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evolvedance OP t1_irz3icq wrote

Reply to comment by jlenko in How did I burn out my brand new sensor switch for bathroom fan? Wiring woes! by evolvedance

I don't think it's extension cord wire. It's an old house so it's whatever what was coming down into the old switch. I assumed connecting the white to the white was neutral, but from your response, I guess not.

So, are you saying the wires coming down are incompatible with that switch, despite being black, green, and white?

Admittedly, though I'm an engineer and come from a mechanic family and work on cars, I know next to nothing about electric other than YouTube and a book i purchased, but planning on taking a community college course. And hiring an electrician if I can't figure this out myself.

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jlenko t1_irz44zp wrote

You would need three conductors and a bond. 14/3 Romex would be perfect.

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evolvedance OP t1_irz5zbf wrote

Thanks for your help. So just to clarify... as is, the wire coming down will not work for the dewstop switch as I need another hot wire to connect to the red "fan" wire?

If it's incompatible, will that original switch work?

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jlenko t1_irz6y1i wrote

Existing wiring won’t work for a smart switch, no. Unless it’s one that doesn’t require a neutral. I’ve installed a bunch of the Dewstops (Costco FTW!), they’re cheap, easy, reliable switches.. but you definitely need that neutral

A regular single pole switch would work just fine. If the old one didn’t work, then just replace it with another

But.. that wiring still bugs me. Is the black outer insulation rubber? Sure looks like cab tire in your picture

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evolvedance OP t1_irzc3hw wrote

Alright. Makes sense.

Yes. It appears to be rubber. House was built around 1940. Parent's house.

I looked up cab tire but didn't find much. Is it dangerous? Probably not in the budget to rewire the house just yet, but would be good to know to line up priorities.

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jlenko t1_is13iz8 wrote

Cab tire.. rubber insulated, SOOW or SJOOW identifier on the rubber jacket

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Viper67857 t1_irz5sqi wrote

Normally, you'd have 2 cables coming into a standard switch box. Neutral carries through, ground carries through with a jumper to the switch for safety, blacks go to the side terminals (one is constant, one is switched).

What you have is referred to as a switch-loop, where the source cable goes to the device first, the neutral is wired directly to the device, and the black is wired to that cable coming down to your switch. The white wire at the switch will be the hot wire going back up to the device. This setup is not compatible with a smart switch as it needs a neutral to power itself. You'd have to replace the cable between the switch and the fan with 14/3 to have a neutral at the box.

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evolvedance OP t1_irzajfr wrote

Whoa. Looking up switch-loop = mind blowing. Thanks for illuminating that for me. It's all starting to make more sense.

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evolvedance OP t1_irz6jzu wrote

Got it. Makes sense. I'll also google switch-loop to further understand what's going on.

Would my original normal switch work?

If so, did it make any sense that the green ground wire was connected into the old switch... and the white wire connected as well, but the black wire coming down was disconnected?

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Viper67857 t1_irz7dvb wrote

The green wire was probably at the very bottom of the switch, no? On a green ground screw? That is required for code purposes, to ground the frame of the switch for safety. It serves no purpose for functionality.

The white should be powering the fan while the black is incoming power (if it was originally wired correctly). If the black was taken loose, it was probably because something was fucked (maybe the switch, maybe the fan) and the old owners didn't feel like fixing it properly, though they should have at least capped the black with a wire-nut instead of leaving it dangling if it's a constant hot. I'd probe each wire with a multimeter to see wtf is actually going on before doing anything else. You should get no voltage between the white and green and 110-120 (or 220-240? I'm not sure what country you're in) between the black and each of the others.

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evolvedance OP t1_is08vuf wrote

>it was probably because something was fucked (maybe the switch, maybe the fan) and the old owners didn't feel like fixing it properly

That very well could have been the case - that old owner being my 80 year old dad. He may have attempted to disconnect the switch, not knowing how to do it properly when the fan went out. Pretty sure he didn't know it was a switch-loop either. He's a chief navy mechanic and is brilliant with automotive and almost anything mechanical, but, admittedly electric wasn't something he ever got to focus on. Which is part of the reason, I'm trying to learn a bit.

I'm in the U.S.

This is helpful though. I'm going to pick up a multimeter tomorrow to test. I had a voltage tester that only told me if there was any type of voltage.

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