| Item | Value |
|---|---|
| Breaker type | Double-pole, 240 V |
| Recommended copper conductor | 6 AWG |
| Recommended aluminum conductor | 4 AWG |
| Minimum per NEC Table 310.16, 75°C | 6 AWG copper (65 A) |
| Minimum NM-B cable, 60°C column | 4 AWG copper (70 A) |
| Equipment grounding conductor | 10 AWG copper / 8 AWG aluminum (NEC Table 250.122) |
| Maximum continuous load (125% rule) | 48 A |
| Maximum non-continuous load | 60 A |
Sub-panels, tankless water heaters, large central air conditioning, 48 A Level 2 EV chargers, electric furnaces
| Load | Notes |
|---|---|
| Detached garage or shop sub-panel | 60 A feeder is very common |
| Tankless electric water heater | Often two or three 60 A circuits |
| Level 2 EV charger (48 A) | 48 × 1.25 = 60 A circuit |
| Large central air conditioner | Check nameplate MOCP |
| Electric furnace | Usually multiple staged circuits |
60 A is where the difference between wire types matters most. 6 AWG copper THHN on 75°C terminations gives 65 A and works. 6 AWG NM-B is limited to the 60°C column at 55 A and does not work — a 60 A circuit in NM-B cable needs 4 AWG.
Outdoor receptacle outlets up to 250 V and 50 A require GFCI under NEC 210.8. Sub-panel feeders themselves do not, but remember a sub-panel must have its neutral and ground bars separated, with four conductors in the feeder (NEC 250.32).
| One-way run | Drop | % of 240V | Verdict |
|---|---|---|---|
| 25 ft | 1.47 V | 0.6% | Within the 3% branch-circuit target |
| 50 ft | 2.95 V | 1.2% | Within the 3% branch-circuit target |
| 75 ft | 4.42 V | 1.8% | Within the 3% branch-circuit target |
| 100 ft | 5.89 V | 2.5% | Within the 3% branch-circuit target |
| 150 ft | 8.84 V | 3.7% | Over 3% — upsize one gauge |
| 200 ft | 11.78 V | 4.9% | Over 3% — upsize one gauge |
The 80% rule: a continuous load is one expected to run for three hours or more — EV chargers, electric heat, and most commercial lighting. NEC 210.20(A) requires the overcurrent device to be rated at not less than 125% of that continuous load, which leaves 48 A usable on a 60 A breaker. A breaker that trips after an hour or two under a steady load is usually a continuous-load sizing mistake, not a faulty breaker.
6 AWG copper or 4 AWG aluminum, per NEC Table 310.16 at the 75°C column. The equipment grounding conductor is 10 AWG copper per NEC Table 250.122.
48 amps. NEC 210.19(A)(1) and 210.20(A) require the circuit to be rated at 125% of a continuous load — one that runs for three hours or more — which works out to 80% of the breaker rating available for continuous use. Non-continuous loads may use the full 60 A.
10 AWG copper or 8 AWG aluminum, from NEC Table 250.122. The table lists maximum overcurrent device ratings, so you round up to the next listed row. If the circuit conductors are upsized for voltage drop, NEC 250.122(B) requires the ground to be upsized proportionally too.
Yes. NEC 334.80 requires NM-B ampacity to be taken from the 60°C column of Table 310.16, where 4 AWG copper is rated 70 A. That is why NM-B sometimes needs a larger conductor than THHN in conduit for the same breaker.