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10/3 wire for a subpanel

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  • 10/3 wire for a subpanel

    I live in Ontario,Canada.
    I have a oversized shed about 40 feet from the house and I want to install lights and plugs and maybe 220 volts in future for a compressor. My house main panel is a 20 - S.P. 125 Amp Type Q Load Centre 120-240 Volts AC 1 phase 3 wire. My friend suggest me to run a 3-10 wire from the house to the shed incase i want 220 volt in the future in the shed for a compressor etc... He also suggest me a sub-panel inside the shed. He also says that a 20 Amp would be enough. Inside the shed there will be 5 lights , 5 plugs for now. Now what do you suggest me. Thank You in advance for your comments.

  • #2
    Re: 10/3 wire for a subpanel

    Since your in Canada, I can only hope to be of some help.
    In the US, you MUST run 4 wires to the unattached shed. (NEC 2008). H-H-N-G. In my opinion a 30 amp sub panel is a waste of time. We MUST use at minimum a 70 amp main breaker sub panel in this application.
    I would pull #6 for the H-H-N and #10 for the Ground.
    Go to your big box store and pick out a new main breaker sub panel. Don't be concerned if the best buy is a 100 amp sub with breaker. You can use this 100 amp panel on a 50/60/70 amp feeder if you like. Just make sure you use the right breaker in the main panel to protect the feeder and the sub panel at the structure.
    Licensed Electrician


    • #3
      Re: 10/3 wire for a subpanel

      Welcome Den66
      Good advice from John.
      John, a few more Canadian quirks ...
      Any wire up here listed as XX/3 (10/3, 8/3, 6/3 etc) contains black red white and bare.
      We can run a 20A sub but really like you said - waist of time.
      I have run 8/3 for a 40A sub in the past and that allowed for a 4800W electric heater and a couple of tools with lights in the winter.
      Since you are considering a 220V compressor in the future keep in mind that these generally have big motors, mine requires its own 240 - 20A circuit, what about a welder and the all important beer fridge?
      Since you only want to do this once buy the 6/3 as John suggests.
      Pull a permit so you have all the required info to do this safely and a job done right will always pass inspection