Hi, I have a 1960's era home that I recently bought and am in the process of remodeling.

I was replacing a bathroom light switch that is co-located with a 20-amp GFCI outlet. When I removed the wall plate, I realized the wiring was "funky":

- There are two black wires in the box
- There is one white neutral
- There is one 'jumper' black wire from the light switch to the hot terminal of the GFCI

The white wire went to the outlet's neutral line, as it should.

One black wire went to the outlet's hot line, as it should.

The other black wire went to one of the the light switch's terminals, as it should.

The problem (potentially?) is that there is a jumper black wire that goes from the light switch's second terminal to the HOT GFCI terminal.

So in effect, there are two wires going to the hot GFCI terminal. Worse, the GFCI somehow had two stab openings for the hot terminal, and that is how they had it wired. One of the stab terminals had evidence of heat melt and the wire was loose!

I replaced the GFCI with a new one, I wrapped the hot wire around the hot screw terminal, and inserted the jumper into the screw-down clamp on the same terminal. There are still effectively TWO wires attached to the hot terminal, though this is now secure and not using stabs.

Do I need to rewire? The only thing I can think of is to wire screw the hot feed from the wall, then have two jumpers to the hot terminal of the outlet and one of the outlet switches. Pictures attached

 

By the way, the picture makes it look like the two wires are both under the screw, but actually the two blacks to the hot in the GFCI are
1 is wrapped around the screw terminal
2 is screw clamped in behind the screw terminal.

 

The wiring is fine as far as the GFCI and switch goes. On a GFCI, there are no "stab backs" as they are pressure screw plates and are perfectly fine. I would remove the twisted wire, straighten it, or recut and strip and put both wires under the pressure plate. It will accommodate two, one on either side of the screw.. What you have is a hot wire in to the GFCI, then to the switch to energize it. The other black wire goes to the light fixture, and the white neutral to the GFCI is its neutral. HOWEVER, I do not see a neutral from the light swtich to the fixture. Is there one? Is it connected to the neutral side of the GFCI? It appears someone ran a single wire through a hole in the box to the switch. Obviously your GFCI is tripping, right? Fill us in on that action, Please.

 

Hi Chandler! Thank you for the quick and thorough (and reassuring) reply. Just as a practical question, is there any particular danger if I don't put both wires under the screw plates? Trying to learn all I can.

And you are absolutely correct in that there is NO neutral for the light switch in this box. The switch is interrupting the hot feed. I have rewired many light switches in this house, and they are almost all just like this-- just the hot wire is accessible.

 

The GFI wont trip because the hot to the light is on the line side of the GFI.

Looks like 2) two wire nm cables (with no ground) are in that box and the white was cut off the second one. They effectively wired that box like they ran a three wire nm cable.

 

I don't know, PJ. I was concerned that the neutral may not be on that same circuit. But, you are right, it appears they cheated on a 14-3, and applied the neutral at the light on the same circuit.

 

and the GFCI is not tripping.

 

I apologize for not being as savvy as I should-- is there anything from what you said, PJ and Chandler, that I should worry about? Or in laymen's terms, what did they do here?

 

Aside from the fact that we could not leave it as you have it, nor could we legally wire it that way, your cards are dealt. If it ain't broke, don't fix it. I would like to see a cable strain relief in the hole of the box so the wire won't get chafed.

PJ can elaborate too, but what they probably did was bring power in to the light, then bring it down to the receptacle and simultaneously control the light with a switch. By using a 14-3, with a red/black/white/ground, it would have been simpler, making the black hot to the receptacle, jumping to the switch and red to the light's black wire. Neutrals are all tied together.

 

thank you so much for your help, both!

 

Larry pretty much covered it..... and you're welcome.

 

Yes. Clamp terminals are designed to have the shoulder of the machine screw bear on the face of the clamp plate and apply force evenly to tighten the clamp. Wrapping a conductor around the shaft of the screw between its shoulder and the clamp could cause the force on the inserted wire to be less than is needed to secure it. It could also cause the clamp plate to be distorted.

Both of the black wires terminated to the brass LINE terminal on the GFCI should be straightened, have their insulation stripped to match the strip guide on the back of the GFCI, and be inserted behind the clamp plate.

 

We don't know where the 14-2 feeding the receptacle is coming from, so we don't know whether it is part of the same circuit as the neutral at the light or not. It probably is, but we don't know.

We do know that the black wire feeding switched power to the light is conducting ungrounded potential in a raceway (cable) that does not also contain a neutral for that circuit. Unless, of course, they tied the white wire to the neutral at the light and then cut it off as it entered the wall box.

 

Is it just me, or is that TW wire feeding the box, and wrapped in loom?

 

Justin, that is a distinct possibility. We'll have to wait on the OP to let us know, but it could be a single conductor. I fail to see why someone would run a full cable to a location and not modify it to a 14-3 and do it right. It does seem they ran a single TW down, but I can't tell about the protection. Anyway, for the trouble they took to run the single wire, they could have done it right.

 

the wire seems standard 16 AWG copper, plastic sheathed. Not sure what TW wire is, and the only 'loom' aspect I see is that the box itself, where the wires enter, has some fabric/mesh.

 

The smallest size code compliant wire would be #14 assuming a 15 amp circuit.

TW is a post WWII single conductor wire used in conduit and wiring trays.

 

The loom that Justin was asking about is the material covering the wire or wires that enter in the center of the box, or closer to the camera.

 

Justin, if you're looking at the cable or wire in the center of the box, closer to the camera, that looks like early fabric covered Type NM to me. Besides that, I'm pretty sure there are two wires coming in together there. It looks like the single black wire is coming from the other feed, which looks like later Type NM with the black plastic sheathing.