| Item | Value |
|---|---|
| Breaker type | Single-pole, 120 V |
| Recommended copper conductor | 14 AWG |
| Recommended aluminum conductor | 12 AWG |
| Minimum per NEC Table 310.16, 75°C | 14 AWG copper (20 A, limited to 15 A by NEC 240.4(D)) |
| Minimum NM-B cable, 60°C column | 14 AWG copper (15 A) |
| Equipment grounding conductor | 14 AWG copper / 12 AWG aluminum (NEC Table 250.122) |
| Maximum continuous load (125% rule) | 12 A |
| Maximum non-continuous load | 15 A |
General lighting circuits, bedroom and living-room receptacles, smoke alarms, ceiling fans, garage door openers
| Load | Notes |
|---|---|
| General lighting | Up to 1440 W continuous |
| Bedroom receptacles | AFCI required — NEC 210.12 |
| Smoke and CO alarms | Often on a dedicated 15 A circuit |
| Ceiling fans and light fixtures | Typical whole-room circuit |
15 A is the smallest standard branch circuit in a dwelling. NEC 240.4(D)(3) caps 14 AWG copper at 15 A even though Table 310.16 rates it 20 A at 75°C — this is why you can never legally put 14 AWG on a 20 A breaker.
GFCI required for receptacles in bathrooms, garages, outdoors, crawl spaces, unfinished basements, kitchens, laundry areas, and within 6 feet of any sink (NEC 210.8). AFCI required for most dwelling living areas (NEC 210.12).
| One-way run | Drop | % of 120V | Verdict |
|---|---|---|---|
| 25 ft | 2.35 V | 2.0% | Within the 3% branch-circuit target |
| 50 ft | 4.71 V | 3.9% | Over 3% — upsize one gauge |
| 75 ft | 7.07 V | 5.9% | Well over 3% — upsize two gauges or more |
| 100 ft | 9.42 V | 7.8% | Well over 3% — upsize two gauges or more |
| 150 ft | 14.13 V | 11.8% | Well over 3% — upsize two gauges or more |
| 200 ft | 18.84 V | 15.7% | Well over 3% — upsize two gauges or more |
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 12 A usable on a 15 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.
14 AWG copper or 12 AWG aluminum, per NEC Table 310.16 at the 75°C column. The equipment grounding conductor is 14 AWG copper per NEC Table 250.122.
12 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 15 A.
14 AWG copper or 12 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 14 AWG copper is rated 15 A. That is why NM-B sometimes needs a larger conductor than THHN in conduit for the same breaker.