Bathroom electrical issue
October 18, 2004 11:15 AM   Subscribe

We just moved into a townhouse. In the guest bathroom, the light and fan are operated by the same switch, so that the fan automatically comes on when you turn on the light. We hate the sound of the fan and would prefer to have two separate switches, one for the light and one for the fan. How complicated is this to do? Is it something we could reasonably learn how to do ourselves or should we leave it to an electrician?
posted by widdershins to Home & Garden (10 answers total)
The simplest thing would be to leave the existing switch as it and put a second switch between that box and the fan. Then the fan will run only if both switches are on - you won't be able to run the fan in the dark - is that OK?

But if the switch is a standard outlet box by itself, you could just about as easily replace it with a duplex and wire the light and fan to separate switches in parallel. Shut off the breaker for the room before taking off the wall plate!

Note that if an electrician does it he'll have to bring all the wiring and switches involved up to code, which may cost more than you're expecting to spend. This should be a pretty simple do-it-yourself project.
posted by nicwolff at 12:01 PM on October 18, 2004

If the light and fan are wired separately and only connected at the switch, this is relatively easy. Make sure you turn off the proper circuit breaker (check by flipping the switch in the bathroom) and then unscrew the switch panel. Examine the wires going into the terminals of the switch. You would find two wires connected to each terminal. One pair will control the fan, the other the light. The fun is determining which is which by leaving only one pair of wires connected to the terminals, flipping the circuit breaker back on, and hitting the switch. Mark the wires once you determine what they belong to.

Now buy a switch box with two switches, and connect each appliance to a different switch.
posted by Krrrlson at 12:02 PM on October 18, 2004

You also might be able to install a pull-chain switch right on the fan, which would be the easiest thing to do.

Otherwise it could get tricky. If there is 3-wire (+ground) cable going from the fixture to the switch then it would be easier to do, since you could use the third wire to control the fan. That's probably not the case though. The fact that the one switch controls both leads me to believe they were cutting corners, which means they wouldn't have made the effort to install 3-wire cable.

The hardest part about any wiring job is pulling the cable, especially in an older house. As long as you don't have to pull the cable you should be all set.

In addition to turning the breaker off, you should always test everything with a volt meter (or simple circuit tester) before you go touching the wires. You can buy a cheap one at Sears for $10.00. Small price to pay for potentially saving your life. Wiring is easy and safe as long as you check and double check things first.
posted by bondcliff at 12:17 PM on October 18, 2004

If you have any doubt about your own safety while doing this, call an electrician. Or find someone who's done this sort of thing before. It'll cause less headaches (as someone who tries DIY too often and usually fails).
posted by angry modem at 12:20 PM on October 18, 2004

Oh, right, as Krrrison implies, it's possible that the light and the fan are wired in series - that one loop of wire powers both. In which case you'll find only one pair of wires coming off each side of the switch, and in which case you'll have to have the room rewired to add a second switch, or replace the fan with one that has its own internal switch.
posted by nicwolff at 12:23 PM on October 18, 2004

The light won't be in series with the fan (you'd need weird non standard voltage bulbs if that was the case) but in parralel.

I can practically guarentee their is only a single circuit going to your light/fan. Otherwise you'd already have two switches on the wall. Running another wire to the fixture may be easy or impossible (short of punching holes in gyproc) depending on your exact setup.

If the wire run is short and therefor not stapled anywhere and you can get to the clamps at the boxes on both ends you can sometimes use the existing wire to pull new wire. Even if so I wouldn't attempt this as your first electrical job.

A warning: If you have more than 60-100W of bulb in the fixture the fan may be required to be on at all times the light is on to cool the fixture. This goes double if the fixture is recessed and redoubled if the fixture is recessed into an insulated space. Disconnecting the fan or putting it on it's own switch could case a fire.

Another way to go is with a smart switch. You can get switches and remote units designed to run retrofitted ceiling fans. They use a microprocessor to switch two switches at the ceiling fixture from a special switch on the wall. They go for less than C$100 and I've seen them at home depot/Rona. Way cheaper than hiring an electrician for this job.
posted by Mitheral at 12:46 PM on October 18, 2004

Have you looked under the cover of the fan? If the fan and light are on the same switch it's possible that the fan is plugged into an electrical outlet that goes to the light - (depends on age of the fan/wiring/townhouse). In which case, just unplug it. (It will be super obvious if this is the case once you pop the fan cover and have a look-see.) I've done this in several apartments over the years.

Since you're talking about a guest bathroom - I'm assuming that the shower isn't used for hours on end every day. As long as the room gets aired out reasonably quickly after the shower is used there shouldn't be too much of an issue. (What Mitheral just said about lightbulb wattage is also an important consideration though.)

I offer this up as a potential quick and temporary fix. For the longterm fix - read up about basic wiring online (start by looking up your particular fan model) and see if you think it's something you can do. If you have *any* doubts - call in the professionals.
posted by fluffy battle kitten at 12:54 PM on October 18, 2004

Your bathroom may be required to be that way by law. Where I live, in Connecticut, it's actually in the building codes that a bathroom without an exterior window must have a fan that vents to the outside, and that fan must be on the same switch as the light. I can't vouch for any other state, but any licensed building contractor should be able to tell you what the requirements are in your state.

If that's the case, I'd suggest replacing the current fan with a low-speed or quiet fan instead of rewiring it to be on a separate switch. While you're obviously can't get arrested over something minor like this, it still may end up being a hassle if you end up selling the house or getting other electrical work done.
posted by boaz at 12:55 PM on October 18, 2004

Eek! boaz, we are in CT too and would definitely not want to do something that's not in code since we will probably sell within 5 years or so. It looks like I'll look into the quiet fan option instead.

Thank you all for your help!
posted by widdershins at 2:04 PM on October 18, 2004

I am certain that there is but a single line running from the switch to the fan, as I installed just such a system the other day.

My suggestion is that you replace the fan with an ultra-quiet version. They'll run you around $50-100 depending on the airflow volume, and you should have little difficulty finding one that is <2 .5 sone loudness (about twice as loud as a refridgerator).br>
The biggest reason for staying within-code is that your insurance company may screw you over royally even if the non-compliant wiring wasn't remotely associated with the house burning down.
posted by five fresh fish at 5:48 PM on October 18, 2004

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