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I have a 30 amp double breaker in my main home panel feeding my detached garage 100amp sub panel. Can i run a electric furnace with a 90 amp breaker in the subpanel. Or is this setup all wrong

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  • What type of furnace takes 90 amps?
    – isherwood
    Dec 7, 2015 at 18:40
  • coleman evon eb15b 2 circuits a 60 and 30 0r one 90 amp with jumper bar
    – rstrosn
    Dec 7, 2015 at 19:03
  • Ah, it's all electric. Don't see many of those here in the frigid north. Would be cheaper to burn cash. :P
    – isherwood
    Dec 7, 2015 at 22:02

2 Answers 2

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No, that's not going to work. The furnace requires more power (maybe 3 times more!) than the whole subpanel feed can supply.

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If the second panel is fed by a 30 ampere breaker, then the maximum capacity of the second panel is 30 amperes. If you try to draw more than 30 amperes, the breaker in the main panel will trip.

You may be able to increase the size of the feeder breaker, but only if the wires feeding the second panel are large enough (which is not likely). You could probably increase the size of the feeder breaker, and the feeder wires. That would increase the capacity of the second panel, and possibly allow you to supply the heater.

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  • Thamk you that's what i thought. Now if i added a 100 amp breaker to my main panel to the sub panel do you know what size wire i would need? to feed subpanel ( about 30' to garage )
    – rstrosn
    Dec 7, 2015 at 19:08
  • Maybe helpful: diy.stackexchange.com/questions/29057/…
    – isherwood
    Dec 7, 2015 at 22:03

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