I am installing a vent fan in my basement bathroom. I am ready to wire it in, but I do not know what this red wire is for:

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I also am not sure what the green ground wire in the fan is supposed to be attached to. I saw on some other posts here that you shouldn't wire the green ground to the white because you can shock yourself when you turn on the switch. That was in reference to a ceiling fan, so I would imagine an exhaust fan would be the same.

I appreciate any clarification :).

Edit: added some more pictures for clarification.

  • 1
    It's really hard to see what's going on in that box with all the wires stuffed in there like that. Perhaps you can take a better picture after you pull the wires out a bit? Jul 4 '18 at 2:25
  • I added more pictures to make things more clear. There is a red and black wire capped to together, two blacks capped together, and a two pairs of white wires capped together. Jul 4 '18 at 16:10

Grounds are super simple. They are all green, green/yellow or bare. They should all be connected to each other and to nothing else. Ever. EVER.

This is one of the few really hard-and-fast rules in electrical, and it applies everywhere in the world except some old Soviet installations.

If you have connected all the grounds that are present, that is all you can do.

If a site doesn't have any grounds, you can ignore it, or if code requires, you can retrofit a ground wire. This process has rules which are, again, unique to grounds (far more permissive, actually).

  • Grounds should also be connected to the green screw or the attachment with the grounding symbol. Jul 4 '18 at 9:20
  • So if there is no ground wire in the ceiling junction box, I should just cap the green wire on the fan off? Jul 4 '18 at 15:49

It's possible that box does not contain a ground. I see a copper pipe there, that MIGHT be grounded. If so you could get a copper pipe ground connector and ground the box to the pipe then connect the fan to that ground in the box. Otherwise you'll have to run a ground from that box to a ground elsewhere in the house.

If I'm seeing this correctly, it appears the red wire is already connected to the black. Red is generally an alternate power used in romex 14/3 or 12/3 to carry current from a switch (though it doesn't have to be), allowing the black to remain unswitched thus providing both a switched current and an unswitched current to the same box from the same romex. Without tracing the wires, though, it'll be difficult to tell what function that red wire serves.

  • 2
    Copper pipes are NOT necessarily grounded. While that was the "traditional" way of grounding, plumbing may have a mix of copper and plastic so that there is not necessarily a grounding path. Jul 4 '18 at 2:34
  • 1
    @manassehkatz thanks; you are right the pipe may not be grounded. I changed my answer to be less certain that it is a good ground.
    – Eric Horne
    Jul 4 '18 at 13:27
  • The red wire is capped to the black wire in the box. What you are saying is that the red wire would provide current to power the fixture even with the switch off, correct? Can I test with a multimeter? If so what would I look for? If it is a continuous current wire, Would I just disconnect from the black and cap it off? Jul 4 '18 at 15:52
  • If the red wire is connected to the black, it's likely serving some purpose already. The only way to tell what it is feeding is to trace the red wire to see where it goes. Sorry, I could take a guess, but doing so may be dangerous. Connect a multimeter to the red/black cap and a set of whites, if there is no power there is likely a switch involved; if there is power it could be a switch that's switched on. Look for switches in the room and see if any toggle the power. If they do, then you've likely found the source of the red wire.
    – Eric Horne
    Jul 4 '18 at 20:10

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