Lamps blowing

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elvis_931

Senior Member
Location
Tennessee
I went to a restaraunt today to check on a problem they are having with some of their lights. They have about six different fixtures throughout the place that keep blowing lamps. The fixtures are on 2-3 different circuits, not every fixture on the circuits are blowing lamps. These are pendant mount incandescent fixtures with 60watt lamps. Owner says that sometimes the lamps will last a few days, and sometimes they blow after a few hours. On one circuit, there are three fixtures: when the first lamp goes out the other two go out about an hour later(according to the owner). Their is 118v at the socket. I just started looking into the problem when the lunch hour came and i had to leave. I have to go back later. Any ideas what might be causing this problem?
 
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elvis_931

Senior Member
Location
Tennessee
I thought about that, and may end up trying it, but i wonder why the rest of the fixtures in the building with the same lamps and voltage, even some on the same circuits dont give any trouble?:confused:
 
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elvis_931

Senior Member
Location
Tennessee
What kind of neutral problem? Loose neutral would most likely only cause the lamps to go off not blow out. Unless it caused the lamps to cycle on and off repeatedly then blow, but said they never flickered. Possible i guess.
 
mivey

mivey

Senior Member
Are you sure they are blown? If they are getting hot, the solder on the base will melt and it won't make good contact, especially if the tab in the socket barely makes good contact with a new lamp.

Possible heat issue? Maybe poor contact in the socket causing arcing?

I also like the bang your head theory in #7. Are the trouble fixtures hanging different than the others, different shaped tables, seating access, etc. Try some rough service lamps and see what happens (as a customer though, I don't like the bare-bottomed lamps as they glare too much).
 
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prh1700

Member
Location
edgewater, md
Are the lamps blown? Is there thermal overloads in those fixtures? I had a problem like that once. Turned out the guy put 150 watt lamps in fixtures only rated for 100 watts. Although they would come back on when the lamps cooled down.....
 
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charlietuna

Senior Member
One of two things---low voltage (power quality) or vibration. If the circuits involved (blowing lamps) are all on one particular phase that could narrow down the possible problem paths. Multi wire branch circuits can effect voltages on the other common neutral fed circuits. Make sure there isn't an air handler mounted above the ceiling causing the fixtures or entire ceiling to vibrate. Install a data logger on the effected circuit for a few days...
 
ultramegabob

ultramegabob

Senior Member
Location
Indiana
I am assuming these are fixtures with medium base lamps, if that is the case, look up inside the sockets and see if the little brass rivets that make contact with the metal tab and screw base have signs of arcing (black carbon residue) I have run across this quite a bit. They can arc and cause incandescent lamps to fail prematurely.
 
PetrosA

PetrosA

Senior Member
Location
Lancaster, Pennsylvania
I'd also ask if the bulbs that are blowing are all from the same case/batch, and where they got them. I've seen whole cases of incandescent and fluorescent bulbs and tubes that were faulty and short-lived. For some reason they tend to come from places like The Home Depot... ;)
 
GUNNING

GUNNING

Senior Member
Location
Gainesville, Florida
118 volts, Is that normal for that area? Might be on a multi wire branch circuit with an overloaded neutral. Or the lamps are too hot for the fixture, check the wattage on the fixture. Are the polarity on the screw shell and the tab reversed? I have run into where the neutral and hot are reversed on the fixture and the screw shell is the hot side. It blew lamps out too. I wired the fixture right and got the long lasting lamps, They lasted only slightly longer. Whole thing got REAL hot and burned out the lamps all the time.
If I were you I would look for a multi wire feed and associated neutral, split the circuit and run a separate feed for those fixtures. As insurance do the hard use lamps.
 
mivey

mivey

Senior Member
GUNNING said:
Are the polarity on the screw shell and the tab reversed? I have run into where the neutral and hot are reversed on the fixture and the screw shell is the hot side. It blew lamps out too. I wired the fixture right and got the long lasting lamps, They lasted only slightly longer.
Click to expand...
That does not compute. That does not compute. That does not compute...:smile:
 
GUNNING

GUNNING

Senior Member
Location
Gainesville, Florida
It didn't make sense at the time to me either but if your neutral is reversed on an incandescent fixture it can be a big surprise when you re lamp.
Nobody said what kind of light bulbs were being used. AND the only common problem with the fixtures I had problems with lamps blowing, was the reversed neutral. Taught me how to identify the neutral on a fixture wire. I'm waiting for a real answer to this problem.
Ive seen it before and my fix wasn't a good one. In my case the lamps would come loose from the base. Cheap glue on the lamp, but the ultimate cause was the heat from the contact in the screw shell. At the time I thought it was an incompatible material issue of the aluminum screw shell and the screw base of the lamp. If the unbalanced current was leaving through the tip and the current was entering through the screw shell the area of the screw shell is more. More area to heat up. No limiting values of only entering through the point of the lamp base. The heat translates into shorter life of the lamp. My solution was to wire the fixture correctly.
 
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