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Subpanel

pelagic2 | Posted in General Discussion on April 18, 2006 03:49am

I know this isn’t Fine Electrical, but here goes anyway. I have a subpanel in an outbuilding with a heavy  guage  2 wire/w ground supply wire(110/110/common+ground )coming  underground from another outbuilding 20′ away, which is wired like a main panel, with a 3 wire+ground feed from the main house.I don’t know if this panel has it’s own ground. So my problem is do I switch one wire to a common and just have  one leg of 110,and  or should I ground the subpanel and risk leakage through ground back to the main panel? I would like to keep 220 for AC, but I also am installing a gas HW heater with infloor heat, and stray current makes me nervous. It’s an office with phone computer fax, TV etc and I wonder if  one 110 leg would be sufficient .  Any ideas? thanks, John Eaton 

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Replies

  1. BryanSayer | Apr 18, 2006 04:36pm | #1

    Is the service cable from the main panel to the sub-panel in conduit? If so, is it metal or plastic? If it is metal, do your codes allow that to be the ground?

  2. junkhound | Apr 18, 2006 04:48pm | #2

    Se this is just your second post, so welcome.

    Orig. post somewhat confusing.

    2 wire/w ground supply wire   sounds like a black and white wire and a bare wire.

    whereas: (110/110/common+ground ) sounds like a 4 wire setup already, which is what you want. black, red, white, plus bare or green

    What is it you have exactly? A pix would help if yu have a digital camera.   The white wire should all be on the same bus in the outbuilding panel and not tied to the box, the ground wires on a separte  ground block that is tied to the box..

    What is heavy gauge, the cable should have a number on it. 

    You are going to probably get flak from some that if you know so little to start with you should quote "hire an electrician" endquote.  However we all have to start somewhere, and you are correct in being concerned about ground loop stray currents, etc.



    Edited 4/18/2006 9:49 am ET by junkhound

    1. philarenewal | Apr 18, 2006 05:36pm | #3

      Hey Junkhound,

      I had to re-read his post several times but what I get is:

      (110)/(110)/(common+ground) -- i.e. when he says common+ground he means it's the same single wire.

      Anyway, how goes?  Hope all is well.  Spring has arrived here and it's fantastic. 

      "Let's get crack-a-lackin"  --- Adam Carolla

      1. junkhound | Apr 18, 2006 08:33pm | #4

        Thinkk you are right on the interpretation.

        Great day today, maybe get into the 60's.

        Was moving a couple of 5x10 ft sheets of ply around yeaterday and was thinking about the pain of getting stuff into and out of your basement!  Maybe you should look at putting in a cellar door like the guy down the block east of you has (the shiny black one).

        1. philarenewal | Apr 19, 2006 02:42pm | #8

          >>"Maybe you should look at putting in a cellar door like the guy down the block east of you has (the shiny black one).

          Still have an eye out for some salvage marble blocks, but don't say cellar door too loud -- if Kim found out, she'd have me out there with a shovel tomorrow. ;-) 

          "Let's get crack-a-lackin"  --- Adam Carolla

    2. pelagic2 | Apr 19, 2006 12:55am | #5

      Yeah, I have two legs of 110 and a bare wire used for carrying the common and the ground. I'm thinking the best thing to do is use one 110 leg, then the other wire for a return and the bare wire as a ground back to the panel. I guess that would limit me to one 30 amp breaker. Also the sub panel I'm going to is wired like a main panel instead of a subpanel. Maybe I do need an electrician. anyway, thanks for the input.

      1. junkhound | Apr 19, 2006 03:06am | #6

        You probably dont need an electrician. 

        Is the existing wire in a conduit? you can pull and repull with another wire added.  If not in conduit and is as described black, white, bare), it should have just been 120V circuit to start with, and if you convert it to such, it will be OK.  You may need to wire nut all the white wires together and use the ground bus for just the grounds, or add another bus bar for the grounds, and pull the screw out of the present bus bar that ties it eletrically to the box and use that bus for the white wires.

        1. User avater
          BillHartmann | Apr 19, 2006 03:39am | #7

          Actually it might have been wired correclty, at the time. But not now with that usage.Without a metallic path back to the main panel you can wire the outbuilding as a service entrance. 2 hot s and neutral. Bond the ground to the neutral in the box and connect the ground electrode system.But with phone lines and water pipes it needs to be treated as sub-panel with 4-wire feed.

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