White and black wires, no green and blue?
July 28, 2006 4:09 PM   Subscribe

I want to install a timer wall switch to my bathroom fan, and have a wiring question.

The current switch just has two wires, white and black. The timer switch has these two, plus a green and blue wire. The green one is supposed to go to the circuit's grounding conductor, and the blue one to the circuit's load conductor, according to the instructions. Considering I only have the white and black in my wall, do I install the switch by connecting those wires and leaving the green and blue wires as is (closing with electrical tape)?
posted by Blue Buddha to Home & Garden (8 answers total)
I've seen an extra wire used on fan speed switches so that the switch can tell the fan what speed to go to, in addition to supplying power. Maybe that's what that blue wire is for, and since you have a single speed fan, indeed you should just tape it off.

Oddly, I have installed both a fan speed switch and a timer switch in the past month.
posted by intermod at 4:17 PM on July 28, 2006

"Conductor" in this case probably just means "wire." According to the instructions, where are the black and white wires supposed to go?
posted by muddgirl at 4:40 PM on July 28, 2006

Response by poster: According to the instruction: [B]lack lead to circuit's Line conductor...For 20A unit ONLY: Connect White lead to the circuit's Neutral conductor."

And like I said, the switch I have on now just has a black and a white wire, if they are used for the same purpose...
posted by Blue Buddha at 4:43 PM on July 28, 2006

Hmmm...This switch goes in the wall, right? I bet there's a green/grounding wire in the wall socket somewhere. Usually, for AC powered device, you'll have three wires - black (which is line or load), white (which is neutral), and green (which is ground). If I were in this situation, I'd connect the black and white wires, screw the green wire to the (metal) wall socket somewhere, tape up the blue wire, and see if it works. Of course, I barely know enough about electrical wiring not to kill myself.

(btw, don't use electrical tape. At least use these.)
posted by muddgirl at 5:48 PM on July 28, 2006

I think you should get an electrician to do it.

Green is the safety ground, and should definitely be connected to ground. If your system is made right, the metal box your old switch was in should be ground.

Black/Line and Blue/Load should be hooked up to the two wires in there now, again if your system is wired correctly. Line should go to your system's Hot wire and Load to the fan's Hot wire. I don't know enough electrician stuff to say which is which in your current set up.

I don't know how this switch works so I can't say for sure what's up with the White/Neutral wire if you have one, but the connection to it in your wiring is probably on the other end of the fan, not in the place you are looking at right now.

What you propose definitely won't work. If you wire up Black and Blue to the two wires in there now, it might work, depending on if you get it backwards and if it matters if you get it backwards, but I think you should get someone who knows what they are doing in.
posted by TheOnlyCoolTim at 5:49 PM on July 28, 2006

Yeah, upon thinking I agree with TheOnlyCoolTim. If you're not comfortable enough to experiment before asking random strangers (which is moderately safer, I suppose), then pay someone who knows what to do.
posted by muddgirl at 5:55 PM on July 28, 2006

black -*- |      |--green--circuitBoxScrew
          |timer |                      _____ 
white--*- |______|---blue---*---black---|   |
       |                                |Fan|
Where "*" indicates a wirenut.
posted by MonkeySaltedNuts at 6:03 PM on July 28, 2006

I'm not an electrician, but I am a home remodling contractor, so here's my limited professional knowledge.

1. You can hire an electrician to do it for fifty or a hundred bucks and know that it's done safely and correctly.

2. You should have two pair of black and white wires coming into the box. The timer's black wire connects to the line conductor (yep, fancy word for wire), which is the black wire coming from the service panel; it's bringing power to the box. The timer's blue lead connects to the load conductor, which is the black wire going to the fan; when the switch is on, it takes power to the fan. If you have a 20-amp circuit, you connect the switch's neutral (white) wire to the others. Why the instructions tell you to do that only for a 20A circuit, I have no idea. Again, not an electrician. Most modern bathrooms will have 20A circuits, but your lack of ground, makes me think it may not be the most modern.

3. If you only have one pair of wires coming into the box, the switch is most likely on a switch loop, and the white wire wasn't marked as hot. In this configuration, one wire brings power to the switch and the other returns it to the fixture when the switch is activated. Are you installing a timer switch or a time delay switch? A timer activates a device at a specified time. It needs power to operate and requires a neutral lead. If you're on a switch loop, you can't install it. Since it would seem wierd to ask your fan to turn on and off at given times, I assume it's a time delay switch, which gives power to the device for some duration of time. Typically, these only need the hot wires to work, and you could install your switch - just connect your line and load wires as above. But only on a 15A circuit, since your switch has that white lead required on 20A circuits.
posted by lost_cause at 6:26 PM on July 28, 2006

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