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Article 311 Medium Voltage Conductors and Cable |
Article 311 Medium Voltage Conductors and Cable
Part I. General
311.1 Scope.
This article covers the use, installation, construction specifications, and ampacities for Type MV medium voltage conductors and cable.
311.2 Definitions.
The definitions in this section shall apply within this article and throughout the Code.
Electrical Ducts.
Electrical conduits, or other raceways round in cross section, that are suitable for use underground or embedded in concrete.
Medium Voltage Cable, Type MV.
A single or multiconductor solid dielectric insulated cable rated 2001 volts up to and including 35,000 volts, nominal.
Thermal Resistivity.
As used in this Code, the heat transfer capability through a substance by conduction.
[!info] Informational Note: Thermal resistivity is the reciprocal of thermal conductivity and is designated Rho, which is expressed in the units °C-cm/W.
311.6 Listing Requirements.
Type MV cables and associated fittings shall be listed.
Part II. Construction Specifications
311.10 Constructions and Applications.
Type MV cables shall comply with the applicable provisions in 311.10(A) through (C).
311.10(A) Conductor Application and Insulation.
Conductor application and insulation shall comply with Table 311.10(A).
Table 311.10(A) Conductor Application and Insulation Rated 2001 Volts and Higher
| Trade Name | Type Letter | Maximum Operating Temperature | Application Provision | Insulation | Outer Covering |
|---|---|---|---|---|---|
| Medium voltage solid dielectric | MV-90 | 90°C | Dry or wet locations | Thermoplastic or thermosetting | Jacket, sheath, or armor |
| ^ | MV-105* | 105°C | ^ | ^ | ^ |
*Where design conditions require maximum conductor temperatures above 90°C.
311.10(B) Thickness of Insulation and Jacket for Nonshielded Insulated Conductors.
Thickness of insulation and jacket for nonshielded solid dielectric insulated conductors rated 2001 volts to 5000 volts shall comply with Table 311.10(B).
Table 311.10(B) Thickness of Insulation and Jacket for Nonshielded Solid Dielectric Insulated Conductors Rated 2001 Volts to 5000 Volts
| Conductor Size (AWG or kcmil) | < | < | 8 | 6 | 4—2 | 1—2/0 | 3/0—4/0 | 213—500 | 501—750 | 751—1000 | 1001—1250 | 1251—1500 | 1501—2000 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Dry Locations, Single Conductor | Without Jacket Insulation | < | 110mils (2.79mm) | 110mils (2.79mm) | 110mils (2.79mm) | 110mils (2.79mm) | 110mils (2.79mm) | 120mils (3.05mm) | 130mils (3.3mm) | 130mils (3.3mm) | 140mils (3.56mm) | 140mils (3.56mm) | 140mils (3.56mm) |
| ^ | With Jacket | Insulation | 90mils (2.29mm) | 90mils (2.29mm) | 90mils (2.29mm) | 90mils (2.29mm) | 90mils (2.29mm) | 90mils (2.29mm) | 90mils (2.29mm) | 90mils (2.29mm) | 115mils (2.92mm) | 115mils (2.92mm) | 115mils (2.92mm) |
| ^ | ^ | Jacket | 30mils (0.76mm) | 30mils (0.76mm) | 45mils (1.14mm) | 45mils (1.14mm) | 65mils (1.65mm) | 65mils (1.65mm) | 65mils (1.65mm) | 65mils (1.65mm) | 65mils (1.65mm) | 80mils (2.03mm) | 80mils (2.03mm) |
| Wet or Dry Locations | Single Conductor | Insulation | 125mils (3.18mm) | 125mils (3.18mm) | 125mils (3.18mm) | 125mils (3.18mm) | 125mils (3.18mm) | 140mils (3.56mm) | 155mils (3.94mm) | 155mils (3.94mm) | 170mils (4.32mm) | 170mils (4.32mm) | 170mils (4.32mm) |
| ^ | ^ | Jacket | 80mils (2.03mm) | 80mils (2.03mm) | 80mils (2.03mm) | 80mils (2.03mm) | 95mils (2.41mm) | 110mils (2.79mm) | 125mils (3.18mm) | 125mils (3.18mm) | 140mils (3.56mm) | 140mils (3.56mm) | 155mils (3.94mm) |
| ^ | Multiconductor Insulation* | < | 90mils (2.29mm) | 90mils (2.29mm) | 90mils (2.29mm) | 90mils (2.29mm) | 90mils (2.29mm) | 90mils (2.29mm) | 90mils (2.29mm) | 90mils (2.29mm) | 115mils (2.92mm) | 115mils (2.92mm) | 140mils (3.56mm) |
*Under a common overall covering such as a jacket, sheath, or armor.
311.10(C) Thickness of Insulation for Shielded Insulated Conductors.
Thickness of insulation for shielded solid dielectric insulated conductors rated 2001 volts to 35,000 volts shall comply with Table 311.10(C) and 311.10(C)(1) through (C)(3).
Table 311.10(C) Thickness of Insulation for Shielded Solid Dielectric Insulated Conductors Rated 2001 Volts to 35,000 Volts
| Conductor Size (AWG or kcmil) | Insulation Level | < | < | |
|---|---|---|---|---|
| 100 Percent | 133 Percent | 173 Percent | ||
| 2001—5000 Volts | 1 | 90mils (2.29mm) | ||
| ^ | 2 | 90mils (2.29mm) | ||
| ^ | 8 | 90mils (2.29mm) | ||
| ^ | 1/0—2000 | 90mils (2.29mm) | ||
| ^ | 6—4 | 90mils (2.29mm) | ||
| 5001—8000 Volts | 1 | 115mils (2.92mm) | 140mils (3.56mm) | 175mils (4.45mm) |
| ^ | 2 | 115mils (2.92mm) | 140mils (3.56mm) | 175mils (4.45mm) |
| ^ | 1/0—2000 | 115mils (2.92mm) | 140mils (3.56mm) | 175mils (4.45mm) |
| ^ | 6—4 | 115mils (2.92mm) | 140mils (3.56mm) | 175mils (4.45mm) |
| 8001—15,000 Volts | 1 | 175mils (4.45mm) | 220mils (5.59mm) | 260mils (6.6mm) |
| ^ | 1/0—2000 | 175mils (4.45mm) | 220mils (5.59mm) | 260mils (6.6mm) |
| ^ | 2 | 175mils (445mm) | 220mils (5.59mm) | 260mils (6.6mm) |
| 15,001—25,000 Volts | 1 | 260mils (6.6mm) | 320mils (8.13mm) | 420mils (10.67mm) |
| ^ | 1/0—2000 | 260mils (6.6mm) | 320mils (8.13mm) | 420mils (10.67mm) |
| 25,001—28,000 Volts | 1 | 280mils (7.11mm) | 345mils (8.76mm) | 445mils (11.3mm) |
| ^ | 1/0—2000 | 280mils (7.11mm) | 345mils (8.76mm) | 445mils (11.3mm) |
| 28,001—35,000 Volts | 1/0—2000 | 345mils (8.76mm) | 420mils (10.67mm) | 580mils (14.73mm) |
311.10(C)(1) 100 Percent Insulation Level.
Cables shall be permitted to be applied where the system is provided with relay protection such that ground faults will be cleared as rapidly as possible but, in any case, within 1 minute. These cables are applicable to cable installations that are on grounded systems and shall be permitted to be used on other systems provided the above clearing requirements are met in completely de-energizing the faulted section.
311.10(C)(2) 133 Percent Insulation Level.
Cables shall be permitted to be applied in situations where the clearing time requirements of the 100 percent level category cannot be met and the faulted section will be de-energized in a time not exceeding 1 hour. Cable shall be permitted to be used in 100 percent insulation level applications where the installation requires additional insulation.
311.10(C)(3) 173 Percent Insulation Level.
Cables shall be permitted to be applied under all of the following conditions:
-
(1) In industrial establishments where the conditions of maintenance and supervision ensure only qualified persons service the installation
-
(2) Where the fault clearing time requirements of the 133 percent level category cannot be met
-
(3) Where an orderly shutdown is required to protect equipment and personnel
-
(4) Where the faulted section will be de-energized in an orderly shutdown
Cables shall be permitted to be used in 100 percent or 133 percent insulation level applications where the installation requires additional insulation.
