Maximum Ampacities for Wire
Maximum Ampacities for Wire
The following table shows the allowable ampacities of conductors (wires) in conduit, raceway, cable or directly buried, based on ambient temperature of 30 degrees Celsius (86 degrees Fahrenheit). National Electrical Code (NEC) allows rounding up cable ampacity to next size standard fuse or breaker.
Wire Size | Copper Conductor Temp Rating | Aluminum Conductor Temp Rating | ||
75 Degrees Celsius (167 Degrees Fahrenheit) | 90 Degrees Celsius (194 Degrees Fahrenheit) | 75 Degrees Celsius (167 Degrees Fahrenheit) | 90 Degrees Celsius (194 Degrees Fahrenheit) | |
*14 | 20 | 25 | ||
*12 | 25 | 30 | 20 | 25 |
*10 | 35 | 40 | 30 | 35 |
8 | 50 | 55 | 40 | 45 |
6 | 65 | 75 | 50 | 60 |
4 | 85 | 95 | 65 | 75 |
2 | 115 | 130 | 90 | 100 |
1 | 130 | 150 | 100 | 115 |
1/0 | 150 | 170 | 120 | 135 |
2/0 | 175 | 195 | 135 | 150 |
3/0 | 200 | 225 | 155 | 175 |
4/0 | 230 | 260 | 180 | 205 |
NEC specifies that the over-current protection device not exceed 30A for 10 AWG wire, 20A for 12 AWG wire and 15A for 14 AWG wire.
For ambient temperatures above, multiply the allowable ampacities by the correction factor listed under the insulation temperature rating below:
Temperature range | 75 Degrees Fahrenheit Insulation | 90 Degrees Fahrenheit Insulation | |
31-35 Degrees Celsius | 87-95 Degrees Fahrenheit | 0.94 | 0.96 |
36-40 Degrees Celsius | 96-104 Degrees Fahrenheit | 0.88 | 0.91 |
41-45 Degrees Celsius | 105-113 Degrees Fahrenheit | 0.82 | 0.87 |
46-50 Degrees Celsius | 114-122 Degrees Fahrenheit | 0.75 | 0.82 |
51-55 Degrees Celsius | 123-131 Degrees Fahrenheit | 0.67 | 0.76 |
56-60 Degrees Celsius | 132-140 Degrees Fahrenheit | 0.58 | 0.71 |
Recommended Inverter Cable and Overcurrent Protection
Use this table to decide cable size and fuse or breaker size for common inverter models. Smaller cable sizes can be used if fuse or breaker size is reduced but this can cause problems if the inverter is run near its maximum output wattage. Larger cables may be necessary if the distance from the inverter to the battery is greater than 10 feet.
Inverter Voltage | Continuous Watts | Maximum Inverter Input Amps | Fuse Size (amps) | Circuit Breaker (amps) | Wire Size (AWG) |
12 Volt | 600 800 1000 1500 2400 2500 2800 3000 |
80 107 134 200 320 334 382 400 |
80 110 200 300 400 400 400 400 |
80 110 175 250 250 250 250 250 |
2 2 2/0 4/0 4/0 4/0 4/0 4/0 |
24 Volt | 600 800 1000 1500 2400 2500 3000 3500 4000 |
40 54 67 100 160 167 200 230 265 |
50 75 80 110 200 200 300 300 300 |
50 75 100 110 175 175 250 250 250 |
8 4 2 2/0 2/0 2/0 4/0 4/0 4/0 |
48 Volt | 3000 3600 4000 5500 |
76 90 148 185 |
110 110 200 400 |
110 110 175 250 |
2/0 2/0 2/0 4/0 |
For more info and recommendations on pairing the right fuse and cables to your DC to AC power inverter, watch Jeff’s YouTube video below:
DC to AC Inverter Fuse and Cable Sizing
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