Is this an electrical fault ?
October 7, 2006 4:20 AM   Subscribe

I know, I know, light bulbs seem to fail in clusters, but I don't think this is to do with putting a bunch of lights in at the same time. This week for instance, I got up and turned on my kitchen lights (8 x 50w small spots) and one blew and tripped my Ground Floor Light fuse. A day later and I get home and turn on the same lights, another goes and trips the lights circuit again. Later in the week, another goes in my study. I replaced all the bulbs today. I turn them on, everything is fine, I go outside and turn on the porch/side lights (3 x 60w) and two of them blow. I nearly always have an inop light or two. My question is this : Is there an electrical fault which might explain this pattern of failure ? Thanks
posted by matholio to Home & Garden (11 answers total)
Power surges can weaken the filaments in light bulbs.
posted by Pigpen at 4:30 AM on October 7, 2006

How old is your home and what is your service amperage?
You might need to upgrade your service.
posted by Thorzdad at 5:02 AM on October 7, 2006

Plus, you mention tripping the light fuse. Did you really mean fuse or were you referring to the breaker?
posted by Thorzdad at 5:04 AM on October 7, 2006

Overly high wattage bulbs in poorly ventilated fittings can lead to drastic reductions in life. However, since this has happened in three different locations, you'd have to be quite pathological about installing bulbs above the suggested rating wherever you get the chance.
posted by Busy Old Fool at 5:06 AM on October 7, 2006

Response by poster: @Thorzdad
My home was built about 1920 but I'm not sure what you mean by Service Amperage.

FWIW, I've been in the roof, and I've seen the wires, they're not the old white fabric or backl rubber.

I'm facinated with the fact that I turn some bulbs on and other blow. what's that about, it's not how I thought electricity worked.
posted by matholio at 5:11 AM on October 7, 2006

I'm eagerly awaiting a response here...

Ever since we replaced the bulbs in our kitchen, they've proceeded to blow out at an astronomically quick rate, even for a room as highly-trafficked as the kitchen. They seem to do so much more quickly when all are replaced at once, but we've had an EE look at our lines and found no faults. Our house was built much more recently, but still, sometimes I think electricity just does weird things.
posted by disillusioned at 6:58 AM on October 7, 2006

If the wall voltage is higher, light bulbs last less long. Usually the power company tries to make sure that the voltage stays very stable, but it could have gone up.
posted by Steven C. Den Beste at 7:31 AM on October 7, 2006

Beware of brands of bulbs, too. I was plagued by blowouts in my kitchen, very similar (small spots in a fixture with 3). Sometimes the breaker went, sometimes not. Then I had to change where I bought bulbs, and the other store were a different brand. The blow-outs stopped. The good ones from Phillips, the bad ones, some off brand. The lamps are R50 lamps (common enough in Europe).

My kitchen was lit by an idiot. 3 spots in the center ceiling. Anywhere you stand at a counter to work, you cast a shadow.
posted by Goofyy at 8:23 AM on October 7, 2006

In Australia, if that is still the area to which this question is specific, you use 230 VAC 50 Hz power, with a residential distribution system that is more akin to European standards than to U.S. standards, where we use a single phase 240 VAC 60 Hz service, split into 2 X 120 VAC legs by a center tap from the transformer winding ("neutral leg") which supplies each residence service panel. So, in the U.S. we have 240 VAC available across the whole service drop, for powering high load appliances like stoves and clothes dryers, but our lighting and household branch circuits are nominal 120 VAC circuits. So, there can be circuit imbalances within a home created if people inadvertently connect a lot more branch circuit equipment or lighting on one "side" of their 240 VAC service, such that 1 or 2 of the 120 VAC branch circuits are supplying most of the electrical load in their homes. In that case, lights on the lightly loaded leg will see substanially higher nominal voltage than 120 VAC, and blow quickly.

In Australia and Europe, there is less likelihood of that happening, since your system is essentially a straight delta tapped single phase connection out on the power pole, but if your neighbors have vastly greater power use, or a fault develops in the transformer windings supplying your home, you can still get elevated voltage to your own house, which will dramatically shorten the life of light bulbs and other equipment.

The best way of checking for this is to have an electrical contractor put a strip recorder, or peak meter, on your electrical service for a day or two. This device will typically record minimum and maximum voltage readings in a period of time, to demostrate if you are getting radically higher voltage events than you should be typically experiencing. Some actually produce a paper "graph" of delivered voltage over time. Here in the States, we can often request such studies, at no cost to us, from our electrical company, if we experience a repeated pattern of electrical problems. But you can also get inexpensive digital multi-meters which have peak memory functions for recording high and low voltages of a circuit over time, and do a mini-study yourself. If you find high voltages being delivered, you may still need help from your power distribution company to find and correct the fault, but you may make a better case if you are in a position to document your problems with written notes and measurements you've made that substantiate your case. But you could also find that your fault is due to equipment in your home, where something like motor insulation on a frequently cycling refrigerator motor can be creating a functional autoformer winding in your home, "boosting" or "bucking" the mains current, with disasterous consequences for your lights.

If the problem does turn out to be the fault of the power distribution transformer supplying your home, the power company can correct this, by changing taps on the existing distribution transformer to adjust your nominal voltage, or by replacing the faulty transformer. Or, they may recommend that you correct problems with appliances of other equipment in your house if it appears that the problem is entirely within your premises. Perhaps you'll need to install over voltage protection devices ("lightning arrestors") in your mains panel, if the problem is determined to be on your side of the distribution transformer, but this is less likely to be a successful long term fix, as such devices break down over time by design, sacrificing themselves to offer catastrophic protection.
posted by paulsc at 8:28 AM on October 7, 2006

A couple of thoughts:
You mention small spotlights (halogen downlights?). Like all spotlights, these things run hot and have much shorter lives when mounted pointing down. This goes double for downlights in enclosed fittings - the heat can't escape, y'see?

Over time, light bulbs in any given multi-globe fitting or room/area will tend to become the same age. Nobody replaces just one bulb while there's plenty of light coming from the others, particularly halogen downlights which are often expensive and fiddly to change; when a second one goes it's starting to get a bit dark and so they'll replace both. After a few years of this they'll all gradually become the same age, and die around the same time - the 5 incandescent bulbs in my lounge room fitting are guaranteed to all die within a month of each other, even though 15 years ago I made a point of staggering new/old bulbs and using different manufacturers.

(I'm not that anal, it was just a little experiment...)
posted by Pinback at 4:26 PM on October 7, 2006

Oh, and the other thing is that with the popularity of downlights and such, people just have more lights - and so they seem to fail more often. If the average bulb has a 3 year life, and you have 3 light fittings, on average you'll replace 1 a year. If you have 9 fittings, on average you'll be replacing 1 every 4 months.

Count the number of lights you have in each room. You might be surprised. Halogens downlights also have a fairly short life compared to incandescents, so with 8 in your kitchen it wouldn't surprise me if you're replacing one every month or two...
posted by Pinback at 4:35 PM on October 7, 2006

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