Where insulated conductors 4 AWG or larger are pulled through a wireway, the distance between raceway and cable entries enclosing the same conductor shall not be less than that required in 314.28(A)(1) for straight pulls and in 314.28(A)(2) for angle pulls. When transposing cable size into raceway size, the minimum metric designator (trade size) raceway required for the number and size of conductors in the cable shall be used.

### 378.30 Securing and Supporting.

Nonmetallic wireway shall be supported in accordance with 378.30(A) and (B).

#### 378.30(A) Horizontal Support.

Nonmetallic wireways shall be supported where run horizontally at intervals not to exceed 900 mm (3 ft), and at each end or joint, unless listed for other support intervals. In no case shall the distance between supports exceed 3 m (10 ft).

#### 378.30(B) Vertical Support.

Vertical runs of nonmetallic wireway shall be securely supported at intervals not exceeding 1.2 m (4 ft), unless listed for other support intervals, and shall not have more than one joint between supports. Adjoining nonmetallic wireway sections shall be securely fastened together to provide a rigid joint.

### 378.44 Expansion Fittings.

Expansion fittings for nonmetallic wireway shall be provided to compensate for thermal expansion and contraction where the length change is expected to be 6 mm (0.25 in.) or greater in a straight run.

> [!info] Informational Note:
> See Table 352.44 for expansion characteristics of PVC conduit. The expansion characteristics of PVC nonmetallic wireway are identical.

### 378.56 Splices and Taps.

Splices and taps shall be permitted within a nonmetallic wireway, provided they are accessible. The conductors, including splices and taps, shall not fill the nonmetallic wireway to more than 75 percent of its area at that point.

### 378.58 Dead Ends.

Dead ends of nonmetallic wireway shall be closed using listed fittings.

### 378.60 Grounding.

Where equipment grounding is required, a separate equipment grounding conductor shall be installed in the nonmetallic wireway. A separate equipment grounding conductor shall not be required where the grounded conductor is used to ground equipment as permitted in 250.142.

### 378.70 Extensions from Nonmetallic Wireways.

Extensions from nonmetallic wireway shall be made with cord pendants or any wiring method of Chapter 3. A separate equipment grounding conductor shall be installed in, or an equipment grounding connection shall be made to, any of the wiring methods used for the extension.

## Part III. Construction Specifications

### 378.120 Marking.

Nonmetallic wireways shall be marked so that the manufacturer’s name or trademark and interior cross-sectional area in square inches shall be visible after installation. Marking for limited smoke shall be permitted on the nonmetallic wireways that have limited smokeproducing characteristics.

# Article 380 Multioutlet Assembly

## Part I. General

### 380.1 Scope.

This article covers the use and installation requirements for multioutlet assemblies.

> [!info] Informational Note:
> See the definition of multioutlet assembly in Article 100.

## Part II. Installation

### 380.10 Uses Permitted.

The use of a multioutlet assembly shall be permitted in dry locations.

### 380.12 Uses Not Permitted.

A multioutlet assembly shall not be installed as follows:

* (1) Where concealed, except that it shall be permissible to surround the back and sides of a metal multioutlet assembly by the building finish or recess a nonmetallic multioutlet assembly in a baseboard

* (2) Where subject to severe physical damage

* (3) Where the voltage is 300 volts or more between conductors unless the assembly is of metal having a thickness of not less than
1.02 mm (0.040 in.)

* (4) Where subject to corrosive vapors

* (5) In hoistways

* (6) In any hazardous (classified) location, except as permitted by other articles in this Code

* (7) Where cord and plug connected

### 380.23 Insulated Conductors.

For field-assembled multioutlet assemblies, insulated conductors shall comply with 380.23(A) and (B), as applicable.

#### 380.23(A) Deflected Insulated Conductors.

Where insulated conductors are deflected within a multioutlet assembly, either at the ends or where conduits, fittings, or other raceways or cables enter or leave the multioutlet assembly, or where the direction of the multioutlet assembly is deflected greater than
30 degrees, dimensions corresponding to one wire per terminal in Table 312.6(A) shall apply.

#### 380.23(B) Multioutlet Assemblies Used as Pull Boxes.

Where insulated conductors 4 AWG or larger are pulled through a multioutlet assembly, the distance between raceway and cable entries enclosing the same conductor shall not be less than that required by 314.28(A)(1) for straight pulls and 314.28(A)(2) for angle pulls. When transposing cable size into raceway size, the minimum metric designator (trade size) raceway required for the number and size of conductors in the cable shall be used.

### 380.76 Metal Multioutlet Assembly Through Dry Partitions.

It shall be permissible to extend a metal multioutlet assembly through (not run within) dry partitions if arrangements are made for removing the cap or cover on all exposed portions and no outlet is located within the partitions.

# Article 382 Nonmetallic Extensions

## Part I. General

### 382.1 Scope.

This article covers the use, installation, and construction specifications for nonmetallic extensions.

### 382.2 Definitions.

The definitions in this section shall apply within this article and throughout the Code.

#### Concealable Nonmetallic Extension.

A listed assembly of two, three, or four insulated circuit conductors within a nonmetallic jacket, an extruded thermoplastic covering, or a sealed nonmetallic covering. The classification includes surface extensions intended for mounting directly on the surface of walls or ceilings and concealed with paint, texture, joint compound, plaster, wallpaper, tile, wall paneling, or other similar materials.

#### Nonmetallic Extension.

An assembly of two insulated conductors within a nonmetallic jacket or an extruded thermoplastic covering. The classification includes surface extensions intended for mounting directly on the surface of walls or ceilings.

### 382.6 Listing Requirements.

Concealable nonmetallic extensions and associated fittings and devices shall be listed. The starting/source tap device for the extension shall contain and provide the following protection for all load-side extensions and devices:

* (1) Supplementary overcurrent protection

* (2) Level of protection equivalent to a Class A GFCI

* (3) Level of protection equivalent to a portable GFCI

* (4) Line and load-side miswire protection

* (5) Provide protection from the effects of arc faults

## Part II. Installation

### 382.10 Uses Permitted.

Nonmetallic extensions shall be permitted only in accordance with 382.10(A), (B), and (C).

#### 382.10(A) From an Existing Outlet.

The extension shall be from an existing outlet on a 15- or 20-ampere branch circuit. Where a concealable nonmetallic extension originates from a non–grounding-type receptacle, the installation shall comply with 250.130(C), 406.4(D)(2)(b), or 406.4(D)(2)(c).

#### 382.10(B) Exposed and in a Dry Location.

The extension shall be run exposed, or concealed as permitted in 382.15, and in a dry location.

#### 382.10(C) Residential or Offices.

For nonmetallic surface extensions mounted directly on the surface of walls or ceilings, the building shall be occupied for residential or office purposes and shall not exceed three floors abovegrade. Where identified for the use, concealable nonmetallic extensions shall be permitted more than three floors abovegrade.

> [!info] Informational Note No. 1:
> See 310.14(A)(3) for temperature limitation of conductors.

> [!info] Informational Note No. 2:
> See 362.10 for definition of First Floor.

