Rewiring-going through bulbs very quickly.

TimBuckTeeth

dil1976 wrote: »

How is this possible unless the laws of physics have changed, a 60 watt lamp will always draw 60 watts regardless of what voltage is being applied to it.

The power consumed by a 60W lamp very much depends on the voltage applied to it. Supplied with 120V a 240V lamp will consume around 30W *

Ohms law states the current, I = V / R (voltage / resistance of the filament)

and the power, P = V x I (voltage x current)

so the power, P = V² / R

showing that the power consumed depends on the voltage applied and the resistance of the filament.

* Actually using the equation P = V² / R the power at 120V is a quarter of that at 240V if the resistance of the filament stays the same. However in practice the resistance of the filament increases considerably as its temperature increases.

fluffpot

who supplied the light bulbs and what make/brand are they?

Cheap ones often don't last and if they've been in the back of a van or tossed around the warehouse this will shorten life too

Ectophile

pokey128 wrote: »

hi
We got completely rewired a couple of months ago and since then we seem to be changing bulbs all the time-we've had to change every bulb at least once since the work was done.
Can anyone suggest a reason for this? Should I get the Electricia back out?
thanks

Are you buying cheap lamps? Avoid cheap supermarket or discount store ones, and go for decent name-brand ones instead.

fwor

dil1976 wrote: »

How is this possible unless the laws of physics have changed, a 60 watt lamp will always draw 60 watts regardless of what voltage is being applied to it.

As TimBuckTeeth has illustrated, you obviously weren't paying enough attention during physics lessons!

ListysDad

To the OP. You mentioned the lamps that are failing are halogen. Are these downlights and in the ground floor ceiling?

tlh858

Lamps failing has nothing to do with the wiring.

The usual causes are:
1. Cheap lamps, such as those from supermarkets where they are not only poor quality, they have been poorly handled in the warehouse, on the shelf etc.
2. Incorrect voltage - lamps for Europe are 230V, those for the UK are 240V. Fit the 230V ones and they will fail very quickly. The 230V ones usually show up where some supplier has obtained a load of them cheaply from some European source and didn't bother checking the voltage before shoving them on eBay or some similar place.
3. Lights fixed directly to a ceiling, or recessed into the ceiling will fail more often because people walking on the floor above will cause vibration. Not an issue with pendant lights because the flex or whatever else it hangs by removes most of the vibration.
4. Downlights are often installed incorrectly with inadequate ventilation above. Usually it's a wedge of loft insulation piled over them, which results in overheating. The lamp usually fails before it sets the house on fire.
5. Downlights should have PAR / aluminium reflector lamps in them. Unfortunately plenty of people install dichroic lamps which will cause overheating.
6. If you now have rows of downlights where you had a single hanging light before, it is inevitable that more lamps will need to be replaced, simply due to the fact you have far more of them. Your electricity bill will also increase substantially.

Less likely possibilities include:
Damaged or poor lampholders, which will result in the pins or base of the lamp being damaged.
The voltage to your home being on the high side - up to 253V is permitted but this will result in the lamps failing quickly. Almost nothing you can do unless it's really high (over 253) in which case you would also expect to see various other problems as well.

ListysDad

5 was where I was headed and the most frequent cause of lamp failure I see.