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Thread: Grounding question

  1. #1
    DIY Member idoc4u's Avatar
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    Default Grounding question

    I am running a new 20A circuit to an unfinished basement bathroom. I am also running my #12 hot, neutral and ground through 1/2" EMT conduit. The conduit, I realize is a functioning ground. However, here is the question. When the wires enter the metal boxes for switches and outlets, it would make sense that if I didn't have a ground wire, the metal box attached to the conduit would act as a ground itself. When the conduit connects with the plastic housing of the exhaust fan wouldn't the ground be broken due to the insulating nature of the plastic? This is why I ran a ground to connect to the ground of the fixtures and this exhaust fan.

    In my breaker box, there is one ground wire, I think a #6 or possibly #4. That is supposed to gound the circuits, but as you can hopefully see, I was concerned about the absence of adequate ground for the plastic housed fixtures.

    Am I wrong? Should I just run a hot and neutral in this case?


    Thanks for replys, as always!

  2. #2

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    Your not wrong, but you shouldn't be using the fan as a junction box (if thats what you are doing) unless its rated for it. Most, if not all are not. I've also never seen a plastic fan housing, so this is a little different from what I'm used to. If the housing is plastic, but there are components inside that require grounding I would just run a piece of #12 awg from your switch location up to the fan.

    -rick

  3. #3
    Test, Don't Guess! cacher_chick's Avatar
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    I've not seen a fan with a plastic housing either but the fan assy will have a ground connection point. EMT is an acceptable conductor but metal boxes including that for switches, receptacles, and if so, the fan assy, must have a ground wire between the box and device. There are green grounding machine thread screws & pigtails sold that are for this exact purpose.



    Last edited by cacher_chick; 03-03-2010 at 04:33 PM.

  4. #4
    DIY Member idoc4u's Avatar
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    Thanks for replys! The fan box is not being used as a junction. The housing is definitely plastic, however.

    I was thinking it would be acceptable to not run a ground from the breaker to the switch box, but have a ground from the switch box to the fixtures. Conduit would be my ground from the breaker to the switch box.

    Thanks again.

  5. #5
    DIY Member idoc4u's Avatar
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    I have seen wiring diagrams that do not include connecting a ground to switches in a switch box. There is a ground that comes in from the breaker and is clamped to the switch box and then runs out to the fixture without being connected to the switch itself.

    My rocker switches have a ground screw on them. Is it optional to ground the switch?

  6. #6

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    Quote Originally Posted by idoc4u View Post
    I have seen wiring diagrams that do not include connecting a ground to switches in a switch box. There is a ground that comes in from the breaker and is clamped to the switch box and then runs out to the fixture without being connected to the switch itself.

    My rocker switches have a ground screw on them. Is it optional to ground the switch?
    To make a long story short, no it is not optional. You are supposed to ground the switch.

    -rick

  7. #7
    DIY Member idoc4u's Avatar
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    Would the following make sense; have conduit running from the breaker box to the switch box. Ground the switches to the box and then run the ground to the fixtures. In this case, I would NOT have a ground running from the breaker to the switch box, but rather the ground would "begin" at the first switch box. The switches would be grounded to the box and then via pigtails ground would travel to fixtures. The "ground" from the breaker to the switch box would be the conduit itself.

    I hope that makes sense.

  8. #8
    Test, Don't Guess! cacher_chick's Avatar
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    Yes, that makes sense.

    A similar example would be EMT run to the switch box (using the EMT for the ground), and then running NM cable with ground from the switch box to the fixture.

  9. #9

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    If I can use NM, I'm not going to the trouble of installing EMT. The only way that would make sense is if the run to the switch box was exposed and then went to the fan in the wall. Use your conduit as the ground for everything that has a metal box. For your fan, ground the switch to the box and run a separate ground also attached to the box to the fan. The fan has to have some sort of grounding connection, whether it be a grounding lead or an attachment to the chassis itself.
    I consider myself an accomplished DIY'er. I don't know everything but help where I can. I'm not a pro, but like to think I'm professional.

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