Hey folks! I'm in the home stretch of getting my DIY grid-tied solar system ready to submit to my utility and city for approvals, and I'm hoping to get some clarity on sizing a backfeed breaker. I'm in California, working with an EG4 12kPV inverter and about 6.5 kW of DC panel capacity, plus a PowerPro battery. The inverter has a max AC output of 32 amps, so it seems like a 40-amp backfeed breaker is what I'd need. However, I want to power a critical loads subpanel with an 80-amp passthrough, and I'm concerned about how this interacts with my main panel's capabilities without derating the main breaker. According to California's electric code, it looks like as long as my inverter can handle 32 amps, I might be able to install a breaker larger than 40 amps. But I'm struggling to find definitive guidance on this. Any insights would be super helpful, thanks!
1 Answer
You're spot on to consider the code. Since your inverter outputs 32 amps, that gives you a cap of 40 amps for the backfeed breaker when accounting for the 120% rule. You'll likely need a licensed electrical engineer to draw plans if you want to push the limits legally. If your budget allows, think about a new main panel set up, which could handle everything without derating. A friendly AHJ could potentially work with you too! Also, upgrading to a more powerful inverter could be a solid option if that's feasible.
Yeah, I had a similar situation, and a line-side tap was a workaround. But since that isn't possible in your case, stick to what the AHJ says. Hopefully, they can suggest a path that won’t break the bank!