Where to look in apartment building for a mystery circuit breaker

July 15, 2004 10:37 PM

I want to replace the horrid ceiling light fixture in my office. Step 1 is to turn off the appropriate breaker, but...duh...I can't find it. [more inside]

I rent an old adobe house. There is one breaker box in one bathroom (which was added on to the main house at some point - the door is actually an outside door). None of those (7-8) switches are the right one. Actually, only two of them seem to do anything at all.

There's another breaker box outside, near the water meter, cable box, etc. None of are it either - and once again, most of those don't seem to shut anything off at all.

I'd prefer to do this myself and not get my landlady involved. What am I missing? Oh yeah, there is another small apartment on the same property, which might account for some of the breakers that didn't seem to do anything.

posted by gottabefunky to Home & Garden (9 answers total)

Hmm. First, check your lease; you probably can't make an alteration like this without permission from the landlord. If it's discovered, you can be evicted. If it causes a fire, you can be sued. Tough, but that's life for renters.

It's not a good situation that you have a breaker box that does nothing obvious. There should, at least, be a single main shutoff that really does shut everything off. That's more or less modern code. Older, crufty, modified electrical systems often have wacky things like this as the end result.

What you need to do, probably, is backtrack from the electrical service itself. Where does the line come into the building? Where does it go (often through conduit)? That should give you a clue to find the main panel. Anything else, such as the panel in the remodeled addition, should be a subpanel supplied from the main. In an ideal world, the separate apartment would have its very own subpanel handling each of its circuits separately, but of course houses are often chopped up without regard for such things.
posted by dhartung at 11:07 PM on July 15, 2004

Just turn the light off at the switch and make sure nobody turns it on while you are working on the fitting. If the switch is off, there is no power to the fitting.
posted by dg at 11:48 PM on July 15, 2004

I believe you can still be shocked with the light switch off. 120V power has a "hot" line and a "neutral" line but the switch just breaks the hot line. The neutral line (the white wire) can shock you also. Try it with a multimeter, measuring between the ground wire and the white wire with the switch off.
posted by RustyBrooks at 5:24 AM on July 16, 2004

You'll need to turn the circuit to that current off from the breaker, wherever it is.

However, as said before, I would get the landlord involved. Most rental units prohibit repairs and/or changes to the property. However, some landlords are more lenient. A friend of mine, for whom I just replaced a ceiling fan for, was told by his landlord that he could make most any changes. My landlord, on the other hand, is more strict, and prefers standardized fixtures and prefers to do the work himself.
posted by benjh at 7:22 AM on July 16, 2004

An electrician would likely replace the fixture without turning off the power at the circuit breaker even if you could find it. With the wall switch off no power should be on the hot wire, assuming the switch is properly wired into the hot and not into the neutral wiring. I would double check it with a meter or a spare bulb. The neutral wire should be at ground potential, but may not be, in which case Rusty is right and it can shock you as well.

As long as you do not complete a circuit, either to the neutral wire or to ground, you should be fine. An old electrician's trick is to keep one hand in their pocket so as not to accidentally complete the circuit through their bodies. Of course if you screw-up, we won't be hearing from you here on MeFi any longer. Electricians are much cheaper than plumbers; that would be the safe way to proceed.
posted by caddis at 7:23 AM on July 16, 2004

Response by poster: Oops, forgot to add that there is one larger breaker switch near the outside box, which I assume turns off power to the whole house (?).

Is that normal, to have breaker switches not connected to anything?

And I don't really trust the switch to be properly wired - around here, contractor-type things often tend to be done kinda half-assed.
posted by gottabefunky at 8:55 AM on July 16, 2004

No, I do not think it normal to have breaker switches unconnected to anything. Usually if there are more spaces in the breaker panel than needed the spaces are not filled with unconnected switches but just left blank. However, it can be difficult to figure out what a switch connects to. It might be a single outlet or an outdoor fixture or as someone suggested something in the other apartment.
posted by caddis at 9:49 AM on July 16, 2004

I believe you can still be shocked with the light switch off. 120V power has a "hot" line and a "neutral" line but the switch just breaks the hot line. The neutral line (the white wire) can shock you also.

This is true but not for the reason you gave. The neutral line carries no current and can not shock you. If it were possible to get a shock from the neutral line then shutting off the breaker would not help - it is basically the same thing as an ordinary switch, except that it is conveniently located in the breaker box and can shut itself off when a short circuit occurs.

So, why shut off the breaker instead of just using the light switch? To protect yourself from crappy DIY electrical work. Some clueless amateur (or drunk professional?) may have rewired the switch so that it controls the neutral wire instead of the hot wire. This is very rare but you don't want to be the one-in-a-million case that gets shocked as a result.
posted by Mars Saxman at 10:06 AM on July 16, 2004

You also can never tell when some winner may have tapped into half of a 3 wire split cuircuit. So you could test it with a meter and find it dead and then just as you got a good hold on the bare neutral wire your room-mate fires up the blender and you're getting electricuted.

Electricians who do renovations are some of the most parinoid professionals and with good reason.
posted by Mitheral at 12:10 PM on July 16, 2004