Two different sizing rules in the same calculator — a general continuous/non-continuous load, and a motor branch circuit sized for starting-current withstand instead of running current.
| General load — continuous | 80 A |
| General load — non-continuous | 20 A |
| Cable ampacity (Iz) | 130 A |
| Motor full-load current (FLC) | 34 A |
| Motor category | "Other" (NEC Table 430.52(C)(1)) |
| OCPD type (motor path) | Time-delay fuse |
NEC 210.19(A)(1)/215.2(A)(1) require 125% of continuous load plus 100% of non-continuous load.
NEC 430.52(C)(1) sizes the branch-circuit OCPD as a percentage of motor full-load current to survive inrush/starting current, not steady-state running current. "Other" motors on a time-delay fuse use 175%.
If the standard 175% size genuinely can't carry the motor's starting current without nuisance tripping, the exception permits going up to 225% for a time-delay fuse — but only as high as needed, and rounded down to the nearest standard size.
| Check | Requirement | Actual | Status |
|---|---|---|---|
| General load OCPD protects the cable | OCPD ≤ Iz | 125 A ≤ 130 A | ✓ PASS |
| Motor branch OCPD within NEC 430.52 window | 60 A – 70 A (standard to exception ceiling) | 60 A recommended | ✓ PASS |
Key insight: Motor branch-circuit protection is deliberately sized off starting-current withstand (via a percentage of FLC), not the general continuous-load rule — a motor's running current is far below its OCPD rating by design, because the device has to ride through several seconds of inrush at 5-8x FLC without tripping.
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Open Circuit Breaker & Fuse Sizer calculator →A motor's OCPD has to survive its own starting current — typically several times FLC for a few seconds during across-the-line starting — without tripping, which is why NEC 430.52 permits sizing it well above running current. A general load's OCPD only has to cover normal continuous operation with a duty-cycle margin, so it stays much closer to actual load.
NEC 240.4(B) allows using the next higher standard OCPD size than the cable's ampacity in specific circumstances (generally up to 800 A, and only where the ampacity doesn't itself correspond to a standard size) — but if that exception doesn't apply, the cable must be upsized instead of oversizing the protective device beyond what the conductor can safely carry.