311.12 Conductors.
311.12(A) Minimum Size of Conductors.
The minimum size of conductors shall be as shown in Table 311.12(A), except as permitted elsewhere in this Code.
Table 311.12(A) Minimum Size of Conductors
| Conductor Voltage Rating (Volts) | Minimum Conductor Size (AWG) Copper, Aluminum, or Copper-Clad Aluminum |
|---|---|
| 2001–5000 | 8 |
| 5001–8000 | 6 |
| 8001–15,000 | 2 |
| 15,001–28,000 | 1 |
| 28,001–35,000 | 1/0 |
311.12(B) Conductor Material.
Conductors shall be of aluminum, copper-clad aluminum, or copper unless otherwise specified.
311.12(C) Stranded Conductors.
Where installed in raceways, conductors not specifically permitted or required elsewhere in this Code to be solid shall be stranded.
311.14 Conductor Identification.
Conductors that are intended for use as ungrounded conductors, whether used as a single conductor or in multiconductor cables, shall be finished to be clearly distinguishable from grounded and grounding conductors. Distinguishing markings shall not conflict in any manner with the surface markings required by 311.16(B)(1). Branch-circuit ungrounded conductors shall be identified in accordance with 210.5(C). Feeders shall be identified in accordance with 215.12.
311.16 Marking.
311.16(A) Required Information.
All conductors and cables shall be marked to indicate the following information, using the applicable method described in 311.16(B):
-
(1) The maximum rated voltage
-
(2) The proper type letter or letters for the type of wire or cable as specified elsewhere in this Code
-
(3) The manufacturer’s name, trademark, or other distinctive marking by which the organization responsible for the product can be readily identified
-
(4) The AWG size or circular mil area
[!info] Informational Note: See Chapter 9, Table 8, Conductor Properties, for conductor area expressed in SI units for conductor sizes specified in AWG or circular mil area.
311.16(B) Method of Marking.
One or more of the methods in 311.16(B)(1) through (B)(4) shall be used for marking of cable.
311.16(B)(1) Surface Marking.
Cables shall be durably marked on the surface. The AWG size or circular mil area shall be repeated at intervals not exceeding 610 mm (24 in.). All other markings shall be repeated at intervals not exceeding 1.0 m (40 in.).
311.16(B)(2) Marker Tape.
Metal-covered multiconductor cables shall employ a marker tape located within the cable and along its complete length.
311.16(B)(3) Tag Marking.
Metal-covered, single-conductor cables shall be marked by means of a printed tag attached to the reel.
311.16(B)(4) Optional Marking of Wire Size.
The information required in 311.16(A)(4) shall be permitted to be marked on the surface of the individual insulated conductors for multiconductor Type MC cable.
311.16(C) Optional Markings.
Cables shall be permitted to be marked to indicate special characteristics of the cable materials, such as limited smoke and sunlight resistance.
Part III. Installation
311.30 Installation.
Type MV cable shall be installed, terminated, and tested by qualified persons.
[!info] Informational Note No. 1: Information about accepted industry practices and installation procedures for medium-voltage cable are described in ANSI/NECA/NCSCB 600, Standard for Installing and Maintaining Medium-Voltage Cable, and in IEEE 576, Recommended Practice for Installation, Termination, and Testing of Insulated Power Cables as Used in Industrial and Commercial Applications.
[!info] Informational Note No. 2: Where medium-voltage cable is used for dc circuits, low frequency polarization can create hazardous voltages. When handling the cable these voltages may be present or may develop on dc stressed cable while the circuit is energized.
Solidly grounding the cable prior to contacting, cutting or disconnecting cables in dc circuits is a method to discharge these voltages.
311.32 Uses Permitted.
Type MV cable shall be permitted for use on power systems rated up to and including 35,000 volts, nominal, as follows:
-
(1) In wet or dry locations.
-
(2) In raceways.
-
(3) In cable trays, where identified for the use, in accordance with 392.10, 392.20(B), (C), and (D), 392.22(C), 392.30(B)(1), 392.46, 392.56, and 392.60. Type MV cable that has an overall metallic sheath or armor, complies with the requirements for Type MC cable, and is identified as “MV or MC” shall be permitted to be installed in cable trays in accordance with 392.10(B)(2).
-
(4) In messenger-supported wiring in accordance with Part II of Article 396.
-
(5) As exposed runs in accordance with 300.37. Type MV cable that has an overall metallic sheath or armor, complies with the requirements for Type MC cable, and is identified as “MV or MC” shall be permitted to be installed as exposed runs of metal-clad cable in accordance with 300.37.
-
(6) Corrosive conditions where exposed to oils, greases, vapors, gases, fumes, liquids, or other substances having a deleterious effect on the conductor or insulation shall be of a type suitable for the application.
-
(7) Conductors in parallel in accordance with 310.10(G).
-
(8) Type MV cable used where exposed to direct sunlight shall be identified for the use.
[!info] Informational Note: The “uses permitted” is not an all-inclusive list.
311.36 Direct-Burial Conductors.
Type MV conductors and cables used for direct burial applications shall be shielded, identified for such use, and installed in accordance with 300.50.
[!important] Exception No. 1: Nonshielded multiconductor cables rated 2001 volts to 2400 volts shall be permitted if the cable has an overall metallic sheath or armor. The metallic shield, sheath, or armor shall be connected to a grounding electrode conductor, a grounding busbar, or a grounding electrode.
[!important] Exception No. 2: Airfield lighting cable used in series circuits that are rated up to 5000 volts and are powered by regulators shall be permitted to be nonshielded.
[!info] Informational Note to Exception No. 2: Federal Aviation Administration (FAA) Advisory Circulars (ACs) provide additional practices and methods for airport lighting.
311.40 Support.
Type MV cable terminated in equipment or installed in pull boxes or vaults shall be secured and supported by metallic or nonmetallic supports suitable to withstand the weight by cable ties listed and identified for securement and support, or other approved means, at intervals not exceeding 1.5 m (5 ft) from terminations or a maximum of 1.8 m (6 ft) between supports.
311.44 Shielding.
Nonshielded, ozone-resistant insulated conductors with a maximum phase-to-phase voltage of 5000 volts shall be permitted in Type MC cables in industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons service the installation. For other establishments, solid dielectric insulated conductors operated above 2000 volts in permanent installations shall have ozone-resistant insulation and shall be shielded. All metallic insulation shields shall be connected to a grounding electrode conductor, a grounding busbar, an equipment grounding conductor, or a grounding electrode.
[!info] Informational Note: The primary purposes of shielding are to confine the voltage stresses to the insulation, dissipate insulation leakage current, drain off the capacitive charging current, and carry ground-fault current to facilitate operation of ground-fault protective devices in the event of an electrical cable fault.
[!important] Exception No. 1: Nonshielded insulated conductors listed by a qualified testing laboratory shall be permitted for use up to 2400 volts under the following conditions:
(1) Conductors shall have insulation resistant to electric discharge and surface tracking, or the insulated conductor(s) shall be covered with a material resistant to ozone, electric discharge, and surface tracking.
(2) Where used in wet locations, the insulated conductor(s) shall have an overall nonmetallic jacket or a continuous metallic sheath.
(3) Insulation and jacket thicknesses shall be in accordance with Table 311.10(B).
[!important] Exception No. 2: Nonshielded insulated conductors listed by a qualified testing laboratory shall be permitted for use up to 5000 volts to replace existing nonshielded conductors, on existing equipment in industrial establishments only, under the following conditions:
(1) Where the condition of maintenance and supervision ensures that only qualified personnel install and service the installation.
(2) Conductors shall have insulation resistant to electric discharge and surface tracking, or the insulated conductor(s) shall be covered with a material resistant to ozone, electric discharge, and surface tracking.
(3) Where used in wet locations, the insulated conductor(s) shall have an overall nonmetallic jacket or a continuous metallic sheath.
(4) Insulation and jacket thicknesses shall be in accordance with Table 311.10(B).
