Solar Panel Circuit Breaker Size

Breaker box for ac distribution rated for 40a.

Solar panel circuit breaker size.

The general rule of thumb is that circuit breaker size should be 125 of the ampacity of cable and wire or the circuit which has to be protected by the cb. A maximum output current of 22a multiplied by a 125 percent safety factor equals 27 5a. Nec requires the breakers be sized at 125 of the inverter s rated output. 200a x 1 2 200a 40a in this example the maximum output of our pv system can be 40a or approximately 9 6kw.

If the panels are connected in series the voltage of each panel is added but the amperage stays the same. The size of this fuse is dependent on how many solar panels you have and how they are connected series parallel or series parallel. This provides for a 30a input from the inverter and 3 x 15a 1 x 20a load circuits. Since a grid tie inverter is generally running more than 3 hours it is considered continuous load.

This box accommodates 3 x 1 wide single pole or double pole tandem breakers. Two standard pv breaker examples. This would satisfy the busbar rating without an issue. So for example if you have a 200a service you cannot install more than 40a of solar circuit breakers 200 0 2.

To determine the appropriate size of circuit breaker for single phase supply it depends on multiple factors like type of load cable material and environment temperature etc. There is a code rule nec 690 64 b 2 that s says you must not exceed a certain size circuit breaker for solar. If the utility requires a disconnect between the inverter and main panel board this could be a 60a fused or non fused disconnect dependig on their requirements. This happens to be a standard breaker size.

Our most popular selection is 30 15 15 20 15 15. This is defined as 20 of the overall home s service rating. Take 35 5a x 1 25 44 4a round up to the next standard trade size which will be 50a. In it we have a 200 amp main breaker.

From there you d land your inverter s output into a 50a breaker and your done.