Motor Circuit Calculator
Pick the motor, get the Article 430 numbers: table FLA, minimum conductor ampacity, and the maximum breaker or fuse.
Table FLA
8 A
Min conductor (125%)
10.0 A
Suggested Cu 75°C
#14
Max OCPD (250%)
20 A
FLA from NEC Tables 430.248/430.250 (use the table, not the nameplate, for conductors and OCPD). Conductors per 430.22 at 125% of FLA; maximum branch protection per Table 430.52 rounded up to the next standard size per 430.52(C)(1) Ex. 1. Overload protection (430.32) DOES use the nameplate and is separate from this. Suggested wire ignores voltage drop and derating — check those too. Verify against the current code.
The part that trips people up
Motor circuits break the "breaker protects the wire" intuition. The branch-circuit device (sized big — up to 250% for a breaker) only protects against shorts and ground faults, because it has to let the starting inrush through. The overload protection — sized near the nameplate current per 430.32 — is what protects the motor and conductors from running too hard. Two different devices, two different jobs, and the reason a 10 A motor can legally sit behind a 25 A breaker.
Remember: conductors and branch protection come from the table FLA, overloads from the nameplate. It's the most-missed question on every journeyman exam for a reason.