[!info] Informational Note: Relocation or replacement of equipment may not comply with the term existing as related to this exception.
[!important] Exception No. 3: Where permitted in 311.36, Exception No. 2.
Part IV. Ampacities
311.60 Ampacities of Conductors.
311.60(A) General.
311.60(A)(1) Tables or Engineering Supervision.
Ampacities for solid dielectric-insulated conductors shall be permitted to be determined by tables or under engineering supervision, as provided in 311.60(B) and (C).
The ampacity of Type MV cable installed in cable tray shall be determined in accordance with nfpa-70_392_cable-tray#392.80(B) Ampacity of Type MV and Type MC Cables (2001 Volts or Over) in Cable Trays..
311.60(A)(2) Selection of Ampacity.
Where more than one calculated or tabulated ampacity could apply for a given circuit length, the lowest value shall be used.
[!important] Exception: Where different ampacities apply to portions of a circuit, the higher ampacity shall be permitted to be used if the total portion(s) of the circuit with the lower ampacity does not exceed the lesser of 3.0 m (10 ft) or 10 percent of the total circuit.
[!info] Informational Note: See 110.40 for conductor temperature limitations due to termination provisions.
311.60(B) Engineering Supervision.
Under engineering supervision, conductor ampacities shall be permitted to be calculated by using the following general equation:
Equation 311.60(B)
I = \sqrt{ \frac{ T_{c} - ( T_{a} + \Delta T_{d} ) }{R_{dc} ( 1 + Y_{c}) R_{ca}} } \times 10^3~\text{amperes}
where:
T_{c}conductor temperature (°C)T_{a}ambient temperature (°C)\Delta T_{d}dielectric loss temperature riseR_{dc}dc resistance of conductor at temperature,T_{c}Y_{c}component ac resistance resulting from skin effect and proximity effectR_{ca}effective thermal resistance between conductor and surrounding ambient
[!info] Informational Note: The dielectric loss temperature rise (
\Delta T_{d}) is negligible for single circuit extruded dielectric cables rated below 46 kilovolts.
311.60(C) Tables.
Ampacities for conductors rated 2001 volts to 35,000 volts shall be as specified in Table 311.60(C)(67) through Table 311.60(C)(86).
Ampacities for ambient temperatures other than those specified in the ampacity tables shall be corrected in accordance with 311.60(D)(4).
[!info] Informational Note No. 1: For ampacities calculated in accordance with 311.60(A), reference IEEE 835, Standard Power Cable Ampacity Tables, and the references therein for availability of all factors and constants.
[!info] Informational Note No. 2: Ampacities provided by this section do not take voltage drop into consideration. See 210.19(A), Informational Note No. 4, for branch circuits and 215.2(A), Informational Note No. 2, for feeders.
Table 311.60(C)(67) Ampacities of Insulated Single Copper Conductor Cables Triplexed in Air
| Conductor Size (AWG or kcmil) | Temperature Rating of Conductor | < | < | < |
|---|---|---|---|---|
| ^ | 2001—5000 Volts Ampacity | < | 5001—35,000 Volts Ampacity | < |
| ^ | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 |
| 8 | 65 | 74 | — | — |
| 6 | 90 | 99 | 100 | 110 |
| 4 | 120 | 130 | 130 | 140 |
| 2 | 160 | 175 | 170 | 195 |
| 1 | 185 | 205 | 195 | 225 |
| 1/0 | 215 | 240 | 225 | 255 |
| 2/0 | 250 | 275 | 260 | 295 |
| 3/0 | 290 | 320 | 300 | 340 |
| 4/0 | 335 | 375 | 345 | 390 |
| 250 | 375 | 415 | 380 | 430 |
| 350 | 465 | 515 | 470 | 525 |
| 500 | 580 | 645 | 580 | 650 |
| 750 | 750 | 835 | 730 | 820 |
| 1000 | 880 | 980 | 850 | 950 |
Note: Refer to 311.60(E) for the basis of ampacities, 311.10(A) for conductor maximum operating temperature and application, and 311.60(D)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F).
Table 311.60(C)(68) Ampacities of Insulated Single Aluminum Conductor Cables Triplexed in Air
| Conductor Size (AWG or kcmil) | Temperature Rating of Conductor | < | < | < |
|---|---|---|---|---|
| ^ | 2001—5000 Volts Ampacity | < | 5001—35,000 Volts Ampacity | < |
| ^ | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 |
| 8 | 50 | 57 | — | — |
| 6 | 70 | 77 | 75 | 84 |
| 4 | 90 | 100 | 100 | 110 |
| 2 | 125 | 135 | 130 | 150 |
| 1 | 145 | 160 | 150 | 175 |
| 1/0 | 170 | 185 | 175 | 200 |
| 2/0 | 195 | 215 | 200 | 230 |
| 3/0 | 225 | 250 | 230 | 265 |
| 4/0 | 265 | 290 | 270 | 305 |
| 250 | 295 | 325 | 300 | 335 |
| 350 | 365 | 405 | 370 | 415 |
| 500 | 460 | 510 | 460 | 515 |
| 750 | 600 | 665 | 590 | 660 |
| 1000 | 715 | 800 | 700 | 780 |
Note: Refer to 311.60(E) for basis of ampacities, 311.10(A) for conductor maximum operating temperature and application, and 311.60(D)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F).
Table 311.60(C)(69) Ampacities of Insulated Single Copper Conductor Isolated in Air
| Conductor Size (AWG or kcmil) | Temperature Rating of Conductor | < | < | < | < | < |
|---|---|---|---|---|---|---|
| ^ | 2001—5000 Volts Ampacity | < | 5001—15,000 Volts Ampacity | < | 15,001—35,000 Volts Ampacity | < |
| ^ | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 |
| 8 | 83 | 93 | — | — | — | — |
| 6 | 110 | 120 | 110 | 125 | — | — |
| 4 | 145 | 160 | 150 | 165 | — | — |
| 2 | 190 | 215 | 195 | 215 | — | — |
| 1 | 225 | 250 | 225 | 250 | 225 | 250 |
| 1/0 | 260 | 290 | 260 | 290 | 260 | 290 |
| 2/0 | 300 | 330 | 300 | 335 | 300 | 330 |
| 3/0 | 345 | 385 | 345 | 385 | 345 | 380 |
| 4/0 | 400 | 445 | 400 | 445 | 395 | 445 |
| 250 | 445 | 495 | 445 | 495 | 440 | 490 |
| 350 | 550 | 615 | 550 | 610 | 545 | 605 |
| 500 | 695 | 775 | 685 | 765 | 680 | 755 |
| 750 | 900 | 1000 | 885 | 990 | 870 | 970 |
| 1000 | 1075 | 1200 | 1060 | 1185 | 1040 | 1160 |
| 1250 | 1230 | 1370 | 1210 | 1350 | 1185 | 1320 |
| 1500 | 1365 | 1525 | 1345 | 1500 | 1315 | 1465 |
| 1750 | 1495 | 1665 | 1470 | 1640 | 1430 | 1595 |
| 2000 | 1605 | 1790 | 1575 | 1755 | 1535 | 1710 |
Note: Refer to 311.60(E) for the basis of ampacities, 311.10(A) for conductor maximum operating temperature and application, and 311.60(D)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F).
