How to size a circuit breaker?

For continuous loads: breaker = 125% of load current, rounded up to standard size. For motors: up to 250% of FLA.

What are standard breaker sizes?

Standard sizes per NEC: 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350, 400A.

Continuous load: 20A × 1.25 = 25A. Next standard size = 25A breaker.

NEC requires different multipliers: continuous loads (≥3 hrs): ×1.25. Motors: up to ×2.5 of FLA.

The calculated value is rounded up to the next standard breaker size: 15, 20, 25, 30, 40, 50, 60, 70, 80, 90, 100, 125, 150, 175, 200A.

Load × 1.25 (continuous), round up to standard size.

15, 20, 25, 30, 40, 50, 60... up to 400A.

20 × 1.25 = 25A. Use 25A breaker.