---
aliases:
  - nec-311
tags:
  - authorship/other
  - destiny/uncertain
  - exclude-from-word-count
  - status/draft
  - topic/construction/electrical
  - type/media/reference
title: 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<br>MV-105* |         90°C<br>105°C         | Dry or wet locations  | Thermoplastic or thermosetting | Jacket, sheath, or armor |

\*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)

Dry Locations, Single Conductor Wet or Dry Locations

Without Jacket

Insulation

With Jacket Single Conductor Multiconductor

Insulation*

Insulation Jacket Insulation Jacket mm mils mm mils mm mils mm mils mm mils mm mils
8 2.79 110 2.29 90 0.76 30 3.18 125 2.03 80 2.29 90
6 2.79 110 2.29 90 0.76 30 3.18 125 2.03 80 2.29 90
4–2 2.79 110 2.29 90 1.14 45 3.18 125 2.03 80 2.29 90

Conductor

Size
(AWG or kcmil)

Dry Locations, Single Conductor Wet or Dry Locations

Without Jacket

Insulation

With Jacket Single Conductor Multiconductor

Insulation*

Insulation Jacket Insulation Jacket mm mils mm mils mm mils mm mils mm mils mm mils
1–2/0 2.79 110 2.29 90 1.14 45 3.18 125 2.03 80 2.29 90
3/0–4/0 2.79 110 2.29 90 1.65 65 3.18 125 2.41 95 2.29 90
213–500 3.05 120 2.29 90 1.65 65 3.56 140 2.79 110 2.29 90
501–750 3.30 130 2.29 90 1.65 65 3.94 155 3.18 125 2.29 90
751–1000 3.30 130 2.29 90 1.65 65 3.94 155 3.18 125 2.29 90
1001–1250 3.56 140 2.92 115 1.65 65 4.32 170 3.56 140 2.92 115
1251–1500 3.56 140 2.92 115 2.03 80 4.32 170 3.56 140 2.92 115
1501–2000 3.56 140 2.92 115 2.03 80 4.32 170 3.94 155 3.56 140
*Under a common overall covering such as a jacket, sheath, or armor.

Conductor

Size
(AWG or kcmil)
25,001–28,000 Volts 28,001–35,000 Volts
100

Percent

Insulation

Level
133

Percent

Insulation

Level
173

Percent

Insulation

Level
100

Percent

Insulation

Level
133

Percent

Insulation

Level
173

Percent

Insulation

Level mm mils mm mils mm mils mm mils mm mils mm mils
1 7.11 280 8.76 345 11.30 445 — — — — — —
1/0–2000 7.11 280 8.76 345 11.30 445 8.76 345 10.67 420 14.73 580

#### 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).

##### 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.

##### Table 311.10(C) Thickness of Insulation for Shielded Solid Dielectric Insulated Conductors Rated 2001 Vol

2001–5000 Volts 5001–8000 Volts 8001–15,000 Volts

Conductor

Size
(AWG or kcmil)
100

Percent

Insulation

Level
100

Percent

Insulation

Level
133

Percent

Insulation

Level
173

Percent

Insulation

Level
100

Percent

Insulation

Level
133

Percent

Insulation

Level
173

Percent

Insulation

Level
100

Percen

Insulat

Leve mm mils mm mils mm mils mm mils mm mils mm mils mm mils mm m
8 2.29 90 — — — — — — — — — — — — — —
6–4 2.29 90 2.92 115 3.56 140 4.45 175 — — — — — — — —
2 2.29 90 2.92 115 3.56 140 4.45 175 4.45 175 5.59 220 6.60 260 — —
1 2.29 90 2.92 115 3.56 140 4.45 175 4.45 175 5.59 220 6.60 260 6.60 2
1/0–2000 2.29 90 2.92 115 3.56 140 4.45 175 4.45 175 5.59 220 6.60 260 6.60 2