Table 311.60(C)(70) Ampacities of Insulated Single Aluminum Conductor Isolated in Air
| Conductor Size (AWG or kcmil) | Temperature Rating of Conductor | < | < | < | < | < |
|---|---|---|---|---|---|---|
| ^ | 2001—5000 Volts Ampacity | < | 5001—15,000 Volts Ampacity | < | 15,001—35,000 Volts Ampacity | < |
| ^ | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 |
| 8 | 64 | 71 | — | — | — | — |
| 6 | 85 | 95 | 87 | 97 | — | — |
| 4 | 115 | 125 | 115 | 130 | — | — |
| 2 | 150 | 165 | 150 | 170 | — | — |
| 1 | 175 | 195 | 175 | 195 | 175 | 195 |
| 1/0 | 200 | 225 | 200 | 225 | 200 | 225 |
| 2/0 | 230 | 260 | 235 | 260 | 230 | 260 |
| 3/0 | 270 | 300 | 270 | 300 | 270 | 300 |
| 4/0 | 310 | 350 | 310 | 350 | 310 | 345 |
| 250 | 345 | 385 | 345 | 385 | 345 | 380 |
| 350 | 430 | 480 | 430 | 480 | 430 | 475 |
| 500 | 545 | 605 | 535 | 600 | 530 | 590 |
| 750 | 710 | 790 | 700 | 780 | 685 | 765 |
| 1000 | 855 | 950 | 840 | 940 | 825 | 920 |
| 1250 | 980 | 1095 | 970 | 1080 | 950 | 1055 |
| 1500 | 1105 | 1230 | 1085 | 1215 | 1060 | 1180 |
| 1750 | 1215 | 1355 | 1195 | 1335 | 1165 | 1300 |
| 2000 | 1320 | 1475 | 1295 | 1445 | 1265 | 1410 |
Note: Refer to 311.60(E) for the basis of ampacities, 311.10(A) for conductor maximum operating temperature and application, and 311.60(D)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F).
Table 311.60(C)(71) Ampacities of an Insulated Three-Conductor Copper Cable Isolated in Air
| Conductor Size (AWG or kcmil) | Temperature Rating of Conductor | < | < | < |
|---|---|---|---|---|
| ^ | 2001—5000 Volts Ampacity | < | 5001—35,000 Volts Ampacity | < |
| ^ | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 |
| 8 | 59 | 66 | — | — |
| 6 | 79 | 88 | 93 | 105 |
| 4 | 105 | 115 | 120 | 135 |
| 2 | 140 | 154 | 165 | 185 |
| 1 | 160 | 180 | 185 | 210 |
| 1/0 | 185 | 205 | 215 | 240 |
| 2/0 | 215 | 240 | 245 | 275 |
| 3/0 | 250 | 280 | 285 | 315 |
| 4/0 | 285 | 320 | 325 | 360 |
| 250 | 320 | 355 | 360 | 400 |
| 350 | 395 | 440 | 435 | 490 |
| 500 | 485 | 545 | 535 | 600 |
| 750 | 615 | 685 | 670 | 745 |
| 1000 | 705 | 790 | 770 | 860 |
Note: Refer to 311.60(E) for the basis of ampacities, 311.10(A) for conductor maximum operating temperature and application, and 311.60(D)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F).
Table 311.60(C)(72) Ampacities of an Insulated Three-Conductor Aluminum Cable Isolated in Air
| Conductor Size (AWG or kcmil) | Temperature Rating of Conductor | < | < | < |
|---|---|---|---|---|
| ^ | 2001—5000 Volts Ampacity | < | 5001—35,000 Volts Ampacity | < |
| ^ | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 |
| 8 | 46 | 51 | — | — |
| 6 | 61 | 68 | 72 | 80 |
| 4 | 81 | 90 | 95 | 105 |
| 2 | 110 | 120 | 125 | 145 |
| 1 | 125 | 140 | 145 | 165 |
| 1/0 | 145 | 160 | 170 | 185 |
| 2/0 | 170 | 185 | 190 | 215 |
| 3/0 | 195 | 215 | 220 | 245 |
| 4/0 | 225 | 250 | 255 | 285 |
| 250 | 250 | 280 | 280 | 315 |
| 350 | 310 | 345 | 345 | 385 |
| 500 | 385 | 430 | 425 | 475 |
| 750 | 495 | 550 | 540 | 600 |
| 1000 | 585 | 650 | 635 | 705 |
Note: Refer to 311.60(E) for the basis of ampacities, 311.10(A) for conductor maximum operating temperature and application, and 311.60(D)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F).
Table 311.60(C)(73) Ampacities of an Insulated Triplexed or Three Single-Conductor Copper Cables in Isolated Conduit in Air
| Conductor Size (AWG or kcmil) | Temperature Rating of Conductor | < | < | < |
|---|---|---|---|---|
| ^ | 2001—5000 Volts Ampacity | < | 5001—35,000 Volts Ampacity | < |
| ^ | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 |
| 8 | 55 | 61 | — | — |
| 6 | 75 | 84 | 83 | 93 |
| 4 | 97 | 110 | 110 | 120 |
| 2 | 130 | 145 | 150 | 165 |
| 1 | 155 | 175 | 170 | 190 |
| 1/0 | 180 | 200 | 195 | 215 |
| 2/0 | 205 | 225 | 225 | 255 |
| 3/0 | 240 | 270 | 260 | 290 |
| 4/0 | 280 | 305 | 295 | 330 |
| 250 | 315 | 355 | 330 | 365 |
| 350 | 385 | 430 | 395 | 440 |
| 500 | 475 | 530 | 480 | 535 |
| 750 | 600 | 665 | 585 | 655 |
| 1000 | 690 | 770 | 675 | 755 |
Note: Refer to 311.60(E) for the basis of ampacities, 311.10(A) for conductor maximum operating temperature and application, and 311.60(D)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F).
Table 311.60(C)(74) Ampacities of an Insulated Triplexed or Three Single-Conductor Aluminum Cables in Isolated Conduit in Air
| Conductor Size (AWG or kcmil) | Temperature Rating of Conductor | < | < | < |
|---|---|---|---|---|
| ^ | 2001—5000 Volts Ampacity | < | 5001—35,000 Volts Ampacity | < |
| ^ | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 |
| 8 | 43 | 48 | — | — |
| 6 | 58 | 65 | 65 | 72 |
| 4 | 76 | 85 | 84 | 94 |
| 2 | 100 | 115 | 115 | 130 |
| 1 | 120 | 135 | 130 | 150 |
| 1/0 | 140 | 155 | 150 | 170 |
| 2/0 | 160 | 175 | 175 | 200 |
| 3/0 | 190 | 210 | 200 | 225 |
| 4/0 | 215 | 240 | 230 | 260 |
| 250 | 250 | 280 | 255 | 290 |
| 350 | 305 | 340 | 310 | 350 |
| 500 | 380 | 425 | 385 | 430 |
| 750 | 490 | 545 | 485 | 540 |
| 1000 | 580 | 645 | 565 | 640 |
Note: Refer to 311.60(E) for the basis of ampacities, 311.10(A) for conductor maximum operating temperature and application, and 311.60(D)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F).
Table 311.60(C)(75) Ampacities of an Insulated Three-Conductor Copper Cable in Isolated Conduit in Air
| Conductor Size (AWG or kcmil) | Temperature Rating of Conductor | < | < | < |
|---|---|---|---|---|
| ^ | 2001—5000 Volts Ampacity | < | 5001—35,000 Volts Ampacity | < |
| ^ | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 |
| 8 | 52 | 58 | — | — |
| 6 | 69 | 77 | 83 | 92 |
| 4 | 91 | 100 | 105 | 120 |
| 2 | 125 | 135 | 145 | 165 |
| 1 | 140 | 155 | 165 | 185 |
| 1/0 | 165 | 185 | 195 | 215 |
| 2/0 | 190 | 210 | 220 | 245 |
| 3/0 | 220 | 245 | 250 | 280 |
| 4/0 | 255 | 285 | 290 | 320 |
| 250 | 280 | 315 | 315 | 350 |
| 350 | 350 | 390 | 385 | 430 |
| 500 | 425 | 475 | 470 | 525 |
| 750 | 525 | 585 | 570 | 635 |
| 1000 | 590 | 660 | 650 | 725 |
Note: Refer to 311.60(E) for the basis of ampacities, 311.10(A) for conductor maximum operating temperature and application, and 311.60(D)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F).
