Allowable Ampacities

Information for:

•Table 1 - Single Copper Conductors in Free Air
•Table 2 - Not more than 3 Copper Conductors in Raceway or Cable
•Table 3 - Single Aluminum Conductors in Free Air
•Table 4 - Not more than 3 Aluminum Conductors in Raceway or Cable

TABLE 1 - ALLOWABLE AMPACITIES† FOR SINGLE COPPER CONDUCTORS IN FREE AIR

Based on Ambient Temperature of 30ºC*

(See Rules 4-004, 8-104, 12-2212, 26-000, 26-742, 42-016 and Tables 5A, 5B, 19, and D3)

* See Table 5A for the correction factors to be applied to the values in Columns 2 to 7 for ambient temperatures over 30°C.

† The ampacity of single-conductor aluminum-sheathed cable is based on the type of insulation used on the copper conductor.

‡ These are maximum allowable conductor temperatures for single conductors run in free air and may be used in determining the ampacity of other conductor types in Table 19, which are so run, as follows:  From Table 19 determine the maximum allowable conductor temperature for that particular type;  then from Table 1 determine the ampacity under the column of corresponding temperature rating.

§ These ratings are based on the use of 90°C insulation on the emerging conductors and for sealing.  Where a deviation has been allowed in accordance with Rule 2-030, mineral-insulated cable may be used at higher temperatures without decrease in allowable ampacity, provided that insulation and sealing material approved for such high temperature is used.

NOTES:

1. The ratings of Table 1 may be applied to a conductor mounted on a plane surface of masonry, plaster wood, or any material having a conductivity not less than 0.4 W/(m°C).
2. For correction factors where from 2 to 4 conductors are present and in contact, see Table 5B.
3. These ampacities are only applicable under special circumstances where the use of insulated conductors having this temperature rating are acceptable.
4. Type R90 silicone wire may be used in ambient temperatures up to 65°C without applying the correction factors for ambient temperatures above 30°C provided the temperature of the conductor at the termination does not exceed 90°C.

TABLE 2 - ALLOWABLE AMPACITIES FOR NOT MORE THAN 3 COPPER CONDUCTORS IN RACEWAY OR CABLE

Based on Ambient Temperature of 30ºC*

(See Rules 4-004, 8-104, 12-012, 12-2212, 26-000, 26-742, 42-008, and 42-016 and Tables 5A, 5C, 19, and D3)

* See Table 5A for the correction factors to be applied to the values in Columns 2 to 7 for ambient temperatures over 30°C.

† The ampacity of aluminum-sheathed cable is based on the type of insulation used on the copper conductors.

‡ These are maximum allowable conductor temperatures for 1, 2, or 3 conductors run in a raceway, or 2 or 3 conductors run in a cable and may be used in determining the ampacity of other conductor types in Table 19, which are so run, as follows:  From Table 19 determine the maximum allowable conductor temperature for that particular type; then from Table 2 determine the ampacity under the column of corresponding temperature rating.

** These ratings are based on the use of 90°C insulation on the emerging conductors and for sealing.  Where a deviation has been allowed in accordance with Rule 2-030, mineral-insulated cable may be used at higher temperatures without decrease in allowable ampacity, provided that insulation and sealing material approved for such higher temperature is used.

†† For 3-wire 120/240 and 120/208V residential services or subservices, the allowable ampacity for sizes No. 6 and No. 2/0 AWG shall be 60A and 200A respectively.  In this case, the 5% adjustment of Rule 8-106(1) cannot be applied.

‡‡ See Table 5C for the correction factors to be applied to the values in Columns 2 to 7 where there are more than 3 conductors in a run of raceway or cable.

NOTES:

1. These ampacities are only applicable under special circumstances where the use of insulated conductors having this temperature rating are acceptable.
2. Type R90 silicone wire may be used in ambient temperatures up to 65°C without applying the correction factors for ambient temperatures above 30°C, provided the temperature of the conductor at the terminations does not exceed 90°C.

TABLE 3 - ALLOWABLE AMPACITIES FOR SINGLE ALUMINUM CONDUCTORS IN FREE AIR

Based on Ambient Temperature of 30ºC*

(See Rules 4-004, 8-104, 12-2212, 26-000, 26-742, 42-008, and 42-016 and Tables 5A, 5B, and D3)

* See Table 5A for the correction factors to be applied to the values in Columns 2 to 7 for ambient temperatures over 30°C.

† The ampacity of single-conductor aluminum-sheathed cable is based on the type of insulation used on the aluminum conductor.

‡ These are maximum allowable conductor temperatures for single conductors run in free air and may be used in determining the ampacity of other conductor types in Table 19, which are so run, as follows:   From Table 19 determine the maximum allowable conductor temperature for that particular type; then from Table 3 determine the ampacity under the column of corresponding temperature rating.

NOTES:

1. The ratings of Table 3 may be applied to a conductor mounted on a plane surface of masonry, plaster, wood, or any material having a conductivity not less than 0.4W/(m°C).
2. For correction factors where from 2 to 4 conductors are present and in contact, see Table 5B
3. These ampacities are only applicable under special circumstances where the use of insulated conductors having this temperature rating are acceptable.

TABLE 4 - ALLOWABLE AMPACITIES FOR NOT MORE THAN 3 ALUMINUM CONDUCTORS IN RACEWAY OR CABLE

Based on Ambient Temperature of 30ºC*

(See Rules 4-004, 8-104, 12-2212, 26-000, 26-742, 42-008, and 42-016 and Tables 5A, 5C, and D3)

* See Table 5A for the correction factors to be applied to the values in Columns 2 to 7 for ambient temperatures over 30°C.

† The ampacity of aluminum-sheathed cable is based on the type of insulation used on the aluminum conductors.

‡These are maximum allowable conductor temperatures for 1, 2, or 3 conductors run in a raceway, or 2 or 3 conductors run in a cable and may be used in determining the capacity of other conductor types in Table 19, which are so run, as follows:  From Table 19 determine the maximum allowable conductor temperature for the particular type;  then from Table 4 determine the ampacity under the column of corresponding temperature rating.

§ See Table 5C for the correction factors to be applied to the values in Columns 2 to 7 where there are more than 3 conductors in a run of raceway or cable.

** For 3-wire 120/240 and 120/208V residential services or subservices, the allowable ampacity for sizes NO. 6, No. 2, and 4/0 AWG shall be 60A, 100A, and 200A respectively.  In this case, the 5% adjustment of Rule 8-106(1) cannot be applied.

NOTE:

1. These ampacities are only applicable under special circumstances where the use of insulated conductors having this temperature rating are acceptable.

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