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I am trying to wire two lights in my shed with a switch at the end of the circuit. Power comes from a subpanel on the back of my house and is connected to a GFI outlet. Power then goes underground and into the shed in a junction box. The wire comes out of the junction box to an outlet, and then to light no. 1 then to light no. 2 and then to the switch. I am using 14/2 for everything inside the shed, except in between the two fixtures, where I am using 14/3.

I connected everything and it worked fine, but after pushing the wires for the two lights into their respective junction boxes, and mounting the light fixtures to the boxes, nothing works anymore. It keeps tripping the GFI outlet every time I flip the switch.

I'm fairly sure I have it wired correctly but here's what I have. First light:

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Second light:

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I don't have a picture of the switch, but it's just black on bottom, white on top, and neutral to neutral screw.

Anybody know what I've done wrong?

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    It is possible that you did not carefully bend the bare copper safety ground wires first thing up into the back of the electrical box. If that was not done it would be very easy for the contacts and screws of the light sockets to short against the safety ground. This could account for what is tripping your GFCI outlet....especially if the lighting circuit is wired to the "LOAD" side of the GFCI outlet. – Michael Karas Oct 20 at 22:15
  • As noted below RE: a switch loop, a GFCI is measuring current delta, if any part of the circuit is leaking current or unbalanced, a GFCI can trip. (it only takes a couple of mA) – noybman Oct 20 at 22:51
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    I fixed it... it was an issue with the wiring inside the subpanel and not anything shown. I think I had a short when I pushed the wiring into the box. That tripped the GFI and in the course of figuring that out, I switched a wire in the subpanel that caused another short. Once I fixed the wiring inside the subpanel, everything started working. – Kevin Bright Oct 21 at 1:17
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It's your ground wires. They're on top.

They're biffing onto a neutral or hot terminal.

Also, you need to use the #10-32 screw in the steel box and put a pigtail on that, and join that to the ground wires. Alternately you could use ground clips to attach to the sides of the box.

The key here, however, is to push the grounds into the back of the box behind all other wires. You should do this as the very first thing, and then never think about them again. This will greatly aid troubleshooting; often people wire grounds last after testing, and discover connecting grounds breaks the circuit. This leads them on a snipe hunt looking for a ground problem, when it's something else.

The next layer above grounds is everything that doesn't tie to the lamp, i.e. those black bundles one of which will soon be a black-white-marked.

Then finally the wires go in that actually attach to the lamp socket. That should solve it; there's plenty of depth in a 1.5" octagon box to keep the grounds far away from the socket back face.

Your switch loop is wrong

Code requires a /3 cable for a switch loop so neutral is present for smart switches etc. Use of a /2 switch loop is allowed if changing the cable is easy without tearing apart any part of the building, i.e. Conduit or unimproved work. However you must do BOTH these things:

  • Use the white wire for always-hot, not switched-hot as you have. That is so the white wire will definitely test hot at all times, and it's not likely to be confused for a neutral. AND
  • Mark both ends of the white wire with colored paint, tape or shrinkwrap.
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You have connected the light #2 incorrectly. The white wires should connect to the same side of the light socket just as you did at light #1.

It appears from the pictures that the light sockets have have two screws for each side of the light. Two of these should be connected to the threaded sleeve part of the light socket and this is where you want to make sure to connect your white wires. The other two screws should connect to the center contact in the light socket and this is where you want to make sure to connect the red wires.

In addition you have to run 14-3 from light #2 over to the switch location. The red wire of that 14-3 connects to the same side of the light socket as the red wire coming over from light #1.

At the switch location if you are using a conventional simple toggle switch the black power wire of coming into the switch box will connect to the brass colored screw and the red wire will connect to the silver colored screw of the switch. That is if the switch comes with differing colored screws. If same color you can pick which screws the red and black connect to. The white wire coming into the box will simply be capped off.

If the switch is a smart switch with the typical pigtail wires out the back the black wire will connect to the switch black. The white to the switch white wire and the red from the 14-3 connects to the load wire of the switch which may very well be red (but may also be blue or some other color).

The safety ground wire at the switch box will also connect the safety ground screw or pigtail depending on the type of switch used.

In all of the electrical boxes the safety ground wire should also connect to the metal electrical box via a green screw. It appears that this step was missed in both of the light electrical boxes. On those boxes you can use a short length of bare copper wire as a pigtail one end of which you connect to the green screw and the other end you bundle in with the wire nutted bare wires (which currently just have two wires each in the wire nut).

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    You are required by code to run neutral to the switch location whether you intend to use a smart switch or not. – Michael Karas Oct 20 at 22:09
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    I realize that, but I'm trying to figure out why it's not working and running a netural to the switch isn't going to make it start working. – Kevin Bright Oct 20 at 22:12
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    Thank you. I added that and routed the ground to the box screw in each box. The problem I was having was actually caused by a wiring issue at the subpanel, and had nothing to do with the wiring inside the shed. Thanks for your help though. – Kevin Bright Oct 21 at 1:14
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    Generally the same logic that says "not gonna put in a proper switch loop because reasons" also leads to "not gonna do other stuff right because reasons". Then you have a bunch of non-standard stuff to worry about when you are chasing a problem. Do it to norms, less trouble. – Harper - Reinstate Monica Oct 21 at 2:22
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    @Harper I'm pretty sure that the NEC has a clause that says regular switch loops are still allowed if the wiring is exposed, as it would be in a shed. My memory might be wrong, so check yourself (also, I might be remembering the Canadian code). Presumably because it would be trivial to replace the 14/2 with 14/3 in future if it were necessary. – user128216 Oct 21 at 12:17

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