Table 311.60(C)(76) Ampacities of an Insulated Three-Conductor Aluminum Cable in Isolated Conduit in Air
| Conductor Size (AWG or kcmil) | Temperature Rating of Conductor | < | < | < |
|---|---|---|---|---|
| ^ | 2001—5000 Volts Ampacity | < | 5001—35,000 Volts Ampacity | < |
| ^ | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 |
| 8 | 41 | 46 | — | — |
| 6 | 53 | 59 | 64 | 71 |
| 4 | 71 | 79 | 84 | 94 |
| 2 | 96 | 105 | 115 | 125 |
| 1 | 110 | 125 | 130 | 145 |
| 1/0 | 130 | 145 | 150 | 170 |
| 2/0 | 150 | 165 | 170 | 190 |
| 3/0 | 170 | 190 | 195 | 220 |
| 4/0 | 200 | 225 | 225 | 255 |
| 250 | 220 | 245 | 250 | 280 |
| 350 | 275 | 305 | 305 | 340 |
| 500 | 340 | 380 | 380 | 425 |
| 750 | 430 | 480 | 470 | 520 |
| 1000 | 505 | 560 | 550 | 615 |
Note: Refer to 311.60(E) for the basis of ampacities, 311.10(A) for conductor maximum operating temperature and application, and 311.60(D)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F).
Table 311.60(C)(77) Ampacities of Three Single-Insulated Copper Conductors in Underground Electrical Ducts (Three Conductors per Electrical Duct)
| Conductor Size (AWG or kcmil) | Temperature Rating of Conductor | < | < | < |
|---|---|---|---|---|
| ^ | 2001—5000 Volts Ampacity | < | 5001—35,000 Volts Ampacity | < |
| ^ | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 |
| One Circuit [See Figure 311.60(D)(3), Detail 1.] | < | < | < | < |
| 8 | 64 | 69 | — | — |
| 6 | 85 | 92 | 90 | 97 |
| 4 | 110 | 120 | 115 | 125 |
| 2 | 145 | 155 | 155 | 165 |
| 1 | 170 | 180 | 175 | 185 |
| 1/0 | 195 | 210 | 200 | 215 |
| 2/0 | 220 | 235 | 230 | 245 |
| 3/0 | 250 | 270 | 260 | 275 |
| 4/0 | 290 | 310 | 295 | 315 |
| 250 | 320 | 345 | 325 | 345 |
| 350 | 385 | 415 | 390 | 415 |
| 500 | 470 | 505 | 465 | 500 |
| 750 | 585 | 630 | 565 | 610 |
| 1000 | 670 | 720 | 640 | 690 |
| Three Circuits [See Figure 311.60(D)(3), Detail 2.] | < | < | < | < |
| 8 | 56 | 60 | — | — |
| 6 | 73 | 79 | 77 | 83 |
| 4 | 95 | 100 | 99 | 105 |
| 2 | 125 | 130 | 130 | 135 |
| 1 | 140 | 150 | 145 | 155 |
| 1/0 | 160 | 175 | 165 | 175 |
| 2/0 | 185 | 195 | 185 | 200 |
| 3/0 | 210 | 225 | 210 | 225 |
| 4/0 | 235 | 255 | 240 | 255 |
| 250 | 260 | 280 | 260 | 280 |
| 350 | 315 | 335 | 310 | 330 |
| 500 | 375 | 405 | 370 | 395 |
| 750 | 460 | 495 | 440 | 475 |
| 1000 | 525 | 565 | 495 | 535 |
| Six Circuits [See Figure 311.60(D)(3), Detail 3.] | < | < | < | < |
| 8 | 48 | 52 | — | — |
| 6 | 62 | 67 | 64 | 68 |
| 4 | 80 | 86 | 82 | 88 |
| 2 | 105 | 110 | 105 | 115 |
| 1 | 115 | 125 | 120 | 125 |
| 1/0 | 135 | 145 | 135 | 145 |
| 2/0 | 150 | 160 | 150 | 165 |
| 3/0 | 170 | 185 | 170 | 185 |
| 4/0 | 195 | 210 | 190 | 205 |
| 250 | 210 | 225 | 210 | 225 |
| 350 | 250 | 270 | 245 | 265 |
| 500 | 300 | 325 | 290 | 310 |
| 750 | 365 | 395 | 350 | 375 |
| 1000 | 410 | 445 | 390 | 415 |
Note: Refer to 311.60(F) for basis of ampacities and Table 311.10(A) for the temperature rating of the conductor.
Table 311.60(C)(78) Ampacities of Three Single-Insulated Aluminum Conductors in Underground Electrical Ducts (Three Conductors per Electrical Duct)
| Conductor Size (AWG or kcmil) | Temperature Rating of Conductor | < | < | < |
|---|---|---|---|---|
| ^ | 2001—5000 Volts Ampacity | < | 5001—35,000 Volts Ampacity | < |
| ^ | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 |
| One Circuit [See Figure 311.60(D)(3), Detail 1.] | < | < | < | < |
| 8 | 50 | 54 | — | — |
| 6 | 66 | 71 | 70 | 75 |
| 4 | 86 | 93 | 91 | 98 |
| 2 | 115 | 125 | 120 | 130 |
| 1 | 130 | 140 | 135 | 145 |
| 1/0 | 150 | 160 | 155 | 165 |
| 2/0 | 170 | 185 | 175 | 190 |
| 3/0 | 195 | 210 | 200 | 215 |
| 4/0 | 225 | 245 | 230 | 245 |
| 250 | 250 | 270 | 250 | 270 |
| 350 | 305 | 325 | 305 | 330 |
| 500 | 370 | 400 | 370 | 400 |
| 750 | 470 | 505 | 455 | 490 |
| 1000 | 545 | 590 | 525 | 565 |
| Three Circuits [See Figure 311.60(D)(3), Detail 2.] | < | < | < | < |
| 8 | 44 | 47 | — | — |
| 6 | 57 | 61 | 60 | 65 |
| 4 | 74 | 80 | 77 | 83 |
| 2 | 96 | 105 | 100 | 105 |
| 1 | 110 | 120 | 110 | 120 |
| 1/0 | 125 | 135 | 125 | 140 |
| 2/0 | 145 | 155 | 145 | 155 |
| 3/0 | 160 | 175 | 165 | 175 |
| 4/0 | 185 | 200 | 185 | 200 |
| 250 | 205 | 220 | 200 | 220 |
| 350 | 245 | 265 | 245 | 260 |
| 500 | 295 | 320 | 290 | 315 |
| 750 | 370 | 395 | 355 | 385 |
| 1000 | 425 | 460 | 405 | 440 |
| Six Circuits [See Figure 311.60(D)(3), Detail 3.] | < | < | < | < |
| 8 | 38 | 41 | — | — |
| 6 | 48 | 52 | 50 | 54 |
| 4 | 62 | 67 | 64 | 69 |
| 2 | 80 | 86 | 80 | 88 |
| 1 | 91 | 98 | 90 | 99 |
| 1/0 | 105 | 110 | 105 | 110 |
| 2/0 | 115 | 125 | 115 | 125 |
| 3/0 | 135 | 145 | 130 | 145 |
| 4/0 | 150 | 165 | 150 | 160 |
| 250 | 165 | 180 | 165 | 175 |
| 350 | 195 | 210 | 195 | 210 |
| 500 | 240 | 255 | 230 | 250 |
| 750 | 290 | 315 | 280 | 305 |
| 1000 | 335 | 360 | 320 | 345 |
Note: Refer to 311.60(F) for basis of ampacities and Table 311.10(A) for the temperature rating of the conductor.