### 382.12 Uses Not Permitted.

Nonmetallic extensions shall not be used as follows:

* (1) In unfinished basements, attics, or roof spaces

* (2) Where the voltage between conductors exceeds 150 volts for nonmetallic surface extensions and 300 volts for aerial cable

* (3) Where subject to corrosive vapors

* (4) Where run through a floor or partition, or outside the room in which it originates

### 382.15 Exposed.

#### 382.15(A) Nonmetallic Extensions.

One or more extensions shall be permitted to be run in any direction from an existing outlet, but not on the floor or within 50 mm (2 in.) from the floor.

#### 382.15(B) Concealable Nonmetallic Extensions.

Where identified for the use, nonmetallic extensions shall be permitted to be concealed with paint, texture, concealing compound, plaster, wallpaper, tile, wall paneling, or other similar materials and installed in accordance with 382.15(A).

### 382.26 Bends.

#### 382.26(A) Nonmetallic Extensions.

A bend that reduces the normal spacing between the conductors shall be covered with a cap to protect the assembly from physical damage.

#### 382.26(B) Concealable Nonmetallic Extensions.

Concealable extensions shall be permitted to be folded back over themselves and flattened as required for installation.

### 382.30 Securing and Supporting.

#### 382.30(A) Nonmetallic Extensions.

Nonmetallic surface extensions shall be secured in place by approved means at intervals not exceeding 200 mm (8 in.), with an allowance for 300 mm (12 in.) to the first fastening where the connection to the supplying outlet is by means of an attachment plug.

There shall be at least one fastening between each two adjacent outlets supplied. An extension shall be attached to only woodwork or plaster finish and shall not be in contact with any metal work or other conductive material other than with metal plates on receptacles.

#### 382.30(B) Concealable Nonmetallic Extensions.

All surface-mounted concealable nonmetallic extension components shall be firmly anchored to the wall or ceiling using an adhesive or mechanical anchoring system identified for this use.

### 382.40 Boxes and Fittings.

Each run shall terminate in a fitting, connector, or box that covers the end of the assembly. All fittings, connectors, and devices shall be of a type identified for the use.

### 382.42 Devices.

#### 382.42(A) Receptacles.

All receptacles, receptacle housings, and self-contained devices used with concealable nonmetallic extensions shall be identified for this use.

#### 382.42(B) Receptacles and Housings.

Receptacle housings and self-contained devices designed either for surface or for recessed mounting shall be permitted for use with concealable nonmetallic extensions. Receptacle housings and self-contained devices shall incorporate means for facilitating entry and termination of concealable nonmetallic extensions and for electrically connecting the housing or device. Receptacle and self-contained devices shall comply with 406.4. Power and communications outlets installed together in common housing shall be permitted in accordance with 805.133(A)(1)(c), Exception No. 2.

### 382.56 Splices and Taps.

Extensions shall consist of a continuous unbroken length of the assembly, without splices, and without exposed conductors between fittings, connectors, or devices. Taps shall be permitted where approved fittings completely covering the tap connections are used.

Aerial cable and its tap connectors shall be provided with an approved means for polarization. Receptacle-type tap connectors shall be of the locking type.

## Part III. Construction Specifications (Concealable Nonmetallic Extensions Only)

### 382.100 Construction.

Concealable nonmetallic extensions shall be of a multilayer flat conductor design consisting of a center ungrounded conductor enclosed by a sectioned grounded conductor and an overall sectioned equipment grounding conductor.

### 382.104 Flat Conductors.

Concealable nonmetallic extensions shall be constructed, using flat copper conductors equivalent to 14 AWG or 12 AWG conductor sizes, and constructed per 382.104(A), (B), and (C).

#### 382.104(A) Ungrounded Conductor (Center Layer).

The ungrounded conductor shall consist of one or more ungrounded flat conductor(s) enclosed in accordance with 382.104(B) and (C) and identified in accordance with 310.6(C).

#### 382.104(B) Grounded Conductor (Inner Sectioned Layers).

The grounded conductor shall consist of two sectioned inner flat conductors that enclose the center ungrounded conductor(s). The sectioned grounded conductor shall be enclosed by the sectioned equipment grounding conductor and identified in accordance with
200.6.

#### 382.104(C) Equipment Grounding Conductor (Outer Sectioned Layers).

The equipment grounding conductor shall consist of two overall sectioned conductors that enclose the grounded conductor and ungrounded conductor(s) and shall comply with 250.4(A)(5). The equipment grounding conductor layers shall be identified by any one of the following methods:

* (1) As permitted in 250.119

* (2) A clear covering

* (3) One or more continuous green stripes or hash marks

* (4) The term “Equipment Grounding Conductor” printed at regular intervals throughout the cable

### 382.112 Insulation.

The ungrounded and grounded flat conductor layers shall be individually insulated and comply with 310.14(A)(3). The equipment grounding conductor shall be covered or insulated.

### 382.120 Marking.

#### 382.120(A) Cable.

Concealable nonmetallic extensions shall be clearly and durably marked on both sides at intervals of not more than 610 mm (24 in.) with the information required by 310.8(A) and with the following additional information:

* (1) Material of conductors

* (2) Maximum temperature rating

* (3) Ampacity

#### 382.120(B) Conductor Identification.

Conductors shall be clearly and durably identified on both sides throughout their length as specified in 382.104.

# Article 384 Strut-Type Channel Raceway

## Part I. General

### 384.1 Scope.

This article covers the use, installation, and construction specifications of strut-type channel raceway.

### 384.2 Definition.

The definition in this section shall apply within this article and throughout the Code.

#### Strut-Type Channel Raceway.

A metal raceway that is intended to be mounted to the surface of or suspended from a structure, with associated accessories for the installation of electrical conductors and cables.

### 384.6 Listing Requirements.

Strut-type channel raceways and accessories shall be listed and identified for such use.

## Part II. Installation

### 384.10 Uses Permitted.

The use of strut-type channel raceways shall be permitted in the following:

* (1) Where exposed.

* (2) In dry locations.

* (3) In locations subject to corrosive vapors where protected by finishes approved for the condition.

* (4) As power poles.

* (5) In hazardous (classified) locations as permitted in Chapter 5.

* (6) As extensions of unbroken lengths through walls, partitions, and floors where closure strips are removable from either side and the portion within the wall, partition, or floor remains covered.

* (7) Ferrous channel raceways and fittings protected from corrosion solely by enamel shall be permitted only indoors.

### 384.12 Uses Not Permitted.

Strut-type channel raceways shall not be used as follows:

* (1) Where concealed.

* (2) Ferrous channel raceways and fittings protected from corrosion solely by enamel shall not be permitted where subject to severe corrosive influences.

### 384.21 Size of Conductors.

No conductor larger than that for which the raceway is listed shall be installed in strut-type channel raceways.

### 384.22 Number of Conductors.

The number of conductors or cables permitted in strut-type channel raceways shall not exceed the percentage fill using Table 384.22 and applicable cross-sectional area of specific types and sizes of wire given in the tables in Chapter 9.

The adjustment factors of 310.15(C)(1) shall not apply to conductors installed in strut-type channel raceways where all of the following conditions are met:

* (1) The cross-sectional area of the raceway exceeds 2500 mm (4 in. ).

* (2) The current-carrying conductors do not exceed 30 in number.

* (3) The sum of the cross-sectional areas of all contained conductors does not exceed 20 percent of the interior cross-sectional area of the strut-type channel raceways.

