Size AC circuit breakers for PV inverter connections including 120% rule backfeed calculations per NEC 705.12.
Input Parameters
Results
--
PV Breaker Size
A
--
Max Backfeed (120% rule)
A
--
Total PV Backfeed
A
--
120% Rule Compliance
Note: The 120% rule allows busbar to be loaded to 120% of rating. PV breaker must be at opposite end from main. Supply-side connection (705.12(A)) avoids the 120% rule.
Reference
PV Breaker = Inverter Output x 1.25
120% Rule: Busbar x 1.2 >= Main + PV Breaker(s)
Max Backfeed = Busbar x 1.2 - Main Breaker
Per NEC 705.12(B)(2)(3)