Bulbs blowing (again).

[Mal]

Hi all, I know there are various threads in here about the frequency with which bulbs blow, but I've got a query with a slightly different slant.

On our upstairs landing we have 2 lights, which are both on the same switch circuit, the bulbs in one of the fittings blows regularly (every 3-4 months), whereas the other fitting hasn't had a bulb blow in years. We have changed the bulb in the 'good' fitting for a flourescent bulb some time ago, we also swapped the bulb in the 'duff' fitting at the same time - we've had normal and flourescent bulbs go in this fitting. Last time a bulb went I checked the wiring for loose connections and didn't find anything, I've just had another one go and went and tightened up all the connections again but didn't see anything out of the ordinary. The 'duff' fitting is wired straight into the connector block of the ceiling rose in the 'good' fitting. There is nothing in the location of the lights which could explain the problems (i.e. neither are subject to draughts, knocks, excess heat etc). Both lights are left on most of the night.

Anyone got any ideas?

M:

[BigWallop]

You may not have noticed that the spring loaded connections which come against the lamp terminals are loose or worn or burned. Do they have enough tension in them to hold tightly against the lamp ? Are they marked with carbon deposits on the tips ? When the lamp is inserted, does the lamp hold tightly into the bayonet connector clasps ?

Try changing the lamp holder itself and see what happens.

[Mal]

Good point, I haven't examined them at all. I'll try it.

Thanks for the tip.

[Andrew Mawson]

Two reasons for premature bulb failure:

a/ Overvoltage

b/ Vibration

Probably not a/ as other one on same circuit.

Andrew Mawson

[Dave Plowman]

One is getting more vibration than the other - for whatever reason.

[Andy Wade]

Is it premature, >> the bulbs in one of the fittings blows regularly (every 3-4

Taking "left on most of the night" to be (say) 10 hours per day, an ordinary

1000-hour GLS lamp is only going to last 100 days on average - which is 3-and-a-bit months. 8 hrs/day would give just over 4 months. These figures will be very sensitive to voltage, which (unless you're in an all-electric storage heater heated area) tends to rise at night when the supply network is lightly loaded.

I think the real question is "why has the other bulb lasted so long"? (And the answer is probably just "luck".)

[Mal]

The other fitting has had two different bulbs - we switched from incandescent to flourescent a couple of years ago, both types of bulb in that fitting have lasted - maybe we're _really_ lucky. Anyway the lights are on for something like 10 hours a day although this annoys me and I'm trying to get them turned off now the kids are getting older (it's costing me money ;-).

Thanks for the reply. M:

[Mal]

I would have expected the one that lasts to be getting the most vibration - it's in the centre of the house, near three doors and the loft hatch, and at the top of the stairs, whereas the one that keeps blowind is near the outside wall, and there's less traffic down that end, I suppose there could be draughts round there - I'll look into it.

Thanks again.