I'm planning to install a large 16kw solar system and want to ensure my electrical setup can handle it. I currently have a 200/200 amp main breaker but I suspect I'll need to derate it to a 175 amp breaker to allow for a 65 amp PV breaker. I also have an existing subpanel in an outbuilding where I want the solar array installed, but it's already full with a 70 amp breaker. I know I'll need to upgrade that subpanel, but I have some confusion about how the 120% rule applies here. Will just a subpanel upgrade be enough once I derate the main breaker, or will there be more complications?
2 Answers
The specific panel brand you're using can affect your setup. For example, some brands like SquareD might have a higher internal rating than what’s printed on the panel, which would influence how you need to apply the 120% rule. Make sure your electrician checks the actual panel you have and whether it can support a larger load before you proceed with any purchases or upgrades. Planning ahead is crucial, especially when you're managing a significant solar installation!
You're hitting on quite a few important points. The 120% rule does apply here, especially since the subpanel feeds multiple devices. You'll want to figure out the total load on your subpanel to see if you need more than just replacing it. If you go with a 65A breaker, remember to check if your current wiring can handle that capacity. Also, you might want to consider if a line-side tap could be a viable option; it connects your subpanel directly to the source, bypassing the main panel for potentially easier load calculation and fewer complications with derating. Definitely get an electrician's opinion on all this before moving forward!