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Thread: ground wire with two circuits and voltage divider

  1. #1
    Join Date
    Jun 2008
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    Ada, Oklahoma
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    ground wire with two circuits and voltage divider

    I am wiring a new shop and using deep 2 gang boxes to put 120 duplex outlets and 240 volt outlets around the walls. I am running them as seperate circuits both with 12 gauge wire for 20 amp circuits. So in most boxes I have 4 cables, two in and two out. My question is can all the ground (bare) wires be tied together with pigtails for the two outlets or do the ground wires for each circuit need to be kept seperate. I know they all end up on the same bar in the main box, but wasn't sure if there was an issue with them all tied together at the outlet box from 2 different circuits.
    A second question is about voltage dividers. When I told the city inspector what I was going to do, he indicated that I would have to put a voltage divider in the box. I found some dividers at home depot, but no boxes that they actually fit. The local wholesale electric outlet said they didn't carry them. The only reference I am able to find requiring their use is if low voltage (data/phone) wires are combined in the same box with line voltage. Is anyone aware of a requirement to use them with dual voltages in a box with 120 and 240?

  2. #2
    Join Date
    Jun 2010
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    You can and probably should combine all of the ground wires at each box.

    In my experience a voltage divider is two resistors, but I think in this case it is an isolator to divide the 240V outlet from the 120V outlet? I can't see how that is required as they're all 120V to ground, maybe the inspector got confused, but if he requires it then you have to do it. Is it an option to put the 120V and 240V outlets in separate boxes?

  3. #3
    Join Date
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    Toronto Ontario
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    Use a multi-wire branch circuit with a 2 pole breaker.

    You'll need 3 conductor cable and will save a lot of mess in the boxes.

    I believe the inspector was asking for a barrier, which could be the case if you had more than one source. (two independant breakers)................Rod.

  4. #4
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    Rod, That was going to be my first approach, but the inspector told me I could not use a multi-wire branch circuit for 240 volt and 120 volt in the same box. Can you make an arrangement like that work with a gfci on the 120 volt side?

  5. #5
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    Agreed, that's what I did. I still had a big job getting all the wire in the boxes, would have been much worse with double the number of cables.

    Quote Originally Posted by Rod Sheridan View Post
    Use a multi-wire branch circuit with a 2 pole breaker.

    You'll need 3 conductor cable and will save a lot of mess in the boxes.

    I believe the inspector was asking for a barrier, which could be the case if you had more than one source. (two independant breakers)................Rod.

  6. #6
    For your multiwire branch circuits, use two boxes at each location. Let you hots hit the 220 outlet first, and feed through to a pair of GFCI recepticals. I would use a junction box at the ceiling at each location to hook up the down stream stuff, and just do a drop down to your recepticals. This way you only have three wires in boxes with recpt's.

  7. #7
    Quote Originally Posted by Bruce Wrenn View Post
    For your multiwire branch circuits, use two boxes at each location. Let you hots hit the 220 outlet first, and feed through to a pair of GFCI recepticals. I would use a junction box at the ceiling at each location to hook up the down stream stuff, and just do a drop down to your recepticals. This way you only have three wires in boxes with recpt's.
    While Bruce most likely knows this, let me add a couple of points here that need to be made if you're going to do this:

    Use a two pole beaker (or two-singles with the handles tied together). There used to be exceptions to this in the code, but they're gone now.
    Once you're on the load side of the (120V) GFCI, you can not do the mutliwire circuit anymore. From then on, the two protected wires (hot and neutral) must not touch any other circuit.

    As to the original question, yes the grounds should be connected. Even with MULTIPLE circuits, at 120V and 240V there's no NEC requirement to provide a separator in the box.

  8. #8
    Join Date
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    Hebron, KY
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    If keeping them separate circuits, why not just put them in separate boxes? You could put them on each side of the stud if you want them close to each other or one above and one below. ( I am not aware of any height restrictions per code.) This way they would be wired as normal. You could use 2 duplex 110 outlets if you wanted. The only extra cost in two boxes is the box, a wire nut, and a few staples. The biggest cost is the breaker and wire, but you are already planning to purchase and install that.

    I havn't seen a cover plate that works for a 220 receptacle and a duplex 110, but then again I havn't looked for one either.

    Mike

  9. #9
    Because I have my DC on a sensor located in the panel box, one of the legs of the 220 passes through sensor. This means 220 and one of the 110 operate the DC. In my case. it's the left recpt in each box. Just the way I did it. When I built my shop, I only had to have recpts closest to the doors be GFCI. Never in 30+ plus years have I plugged a cord into any recpt. other than those located on wall with doors, or the one located outside between doors (also on GFCI circuit.) The two pole breaker must be made that way, or have a tie strap from original manufacturer. On Square D QC breakers previously, you could have used a small nail or piece of wire to tie the two together, but not any more.

  10. #10
    The equipment grounding conductors must be connected together, but the grounded (neutrals) conductors must not be interconnected between circuits.

  11. #11
    leviton outlet 5842 has 220 is a dual voltage outlet
    I have used them multiple times
    http://www.amazon.com/Leviton-5842-I.../dp/B000U3BVMI
    Carpe Lignum

  12. #12
    Join Date
    Jun 2008
    Location
    Ada, Oklahoma
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    283
    Quote Originally Posted by Rollie Meyers View Post
    The equipment grounding conductors must be connected together, but the grounded (neutrals) conductors must not be interconnected between circuits.
    There is no neutral on the 240 volt circuit so this shouldn't be a problem. Although I am using the white wire, it is a hot and I have marked them all with red tape and where there are two in the box, I have a red pigtail to hook to the outlet.

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