Understanding Circuit Box Limitations - Electrical - DIY Chatroom Home Improvement Forum

 DIY Chatroom Home Improvement Forum Understanding circuit box limitations
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10-26-2010, 02:20 AM   #1
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## Understanding circuit box limitations

I am in the process of planning a bathroom remodel and am considering having a jetted Jacuzzi bathtub put it. As I understand the code requirements a separate 20A circuit must be run to the bathroom for the pump. My question is how do I tell if my circuit board can handle another line? It's a Square D and the only number I can find is QoC40U which I think is just the door model designating the 40 spots on the boards. Only 22 are filled and 18 are blank so it would seem there would be no problem, but are there enough amps available on the board? The main shutoff switch says 200 on it, but when I add up the individual circuits they total 265A for 110v circuits and on the bottom 110A for 220v circuits for the kitchen range, AC compressor and clothes dryer. How do you calculate what the max amps your circuit board can handle? Thanks guys.

10-26-2010, 06:17 AM   #2
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If you have 18 empty breaker slots, adding a 20A circuit is a can do. Figuring the actual allowable power from a panel gets complicated, but the total amps on the breakers almost always is more than the main breaker. In reality, you rarely actually have everything on at one time. And there may be 15 or 20A circuits with very little actual load.

 10-26-2010, 06:50 AM #3 Just call me Andrew   Join Date: Mar 2009 Location: Albany, NY Posts: 2,265 Rewards Points: 1,020 You are fine. There's no such thing as amps "available on the board". As long as the used current does not exceed 200 Amps, the main breaker will not trip. The breaker box can handle max 200 amps, but you would have to do a whole-house load calc to figure out what you're actually using. Most houses use nowhere near 200 amps, so you are probably fine. __________________ Andrew

 10-26-2010, 10:11 AM #4 Newbie   Join Date: Jul 2010 Posts: 23 Rewards Points: 10 thanks guys

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