Table 384.22 Channel Size and Inside CrossSectional

Area

Size

Channel

Area 40% Area 25% Area in. mm in. mm in. mm
15⁄8 × 15⁄16 0.887 572 0.355 229 0.222 143
15⁄8 × 1 1.151 743 0.460 297 0.288 186
15⁄8 × 13⁄8 1.677 1076 0.671 433 0.419 270
15⁄8 × 15⁄8 2.028 1308 0.811 523 0.507 327
15⁄8 × 27⁄16 3.169 2045 1.267 817 0.792 511
15⁄8 × 31⁄4 4.308 2780 1.723 1112 1.077 695
11⁄2 × 3⁄4 0.849 548 0.340 219 0.212 137
11⁄2 × 11⁄2 1.828 1179 0.731 472 0.457 295
11⁄2 × 17⁄8 2.301 1485 0.920 594 0.575 371
11⁄2 × 3 3.854 2487 1.542 995 0.964 622

Raceways with external joiners shall use a 40 percent wire fill calculation to determine the number of conductors permitted.

Raceways with internal joiners shall use a 25 percent wire fill calculation to determine the number of conductors permitted.

### 384.30 Securing and Supporting.

#### 384.30(A) Surface Mount.

2 2
* †
2 2 2 2 2 2
*
†

A surface mount strut-type channel raceway shall be secured to the mounting surface with retention straps external to the channel at intervals not exceeding 3 m (10 ft) and within 900 mm (3 ft) of each outlet box, cabinet, junction box, or other channel raceway termination.

#### 384.30(B) Suspension Mount.

Strut-type channel raceways shall be permitted to be suspension mounted in air with identified methods at intervals not to exceed 3 m
(10 ft) and within 900 mm (3 ft) of channel raceway terminations and ends.

### 384.56 Splices and Taps.

Splices and taps shall be permitted in raceways that are accessible after installation by having a removable cover. The conductors, including splices and taps, shall not fill the raceway to more than 75 percent of its area at that point. All splices and taps shall be made by approved methods.

### 384.60 Grounding.

Strut-type channel raceway enclosures providing a transition to or from other wiring methods shall have a means for connecting an equipment grounding conductor. Strut-type channel raceways shall be permitted as an equipment grounding conductor in accordance with 250.118(13). Where a snap-fit metal cover for strut-type channel raceways is used to achieve electrical continuity in accordance with the listing, this cover shall not be permitted as the means for providing electrical continuity for a receptacle mounted in the cover.

## Part III. Construction Specifications

### 384.100 Construction.

Strut-type channel raceways and their accessories shall be of a construction that distinguishes them from other raceways. Raceways and their elbows, couplings, and other fittings shall be designed such that the sections can be electrically and mechanically coupled together and installed without subjecting the wires to abrasion. They shall comply with 384.100(A), (B), and (C).

#### 384.100(A) Material.

Raceways and accessories shall be formed of steel, stainless steel, or aluminum.

#### 384.100(B) Corrosion Protection.

Steel raceways and accessories shall be protected against corrosion by galvanizing or by an organic coating.

> [!info] Informational Note:
> Enamel and PVC coatings are examples of organic coatings that provide corrosion protection.

#### 384.100(C) Cover.

Covers of strut-type channel raceways shall be either metal or nonmetallic.

### 384.120 Marking.

Each length of strut-type channel raceway shall be clearly and durably identified as required in the first sentence of 110.21(A).

# Article 386 Surface Metal Raceways

## Part I. General

### 386.1 Scope.

This article covers the use, installation, and construction specifications for surface metal raceways and associated fittings.

### 386.2 Definition.

The definition in this section shall apply within this article and throughout the Code.

#### Surface Metal Raceway.

A metal raceway that is intended to be mounted to the surface of a structure, with associated couplings, connectors, boxes, and fittings for the installation of electrical conductors.

### 386.6 Listing Requirements.

Surface metal raceway and associated fittings shall be listed.

## Part II. Installation

### 386.10 Uses Permitted.

The use of surface metal raceways shall be permitted in the following:

* (1) In dry locations.

* (2) In Class I, Division 2 hazardous (classified) locations as permitted in 501.10(B)(3).

* (3) Under raised floors, as permitted in 645.5(E)(2).

* (4) Extension through walls and floors. Surface metal raceway shall be permitted to pass transversely through dry walls, dry partitions, and dry floors if the length passing through is unbroken. Access to the conductors shall be maintained on both sides of the wall, partition, or floor.

### 386.12 Uses Not Permitted.

Surface metal raceways shall not be used in the following:

* (1) Where subject to severe physical damage, unless otherwise approved

* (2) Where the voltage is 300 volts or more between conductors, unless the metal has a thickness of not less than 1.02 mm
(0.040 in.) nominal

* (3) Where subject to corrosive vapors

* (4) In hoistways

* (5) Where concealed, except as permitted in 386.10

### 386.21 Size of Conductors.

No conductor larger than that for which the raceway is designed shall be installed in surface metal raceway.

### 386.22 Number of Conductors or Cables.

The number of conductors or cables installed in surface metal raceway shall not be greater than the number for which the raceway is designed. Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles.

The adjustment factors of 310.15(C)(1) shall not apply to conductors installed in surface metal raceways where all of the following conditions are met:

* (1) The cross-sectional area of the raceway exceeds 2500 mm (4 in. ).

* (2) The current-carrying conductors do not exceed 30 in number.

* (3) The sum of the cross-sectional areas of all contained conductors does not exceed 20 percent of the interior cross-sectional area of the surface metal raceway.

### 386.30 Securing and Supporting.

Surface metal raceways and associated fittings shall be supported in accordance with the manufacturer's installation instructions.

### 386.56 Splices and Taps.

Splices and taps shall be permitted in surface metal raceways having a removable cover that is accessible after installation. The conductors, including splices and taps, shall not fill the raceway to more than 75 percent of its area at that point. Splices and taps in surface metal raceways without removable covers shall be made only in boxes. All splices and taps shall be made by approved methods.

Taps of Type FC cable installed in surface metal raceway shall be made in accordance with 322.56(B).

### 386.60 Grounding.

Surface metal raceway enclosures providing a transition from other wiring methods shall have a means for connecting an equipment grounding conductor.

### 386.70 Combination Raceways.

When combination surface metal raceways are used for both signaling and for lighting and power circuits, the different systems shall be run in separate compartments identified by stamping, imprinting, or color coding of the interior finish.

## Part III. Construction Specifications

### 386.100 Construction.

Surface metal raceways shall be of such construction as will distinguish them from other raceways. Surface metal raceways and their elbows, couplings, and similar fittings shall be designed so that the sections can be electrically and mechanically coupled together and installed without subjecting the wires to abrasion.

Where covers and accessories of nonmetallic materials are used on surface metal raceways, they shall be identified for such use.

### 386.120 Marking.

2 2

Each length of surface metal raceway shall be clearly and durably identified as required in the first sentence of 110.21(A).

# Article 388 Surface Nonmetallic Raceways

## Part I. General

### 388.1 Scope.

This article covers the use, installation, and construction specifications for surface nonmetallic raceways and associated fittings.

### 388.2 Definition.

The definition in this section shall apply within this article and throughout the Code.

