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6/3 wire for 60A subpanel

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  • 6/3 wire for 60A subpanel

    I plan to run 6/3 wire to a new 60A subpanel in my garage. The run will be close to 100 feet of wire. Am I pushing it with 6/3 wire? For a 60A subpanel, at what distance would I have to do better than 6/3?

  • #2
    Re: 6/3 wire for 60A subpanel

    100' is about the theoretical max for your application, here is the math behind that statement ...

    CM = (25*I*L)/V

    CM = Circular Mils
    I = Max Load Current
    L = Length in Feet
    V = Max voltage drop

    Given that the max voltage drop should be 2% of supply or in this case 2.4 volts (120V on each 'hot' wire)
    I = 60
    L = 100
    So the required CM = 26500
    6 AWG is about 26251 (working backward would give V of 2.412)

    In theory you should use AWG 4, in reality that circuit will never see 60A so AWG 6 is fine


    • #3
      Re: 6/3 wire for 60A subpanel

      Voltage drop calculators

      100's more
      Push sticks/blocks Save Fingers
      "The true measure of a man is how he treats someone who can do him absolutely no good."
      attributed to Samuel Johnson
      PUBLIC NOTICE: Due to recent budget cuts, the rising cost of electricity, gas, and the current state of the economy............the light at the end of the tunnel, has been turned off.


      • #4
        Re: 6/3 wire for 60A subpanel

        Besides the Voltage drop in the wiring from your main load center and the sub-panel there are other sources for Voltage drops.

        What gauge wire and how long is your main leadin cable? This is from the transformer to your main load center (service entrance point). What is the rating of the transformer supplying your place? In your shop or garage will you have any large motor starting loads to deal with? While you can run a 5 HP 240 Volt single phase motor OK you may have a problem starting it up. In a home shop it's pretty rare to have motors over 3 HP, but I have seen it.

        Something to think about is what is the capacity rating of electrical service at the point of service entrance. What is the rating of your main breaker or fuses in the main fused safety switch?

        What I'm getting at is that you may need to beef up your electrical service while you're working on this project.


        • #5
          Re: 6/3 wire for 60A subpanel

          I don't know the gauge or length of the lead-in cable or the location of the service transformer, or it's rating. My main service is a 100A panel and I may at some point want to get it upgraded to 200A.
          I believe that if I plan for a 60A panel by pulling a 6/3 cable I won't have to worry about doing it again in the future.
          The tools I have that will run simultaneously are a 1 3/4 hp table saw and 1 hp dust collector, an air cleaner (5A?), and some lights. At some point I may get a 3 hp table saw.


          • #6
            Re: 6/3 wire for 60A subpanel

            Please think hard about upgrading to 200 Amp service. Adding the sub-panel and loads in the garage is more than likely going to result in your tripping your main breaker now and then when you have loads on in the house. The 6-3 with ground should work pretty well for the sub panel.

            Please do yourself a favor and have a good electrician stop by for a look and to give you advise. This job may well be more than you'll want to get into on your own. This is really not a DIY kind of job.
            Last edited by Woussko; 10-18-2007, 08:05 AM.


            • #7
              Re: 6/3 wire for 60A subpanel

              Thanks for the concern and the advice. I am going to do the subpanel with a permit and if the inspector says I can only do a 30A subpanel then that's what I'll do until I get the primary service upgraded. There's really not much running off by 100A panel. It's an 1200 sq foot house, we have a gas dryer, gas heat, and we run the AC for about 6 days a year.
              p.s. just where is the Woussko hut located? I looked on google maps and I just couldn't find it.


              • #8
                Re: 6/3 wire for 60A subpanel

                The Woussko Hut is located in Insanityville USA.

                You might as well go with the 60 Amp sub-panel installation. I doubt you'll have any problems unless you try starting large motors or running large electric heaters in your garage. If it's a detached building, you need to check and understand your local codes regarding grounding and if you are to bond neutral to ground in your sub-panel or not. What you never want it to try to have the neutral conductor acting as neutral and ground.

                This is where it pays to consult your codes and also get some help from a licensed electrician. What is allowed in some areas isn't in others and insurance companies get really nasty if anyone ever gets hurt or there's a fire and they find the work was done by a DIYer.
                Last edited by Woussko; 10-18-2007, 08:11 PM.


                • #9
                  Re: 6/3 wire for 60A subpanel

                  My thinking on a separate shop from the house is run #4 copper in conduit a 70amp breaker and upgrade to a 200amp main service.60 amps on a cold winter day with a heater running ,a bigger size shopvac/dust collector.say 2hp, then trying to start a 3hp or 5hp saw..well soon you run out of capacity,plus in winter you'll run more lights.Most end up heating the shop with an electric something..there goes atleast 1500 watts right there.I always too either break the tab on outlets or put 2 outlets in so theres separate circuits for the 120v at an outlet.If separate outlets I'll use a brown and ivory or color up an ivory with a marking pen.Also whatever size subpanel you think you need for number of circuits buy the next size up so you can add more circuits later..All this costs more at first but 3 years from now you won't need to upgrade and the initial cost doing it yourself isnt terribly much.
                  my 2 cents Sam


                  • #10
                    Re: 6/3 wire for 60A subpanel

                    I have a garage 120' from my house. I have 200amp service though and ran 2 guage Aluminum wire with a 60amp breaker in the breaker box in the house feeding a 100amp breaker panel in the garage. The Aluminum wire is much cheaper and is allowed as a feeder in my area atleast and is perfectly safe if installed correctly. Also, with 2 gauge Aluminum you could run the breaker box in the garage at a full 100amps if you upgraded your service to 200amps.

                    Lastly, when I wanted to upgrade to 200amp from 100amps I found out that I hardly had to do anything at all. The wire and everything else up to the meter was sized already for 200amps. All I had to do was re-run a short feeder from the meter to my new Main breaker panel in the house and then replace the panel with a 200amp. I dont know how normal this is though maybe I was just lucky.
                    Last edited by Palomino; 10-22-2007, 08:22 PM.


                    • #11
                      Re: 6/3 wire for 60A subpanel

                      So running #6 wire from the main panel in my house to a sub-panel in the garage at a distance of aprox 60-70' away should pose no problems then? I'll only be running one power tool at atime (table saw/ drill press etc etc) and about 4 4' overhead lamps...

                      I should note that the distance posted is from the main panel to where I plan to install a sub-panel and not the distance between the house and garage
                      How much wood could a woodchuck chuck, if a woodchuck could chuck wood?


                      • #12
                        Re: 6/3 wire for 60A subpanel

                        You will be fine, 60 A breaker max.
                        Check your local code, Chicago has some very strange laws as a result of the big fire.