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enter image description hereI'm wiring a miter box station in my woodshop. Wiring is 12/2 w/ground on its own 20AMP Circuit. Power source is coming from breaker box to a single ceiling light above the miter box.

How would I wire a GFCI outlet behind the miter box downstream to a single pole switch that controls the miter box ceiling light while providing GFCI "load" protection to two outlets downstream from the switch and GFCI receptacle? I don't care if the switch and light are GFCI protected.

Thanks for your help.

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  • Doesn't your light already have a switch? I assumed that it was a loop that can be disregarded. A diagram or better description would be great.
    – isherwood
    Feb 22 at 21:00
  • Side note: It appears that you're running a ground wire inside your conduit. That's redundant and expensive. That metal EMT conduit can be used as your grounding conductor, saving on the wire cost and conduit fill.
    – FreeMan
    Feb 23 at 14:17
  • I edited my answer to reflect that you are in EMT conduit. There is nothing wrong with running ground wires - I do it when I feel the EMT may get nailed by a forklift and have its grounding compromised - but if you do, you must follow the rules. See my edit. Feb 23 at 19:05
  • Harper-Reinstate Monica, thank you very much for your response. I will be taking all of your suggestions improving my wiring. I would like to ask you for a favor. Would you mind attaching a diagram of how it should be wired. I have the GFCI and downstream receptacles working. It's the wiring to the switch and switch to light that is not working. I will go with your second option of "Do not protect the lamp" as I want the light to stay on if Miter Saw Trips the GFCI Thank you.
    – Paul
    Feb 23 at 23:05
  • After reading through recommendations and comments attached to this thread, I was able to complete my wiring successfully. Everything works as I intended. Light stays on when GFCI is tripped and downstream receptacles are tripped as well. Thank you to everyone who contributed to this thread. Very helpful. I was a first time user and will definitely bookmark this site to ask future questions, perhaps maybe contribute as well.
    – Paul
    Feb 26 at 14:05

2 Answers 2

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It's all about GFCI discipline. Since you want to use downline protection for the GFCI, you have to be extremely fastidious about Line vs Load. So...

There are 2 ways to go. Pick one.

DO protect the lamp with GFCI (meaning it goes out when GFCI trips)

The incoming always-hot wires from the service panel get attached only to the GFCI "Line" terminals. They are the only wires that are attached to "Line". Nothing is pigtailed to those supply wires, either.

All other hot/neutral wires are attached or pigtailed to the "Load" terminals.

That means, to power the lamp, we have to double back to the lamp with both switched-hot and neutral. We can't power the lamp from the neutral that is "passing through" because, that would be "pigtailing to it" and that's a no-no.

Further, you must identify this "special, GFCI protected neutral" so it can be distinguished from the supply neutral running through the same conduit.

DO NOT protect the lamp with GFCI (stays on when GFCI trips)

The incoming always-hot black & white wires from the service panel get attached to GFCI "Line" terminals. However:

The hot and neutral wires going onward to the other receptacles are attached to the GFCI "Load" terminals, and they are not pigtailed, and nothing else is attached to the "Load" terminals.

All other hot/neutral wires (all of which will be associated with the lamp or switch) are attached to the "Line" terminals. Note that Line terminals can accept 2 wires per screw (read the instructions for how).

In this case, the lamp can tap the netural which is "passing through".

Notes

GFCIs and switches inside the same junction boxes are rather confusing. It can help to put the GFCI in a different junction box than the light switch.

You're using a basic 99 cent "Handy-Box" to install the GFCI into. I have successfully crammed GFCIs into those, but it took all my skill - those boxes are very claustrophobic for a bulky GFCI. I vastly prefer using a 4x4 box with corner screws, with either a 1-gang domed cover or a 1-gang mud ring depending on whether a wall finish is going up. This gives lots of elbow room for a single GFCI device.

I prefer to use special colors for GFCI protected hot and neutral, e.g. blue and gray (gray being a legal neutral color). Lacking a variety of wire colors, feel free to use colored tape. (home stores have a 5-spool rainbow pack for $5). Since your wires are individual wires in conduit, colored tape on neutrals does not have the effect of declaring it to be a "hot" wire, and you are free to use the tape for circuit identification (in fact, you're required to).

EMT metal conduit serves as a valid grounding path. There is no need for ground wires; that is "belt and suspenders". I only do it if I expect physical damage to the EMT. However, if you do run ground wires, they must go to the metal box FIRST -- do not bypass the box and take the grounds to the devices like you would in plastic/Romex work. The good news is, devices will "pick up ground" in most cases:

  • Switches will automagically pick up ground via their mounting screws.
  • Receptacles which are marked "self-grounding" (including the GFCI) will do the same thing. (because grounding a receptacle is a bit harder since that ground goes to devices).
  • Receptacles NOT marked "self-grounding" will pick up ground via hard flush metal-metal contact with the domed cover or mud ring. (however if they "float" above the mud ring on their drywall ears, then no; you must pigtail a ground wire off the box).
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  • I don't understand your first note. Why are three conductors needed?
    – isherwood
    Feb 22 at 22:16
  • Power enters at the lamp. Always-hot and neutral accounts for 2 conductors, but presumably you want to have a switched-hot also. Feb 22 at 22:26
  • Since OP is in conduit, there's no need for "/3", just pull another wire of a different "hot" color (anything but white, grey, green), right?
    – FreeMan
    Feb 23 at 14:19
  • @FreeMan whoops! When I wrote the answer, the picture hadn't loaded. Feb 23 at 18:52
  • I figured that there had to be some reason Mr. Use Conduit in All Situations was talking about a "/3" when there was clearly conduit on the wall. :)
    – FreeMan
    Feb 23 at 18:57
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You'd simply pull from the most convenient junction box which has a constant hot cable. You can't come from the light box if it's actually a switch loop, or from a switch box that's a loop. You need to create a new circuit branch in parallel with the light loop, wherever it may be.

Then it's just a matter of connecting the source to the line and the downstream outlets to the load on the GFCI.

Since you're operating motors with heavy load, use pigtail connections rather than passing through the outlets via their screw connectors.

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