| Item | Value |
|---|---|
| Breaker type | Single-pole, 120 V |
| Recommended copper conductor | 12 AWG |
| Recommended aluminum conductor | 10 AWG |
| Minimum per NEC Table 310.16, 75°C | 12 AWG copper (25 A, limited to 20 A by NEC 240.4(D)) |
| Minimum NM-B cable, 60°C column | 12 AWG copper (20 A) |
| Equipment grounding conductor | 12 AWG copper / 10 AWG aluminum (NEC Table 250.122) |
| Maximum continuous load (125% rule) | 16 A |
| Maximum non-continuous load | 20 A |
Kitchen small-appliance circuits, bathroom receptacles, laundry, garage and outdoor receptacles, workshop tools
| Load | Notes |
|---|---|
| Kitchen small-appliance circuits | Two required — NEC 210.52(B) |
| Bathroom receptacle circuit | Dedicated 20 A required — NEC 210.11(C)(3) |
| Laundry receptacle circuit | Dedicated 20 A required — NEC 210.11(C)(2) |
| Dishwasher | Commonly 15 A, often wired 20 A |
| Garbage disposal | Typically 15 A or 20 A |
| Microwave (built-in) | Dedicated 20 A circuit |
20 A on 12 AWG copper is the workhorse circuit of modern residential wiring. NEC 240.4(D)(5) caps 12 AWG copper at 20 A despite the 25 A figure in Table 310.16.
GFCI required for all kitchen countertop, bathroom, garage, outdoor, basement, and laundry receptacles (NEC 210.8(A)). AFCI required in most dwelling rooms (NEC 210.12(A)).
| One-way run | Drop | % of 120V | Verdict |
|---|---|---|---|
| 25 ft | 1.98 V | 1.6% | Within the 3% branch-circuit target |
| 50 ft | 3.96 V | 3.3% | Over 3% — upsize one gauge |
| 75 ft | 5.94 V | 4.9% | Over 3% — upsize one gauge |
| 100 ft | 7.92 V | 6.6% | Well over 3% — upsize two gauges or more |
| 150 ft | 11.88 V | 9.9% | Well over 3% — upsize two gauges or more |
| 200 ft | 15.84 V | 13.2% | 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 16 A usable on a 20 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.
12 AWG copper or 10 AWG aluminum, per NEC Table 310.16 at the 75°C column. The equipment grounding conductor is 12 AWG copper per NEC Table 250.122.
16 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 20 A.
12 AWG copper or 10 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 12 AWG copper is rated 20 A. That is why NM-B sometimes needs a larger conductor than THHN in conduit for the same breaker.