AC Disconnect & Breaker Calculator
Size AC disconnects and breakers for solar inverters per NEC requirements.
NEC Requirements Summary
NEC 705.12(B)(2) - 120% Rule
The sum of the main breaker and all solar breakers cannot exceed 120% of the bus bar rating.
Main Breaker + Solar Breakers <= 1.2 x Bus Rating
NEC 690.8 - Circuit Sizing
Inverter output circuits must be sized at 125% of maximum continuous current.
NEC 690.13 - Disconnect
AC disconnect must be rated for maximum circuit current and voltage. Must be accessible and lockable.
Standard Breaker Sizes
Common residential/commercial breaker ratings:
15A, 20A, 25A, 30A, 35A, 40A, 45A, 50A, 60A, 70A, 80A, 100A
Wire Sizing Guide (Copper THWN)
| Breaker | Min Wire | Ampacity (75C) |
|---|---|---|
| 20A | 12 AWG | 25A |
| 30A | 10 AWG | 35A |
| 40A | 8 AWG | 50A |
| 50A | 6 AWG | 65A |
| 60A | 6 AWG | 65A |
| 100A | 3 AWG | 100A |