#### Surface Nonmetallic Raceway.

A nonmetallic raceway that is intended to be mounted to the surface of a structure, with associated couplings, connectors, boxes, and fittings for the installation of electrical conductors.

### 388.6 Listing Requirements.

Surface nonmetallic raceway and associated fittings shall be listed.

## Part II. Installation

### 388.10 Uses Permitted.

Surface nonmetallic raceways shall be permitted as follows:

* (1) The use of surface nonmetallic raceways shall be permitted in dry locations.

* (2) Extension through walls and floors shall be permitted. Surface nonmetallic raceway shall be permitted to pass transversely through dry walls, dry partitions, and dry floors if the length passing through is unbroken. Access to the conductors shall be maintained on both sides of the wall, partition, or floor.

### 388.12 Uses Not Permitted.

Surface nonmetallic raceways shall not be used in the following:

* (1) Where concealed, except as permitted in 388.10(2)

* (2) Where subject to severe physical damage

* (3) Where the voltage is 300 volts or more between conductors, unless listed for higher voltage

* (4) In hoistways

* (5) In any hazardous (classified) location, except as permitted by other articles in this Code

* (6) Where subject to ambient temperatures exceeding those for which the nonmetallic raceway is listed

* (7) For conductors whose insulation temperature limitations would exceed those for which the nonmetallic raceway is listed

### 388.21 Size of Conductors.

No conductor larger than that for which the raceway is designed shall be installed in surface nonmetallic raceway.

### 388.22 Number of Conductors or Cables.

The number of conductors or cables installed in surface nonmetallic raceway shall not be greater than the number for which the raceway is designed. Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles.

### 388.30 Securing and Supporting.

Surface nonmetallic raceways and associated fittings shall be supported in accordance with the manufacturer's installation instructions.

### 388.56 Splices and Taps.

Splices and taps shall be permitted in surface nonmetallic raceways having a cover capable of being opened in place that is accessible after installation. The conductors, including splices and taps, shall not fill the raceway to more than 75 percent of its area at that point.

Splices and taps in surface nonmetallic raceways without covers capable of being opened in place shall be made only in boxes. All splices and taps shall be made by approved methods.

### 388.60 Grounding.

Where equipment grounding is required, a separate equipment grounding conductor shall be installed in the raceway.

### 388.70 Combination Raceways.

When combination surface nonmetallic raceways are used both for signaling and for lighting and power circuits, the different systems shall be run in separate compartments identified by stamping, imprinting, or color coding of the interior finish.

## Part III. Construction Specifications

### 388.100 Construction.

Surface nonmetallic raceways shall be of such construction as will distinguish them from other raceways. Surface nonmetallic raceways and their elbows, couplings, and similar fittings shall be designed so that the sections can be mechanically coupled together and installed without subjecting the wires to abrasion.

Surface nonmetallic raceways and fittings are made of suitable nonmetallic material that is resistant to moisture and chemical atmospheres. It shall also be flame retardant, resistant to impact and crushing, resistant to distortion from heat under conditions likely to be encountered in service, and resistant to low-temperature effects.

### 388.120 Marking.

Surface nonmetallic raceways that have limited smoke-producing characteristics shall be permitted to be so identified. Each length of surface nonmetallic raceway shall be clearly and durably identified as required in the first sentence of 110.21(A).

# Article 390 Underfloor Raceways

## Part I. General

### 390.1 Scope.

This article covers the use and installation requirements for underfloor raceways.

### 390.2 Definition.

The definition in this section shall apply within this article and throughout the Code.

#### Underfloor Raceway.

A raceway and associated components designed and intended for installation beneath or flush with the surface of a floor for the installation of cables and electrical conductors.

## Part II. Installation

### 390.10 Uses Permitted.

The installation of underfloor raceways shall be permitted beneath the surface of concrete or other flooring material or in office occupancies where laid flush with the concrete floor and covered with linoleum or equivalent floor covering.

### 390.12 Uses Not Permitted.

Underfloor raceways shall not be installed (1) where subject to corrosive vapors or (2) in any hazardous (classified) locations, except as permitted by 504.20 and in Class I, Division 2 locations as permitted in 501.10(B) (3). Unless made of a material approved for the condition or unless corrosion protection approved for the condition is provided, metal underfloor raceways, junction boxes, and fittings shall not be installed in concrete or in areas subject to severe corrosive influences.

### 390.15 Covering.

Raceway coverings shall comply with 390.15(A) through (D).

#### 390.15(A) Raceways Not over 100 mm (4 in.) Wide.

Half-round and flat-top raceways not over 100 mm (4 in.) in width shall have not less than 20 mm (3⁄4 in.) of concrete or wood above the raceway.

> [!important] Exception:
> As permitted in 390.15(C) and (D) for flat-top raceways.

#### 390.15(B) Raceways over 100 mm (4 in.) Wide But Not over 200 mm (8 in.) Wide.

Flat-top raceways over 100 mm (4 in.) but not over 200 mm (8 in.) wide with a minimum of 25 mm (1 in.) spacing between raceways shall be covered with concrete to a depth of not less than 25 mm (1 in.). Raceways spaced less than 25 mm (1 in.) apart shall be covered with concrete to a depth of 38 mm (11⁄2 in.).

#### 390.15(C) Trench-Type Raceways Flush with Concrete.

Trench-type flush raceways with removable covers shall be permitted to be laid flush with the floor surface. Such approved raceways shall be designed so that the cover plates provide adequate mechanical protection and rigidity equivalent to junction box covers.

#### 390.15(D) Other Raceways Flush with Concrete.

In office occupancies, approved metal flat-top raceways, if not over 100 mm (4 in.) in width, shall be permitted to be laid flush with the concrete floor surface, provided they are covered with substantial linoleum that is not less than 1.6 mm (1⁄16 in.) thick or with equivalent floor covering. Where more than one and not more than three single raceways are each installed flush with the concrete, they shall be contiguous with each other and joined to form a rigid assembly.

### 390.20 Size of Conductors.

No conductor larger than that for which the raceway is designed shall be installed in underfloor raceways.

### 390.22 Maximum Number of Conductors in Raceway.

The combined cross-sectional area of all conductors or cables shall not exceed 40 percent of the interior cross-sectional area of the raceway.

### 390.23 Ampacity of Conductors.

The ampacity adjustment factors in 310.15(C) shall apply to conductors installed in underfloor raceways.

### 390.56 Splices and Taps.

Splices and taps shall be made only in junction boxes.

For the purposes of this section, so-called loop wiring (continuous, unbroken conductor connecting the individual outlets) shall not be considered to be a splice or tap.

> [!important] Exception:
> Splices and taps shall be permitted in trench-type flush raceway having a removable cover that is accessible after installation. The conductors, including splices and taps, shall not fill more than 75 percent of the raceway area at that point.

### 390.57 Discontinued Outlets.

When an outlet is abandoned, discontinued, or removed, the sections of circuit conductors supplying the outlet shall be removed from the raceway. No splices or reinsulated conductors, such as would be the case with abandoned outlets on loop wiring, shall be allowed in raceways.

### 390.70 Laid in Straight Lines.

Underfloor raceways shall be laid so that a straight line from the center of one junction box to the center of the next junction box coincides with the centerline of the raceway system. Raceways shall be firmly held in place to prevent disturbing this alignment during construction.