Table 311.60(C)(79) Ampacities of Three Insulated Copper Conductors Cabled Within an Overall Covering (Three-Conductor Cable) in Underground Electrical Ducts (One Cable per Electrical Duct)
| Conductor Size (AWG or kcmil) | Temperature Rating of Conductor | < | < | < |
|---|---|---|---|---|
| ^ | 2001—5000 Volts Ampacity | < | 5001—35,000 Volts Ampacity | < |
| ^ | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 |
| One Circuit [See Figure 311.60(D)(3), Detail 1.] | < | < | < | < |
| 8 | 59 | 64 | — | — |
| 6 | 78 | 84 | 88 | 95 |
| 4 | 100 | 110 | 115 | 125 |
| 2 | 135 | 145 | 150 | 160 |
| 1 | 155 | 165 | 170 | 185 |
| 1/0 | 175 | 190 | 195 | 210 |
| 2/0 | 200 | 220 | 220 | 235 |
| 3/0 | 230 | 250 | 250 | 270 |
| 4/0 | 265 | 285 | 285 | 305 |
| 250 | 290 | 315 | 310 | 335 |
| 350 | 355 | 380 | 375 | 400 |
| 500 | 430 | 460 | 450 | 485 |
| 750 | 530 | 570 | 545 | 585 |
| 1000 | 600 | 645 | 615 | 660 |
| Three Circuits [See Figure 311.60(D)(3), Detail 2.] | < | < | < | < |
| 8 | 53 | 57 | — | — |
| 6 | 69 | 74 | 75 | 81 |
| 4 | 89 | 96 | 97 | 105 |
| 2 | 115 | 125 | 125 | 135 |
| 1 | 135 | 145 | 140 | 155 |
| 1/0 | 150 | 165 | 160 | 175 |
| 2/0 | 170 | 185 | 185 | 195 |
| 3/0 | 195 | 210 | 205 | 220 |
| 4/0 | 225 | 240 | 230 | 250 |
| 250 | 245 | 265 | 255 | 270 |
| 350 | 295 | 315 | 305 | 325 |
| 500 | 355 | 380 | 360 | 385 |
| 750 | 430 | 465 | 430 | 465 |
| 1000 | 485 | 520 | 485 | 515 |
| Six Circuits [See Figure 311.60(D)(3), Detail 3.] | < | < | < | < |
| 8 | 46 | 50 | — | — |
| 6 | 60 | 65 | 63 | 68 |
| 4 | 77 | 83 | 81 | 87 |
| 2 | 98 | 105 | 105 | 110 |
| 1 | 110 | 120 | 115 | 125 |
| 1/0 | 125 | 135 | 130 | 145 |
| 2/0 | 145 | 155 | 150 | 160 |
| 3/0 | 165 | 175 | 170 | 180 |
| 4/0 | 185 | 200 | 190 | 200 |
| 250 | 200 | 220 | 205 | 220 |
| 350 | 240 | 270 | 245 | 275 |
| 500 | 290 | 310 | 290 | 305 |
| 750 | 350 | 375 | 340 | 365 |
| 1000 | 390 | 420 | 380 | 405 |
Note: Refer to 311.60(F) for basis of ampacities and Table 311.10(A) for the temperature rating of the conductor.
Table 311.60(C)(80) Ampacities of Three Insulated Aluminum Conductors Cabled Within an Overall Covering (Three-Conductor Cable) in Underground Electrical Ducts (One Cable per Electrical Duct)
| Conductor Size (AWG or kcmil) | Temperature Rating of Conductor | < | < | < |
|---|---|---|---|---|
| ^ | 2001—5000 Volts Ampacity | < | 5001—35,000 Volts Ampacity | < |
| ^ | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 |
| One Circuit [See Figure 311.60(D)(3), Detail 1.] | < | < | < | < |
| 8 | 46 | 50 | — | — |
| 6 | 61 | 66 | 69 | 74 |
| 4 | 80 | 86 | 89 | 96 |
| 2 | 105 | 110 | 115 | 125 |
| 1 | 120 | 130 | 135 | 145 |
| 1/0 | 140 | 150 | 150 | 165 |
| 2/0 | 160 | 170 | 170 | 185 |
| 3/0 | 180 | 195 | 195 | 210 |
| 4/0 | 205 | 220 | 220 | 240 |
| 250 | 230 | 245 | 245 | 265 |
| 350 | 280 | 310 | 295 | 315 |
| 500 | 340 | 365 | 355 | 385 |
| 750 | 425 | 460 | 440 | 475 |
| 1000 | 495 | 535 | 510 | 545 |
| Three Circuits [See Figure 311.60(D)(3), Detail 2.] | < | < | < | < |
| 8 | 41 | 44 | — | — |
| 6 | 54 | 58 | 59 | 64 |
| 4 | 70 | 75 | 75 | 81 |
| 2 | 90 | 97 | 100 | 105 |
| 1 | 105 | 110 | 110 | 120 |
| 1/0 | 120 | 125 | 125 | 135 |
| 2/0 | 135 | 145 | 140 | 155 |
| 3/0 | 155 | 165 | 160 | 175 |
| 4/0 | 175 | 185 | 180 | 195 |
| 250 | 190 | 205 | 200 | 215 |
| 350 | 230 | 250 | 240 | 255 |
| 500 | 280 | 300 | 285 | 305 |
| 750 | 345 | 375 | 350 | 375 |
| 1000 | 400 | 430 | 400 | 430 |
| Six Circuits [See Figure 311.60(D)(3), Detail 3.] | < | < | < | < |
| 8 | 36 | 39 | — | — |
| 6 | 46 | 50 | 49 | 53 |
| 4 | 60 | 65 | 63 | 68 |
| 2 | 77 | 83 | 80 | 86 |
| 1 | 87 | 94 | 90 | 98 |
| 1/0 | 99 | 105 | 105 | 110 |
| 2/0 | 110 | 120 | 115 | 125 |
| 3/0 | 130 | 140 | 130 | 140 |
| 4/0 | 145 | 155 | 150 | 160 |
| 250 | 160 | 170 | 160 | 170 |
| 350 | 190 | 205 | 190 | 205 |
| 500 | 230 | 245 | 230 | 245 |
| 750 | 280 | 305 | 275 | 295 |
| 1000 | 320 | 345 | 315 | 335 |
Note: Refer to 311.60(F) for basis of ampacities and Table 311.10(A) for the temperature rating of the conductor.
Table 311.60(C)(81) Ampacities of Single Insulated Copper Conductors Directly Buried in Earth
| Conductor Size (AWG or kcmil) | Temperature Rating of Conductor | < | < | < |
|---|---|---|---|---|
| ^ | 2001—5000 Volts Ampacity | < | 5001—35,000 Volts Ampacity | < |
| ^ | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 |
| One Circuit, Three Conductors [See Figure 311.60(D)(3), Detail 9.] | < | < | < | < |
| 8 | 110 | 115 | — | — |
| 6 | 140 | 150 | 130 | 140 |
| 4 | 180 | 195 | 170 | 180 |
| 2 | 230 | 250 | 210 | 225 |
| 1 | 260 | 280 | 240 | 260 |
| 1/0 | 295 | 320 | 275 | 295 |
| 2/0 | 335 | 365 | 310 | 335 |
| 3/0 | 385 | 415 | 355 | 380 |
| 4/0 | 435 | 465 | 405 | 435 |
| 250 | 470 | 510 | 440 | 475 |
| 350 | 570 | 615 | 535 | 575 |
| 500 | 690 | 745 | 650 | 700 |
| 750 | 845 | 910 | 805 | 865 |
| 1000 | 980 | 1055 | 930 | 1005 |
| Two Circuits, Six Conductors [See Figure 311.60(D)(3), Detail 10.] | < | < | < | < |
| 8 | 100 | 110 | — | — |
| 6 | 130 | 140 | 120 | 130 |
| 4 | 165 | 180 | 160 | 170 |
| 2 | 215 | 230 | 195 | 210 |
| 1 | 240 | 260 | 225 | 240 |
| 1/0 | 275 | 295 | 255 | 275 |
| 2/0 | 310 | 335 | 290 | 315 |
| 3/0 | 355 | 380 | 330 | 355 |
| 4/0 | 400 | 430 | 375 | 405 |
| 250 | 435 | 470 | 410 | 440 |
| 350 | 520 | 560 | 495 | 530 |
| 500 | 630 | 680 | 600 | 645 |
| 750 | 775 | 835 | 740 | 795 |
| 1000 | 890 | 960 | 855 | 920 |
Note: Refer to 311.60(F) for basis of ampacities and Table 311.10(A) for the temperature rating of the conductor.
