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	Teflon
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	Teflon
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	Teflon
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	Teflon
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