WTF is up with this maddening lamp?
January 25, 2016 9:55 AM   Subscribe

I have three pendant lights in my kitchen, in a row over the counter. I've replaced the bulbs in two of them, maybe... never? Once? But the middle one burns out after a few weeks. WHY WHY WHY?

The lamps all look the same on the inside. They're all on the same switch and are on for the same amount of time, and when they're working they look the same. I'm fine doing some home repairs but am intimidated by wiring, so I haven't done any in-depth exploration. What could it be? Do I need to hire an electrician to take care of this? Is my house going to burn down because of this one lamp?
posted by The corpse in the library to Home & Garden (11 answers total) 1 user marked this as a favorite
could it be that by chance this one failed first, and the others never have? and that when you put in a new bulb you are not being careful to avoid touching it? see the bulb packaging (although it may be an urban legend).
posted by andrewcooke at 10:03 AM on January 25, 2016

Is the one that is burning out shaking or vibrating more than the others. i.e. from footsteps upstairs?
posted by achrise at 10:08 AM on January 25, 2016 [2 favorites]

This might sound dead simple, but juuuuussst in case it's this easy... in my own case of the One Mystery Pendant Lamp the Keeps Burning Out, it turns out...I was putting in the wrong wattage bulbs (my landlord had the wrong one in to begin with, so I just kept replacing it with the same kind, instead of checking the fixture for details).
posted by the thorn bushes have roses at 10:15 AM on January 25, 2016 [3 favorites]

You should wear clean cotton gloves when changing these bulbs.

You could also put bulb #1 into socket #2 (middle) and put new bulb into #1. This will tell you if it is the socket or the bulb.
posted by H21 at 10:17 AM on January 25, 2016 [4 favorites]

Yep. Are you changing those with your bare hands touching the glass?
posted by humboldt32 at 10:19 AM on January 25, 2016

I doubt it's the wiring because fused quartz is very tricky stuff:
Contamination in almost any form is detrimental. Alkaline solutions, salts, or vapors are particularly deleterious. Handling of fused quartz with the bare hands deposits sufficient alkali from perspiration to leave clearly defined fingerprints upon devitrification. Drops of water allowed to stand on the surface will collect enough contamination from the air to promote devitrified spots and water marks. Surface contamination affects devitrification in two ways. First, the contaminant promotes nucleation of the cristobalite. Second, it acts as a flux to enhance the cristobalite to (high) tridymite transformation. Under some conditions, the tridymite devitrification will grow deeply and rapidly into the interior of the fused quartz.
I would try to figure out whether this light is exposed to more steam and water vapor, smoke, or vapor from cooking fats than the other two, and if it is, I might try to fit a heat resistant glass disk of some kind into the end of the bell to keep those things out.

But if you do that, you'll need to monitor the temperature of that one (by touching the outside of it very briefly along the length, say) to make sure it's not getting significantly hotter than the other two.
posted by jamjam at 10:43 AM on January 25, 2016

I never touch the bulbs with my hands. The lamps are a few feet from each other -- they'd all vibrate more or less the same, I presume, from upstairs activity, and are exposed to basically the same kitchen stuff. The one that goes out is in the middle.

I'll try switching the bulbs around, and double check that it's the right kind.
posted by The corpse in the library at 10:58 AM on January 25, 2016

I have certain lights in my house that do the same, I don’t know if it’s from vibration or what, but I gave up and replaced them with LED’s or CFL’s. They are starting to make them in different configurations now.
posted by bongo_x at 11:38 AM on January 25, 2016 [1 favorite]

If it's a consistent problem with one socket (and not just random chance) I'd assume that it's a problem with a bad joint somewhere (solder, crimp, something) that's causing a difference in current draw. I'd be very curious to learn if each bulb was the same temperature when lit, or if the one in the suspect fixture is running hotter than the others.

NB: in an apartment with similar pendants we had one that failed more often than the others, and eventually building management came through and replaced every socket in every pendant in every apartment with a different socket with a different fitting. It seems there was a manufacturing problem that affected so many lamps (across the whole building) that large scale replacement was worthwhile.
posted by fedward at 11:51 AM on January 25, 2016 [2 favorites]

if the one in the suspect fixture is running hotter than the others.

More likely the problem is too cool not too hot. This would be the case if the current in the problem fixture is lower because of a bad connection.

Halogen bulbs have fused quartz and small capsules because they require high temperatures on the glass so that tungsten that boils off the filament and condenses on the glass re-evaporates in the presence of the halogen and is deposited back on the filament.

If the burned out bulb is noticeably blackened, this might indicate that the bulb is running too cool for the intended halogen to recycle the tungsten, causing the filament to fail.
posted by JackFlash at 12:22 PM on January 25, 2016 [1 favorite]

Are you always buying the same brand from the same location? Could be those are just poor quality bulbs. Try going to a different store and buying a different brand (this can be tricky because a lot brands are owned by the same umbrella corporation).
posted by Mitheral at 3:09 PM on January 25, 2016

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