Table 311.60(C)(82) Ampacities of Single Insulated Aluminum Conductors Directly Buried in Earth
| Conductor Size (AWG or kcmil) | Temperature Rating of Conductor | < | < | < |
|---|---|---|---|---|
| ^ | 2001—5000 Volts Ampacity | < | 5001—35,000 Volts Ampacity | < |
| ^ | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 |
| One Circuit, Three Conductors [See Figure 311.60(D)(3), Detail 9.] | < | < | < | < |
| 8 | 85 | 90 | — | — |
| 6 | 110 | 115 | 100 | 110 |
| 4 | 140 | 150 | 130 | 140 |
| 2 | 180 | 195 | 165 | 175 |
| 1 | 205 | 220 | 185 | 200 |
| 1/0 | 230 | 250 | 215 | 230 |
| 2/0 | 265 | 285 | 245 | 260 |
| 3/0 | 300 | 320 | 275 | 295 |
| 4/0 | 340 | 365 | 315 | 340 |
| 250 | 370 | 395 | 345 | 370 |
| 350 | 445 | 480 | 415 | 450 |
| 500 | 540 | 580 | 510 | 545 |
| 750 | 665 | 720 | 635 | 680 |
| 1000 | 780 | 840 | 740 | 795 |
| Two Circuits, Six Conductors [See Figure 311.60(D)(3), Detail 10.] | < | < | < | < |
| 8 | 80 | 85 | — | — |
| 6 | 100 | 110 | 95 | 100 |
| 4 | 130 | 140 | 125 | 130 |
| 2 | 165 | 180 | 155 | 165 |
| 1 | 190 | 200 | 175 | 190 |
| 1/0 | 215 | 230 | 200 | 215 |
| 2/0 | 245 | 260 | 225 | 245 |
| 3/0 | 275 | 295 | 255 | 275 |
| 4/0 | 310 | 335 | 290 | 315 |
| 250 | 340 | 365 | 320 | 345 |
| 350 | 410 | 440 | 385 | 415 |
| 500 | 495 | 530 | 470 | 505 |
| 750 | 610 | 655 | 580 | 625 |
| 1000 | 710 | 765 | 680 | 730 |
Note: Refer to 311.60(F) for basis of ampacities and Table 311.10(A) for the temperature rating of the conductor.
Table 311.60(C)(83) Ampacities of Three Insulated Copper Conductors Cabled Within an Overall Covering (Three-Conductor Cable), Directly Buried in Earth
| Conductor Size (AWG or kcmil) | Temperature Rating of Conductor | < | < | < |
|---|---|---|---|---|
| ^ | 2001—5000 Volts Ampacity | < | 5001—35,000 Volts Ampacity | < |
| ^ | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 |
| One Circuit [See Figure 311.60(D)(3), Detail 5.] | < | < | < | < |
| 8 | 85 | 89 | — | — |
| 6 | 105 | 115 | 115 | 120 |
| 4 | 135 | 150 | 145 | 155 |
| 2 | 180 | 190 | 185 | 200 |
| 1 | 200 | 215 | 210 | 225 |
| 1/0 | 230 | 245 | 240 | 255 |
| 2/0 | 260 | 280 | 270 | 290 |
| 3/0 | 295 | 320 | 305 | 330 |
| 4/0 | 335 | 360 | 350 | 375 |
| 250 | 365 | 395 | 380 | 410 |
| 350 | 440 | 475 | 460 | 495 |
| 500 | 530 | 570 | 550 | 590 |
| 750 | 650 | 700 | 665 | 720 |
| 1000 | 730 | 785 | 750 | 810 |
| Two Circuits [See Figure 311.60(D)(3), Detail 6.] | < | < | < | < |
| 8 | 80 | 84 | — | — |
| 6 | 100 | 105 | 105 | 115 |
| 4 | 130 | 140 | 135 | 145 |
| 2 | 165 | 180 | 170 | 185 |
| 1 | 185 | 200 | 195 | 210 |
| 1/0 | 215 | 230 | 220 | 235 |
| 2/0 | 240 | 260 | 250 | 270 |
| 3/0 | 275 | 295 | 280 | 305 |
| 4/0 | 310 | 335 | 320 | 345 |
| 250 | 340 | 365 | 350 | 375 |
| 350 | 410 | 440 | 420 | 450 |
| 500 | 490 | 525 | 500 | 535 |
| 750 | 595 | 640 | 605 | 650 |
| 1000 | 665 | 715 | 675 | 730 |
Note: Refer to 311.60(F) for basis of ampacities and Table 311.10(A) for the temperature rating of the conductor.
Table 311.60(C)(84) Ampacities of Three Insulated Aluminum Conductors Cabled Within an Overall Covering (Three-Conductor Cable), Directly Buried in Earth
| Conductor Size (AWG or kcmil) | Temperature Rating of Conductor | < | < | < |
|---|---|---|---|---|
| ^ | 2001—5000 Volts Ampacity | < | 5001—35,000 Volts Ampacity | < |
| ^ | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 |
| One Circuit [See Figure 311.60(D)(3), Detail 5.] | < | < | < | < |
| 8 | 65 | 70 | — | — |
| 6 | 80 | 88 | 90 | 95 |
| 4 | 105 | 115 | 115 | 125 |
| 2 | 140 | 150 | 145 | 155 |
| 1 | 155 | 170 | 165 | 175 |
| 1/0 | 180 | 190 | 185 | 200 |
| 2/0 | 205 | 220 | 210 | 225 |
| 3/0 | 230 | 250 | 240 | 260 |
| 4/0 | 260 | 280 | 270 | 295 |
| 250 | 285 | 310 | 300 | 320 |
| 350 | 345 | 375 | 360 | 390 |
| 500 | 420 | 450 | 435 | 470 |
| 750 | 520 | 560 | 540 | 580 |
| 1000 | 600 | 650 | 620 | 665 |
| Two Circuits [See Figure 311.60(D)(3), Detail 6.] | < | < | < | < |
| 8 | 60 | 66 | — | — |
| 6 | 75 | 83 | 80 | 95 |
| 4 | 100 | 110 | 105 | 115 |
| 2 | 130 | 140 | 135 | 145 |
| 1 | 145 | 155 | 150 | 165 |
| 1/0 | 165 | 180 | 170 | 185 |
| 2/0 | 190 | 205 | 195 | 210 |
| 3/0 | 215 | 230 | 220 | 240 |
| 4/0 | 245 | 260 | 250 | 270 |
| 250 | 265 | 285 | 275 | 295 |
| 350 | 320 | 345 | 330 | 355 |
| 500 | 385 | 415 | 395 | 425 |
| 750 | 480 | 515 | 485 | 525 |
| 1000 | 550 | 590 | 560 | 600 |
Note: Refer to 311.60(F) for basis of ampacities and Table 311.10(A) for the temperature rating of the conductor.
Table 311.60(C)(85) Ampacities of Three Triplexed Single Insulated Copper Conductors Directly Buried in Earth
| Conductor Size (AWG or kcmil) | Temperature Rating of Conductor | < | < | < |
|---|---|---|---|---|
| ^ | 2001—5000 Volts Ampacity | < | 5001—35,000 Volts Ampacity | < |
| ^ | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 |
| One Circuit, Three Conductors [See Figure 311.60(D)(3), Detail 7.] | < | < | < | < |
| 8 | 90 | 95 | — | — |
| 6 | 120 | 130 | 115 | 120 |
| 4 | 150 | 165 | 150 | 160 |
| 2 | 195 | 205 | 190 | 205 |
| 1 | 225 | 240 | 215 | 230 |
| 1/0 | 255 | 270 | 245 | 260 |
| 2/0 | 290 | 310 | 275 | 295 |
| 3/0 | 330 | 360 | 315 | 340 |
| 4/0 | 375 | 405 | 360 | 385 |
| 250 | 410 | 445 | 390 | 410 |
| 350 | 490 | 580 | 470 | 505 |
| 500 | 590 | 635 | 565 | 605 |
| 750 | 725 | 780 | 685 | 740 |
| 1000 | 825 | 885 | 770 | 830 |
| Two Circuits, Six Conductors [See Figure 311.60(D)(3), Detail 8.] | < | < | < | < |
| 8 | 85 | 90 | — | — |
| 6 | 110 | 115 | 105 | 115 |
| 4 | 140 | 150 | 140 | 150 |
| 2 | 180 | 195 | 175 | 190 |
| 1 | 205 | 220 | 200 | 215 |
| 1/0 | 235 | 250 | 225 | 240 |
| 2/0 | 265 | 285 | 255 | 275 |
| 3/0 | 300 | 320 | 290 | 315 |
| 4/0 | 340 | 365 | 325 | 350 |
| 250 | 370 | 395 | 355 | 380 |
| 350 | 445 | 480 | 425 | 455 |
| 500 | 535 | 575 | 510 | 545 |
| 750 | 650 | 700 | 615 | 660 |
| 1000 | 740 | 795 | 690 | 745 |
Note: Refer to 311.60(F) for basis of ampacities and Table 311.10(A) for the temperature rating of the conductor.
