Current Carrying Capacity of Copper Conductors

Published in Conductors

Current carrying capacity is defined as the amperage a conductor can safely carry before melting occurs in the conductor and/or the insulation. There are many factors that will limit the amount of current that can be passed through a wire. Determining factors include:

Conductor Size—The larger the circular mil area, the greater the current capacity.

Insulation—The amount of heat generated should never exceed the maximum temperature rating of the insulation material.

Ambient (surrounding) temperature—The higher the ambient temperature, the less heat required to reach the maximum temperature rating of the insulation.

Conductor Number—Heat dissipation is lessened as the number of individually insulated conductors, bundled together, is increased.

Installation Conditions—Restricting the heat dissipation by installing the conductor in conduit, duct, trays or raceways lessens the current carrying capacity. This restriction can be alleviated somewhat by using proper ventilation methods, forced air cooling, etc.

Taking into account all the variables involved, no simple chart of current ratings can be developed. The chart below should be used ONLY as an estimations guide.

 

Derating Factors
# Conductors
Factors
1 1.0
2-3 0.95
4-5 0.81
6-15 0.72
16-30 0.53
31-100 0.38

 

To use this chart, select the gauge of conductor that will give the desired amperage under the 10°C temperature rise line. For a bundled construction, multiply the amperage by the derating factor to find the recommended current capacity for individual conductor in a bundle.


 

Maximum 1 Ampere - Ambient Temp. 20°C (78°F)
# Conductor
AWG Size Solid Strand
Ref. Resist Ohms/1000 ft PVC
80°C
PVC
105°C
Polyethylene TFE
24 25.7 3.7 11.5 3.7 23.5
22 16.2 4.6 14.9 4.6 31.2
20 10.1 6.1 19.0 6.1 41.0
18 6.39 8.3 25.0 8.3 56.0
16 4.02 11.0 35.0 11.0 68.0
14 2.52 14.0 46.0 14.0 92.0
12 1.59 19.0 60.0 19.0 118.0
10 0.99 25.0 83.0 25.0 160.0
8 0.63 36.0 113.0 36.0 212.0
6 0.39 49.0 152.0 49.0 283.0
Maximum 2-3 - Ambient Temp. 20°C (78°F)
# Conductor
AWG Size Solid Strand
Ref. Resist Ohms/1000 ft PVC
80°C
PVC
105°C
Polyethylene TFE
24 25.7 2.3 7.2 2.3 14.7
22 16.2 2.9 9.3 2.9 19.5
20 10.1 3.8 12.0 3.8 26.0
18 6.39 5.2 16.0 5.2 35.0
16 4.02 6.8 22.0 6.8 43.0
14 2.52 9.1 29.0 9.1 58.0
12 1.59 12.0 38.0 12.0 74.0
10 0.99 16.0 52.0 16.0 100.0
8 0.63 23.0 71.0 23.0 133.0
6 0.39 31.0 95.0 31.0 177.0
Maximum 4-5 - Ambient Temp. 20°C (78°F)
# Conductor
AWG Size Solid Strand
Ref. Resist Ohms/1000 ft PVC
80°C
PVC
105°C
Polyethylene TFE
24 25.7 1.8 5.8 1.8 11.8
22 16.2 2.3 7.4 2.3 15.6
20 10.1 3.0 9.6 3.0 20.0
18 6.39 4.2 12.0 4.2 28.0
16 4.02 5.4 17.0 5.4 34.0
14 2.52 7.3 23.0 7.3 46.0
12 1.59 9.6 30.0 9.6 59.0
10 0.99 12.0 41.0 12.0 80.0
8 0.63 18.0 56.0 18.0 106.0
6 0.39 24.0 76.0 24.0 141.0
Maximum 6-15 - Ambient Temp. 20°C (78°F)
# Conductor
AWG Size Solid Strand
Ref. Resist Ohms/1000 ft PVC
80°C
PVC
105°C
Polyethylene TFE
24 25.7 1.6 5.0 1.6 10.3
22 16.2 2.0 6.5 2.0 13.7
20 10.1 2.7 8.4 2.7 18.2
18 6.39 3.6 11.0 3.6 24.0
16 4.02 4.8 15.0 4.8 30.0
14 2.52 6.4 20.0 6.4 40.0
12 1.59 8.4 26.0 8.4 51.0
10 0.99 11.0 36.0 11.0  
8 0.63 16.0 49.0 16.0  
6 0.39 21.0 66.0 21.0 123.0
Read 68271 times Last modified on Monday, 24 March 2014 13:06

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