### 390.71 Markers at Ends.

A suitable marker shall be installed at or near each end of each straight run of raceways to locate the last insert.

### 390.73 Dead Ends.

Dead ends of raceways shall be closed.

### 390.74 Junction Boxes.

Junction boxes shall be leveled to the floor grade and sealed to prevent the free entrance of water or concrete. Junction boxes used with metal raceways shall be metal and shall be electrically continuous with the raceways.

### 390.75 Inserts.

Inserts shall be leveled and sealed to prevent the entrance of concrete. Inserts used with metal raceways shall be metal and shall be electrically continuous with the raceway. Inserts set in or on fiber raceways before the floor is laid shall be mechanically secured to the raceway. Inserts set in fiber raceways after the floor is laid shall be screwed into the raceway. When cutting through the raceway wall and setting inserts, chips and other dirt shall not be allowed to remain in the raceway, and tools shall be used that are designed so as to prevent the tool from entering the raceway and damaging conductors that may be in place.

### 390.76 Connections to Cabinets and Wall Outlets.

Connections from underfloor raceways to distribution centers and wall outlets shall be made by approved fittings or by any of the wiring methods in Chapter 3, where installed in accordance with the respective articles.

# Article 393 Low-Voltage Suspended Ceiling Power Distribution Systems

## Part I. General

### 393.1 Scope.

This article covers the installation of low-voltage suspended ceiling power distribution systems.

### 393.2 Definitions.

The definitions in this section shall apply only within this article.

#### Busbar.

A noninsulated conductor electrically connected to the source of supply and physically supported on an insulator providing a power rail for connection to utilization equipment, such as sensors, actuators, A/V devices, low-voltage luminaire assemblies, and similar electrical equipment.

#### Busbar Support.

An insulator that runs the length of a section of suspended ceiling bus rail that serves to support and isolate the busbars from the suspended grid rail.

#### Connector.

A term used to refer to an electromechanical fitting.

#### Connector, Load.

An electromechanical connector used for power from the busbar to utilization equipment.

#### Connector, Pendant.

An electromechanical or mechanical connector used to suspend low-voltage luminaire or utilization equipment below the grid rail and to supply power to connect from the busbar to utilization equipment.

#### Connector, Power Feed.

An electromechanical connector used to connect the power supply to a power distribution cable, to connect directly to the busbar, or to connect from a power distribution cable to the busbar.

#### Connector, Rail to Rail.

An electromechanical connector used to interconnect busbars from one ceiling grid rail to another grid rail.

#### Grid Bus Rail.

A combination of the busbar, the busbar support, and the structural suspended ceiling grid system.

#### Low-Voltage Suspended Ceiling Power Distribution System.

A system that serves as a support for a finished ceiling surface and consists of a busbar and busbar support system to distribute power to utilization equipment supplied by a Class 2 power supply.

#### Power Supply.

A Class 2 power supply connected between the branch-circuit power distribution system and the busbar low-voltage suspended ceiling power distribution system.

#### Rail.

The structural support for the suspended ceiling system typically forming the ceiling grid supporting the ceiling tile and listed utilization equipment, such as sensors, actuators, A/V devices, and low-voltage luminaires and similar electrical equipment.

#### Reverse Polarity Protection (Backfeed Protection).

A system that prevents two interconnected power supplies, connected positive to negative, from passing current from one power source into a second power source.

#### Suspended Ceiling Grid.

A system that serves as a support for a finished ceiling surface and other utilization equipment.

### 393.6 Listing Requirements.

Suspended ceiling power distribution systems and associated fittings shall be listed as in 393.6(A) or (B).

#### 393.6(A) Listed System.

Low-voltage suspended ceiling distribution systems operating at 30 volts ac or less or 60 volts dc or less shall be listed as a complete system, with the utilization equipment, power supply, and fittings as part of the same identified system.

#### 393.6(B) Assembly of Listed Parts.

A low-voltage suspended ceiling power distribution system assembled from the following parts, listed according to the appropriate function, shall be permitted:

* (1) Listed low-voltage utilization equipment

* (2) Listed Class 2 power supply

* (3) Listed or identified fittings, including connectors and grid rails with bare conductors

* (4) Listed low-voltage cables in accordance with 725.179, conductors in raceways, or other fixed wiring methods for the secondary circuit

## Part II. Installation

### 393.10 Uses Permitted.

Low-voltage suspended ceiling power distribution systems shall be permanently connected and shall be permitted as follows:

* (1) For listed utilization equipment capable of operation at a maximum of 30 volts ac (42.4 volts peak) or 60 volts dc (24.8 volts peak for dc interrupted at a rate of 10 Hz to 200 Hz) and limited to Class 2 power levels in Chapter 9, Table 11(A) and Table
11(B) for lighting, control, and signaling circuits.

* (2) In indoor dry locations.

* (3) For residential, commercial, and industrial installations.

* (4) In other spaces used for environmental air in accordance with 300.22(C), electrical equipment having a metal enclosure, or with a nonmetallic enclosure and fittings, shall be listed for use within an air-handling space and shall have adequate fire-resistant and low-smoke-producing characteristics and associated wiring material suitable for the ambient temperature.

> [!info] Informational Note:
> One method of defining adequate fire-resistant and low-smoke-producing characteristics for electrical equipment with a nonmetallic enclosure is in ANSI/ UL 2043-2013, Fire Test for Heat and Visible Smoke Release for Discrete

Products and Their Accessories Installed in Air-Handling Spaces.

### 393.12 Uses Not Permitted.

Suspended ceiling power distribution systems shall not be installed in the following:

* (1) In damp or wet locations

* (2) Where subject to corrosive fumes or vapors, such as storage battery rooms

* (3) Where subject to physical damage

* (4) In concealed locations

* (5) In hazardous (classified) locations

* (6) As part of a fire-rated floor-ceiling or roof-ceiling assembly, unless specifically listed as part of the assembly

* (7) For lighting in general or critical patient care areas

### 393.14 Installation.

#### 393.14(A) General Requirements.

Support wiring shall be installed in a neat and workmanlike manner. Cables and conductors installed exposed on the surface of ceilings and sidewalls shall be supported by the building structure in such a manner that the cable is not damaged by normal building use. Such cables shall be supported by straps, staples, hangers, cable ties listed and identified for securement and support, or similar fittings designed and installed so as not to damage the cable.

> [!info] Informational Note:
> Suspended ceiling low-voltage power grid distribution systems should be installed by qualified persons in accordance with the manufacturer’s installation instructions.

#### 393.14(B) Insulated Conductors.

Exposed insulated secondary circuit conductors shall be listed, of the type, and installed as described as follows:

* (1) Class 2 cable supplied by a listed Class 2 power source and installed in accordance with Parts I and III of Article 725

* (2) Wiring methods described in Chapter 3

### 393.21 Disconnecting Means.

#### 393.21(A) Location.

A disconnecting means for the Class 2 supply to the power grid system shall be located so as to be accessible and within sight of the

Class 2 power source for servicing or maintenance of the grid system.

#### 393.21(B) Multiwire Branch Circuits.

Where connected to a multiwire branch circuit, the disconnecting means shall simultaneously disconnect all the supply conductors, including the grounded conductors.

