About The Circuit Breaker Sizing Helper

The Circuit Breaker Sizing Helper estimates design current after continuous-load and derating factors, then selects the next listed standard breaker size and checks cable ampacity.

How to Use the Circuit Breaker Sizing Helper Online

1. Enter the load current and continuous-load factor.
2. Set derating percentage and available cable ampacity.
3. Run the helper to review selected breaker size and whether it fits the cable ampacity.

Choosing Options Correctly

Use factors from the applicable electrical code and installation conditions. Breaker type, trip curve, fault rating, coordination, conductor insulation, ambient temperature, and enclosure derating still need engineering review.

Common Use Cases

• Choose a practical next standard breaker rating.
• Check if a cable ampacity is too low for the selected breaker.
• Compare derating and continuous-load assumptions.

Quick FAQ

Does this pick the exact breaker model?
No. It suggests a sizing direction; final selection depends on code rules, trip curve, interrupt rating, poles, enclosure, and coordination.

Should a failed cable check be ignored?
No. Conductor ampacity, voltage drop, derating, insulation, and installation method must support the selected breaker.

What load current should I enter?
Use the design current for the load and apply continuous-load rules or demand factors according to the applicable code.

Can I use it for safety-critical panels?
Use it only as a helper. Final breaker sizing should be reviewed against local electrical code and equipment documentation.