### 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 392.80(B).

##### 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)

%% TODO %%

T =

T =
ΔT =

R =

Y =

R =

where:
conductor temperature (°C) ambient temperature (°C) dielectric loss temperature rise dc resistance of conductor at temperature, T component ac resistance resulting from skin effect and proximity effect effective thermal resistance between conductor and surrounding ambient c a d dc c c ca

> [!info] Informational Note:
> The dielectric loss temperature rise (ΔT ) 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 d

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
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

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
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

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
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 Temperature Rating of Conductor

Size
(AWG or kcmil)
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

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 MV90105°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.\]

Conductor

Size
(AWG or kcmil)

Temperature Rating of Conductor
2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity
90°C (194°F) Type MV90105°C
(221°F) Type

MV-105
90°C (194°F) Type

MV-90
105°C (221°F) Type

MV-105
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 MV90105°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

Conductor

Size
(AWG or kcmil)

Temperature Rating of Conductor
2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity
90°C (194°F) Type MV90105°C
(221°F) Type

MV-105
90°C (194°F) Type

MV-90
105°C (221°F) Type

MV-105

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 MV90105°C
(221°F) Type

MV-105
90°C (194°F) Type

MV-90
105°C (221°F) Type

MV-105

Conductor

Size
(AWG or kcmil)

Temperature Rating of Conductor
2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity
90°C (194°F) Type MV90105°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

Conductor

Size
(AWG or kcmil)

Temperature Rating of Conductor
2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity
90°C (194°F) Type MV90105°C
(221°F) Type

MV-105
90°C (194°F) Type

MV-90
105°C (221°F) Type

MV-105
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 MV90105°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 — —

Conductor

Size
(AWG or kcmil)

Temperature Rating of Conductor
2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity
90°C (194°F) Type MV90105°C
(221°F) Type

MV-105
90°C (194°F) Type

MV-90
105°C (221°F) Type

MV-105
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 \[See Figure
311.60(D)(3), Detail 9.\]

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
8 110 115 — —
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

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

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 Temperature Rating of Conductor

Size
(AWG or kcmil)
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

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

Temperature Rating of Conductor
2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity
(AWG or kcmil) 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

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

Temperature Rating of Conductor
2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity
(AWG or kcmil)
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

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.

* (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.

* (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).

##### 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)

%% TODO %%

I' =

I =

T =

T ' =

T = where: ampacity corrected for ambient temperature ampacity shown in the table for T and T temperature rating of conductor (°C) new ambient temperature (°C) 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
(°C)

Temperature Rating of Conductor Ambient

Temperature
(°F)
90°C 105°C
10 or less 1.26 1.21 50 or less
11–15 1.22 1.18 51–59
16–20 1.18 1.14 60–68
21–25 1.14 1.11 69–77
26–30 1.10 1.07 78–86
31–35 1.05 1.04 87–95
36–40 1.00 1.00 96–104
41–45 0.95 0.96 105–113
46–50 0.89 0.92 114–122
51–55 0.84 0.88 123–131
56–60 0.77 0.83 132–140
61–65 0.71 0.78 141–149
66–70 0.63 0.73 150–158
71–75 0.55 0.68 159–167
76–80 0.45 0.62 168–176
81–85 0.32 0.55 177–185
86–90 — 0.48 186–194
91–95 — 0.39 195–203
96–100 — 0.28 204–212 c a c a a

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:

* (1) Ambient earth temperature of 20°C (68°F)

* (2) Arrangement in accordance with Figure 311.60(D)(3)

* (3) 100 percent load factor

* (4) Thermal resistance (Rho) of 90

* (5) Conductor temperatures 90°C (194°F) and 105°C (221°F)

* (6) Minimum burial depths to the top electrical ducts or cables shall be in accordance with 300.50.

* (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.).

#### 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:

* (1) Conductor temperatures of 90°C (194°F) and 105°C (221°F)

* (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.