### 393.30 Securing and Supporting.

#### 393.30(A) Attached to Building Structure.

A suspended ceiling low-voltage power distribution system shall be secured to the mounting surface of the building structure by hanging wires, screws, or bolts in accordance with the installation and operation instructions. Mounting hardware, such as screws or bolts, shall be either packaged with the suspended ceiling low-voltage lighting power distribution system, or the installation instructions shall specify the types of mounting fasteners to be used.

#### 393.30(B) Attachment of Power Grid Rails.

The individual power grid rails shall be mechanically secured to the overall ceiling grid assembly.

### 393.40 Connectors and Enclosures.

#### 393.40(A) Connectors.

Connections to busbar grid rails, cables, and conductors shall be made with listed insulating devices, and these connections shall be accessible after installation. A soldered connection shall be made mechanically secure before being soldered. Other means of securing leads, such as push-on terminals and spade-type connectors, shall provide a secure mechanical connection. The following connectors shall be permitted to be used as connection or interconnection devices:

* (1) Load connectors shall be used for power from the busbar to listed utilization equipment.

* (2) A pendant connector shall be permitted to suspend low-voltage luminaires or utilization equipment below the grid rail and to supply power from the busbar to the utilization equipment.

* (3) A power feed connector shall be permitted to connect the power supply directly to a power distribution cable and to the busbar.

* (4) Rail-to-rail connectors shall be permitted to interconnect busbars from one ceiling grid rail to another grid rail.

> [!info] Informational Note:
> For quick-connect terminals, see UL 310, Standard for Electrical Quick-Connect, and for mechanical splicing devices, see UL 486A-486B, Standard for Wire Connectors.

#### 393.40(B) Enclosures.

Where made in a wall, connections shall be installed in an enclosure in accordance with Parts I, II, and III of Article 314.

### 393.45 Overcurrent and Reverse Polarity (Backfeed) Protection.

#### 393.45(A) Overcurrent Protection.

The listed Class 2 power supply or transformer primary shall be protected at not greater than 20 amperes.

#### 393.45(B) Interconnection of Power Sources.

Listed Class 2 sources shall not have the output connections paralleled or otherwise interconnected unless listed for such interconnection.

#### 393.45(C) Reverse Polarity (Backfeed) Protection of Direct-Current Systems.

A suspended ceiling low-voltage power distribution system shall be permitted to have reverse polarity (backfeed) protection of dc circuits by one of the following means:

* (1) If the power supply is provided as part of the system, the power supply is provided with reverse polarity (backfeed) protection; or

* (2) If the power supply is not provided as part of the system, reverse polarity or backfeed protection can be provided as part of the grid rail busbar or as a part of the power feed connector.

### 393.56 Splices.

A busbar splice shall be provided with insulation and mechanical protection equivalent to that of the grid rail busbars involved.

### 393.57 Connections.

Connections in busbar grid rails, cables, and conductors shall be made with listed insulating devices and be accessible after installation. Where made in a wall, connections shall be installed in an enclosure in accordance with Parts I, II, and III of Article 314, as applicable.

### 393.60 Grounding.

#### 393.60(A) Grounding of Supply Side of Class 2 Power Source.

The supply side of the Class 2 power source shall be connected to an equipment grounding conductor in accordance with the applicable requirements in Part IV of Article 250.

#### 393.60(B) Grounding of Load Side of Class 2 Power Source.

Class 2 load side circuits for suspended ceiling low-voltage power grid distribution systems shall not be grounded.

## Part III. Construction Specifications

### 393.104 Sizes and Types of Conductors.

#### 393.104(A) Load Side Utilization Conductor Size.

Current-carrying conductors for load side utilization equipment shall be copper and shall be 18 AWG minimum.

> [!important] Exception:
> Conductors of a size smaller than 18 AWG, but not smaller than 24 AWG, shall be permitted to be used for Class 2 circuits.

Where used, these conductors shall be installed using a Chapter 3 wiring method, shall be totally enclosed, shall not be subject to movement or strain, and shall comply with the ampacity requirements in Table 522.22.

#### 393.104(B) Power Feed Bus Rail Conductor Size.

The power feed bus rail shall be 16 AWG minimum or equivalent. For a busbar with a circular cross section, the diameter shall be
1.29 mm (0.051 in.) minimum, and, for other than circular busbars, the area shall be 1.32 mm (0.002 in. ) minimum.

# Article 394 Concealed Knob-and-Tube Wiring

## Part I. General

### 394.1 Scope.

This article covers the use, installation, and construction specifications of concealed knob-and-tube wiring.

### 394.2 Definition.

The definition in this section shall apply within this article and throughout the Code.

#### Concealed Knob-and-Tube Wiring.

A wiring method using knobs, tubes, and flexible nonmetallic tubing for the protection and support of single insulated conductors.

## Part II. Installation

### 394.10 Uses Permitted.

Concealed knob-and-tube wiring shall be permitted to be installed in the hollow spaces of walls and ceilings, or in unfinished attics and roof spaces as provided by 394.23, only as follows:
2 2

* (1) For extensions of existing installations

* (2) Elsewhere by special permission

### 394.12 Uses Not Permitted.

Concealed knob-and-tube wiring shall not be used in the following:

* (1) Commercial garages

* (2) Theaters and similar locations

* (3) Motion picture studios

* (4) Hazardous (classified) locations

* (5) Hollow spaces of walls, ceilings, and attics where such spaces are insulated by loose, rolled, or foamed-in-place insulating material that envelops the conductors

### 394.17 Through or Parallel to Framing Members.

Conductors shall comply with 398.17 where passing through holes in structural members. Where passing through wood cross members in plastered partitions, conductors shall be protected by noncombustible, nonabsorbent, insulating tubes extending not less than 75 mm
(3 in.) beyond the wood member.

### 394.19 Clearances.

#### 394.19(A) General.

A clearance of not less than 75 mm (3 in.) shall be maintained between conductors and a clearance of not less than 25 mm (1 in.) between the conductor and the surface over which it passes.

#### 394.19(B) Limited Conductor Space.

Where space is too limited to provide these minimum clearances, such as at meters, panelboards, outlets, and switch points, the individual conductors shall be enclosed in flexible nonmetallic tubing, which shall be continuous in length between the last support and the enclosure or terminal point.

#### 394.19(C) Clearance from Piping, Exposed Conductors, and So Forth.

Conductors shall comply with 398.19 for clearances from other exposed conductors, piping, and so forth.

### 394.23 In Accessible Attics.

Conductors in unfinished attics and roof spaces shall comply with 394.23(A) or (B).

> [!info] Informational Note:
> See 310.14(A)(3) for temperature limitation of conductors.

#### 394.23(A) Accessible by Stairway or Permanent Ladder.

Conductors shall be installed along the side of or through bored holes in floor joists, studs, or rafters. Where run through bored holes, conductors in the joists and in studs or rafters to a height of not less than 2.1 m (7 ft) above the floor or floor joists shall be protected by substantial running boards extending not less than 25 mm (1 in.) on each side of the conductors. Running boards shall be securely fastened in place. Running boards and guard strips shall not be required where conductors are installed along the sides of joists, studs, or rafters.

#### 394.23(B) Not Accessible by Stairway or Permanent Ladder.

Conductors shall be installed along the sides of or through bored holes in floor joists, studs, or rafters.

