Return to the Electrical Wiring Forum | Post a Follow-Up

Bathroom switch wiring question

Posted by micus (My Page) on
Thu, Sep 12, 13 at 17:44

Hey everyone,

Can someone give me some help with wiring these switches? There are to be two switches, one controlling vanity light, one controlling exhaust fan/light.

Thanks in advance, and let me know if I need to explain anything!


Follow-Up Postings:

RE: Bathroom switch wiring question

What happened to the old switches were there?

RE: Bathroom switch wiring question

You need to know:
-Which cable the power comes in on
-Which cables go to the fan and light
-Where the other cable goes
If the red/white/blue wires go to a fan/light unit, is there another light?
This looks like new wiring. The cables should have been identified.

RE: Bathroom switch wiring question

The red/white/blue wire doesn't seem to have any insulation jacket around it? Where does it go? I hope there aren't individual red/white/blue conductors inside the wall.

If that is new construction, it looks pretty ugly to me. I see an unpainted chunk of drywall compound in the lower right. And what's that bolt doing in the back of the box? This feels like a retrofit to me.

RE: Bathroom switch wiring question

The box is set back to far from the finished surface and in addition to that ugly bolt there's what appears to be a screw on the bottom of it holding it to something. Further,
the box seems to be a shallow one and with two switches and all those cables entering I can almost guarantee that the box fill is exceeded.

I don't see any ground connection to the box either.

I'd recommend you get an electrician (or someoen with a clue) to come in and redo this mess. It's more than just figuring out how to replace the switches you ripped out.

RE: Bathroom switch wiring question

Wow. Some of you are more brutal than me.

-The bolt looks like an anchor into concrete behind the box.
-The mud ring does not look that far back to me. Maybe 1/4".
-The red, white and blue wires are THHN and look to me like they are going into a conduit fitting. Why automatically assume they are in free air?
-There is a bare ground tail on a ground clip on the side of the box. One can only assume the equipment ground for the circuit is one of the romex grounds or the conduit feeding the box.

All that said, if the OP is coming here (or anywhere) asking "How do I wire this" providing just this image then YES, calling an electrician is the safest option. It is pretty clear the OP is in over his head.

RE: Bathroom switch wiring question

I concede the ground clip thing, what I thought was just another cable coming in is the ground wire. What I thought was a black wire is a shadow of the ground wire.

However, I see no mud ring here. What you perceive to be the mudring is in fact, just a crudely hacked hole in the drywall exposing more of the box behind it. I agree that the bolt and extra screw are not illegal, just shows doubtful workman like quality. The blue/red/taped-white might indeed by conduit wiring or it may be the sheath ends inside the NM fitting (nothing requires it to protrude into the box just that you usually can't cut it off that flush).

What it appears to be is a double gang "handy box" entirely behind the surface of 1/2" drywall. Look at the size of the cable fittings to the depth of the box. That box is SHALLOW. I can't see how this can be legal box fill wise for two devices and a couple of other connections.

Assuming all that wire is #14, that's 28 ci of box fill. That box as 21" at best.

RE: Bathroom switch wiring question

Sorry Ron. That is 1000% a 1900 box with a 2-gang mud ring. You can even see the divider notches between the device holes.

RE: Bathroom switch wiring question

That's still not going to cut it. A 1900 box is 21" and the mud ring 5.5, that's still too smal.

RE: Bathroom switch wiring question

how do you do a box fill calc on a fender washer/bolt?

RE: Bathroom switch wiring question

Yep, I missed the conduit fitting for the white/red/blue wires. My bad.

However, assuming that is the light/fan, you don't know what each wire does without opening up the light/fan at the other end and see what goes where.

RE: Bathroom switch wiring question

my guess is, power in on one of the romex's, power out twice from each of the other romex's, red and blue are the switch legs. Total guess though.
good luck cramming it all in there.

RE: Bathroom switch wiring question

I'd be inclined to believe that this is what some would call a charlie foxtrot. This is obviously an old box with lots of hands in it over the years.

My gut reaction is that it started as conduit, unless there's some kind of NM cable with red, blue and no white wire. And who starts with NM and suddenly decides to shove a length of pipe into the bottom of a box? Which probably makes the whole thing illegal.

As for the screw and washer, I don't think they are a means of securing the box but rather a way to cover an open hole. If you look at the screw at the bottom of the box, there's a fender washer there too.

I'd buy that red and blue are switch legs but wires serving a vanity light and fan going out of the bottom of the box in pipe? Why would you run pipe out of the bottom of the box so you can bend it 180 degrees to go up? How about a MWBC that serves the bathroom and something else?

The black and white wires in the upper left, is that a bit of bare copper back there? So is that NM?

 o Post a Follow-Up

Please Note: Only registered members are able to post messages to this forum.

    If you are a member, please log in.

    If you aren't yet a member, join now!

Return to the Electrical Wiring Forum

Information about Posting

  • You must be logged in to post a message. Once you are logged in, a posting window will appear at the bottom of the messages. If you are not a member, please register for an account.
  • Please review our Rules of Play before posting.
  • Posting is a two-step process. Once you have composed your message, you will be taken to the preview page. You will then have a chance to review your post, make changes and upload photos.
  • After posting your message, you may need to refresh the forum page in order to see it.
  • Before posting copyrighted material, please read about Copyright and Fair Use.
  • We have a strict no-advertising policy!
  • If you would like to practice posting or uploading photos, please visit our Test forum.
  • If you need assistance, please Contact Us and we will be happy to help.

Learn more about in-text links on this page here