Table 311.60(C)(86) Ampacities of Three Triplexed Single Insulated Aluminum Conductors Directly Buried in Earth
| Conductor Size (AWG or kcmil) | Temperature Rating of Conductor | < | < | < |
|---|---|---|---|---|
| ^ | 2001—5000 Volts Ampacity | < | 5001—35,000 Volts Ampacity | < |
| ^ | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 | 90°C (194°F) Type MV-90 | 105°C (221°F) Type MV-105 |
| One Circuit, Three Conductors [See Figure 311.60(D)(3), Detail 7.] | < | < | < | < |
| 8 | 70 | 75 | — | — |
| 6 | 90 | 100 | 90 | 95 |
| 4 | 120 | 130 | 115 | 125 |
| 2 | 155 | 165 | 145 | 155 |
| 1 | 175 | 190 | 165 | 175 |
| 1/0 | 200 | 210 | 190 | 205 |
| 2/0 | 225 | 240 | 215 | 230 |
| 3/0 | 255 | 275 | 245 | 265 |
| 4/0 | 290 | 310 | 280 | 305 |
| 250 | 320 | 350 | 305 | 325 |
| 350 | 385 | 420 | 370 | 400 |
| 500 | 465 | 500 | 445 | 480 |
| 750 | 580 | 625 | 550 | 590 |
| 1000 | 670 | 725 | 635 | 680 |
| Two Circuits, Six Conductors [See Figure 311.60(D)(3), Detail 8.] | < | < | < | < |
| 8 | 65 | 70 | — | — |
| 6 | 85 | 95 | 85 | 90 |
| 4 | 110 | 120 | 105 | 115 |
| 2 | 140 | 150 | 135 | 145 |
| 1 | 160 | 170 | 155 | 170 |
| 1/0 | 180 | 195 | 175 | 190 |
| 2/0 | 205 | 220 | 200 | 215 |
| 3/0 | 235 | 250 | 225 | 245 |
| 4/0 | 265 | 285 | 255 | 275 |
| 250 | 290 | 310 | 280 | 300 |
| 350 | 350 | 375 | 335 | 360 |
| 500 | 420 | 455 | 405 | 435 |
| 750 | 520 | 560 | 485 | 525 |
| 1000 | 600 | 645 | 565 | 605 |
Note: Refer to 311.60(F) for basis of ampacities and Table 311.10(A) for the temperature rating of the conductor.
311.60(D) Ampacity Adjustment.
311.60(D)(1) Grounded Shields.
Ampacities shown in Table 311.60(C)(69), Table 311.60(C)(70), Table 311.60(C)(81), and Table 311.60(C)(82) shall apply for cables with shields grounded at one point only. Where shields for these cables are grounded at more than one point, ampacities shall be adjusted to take into consideration the heating due to shield currents.
[!info] Informational Note: Tables other than those listed contain the ampacity of cables with shields grounded at multiple points.
311.60(D)(2) Burial Depth.
Where the burial depth of direct burial or electrical duct bank circuits is modified from the values shown in a figure or table, ampacities shall be permitted to be modified as indicated in 311.60(D)(2)(a) and (D)(2)(b). No ampacity adjustments shall be required where the burial depth is decreased.
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(a) Where burial depths are increased in part(s) of an electrical duct run, a decrease in ampacity of the conductors shall not be required, provided the total length of parts of the duct run increased in depth is less than 25 percent of the total run length.
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(b) Where burial depths are deeper than shown in a specific underground ampacity table or figure, an ampacity derating factor of 6 percent per 300 mm (1 ft) increase in depth for all values of rho shall be permitted.
311.60(D)(3) Electrical Ducts Entering Equipment Enclosures.
At locations where electrical ducts enter equipment enclosures from underground, spacing between such ducts, as shown in Figure 311.60(D)(3), shall be permitted to be reduced without requiring the ampacity of conductors therein to be reduced.
Figure 311.60(D)(3) Cable Installation Dimensions for Use with Table 311.60(C)(77) Through Table 311.60(C)(86).
!
Note: Minimum burial depths to top electrical ducts or cables shall be in accordance with 300.50. Maximum depth to the top of electrical duct banks shall be 750 mm (30 in.) and maximum depth to the top of direct buried cables shall be 900 mm (36 in.).
311.60(D)(4) Ambient Temperature Correction.
Ampacities for ambient temperatures other than those specified in the ampacity tables shall be corrected in accordance with Table 311.60(D)(4) or shall be permitted to be calculated using the following equation:
Equation 311.60(D)(4)
I^{\prime} = I \sqrt{\frac{ T_{c} -T_{a}^{\prime} }{ T_{c} - T_a }}
where:
I\prime= ampacity corrected for ambient temperatureI= ampacity shown in the tablesT_{c}= temperature rating of conductor (°C)T_{a}^{\prime}= new ambient temperature (°C)T_a= ambient temperature used in the table (°C)
Table 311.60(D)(4) Ambient Temperature Correction Factors
For ambient temperatures other than 40°C (104°F), multiply the allowable ampacities specified in the ampacity tables by the appropriate factor shown below.
| Ambient Temperature | < | Temperature Rating of Conductor | < |
|---|---|---|---|
| (°C) | (°F) | 90°C | 105°C |
| 10 or less | 50 or less | 1.26 | 1.21 |
| 11—15 | 51—59 | 1.22 | 1.18 |
| 16—20 | 60—68 | 1.18 | 1.14 |
| 21—25 | 69—77 | 1.14 | 1.11 |
| 26—30 | 78—86 | 1.10 | 1.07 |
| 31—35 | 87—95 | 1.05 | 1.04 |
| 36—40 | 96—104 | 1.00 | 1.00 |
| 41—45 | 105—113 | 0.95 | 0.96 |
| 46—50 | 114—122 | 0.89 | 0.92 |
| 51—55 | 123—131 | 0.84 | 0.88 |
| 56—60 | 132—140 | 0.77 | 0.83 |
| 61—65 | 141—149 | 0.71 | 0.78 |
| 66—70 | 150—158 | 0.63 | 0.73 |
| 71—75 | 159—167 | 0.55 | 0.68 |
| 76—80 | 168—176 | 0.45 | 0.62 |
| 81—85 | 177—185 | 0.32 | 0.55 |
| 86—90 | 186—194 | — | 0.48 |
| 91—95 | 195—203 | — | 0.39 |
| 96—100 | 204—212 | — | 0.28 |
311.60(E) Ampacity in Air.
Ampacities for conductors and cables in air shall be as specified in Table 311.60(C)(67) through Table 311.60(C)(76). Ampacities shall be based on the following:
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(1) Conductor temperatures of 90°C (194°F) and 105°C (221°F)
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(2) Ambient air temperature of 40°C (104°F)
[!info] Informational Note: See 311.60(D)(4) where the ambient air temperature is other than 40°C (104°F).
311.60(F) Ampacity in Underground Electrical Ducts and Direct Buried in Earth.
Ampacities for conductors and cables in underground electrical ducts and direct buried in earth shall be as specified in Table 311.60(C)(77) through Table 311.60(C)(86). Ampacities shall be based on the following:
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(1) Ambient earth temperature of 20°C (68°F)
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(2) Arrangement in accordance with Figure 311.60(D)(3)
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(3) 100 percent load factor
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(4) Thermal resistance (Rho) of 90
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(5) Conductor temperatures 90°C (194°F) and 105°C (221°F)
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(6) Minimum burial depths to the top electrical ducts or cables shall be in accordance with 300.50.
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(7) Maximum depth to the top of electrical duct banks shall be 750 mm (30 in.), and maximum depth to the top of direct-buried cables shall be 900 mm (36 in.).