Lamps blow within a few days - suggestons for possible faults?

[SpannerSpark]

Hi all
I have a job in a week or so time where the householder has two separate rooms with the same wall light fittings (with Silvania 40W E14 Edison screw type candle shape lamps). She has 8 fittings in each room and says that the lamps blow after perhaps 1 to "a few" days. Apart from chronic overheating or a batch problem with the lamps can anyone suggest another fault?. My plan was to inspect the fittings and do a full test on the circuit or circuits, perhaps try another make of lamp (its a big house not sure if two rooms are on the same lighting circuit yet).
If anyone has any other possible faults from their experience i would be much obliged.
tks

 

[RogertheBodger]

It's an old story with householders, they think if a lamp don't last 10 years, there is something wrong with the Electrics.
Do your tests but if you don't find anything wrong ask her to keep a log of how often the lamps go, she might surprise herself!

 

[SpannerSpark]

Yep i know what you are saying. I am fairly newly qualified but i already have some experience of this, the more fittings, the more difficult it is to keep track. I tried to suggest to her that i had found this to be the case with "other" householders in the past. But she says that she has bought 2 sets of lamps and replaced all since last july (when they moved in to the house) and in one room all are now dead, some having been replaced once again in the mean time (she knos this as she only has a few left). She did also say that one or two if the fitting have a "broken" lamp in them, meaning that the ES part of the lamp remains in the holder but the glass part has snapped off. Cant see why this might be a contributing factor, but you never know.

 

[RogertheBodger]

If everything tests out OK, the voltage is within limits, and she's using good quality lamps, there shouldn't be a problem,
She should be happy with that, probably more worried about a fault with her Electrics than having to replace lamps.

 

[malcolmsanford]

Roger as hit it on the head, poor quality lamps. Tell her to get a set of normal lamps she buys and then recommend a good quality lamp, a Philips or Osram, for the other set. Put all her ones in one set and the better quality ones in the other, and see what happens.

 

[telectrix]

and, while she's at buying quality lamps, tell her to look at halogen replacements better light, longer lasting, and more energy efficient. around £3 for a 40w candle.

 

[Smugley]

Why have several of them broken off? Could be a sign of overheating. I guess the fittings are rated at 40W which isn't that high, but can't be sure without seeing them. Perhaps they are tiny decorative luminaires designed for only 20W. In chandeliers etc the SES holders are often only rated at 20W. If they are breaking off, remind her not to screw them in too tight. Screw them in until just tight with two fingers only then unscrew just a bit, maybe a tenth of a turn so that when they heat up and cool down they don't wedge themselves into the holder.

 

[BlueToBits]

Sometimes the live contact in the lampholder becomes bent too far into the fitting to make a proper contact with the lamp. This usually happens because the lamp is screwed in further than it needs to be. Once this has arced a few times a layer of carbon builds up on the contact which encourages prolonged arcing. this causes the metal contact to loose it's temper (springiness), accelerating the deterioration and increasing the arcing. The the arc builds up and causes premature lamp failure (due to the arc causing it to switch on and off very fast) and the heat causes the plastic lampholder to become brittle. Because the temper is lost, each time the lamp is changed it needs to be screwed further and further into the holder to make contact until it can't go any further and breaks off.

 

[MarkieSparkie]

First step I would take is to test Continuity, R1+R2, IR, polarity, Ze & Zs, you will then have a known reference from which to work from, the customer is likely to appreciate your professional attitude to her problem and you will know the installation is sound.
Agree with Smugley, over rated lamps in low wattage fittings, screwed in to tight most likely. Fit a good set of properly rated lamps from a quality manufacturer.
From my experience, ask where she bought the existing lamps. Be particularly suspicious of a bulk pack buy from a pound shop or stack it high flog it cheap outlet. There were a flood of fake branded lamps from the far east a while back. A particularly dodgy brand 'Maxim' is also sold in these places.

 

[oldtimer]

Had the same problem on Friday with GU10 lamps and the tenant was giving it Oh Yea when I tried to tell him that these lamps had a set lifespan so hence one going out on Monday another 2 on Wednesday and so on I explained that if you have these lamps on a bit of track then they will all go around the same time making you think there is a problem Oh Yea he said so I went out to the motor and brought in 2000 and 5000 hour lamps so why have the replacements I bought dont have the lifespan on them thats because they were probably cheap as chips I said. Had the same on another job 10 on one switch (kitchen) and 2 on another (alcove) so why does the alcove lights last longer then I asked do you switch them on at the same time as the other no she said I hardly switch them on at all

 

[marty1234]

i would test the voltage make sure this is all ok , find out what the lamp voltage will work at and make sure your voltages are not to high or to low
also go to the fitting and make sure the lamps are not glowing very low even when the switch is off i have had this problem it was a netraul fault test at the light fitting to make sure no voltage when switch is off

 

[SpannerSpark]

Thanks for all the info. as usual all good stuff that i will log in my noggin.
many thanks to you all.

 

[Paul.M]

Had the same problem on Friday with GU10 lamps and the tenant was giving it Oh Yea when I tried to tell him that these lamps had a set lifespan so hence one going out on Monday another 2 on Wednesday and so on I explained that if you have these lamps on a bit of track then they will all go around the same time making you think there is a problem Oh Yea he said so I went out to the motor and brought in 2000 and 5000 hour lamps so why have the replacements I bought dont have the lifespan on them thats because they were probably cheap as chips I said. Had the same on another job 10 on one switch (kitchen) and 2 on another (alcove) so why does the alcove lights last longer then I asked do you switch them on at the same time as the other no she said I hardly switch them on at all

I've had the same conversation.

Has anybody had the question "it says 2000 hours life in the box and it only lasted about 1000?" WTF do you want me to do about it? I didn't make the bloody things. Oh that's right, it must be my wiring.

 

[Knobhead]

As an apprentice at collage we did Reliability and Testing the lecturer had worked for Ossram. In the QA department they rows upon rows of lamps on test. Each row had samples from a batch. He reckoned that once the first lamp blew within 50 hours they’d all blown. That’s close tolerance for a 1000 hour lamp considering the variance possible in manufacture.
There is always the “Bathtub Theorem” to take in to account. (You look it up. It’s to do with reliability).

 

[SpannerSpark]

Finally got round to do the job. 2x sets of 4off fittings (same fittings) on two circuits, so figured unlikely to be a circuit problem. tested one circuit anyway, Ze, R1+R2 etc all ok, incoming supply 243V.
one or two lamps had "woolworths" on them so i figured they perhaps were "slightly" older than a couple of weeks!! lol
Anyway you could tell the fittings (they were rated to 40W btw) had been getting hot, they were that way plastic gets when its been hot, a bit crazed. Most of centre contacts were pushed back so they only just made contact, dirty/tarnished. re-bent them and clean them up.
they were a twin "torch" type design two separate "flaming torches", but had been fitted with the shades pointing down, that would only have kept in even more heat. fitted them right way round (i think they look nicer like that anyway)
With homeowners agreement fitted various lamps 40W, 25W incands, equivalent halogen and a compact fluor. Marked them all up to tell new from old, will see how long they take to go or if all ok now.
thanks to all for advice.

 

[MarkieSparkie]

Glad the advice was helpful spannerspark . Sounds like you have set up a good test regime to me. Please keep us posted, because I would like to know what conclusions you come to at the end of your trial.