1 AWG ampacity by temperature column
| Conductor | 60°C | 75°C | 90°C | 240.4(D) |
|---|---|---|---|---|
| Copper | 110 A110 A breaker | 130 A150 A breaker | 145 A150 A breaker | no cap |
| Aluminum | 85 A90 A breaker | 100 A100 A breaker | 115 A125 A breaker | no cap |
Ampacities are NEC Table 310.16 values for a conductor at 30°C ambient in a raceway, cable, or direct burial with three or fewer current-carrying conductors. Ambient correction and conductor adjustment are applied to these numbers before the 240.4(D) cap is checked, never after it.
What size breaker for 1 gauge wire
- 1 AWG copper: 110 A on a 60°C column and 150 A on a 75°C column.
- 1 AWG aluminum: 90 A on a 60°C column and 100 A on a 75°C column.
No small-conductor cap applies at this size, so the device follows the column the equipment is listed for: 110 A on the 60°C column and 150 A on the 75°C column. Where an ampacity falls between standard ratings, 240.4(B) permits the next size up, so 150 A protects the 130 A 75°C ampacity. It relaxes the device rather than the conductor: 210.19(A)(1) still requires an ampacity at least equal to the calculated load. The allowance does not reach a multioutlet branch circuit supplying receptacles for cord-and-plug-connected portable loads, and it stops at an 800 A device. Aluminum at this size takes 90 A at 60°C and 100 A at 75°C, since 240.4(B) carries the device to the next standard rating where the ampacity falls between two. 334.80 and 340.80 hold NM-B and UF-B cable to the 60°C column whatever the terminals are marked, so a cable assembly is read from the left-hand column while conductors in raceway are read from the column the equipment is listed for.
What 1 gauge wire is used for
- 125 A services and feeders with 75°C terminations
- Single-conductor pulls for feeders
- Equipment grounding conductor on 600 A circuits
One gauge copper carries 110 A at 60°C, which is itself a standard rating, so a 110 A device needs no next-size-up arithmetic. At 75°C it carries 130 A, and 240.4(B) permits 150 A, the next rating in 240.6(A) above it. The distance between those two answers is decided entirely by 110.14(C) and the termination markings.
This is the conductor a 125 A service uses when the equipment is listed for 75°C conductors, and 1/0 is what the same service uses when it is not. That single column of difference is why service conductors are ordered after the panel and the meter socket are chosen rather than before.
Table 250.122 makes 1 AWG copper the equipment grounding conductor for a 600 A circuit, and Table 250.66 never lists it, so it is never a grounding electrode conductor. Aluminum 1 AWG is a 100 A conductor on a 75°C column, and 125 A appears only in the 90°C column.
Grounding with 1 AWG
As an equipment grounding conductor, 1 AWG is sized from the overcurrent device rather than from the phase conductors. Table 250.122 names 1 AWG copper on the 600 A row and 1 AWG aluminum on the 400 A row. 250.122(B) raises the ground in the same proportion as the phase conductors when they are increased for voltage drop, and 250.122(A) caps it at the size of the conductors it runs with.
Table 250.66 never lists 1 AWG as a grounding electrode conductor, so it is used for phase conductors, neutrals, and equipment grounds rather than for the connection to earth.
Voltage drop and run limits
Chapter 9 Table 8 lists 1 AWG copper at 0.154 ohms per 1000 ft at 75°C and aluminum at 0.253 ohms per 1000 ft. Resistance is what a voltage-drop calculation multiplies by current and length, so a conductor twice as long drops twice the volts.
| Conductor | 120 V single phase | 240 V single phase | 240 V three phase |
|---|---|---|---|
| 1 AWG copper at 110 A | 105 ft | 210 ft | 245 ft |
| 1 AWG aluminum at 85 A | 80 ft | 165 ft | 190 ft |
NEC 210.19(A)(1) Informational Note 4 recommends keeping branch-circuit drop at or below 3%. The lengths above are floored to the nearest 5 ft so a listed length never exceeds the computed limit, and they leave reactance out, which makes a large conductor in steel raceway fall short. Halving the current doubles the distance.
Where 1 AWG sits
| Conductor | 60°C | 75°C | 90°C |
|---|---|---|---|
| 2 AWG copper | 95 A | 115 A | 130 A |
| 1 AWG copper | 110 A | 130 A | 145 A |
| 1/0 AWG copper | 125 A | 150 A | 170 A |
1 AWG questions
- How many amps can 1 gauge wire handle?
- 1 AWG copper handles 110 A at 60°C, 130 A at 75°C, and 145 A at 90°C. No 240.4(D) cap applies at this size, so the breaker follows the column: 110 A at 60°C and 150 A at 75°C. Aluminum at the same size handles 85 A, 100 A, and 115 A.
- What size breaker for 1 gauge wire?
- 110 A on the 60°C column and 150 A on the 75°C column. Where an ampacity falls between standard ratings, 240.4(B) permits the next size up, so 150 A protects the 130 A 75°C ampacity. It relaxes the device rather than the conductor, so a load at the full rating still needs the larger size. Aluminum takes 90 A at 60°C and 100 A at 75°C.
- What is 1 gauge wire used for?
- 125 A services and feeders with 75°C terminations; single-conductor pulls for feeders; equipment grounding conductor on 600 A circuits. One gauge copper carries 110 A at 60°C, which is itself a standard rating, so a 110 A device needs no next-size-up arithmetic. At 75°C it carries 130 A, and 240.4(B) permits 150 A, the next rating in 240.6(A) above it. The distance between those two answers is decided entirely by 110.14(C) and the termination markings.
- What size ground wire with 1 gauge conductors?
- 1 AWG copper is the equipment grounding conductor for 600 A circuits in Table 250.122, and 1 AWG aluminum is the ground for 400 A circuits. The ground is sized from the overcurrent device rather than from the phase conductors, and 250.122(B) raises it in the same proportion if the phase conductors are increased for voltage drop. It never has to be larger than the conductors it runs with.
- Is 1 AWG aluminum as good as copper?
- It carries less. In Table 310.16, 1 AWG aluminum is 85 A, 100 A, and 115 A against 110 A, 130 A, and 145 A for copper, so a load that copper serves at this size usually needs one size larger in aluminum. The lugs and devices it lands on have to be listed for aluminum conductors.