Solar Backfeed Breaker Size

Understand that corresponds to 32a of pv current maximum.

Solar backfeed breaker size.

We sometimes see people adding a 60 or 80 a breaker instead. Having said that a 200a rated panel with a 200a main breaker would allow up to 40a of backfeed breakers placed at the opposite end of the panel busbars from the main breaker. However if we add our pv breakers into a sub panel that is dedicated to only the pv breakers we can land the sub panel into a 40a breaker in the main panel board 10 4a 21a 31 4a x 1 25 39 25a. The sizing of back feed breakers is another point of difficulty.

Select the breaker size that can carry the current with common breaker sizes being 30 amps 40 amps or 50 amps. Nec705 12 b 2 3 b states that where there are two power sources the grid and the solar inverter the sum of their breakers cannot equal more than 120 of the busbar rating of the breaker box. Now these are often included with some inverters but it s a good idea to check. I am not a code expert or electrician.

Use the ampacity tables to select the cable corresponding to the breaker size with a 30 amp breaker requiring a 10 3 cable a 40 amp breaker an 8 3 cable and a 50 amp breaker a 6 3 cable. Then looking at that photo again you can see i have a 30a 2 pole breaker at the other end for my solar inverter.