# Fluorescent bulbs burning out every two weeks



## eddy current (Feb 28, 2009)

Customer tells me that he keeps having to change the bulbs in twelve fixtures every two or three weeks. All the fixtures are on the same circuit, 347volt T-8 two bulb fixtures. Tested voltage, and amperage. All good so I replaced all ballasts and bulbs. Two weeks later they start burning out again.
Some of the fixtures are 3 foot and some are 4 foot so I don't think it's a case of bad bulbs. Lights are controlled by a relay, on at 7am and off at 11pm. 
Building is 40 yrs old, problem started about 3 months ago. There has not been any construction or any changes recently. Circuit is from a panel that has only lights on it, all controlled by relays. Turned on all relays and took some amp readings. Not much load at all on any circuit or the mains.

Anyone ever had a problem like this? Talked to a "lighting guy" and he told me that a bad ground can cause the bulbs to burn quickly. To me that does not make sense. Bad neutral maybe but a bad ground? I've worked in buildings that are so old they don't even have grounds and the bulbs don't burn quickly.

Going back on Monday to do some more digging.


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## drsparky (Nov 13, 2008)

Are the tombstones shunted? If they were t12s and changed to t8s the tombstones must have a jumper between the pins on each end. They will light without the jumpers but the tube life will be very short.


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## BuzzKill (Oct 27, 2008)

there should be a sticky thread dedicated to fluorescents


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## eddy current (Feb 28, 2009)

drsparky said:


> Are the tombstones shunted? If they were t12s and changed to t8s the tombstones must have a jumper between the pins on each end. They will light without the jumpers but the tube life will be very short.


They were changed over aprox 10 yrs ago and I think the sockets were changed as well. I'll will check anyway, thanks


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## slickvic277 (Feb 5, 2009)

Maybe a loose neutral connection some where? Every once in a while the splice "shakes" loose and creates an open neutral condition..just a guess.


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## eddy current (Feb 28, 2009)

slickvic277 said:


> Maybe a loose neutral connection some where? Every once in a while the splice "shakes" loose and creates an open neutral condition..just a guess.


There is one shared neutral for three circuits, circuit #8, 10 and 12. The problem circuit is #10. The other two circuits are working fine.


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## slickvic277 (Feb 5, 2009)

eddy current said:


> There is one shared neutral for three circuits, circuit #8, 10 and 12. The problem circuit is #10. The other two circuits are working fine.



Then there has to be a splice.right?Did you check all the splices?I find most problems with lights are bad neutral splices,or just bad splices in general.


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## BIGRED (Jan 22, 2007)

BuzzKill said:


> there should be a sticky thread dedicated to fluorescents


Start with this one: I had to replace two non grounded surface mounted lights to two 2x2 u-tube fluorescent drop ins. Finish the job, lights working, go home, the homeowner calls me & says that the lights won't come on. I go back the next day & ground the lights, lights work, finish & go home. The homeowner calls me & says the lights won't come on. Now I feel like an idiot, I call a friend who is an EC & tell him the situation. He asks me what type of u-tubes do you have in the fixtures, the type with the metal bar between them or the type with the plastic between them. I tell him the metal ones, he tells me that is the problem & to change the tubes to the plastic ones. I change the tubes and they work fine. Has anyone ever heard of this?


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