I have a 10 kWh 48 V inverter and four 100 amp hour 48 V batteries. The inverter can operate at 120 V single phase or 240 V split phase, and I plan to use the 240 V split phase setup. My question is: what size circuit breaker should I install from my main panel into the inverter for times when my solar and batteries are not sufficient? I'm uncertain if I should divide the 10,000 W by 48 or by 240 to determine the correct amperage from my main panel.
3 Answers
Just clarifying your setup: if it's a 10kWh inverter, isn't that its max output? I’m wondering because the manual doesn’t mention the right breaker size, just that it outputs 10kWh.
To figure out which breaker to use, you need the maximum output current, which you can find in the manufacturer's specs. In the US, there's a rule that requires a 25% overhead if the device runs for more than 4 hours. So for a 10 kW inverter, you'd calculate it like this: 10,000W ÷ 240V = ~41.67A, then multiply by 1.25 giving you about 52.09A. Thus, a 60A breaker would be appropriate, usually paired with #6 AWG wire. Make sure to check your specific situation and any local regulations.
You need to look at the voltage of the breakers you intend to use. For a 240V AC setup, you should divide 10,000W by 240, which gives you a bit over 40 amps. I’d recommend using a 50 amp breaker with 6 AWG wire. But just a heads up, if this is going to be connected to your main panel with a standard branch, you’ll need a 2 pole breaker for the split phase, likely requiring a 100 amp breaker and 2 AWG wire since dividing by 120 gives you more than 80 amps.