> [!important] Exception:
> In buildings completed before the wiring is installed, attic and roof spaces that are not accessible by stairway or permanent ladder and have headroom at all points less than 900 mm (3 ft), the wiring shall be permitted to be installed on the edges of rafters or joists facing the attic or roof space.

### 394.30 Securing and Supporting.

#### 394.30(A) Supporting.

Conductors shall be rigidly supported on noncombustible, nonabsorbent insulating materials and shall not contact any other objects.

Supports shall be installed as follows:

* (1) Within 150 mm (6 in.) of each side of each tap or splice, and

* (2) At intervals not exceeding 1.4 m (41⁄2 ft).

Where it is impracticable to provide supports, conductors shall be permitted to be fished through hollow spaces in dry locations, provided each conductor is individually enclosed in flexible nonmetallic tubing that is in continuous lengths between supports, between boxes, or between a support and a box.

#### 394.30(B) Securing.

Where solid knobs are used, conductors shall be securely tied thereto by tie wires having insulation equivalent to that of the conductor.

### 394.42 Devices.

Switches shall comply with 404.4 and 404.10(B).

### 394.56 Splices and Taps.

Splices shall be soldered unless approved splicing devices are used. In-line or strain splices shall not be used.

## Part III. Construction Specifications

### 394.104 Conductors.

Conductors shall be of a type specified by Article 310.

# Article 396 Messenger-Supported Wiring

## Part I. General

### 396.1 Scope.

This article covers the use, installation, and construction specifications for messenger-supported wiring.

### 396.2 Definitions.

#### Insulated Conductor.

This definition shall apply only within this article.

For the purposes of this article, an insulated conductor includes the following:

* (1) Conductor types described in 310.4, and

* (2) Overhead service conductors encased in a polymeric material that has been evaluated for the applied nominal voltage.

> [!info] Informational Note:
> Evidence of evaluation for the applied nominal voltage can be given by certification that the conductors have met the requirements of ICEA S-76-474-2011, Standard for Neutral Supported Power Cable Assemblies with Weather-Resistant Extruded Insulation Rated 600 Volts.

#### Messenger-Supported Wiring.

This definition shall apply within this article and throughout the Code.

An exposed wiring support system using a messenger wire to support insulated conductors by any one of the following:

* (1) A messenger with rings and saddles for conductor support

* (2) A messenger with a field-installed lashing material for conductor support

* (3) Factory-assembled aerial cable

* (4) Multiplex cables utilizing a bare conductor, factory assembled and twisted with one or more insulated conductors, such as duplex, triplex, or quadruplex type of construction

## Part II. Installation

### 396.10 Uses Permitted.

#### 396.10(A) Cable Types.

The cable types in Table 396.10(A) shall be permitted to be installed in messenger-supported wiring under the conditions described in the article or section referenced for each.

Table 396.10(A) Cable Types

Cable Type Section Article

Cable Type Section Article

Medium-voltage cable 328

Metal-clad cable 330

Mineral-insulated, metal-sheathed cable 332

Multiconductor service-entrance cable 338

Multiconductor underground feeder and branch-circuit cable 340

Other factory-assembled, multiconductor control, signal, or power cables that are identified for the use

Power and control tray cable 336

Power-limited tray cable Table 725.154, 725.135(J), and
725.179(E)

#### 396.10(B) In Industrial Establishments.

In industrial establishments only, where conditions of maintenance and supervision ensure that only qualified persons service the installed messenger-supported wiring, the following shall be permitted:

* (1) Any of the conductor types shown in Table 310.4(A) or Table 310.4(B)

* (2) MV cable

Where exposed to weather, conductors shall be listed for use in wet locations. Where exposed to direct rays of the sun, conductors or cables shall be sunlight resistant.

#### 396.10(C) Hazardous (Classified) Locations.

Messenger-supported wiring shall be permitted to be used in hazardous (classified) locations where the contained cables and messenger-supported wiring are specifically permitted by other articles in this Code.

### 396.12 Uses Not Permitted.

Messenger-supported wiring shall not be used in hoistways or where subject to physical damage.

### 396.30 Messenger.

#### 396.30(A) Support.

The messenger shall be supported at dead ends and at intermediate locations so as to eliminate tension on the conductors. The conductors shall not be permitted to come into contact with the messenger supports or any structural members, walls, or pipes.

#### 396.30(B) Neutral Conductor.

Where the messenger is used as a neutral conductor, it shall comply with the requirements of 225.4, 250.184(A), 250.184(B)(7), and
250.187(B).

#### 396.30(C) Equipment Grounding Conductor.

Where the messenger is used as an equipment grounding conductor, it shall comply with the requirements of 250.32(B), 250.118,
250.184(B)(8), and 250.187(D).

### 396.56 Conductor Splices and Taps.

Conductor splices and taps made and insulated by approved methods shall be permitted in messenger-supported wiring.

### 396.60 Grounding.

The messenger shall be grounded as required by 250.80 and 250.86 for enclosure grounding.

# Article 398 Open Wiring on Insulators

## Part I. General

### 398.1 Scope.

This article covers the use, installation, and construction specifications of open wiring on insulators.

### 398.2 Definition.

The definition in this section shall apply within this article and throughout the Code.

#### Open Wiring on Insulators.

An exposed wiring method using cleats, knobs, tubes, and flexible tubing for the protection and support of single insulated conductors run in or on buildings.

## Part II. Installation

### 398.10 Uses Permitted.

Open wiring on insulators shall be permitted only for industrial or agricultural establishments on systems of 1000 volts, nominal, or less, as follows:

* (1) Indoors or outdoors

* (2) In wet or dry locations

* (3) Where subject to corrosive vapors

* (4) For services

### 398.12 Uses Not Permitted.

Open wiring on insulators shall not be installed where concealed by the building structure.

### 398.15 Exposed Work.

#### 398.15(A) Dry Locations.

In dry locations, where not exposed to physical damage, conductors shall be permitted to be separately enclosed in flexible nonmetallic tubing. The tubing shall be in continuous lengths not exceeding 4.5 m (15 ft) and secured to the surface by straps at intervals not exceeding 1.4 m (41⁄2 ft).

#### 398.15(B) Entering Spaces Subject to Dampness, Wetness, or Corrosive Vapors.

Conductors entering or leaving locations subject to dampness, wetness, or corrosive vapors shall have drip loops formed on them and shall then pass upward and inward from the outside of the buildings, or from the damp, wet, or corrosive location, through noncombustible, nonabsorbent insulating tubes.

> [!info] Informational Note:
> See 230.52 for individual conductors entering buildings or other structures.

#### 398.15(C) Exposed to Physical Damage.

Conductors within 2.1 m (7 ft) from the floor shall be considered exposed to physical damage. Where open conductors cross ceiling joists and wall studs and are exposed to physical damage, they shall be protected by one of the following methods:

* (1) Guard strips not less than 25 mm (1 in.) nominal in thickness and at least as high as the insulating supports, placed on each side of and close to the wiring.

* (2) A substantial running board at least 13 mm (1⁄2 in.) thick in back of the conductors with side protections. Running boards shall extend at least 25 mm (1 in.) outside the conductors, but not more than 50 mm (2 in.), and the protecting sides shall be at least
50 mm (2 in.) high and at least 25 mm (1 in.), nominal, in thickness.

