Solar grids code#
Solar grids plus#

A 200A main breaker and a 60A breaker adds up to 260A, which is 130% of the rated busbar, and not allowed. Therefore, a 10kW inverter would need a 60A breaker (10,000W Г· 240V = 41.6A x 125% = 52.08A, round up to next available size of 60A). That requires a 40A breaker (32A x 125% = 40A). Since a grid-tie inverter is generally running more than 3 hours, it is considered continuous load.В NEC requires theВ breakers be sized at 125% of the inverterвЂ™s rated output. That 30A breaker can handle a 5700W inverter.

Solar grids code#

With a 100A main breaker, and a 30A inverter breaker, I am code compliant with 130A total (100A main breaker + 30A 2-pole inverter input breaker).

In my example in the photos, my 125A breaker box can have a total of 150A (i.e. If both breakers are near each other, the sum can only equal 100% of the busbar. The inverter breaker must be at he opposite end of the breaker box to prevent concentration of the current at one end of the busbar.

Solar grids plus#

What that means is if you have a typical 200A rated main breaker box, and have a 200A main breaker in it, you cannot add another breaker for the inverter that is larger than 40A, because 200A x 120% = 240A, which is the 200A main breaker plus the 40A inverter breaker. 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. Then looking at that photo again, you can see I have a 30A 2-pole breaker at the other end for my solar inverter. Then look at the big main breaker in the box, looking at the photo of the Main Breaker Box Components. In the photo of the label, I have a 125A busbar in my main breaker box. To determine the rating of your main breaker box, read the label on the box. The most common way to connect a residential solar system to the grid is in the main breaker box through a new dedicated breaker, as shown in the schematic.