How is my bedroom wired? Can I fix this myself?

January 24, 2011 4:45 PM

My bedroom is wired like a Myst puzzle. How is my ceiling light fixture supposed to be powered? If this isn't something I can fix myself, how much might an electrician charge? Pictures and diagrams inside.

Just to get this out of the way: Yes, I already work with the breaker off at all times, and always test wires with a multimeter before touching them in any fashion.

What I've determined so far
My bedroom has three fixtures for ceiling lights. The first has already been set up with a can light (seen in the top of the photo). I'd like to deprecate this in favor of a dome light style fixture like I've tried to install on the left. This fixture, however, does not have juice.

What it does have is a single cable with a red wire and a black wire inside (picture though you can't see the interior wires here). Both of the uninstalled fixture spots (the lower 2 in the first picture) have a cable like this; neither are powered right now.

These cables lead to a wall plate on the side wall, where there's one more cable which has red, white, black, and green wires. Picture here - I've labelled the wires coming from the ceiling fixtures according to which side they go to. The 4-wire cable is also unpowered - it's zero volts between any 2 wires even with the breaker on and the lightswitch on.

All of the above-mentioned cables were found cut straight with no termination, so I'm inclined to believe they've never had power.

The sole light switch for the room correctly controls the can light. The wiring in it looks like the "pLL" diagram in the second column of this image (image found here, it's not mine). Obviously the first 'L' is controlling the can light, but I don't know what the second second 'L' in this switch goes to - none of the outlets in the room are controlled by the switch and there aren't any other ceiling fixtures.

What now?
What's my next step for trying to get these lights wired? Is there anything else I can try or look for that doesn't involve cutting huge amounts of drywall? If I have to call an electrician, how much can I expect to pay to get the two additional fixtures wired?

posted by 0xFCAF to home & garden (8 answers total)

The wires with the blue insulation are meant for low voltage circuits and you can't run a regular 110v fixture off of them.

What sort of lights were on these fixtures previously?

Do the other rooms in your house have "unusual" light switches or fixtures?
posted by davey_darling at 4:55 PM on January 24, 2011

Another thought, do you have any rooms with speakers installed in the ceiling? That combination of wires (the blue ones) would lend themselves to having speakers + a volume control installed. Any idea where the four conductor wire ends up? (somewhere near where a stereo receiver/tv might be?)

If this room has unfinished (i.e attic) space above it then you should be able to get proper boxes/wiring installed without too much invasive drywall removal. If there is finished space above then you are in for a bit more work, I'm afraid.
posted by davey_darling at 5:00 PM on January 24, 2011

I haven't looked at any other switches or fixtures in detail. The other bedroom just has the one can light (like in this bedroom) with no other spots for fixtures. Previously the fixtures were just covered with a round plastic insert.

There aren't any installed speakers. I have no idea where the four-conductor wire ends up. It's a condo unit, so the upstairs neighbors are above.

How would I power a low-voltage light? Run something from a DC converter plugged in to an outlet into that wall plate?
posted by 0xFCAF at 5:03 PM on January 24, 2011

Well, are there any blank wall plates down near "outlet level" in any areas of your condo? (i.e. near an entertainment center?). If there are, and the other end of the four conductor wire is behind it, then you can wire up some low voltage lights without much of a problem.

The tricky part would be finding a low voltage fixture that works for you, and that is put together in such a way that you can remove the transformer and locate it elsewhere.
posted by davey_darling at 5:08 PM on January 24, 2011

I guess, actually, since it likely couldn't be controlled by the light switch, I'd probably give up on the idea altogether and replace the can light instead. I'll go hunting around for other blank wall plates in the unit -- I don't recall any off the top of my head, but it could be anywhere based on what you're saying the intended use of these wires is.
posted by 0xFCAF at 5:15 PM on January 24, 2011

There is a way that it could be controlled by a light switch (located in the wall plate that the blue wires come out of)

Basically you would take a regular light switch and wire it in this location (light switches don't care if they are switching low voltages).

You would then need to find the other end of that four conductor and wire your low voltage transformer in. The lights would be mounted in the existing unused locations.

One problem with this idea is that it appears that (at least) the wall box is not a standard line voltage unit, but a plastic low voltage. I don't think that a typical light switch would fit in that location, you'd likely have to cut away some of the part that juts into the center.
posted by davey_darling at 5:28 PM on January 24, 2011

0xFCAF writes "How would I power a low-voltage light? Run something from a DC converter plugged in to an outlet into that wall plate?"

The boxes the blue wires are coming out of are low voltage boxes too and aren't really suitable for mounting a fixture to; if you do end up putting a light fixture there they need to be mounted to the ceiling and not just the box.

If the wire is for a low voltage fixture then the other end would go to a transformer somewhere. Commonly this is either attached directly to a knock out on your electrical panel or attached to a box in your furnace room.

A switch wired PLL (assuming it conforms to standard wiring conventions (IE: don't bet your life)) is either power coming into the box at P and controlling two circuits (often a ceiling fixture and half a wall outlet but in your case could be the can and the transformer for a low voltage circuit) or power is coming in via one of the L lines and then switched power is set out on P with unswitched power exiting the box on the other L. You can figure out which applies with Voltic or a meter.

Depending on how your ceiling is framed it might be a relatively easy thing to fish wire to additional easybox/renobox locations from the existing ceiling box. A couple hours work for an electrician.
posted by Mitheral at 6:05 PM on January 24, 2011

The third fixture might be wired for (future) smoke alarms and that's why there isn't an other end somewhere.
posted by gjc at 6:07 AM on January 25, 2011