* (3) Boxing made in accordance with 398.15(C)(1) or (C)(2) and furnished with a cover kept at least 25 mm (1 in.) away from the conductors within. Where protecting vertical conductors on side walls, the boxing shall be closed at the top and the holes through which the conductors pass shall be bushed.

* (4) Rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, or electrical metallic tubing. When installed in metal piping, the conductors shall be encased in continuous lengths of approved flexible tubing.

### 398.17 Through or Parallel to Framing Members.

Open conductors shall be separated from contact with walls, floors, wood cross members, or partitions through which they pass by tubes or bushings of noncombustible, nonabsorbent insulating material. Where the bushing is shorter than the hole, a waterproof sleeve of noninductive material shall be inserted in the hole and an insulating bushing slipped into the sleeve at each end in such a manner as to keep the conductors absolutely out of contact with the sleeve. Each conductor shall be carried through a separate tube or sleeve.

> [!info] Informational Note:
> See 310.14(A)(3) for temperature limitation of conductors.

### 398.19 Clearances.

Open conductors shall be separated at least 50 mm (2 in.) from metal raceways, piping, or other conducting material, and from any exposed lighting, power, or signaling conductor, or shall be separated therefrom by a continuous and firmly fixed nonconductor in addition to the insulation of the conductor. Where any insulating tube is used, it shall be secured at the ends. Where practicable, conductors shall pass over rather than under any piping subject to leakage or accumulations of moisture.

### 398.23 In Accessible Attics.

Conductors in unfinished attics and roof spaces shall comply with 398.23(A) or (B).

#### 398.23(A) Accessible by Stairway or Permanent Ladder.

Conductors shall be installed along the side of or through bored holes in floor joists, studs, or rafters. Where run through bored holes, conductors in the joists and in studs or rafters to a height of not less than 2.1 m (7 ft) above the floor or floor joists shall be protected by substantial running boards extending not less than 25 mm (1 in.) on each side of the conductors. Running boards shall be securely fastened in place. Running boards and guard strips shall not be required for conductors installed along the sides of joists, studs, or rafters.

#### 398.23(B) Not Accessible by Stairway or Permanent Ladder.

Conductors shall be installed along the sides of or through bored holes in floor joists, studs, or rafters.

> [!important] Exception:
> In buildings completed before the wiring is installed, in attic and roof spaces that are not accessible by stairway or permanent ladder and have headroom at all points less than 900 mm (3 ft), the wiring shall be permitted to be installed on the edges of rafters or joists facing the attic or roof space.

### 398.30 Securing and Supporting.

#### 398.30(A) Conductor Sizes Smaller Than 8 AWG.

Conductors smaller than 8 AWG shall be rigidly supported on noncombustible, nonabsorbent insulating materials and shall not contact any other objects. Supports shall be installed as follows:

* (1) Within 150 mm (6 in.) from a tap or splice

* (2) Within 300 mm (12 in.) of a dead-end connection to a lampholder or receptacle

* (3) At intervals not exceeding 1.4 m (41⁄2 ft) and at closer intervals sufficient to provide adequate support where likely to be disturbed

#### 398.30(B) Conductor Sizes 8 AWG and Larger.

Supports for conductors 8 AWG or larger installed across open spaces shall be permitted up to 4.5 m (15 ft) apart if noncombustible, nonabsorbent insulating spacers are used at least every 1.4 m (41⁄2 ft) to maintain at least 65 mm (21⁄2 in.) between conductors.

Where not likely to be disturbed in buildings of mill construction, 8 AWG and larger conductors shall be permitted to be run across open spaces if supported from each wood cross member on approved insulators maintaining 150 mm (6 in.) between conductors.

#### 398.30(C) Industrial Establishments.

In industrial establishments only, where conditions of maintenance and supervision ensure that only qualified persons service the system, conductors of sizes 250 kcmil and larger shall be permitted to be run across open spaces where supported at intervals up to
9.0 m (30 ft) apart.

#### 398.30(D) Mounting of Conductor Supports.

Where nails are used to mount knobs, they shall not be smaller than tenpenny. Where screws are used to mount knobs, or where nails or screws are used to mount cleats, they shall be of a length sufficient to penetrate the wood to a depth equal to at least one-half the height of the knob and the full thickness of the cleat. Cushion washers shall be used with nails.

#### 398.30(E) Tie Wires.

Conductors 8 AWG or larger and supported on solid knobs shall be securely tied thereto by tie wires having an insulation equivalent to that of the conductor.

### 398.42 Devices.

Surface-type snap switches shall be mounted in accordance with 404.10(A), and boxes shall not be required. Other type switches shall be installed in accordance with 404.4.

## Part III. Construction Specifications

### 398.104 Conductors.

Conductors shall be of a type specified by Article 310.

# Article 399 Outdoor Overhead Conductors over 1000 Volts

### 399.1 Scope.

This article covers the use and installation for outdoor overhead conductors over 1000 volts, nominal.

### 399.2 Definition.

The definitions in this section shall apply only within this article.

#### Outdoor Overhead Conductors.

Single conductors, insulated, covered, or bare, installed outdoors on support structures in free air.

### 399.10 Uses Permitted.

Outdoor overhead conductors over 1000 volts, nominal, shall be permitted only for systems rated over 1000 volts, nominal, as follows:

* (1) Outdoors in free air

* (2) For service conductors, feeders, or branch circuits

> [!info] Informational Note:
> For additional information on outdoor overhead conductors over 1000 volts, see IEEE C2, National Electrical Safety

Code, and ANSI/IEEE 3001.2, Recommended Practice for Evaluating the Electrical Service Requirements of Industrial and Commercial

Power Systems.

### 399.30 Support.

#### 399.30(A) Conductors.

Documentation of the engineered design by a licensed professional engineer engaged primarily in the design of such systems for the spacing between conductors shall be available upon request of the authority having jurisdiction and shall include consideration of the following:

* (1) Applied voltage

* (2) Conductor size

* (3) Distance between support structures

* (4) Type of structure

* (5) Wind/ice loading

* (6) Surge protection

#### 399.30(B) Structures.

Structures of wood, metal, or concrete, or combinations of those materials, shall be provided for support of overhead conductors over
1000 volts, nominal. Documentation of the engineered design by a licensed professional engineer engaged primarily in the design of such systems and the installation of each support structure shall be available upon request of the authority having jurisdiction and shall include consideration of the following:

* (1) Soil conditions

* (2) Foundations and structure settings

* (3) Weight of all supported conductors and equipment

* (4) Weather loading and other conditions such as, but not limited to, ice, wind, temperature, and lightning

* (5) Angle where change of direction occurs

* (6) Spans between adjacent structures

* (7) Effect of dead-end structures

* (8) Strength of guy wires and guy anchors

* (9) Structure size and material(s)

* (10) Hardware

#### 399.30(C) Insulators.

Insulators used to support conductors shall be rated for all of the following:

* (1) Applied phase-to-phase voltage

* (2) Mechanical strength required for each individual installation

* (3) Impulse withstand BIL in accordance with Table 490.24

> [!info] Informational Note:
> 399.30(A), (B), and (C) are not all-inclusive lists.
