Cooker Hood Lights Failing

[thescullster]

Hi all

I have a new (just over year old) Bosch cooker hood with 2 G4 12v 20w halogen lights - very useful. Trouble is they keep blowing. Must have fitted 6 replacements since the unit was fitted. I am careful not to touch the glass of the bulb. They are cheap as chips bulbs its just a PITA having to keep replacing them (and a bit of a fiddly job too).

Anyone suffering the same problem/found a solution? There appear to be LED bulbs available as replacements - are they better at surviving in this application?

Thanks

Phil

[Andrew Gabriel]

Do you use the extractor fan much? Could well be vibration from that, which is really evil for filament lamps.

LEDs won't be affected by vibration. If these are just capsule lamps (as opposed to MR16), you'll struggle to find LEDs which come anywhere near close to the light output, but

80W of 12V halogen lighting close over the cooker does sound rarther excessive. The other problem is that LEDs probably won't draw enough power for the electronic transformer to work. You might need to keep one or two halogens. LEDs might not like the heat from the cooker either - depends if you routinely have the burners running with flames licking halfway up the sides of the pans, like most of my family seem to.

[Bob Minchin]

Check to see what sort of transformer they are using to run the bulbs. Some (most?) electronic ones won't start up unless there is a load of

30-50% of maximum rating applied and LED lamps won't provide this. If you have a test meter, measure the voltage at the lamp holder with the bulbs out, if you get 12v ish possibly AC, then LEDS should work.

[Dave Plowman (News)]

I've got the same in mine - I replaced the old ordinary tungsten with them

- and they've never been replaced in years. Might be worth buying good quality lamps from a wholesaler like TLC - I've found shed and supermarket ones rubbish. Especially B&Q.

[thescullster]

Thanks Andrew

Yes the hood does vibrate a bit in operation and the fan does get used. Where does the 80W come from?

Looks like LEDs are a non-starter.

Phil

[thescullster]

Thanks Dave

I thought that at least some of the bulbs I've fitted have been decent make - although more recently definitely B & Q fare.

I'll try paying more for the bulbs and see if that helps.

Phil

[meow2222]

Maybe you jest. I'd probably go over to LEDs, you'll likely need to run them off a different psu. Underrunning them helps handle the heat.

NT

[Tim Watts]

On Friday 15 November 2013 15:36 Dave Plowman (News) wrote in uk.d-i-y:

I was having 12V G4 halogens blow like a bitch before I put in a soft start dimmer - now they last forver (as in have not had one go in 2-3 years!).

The mains ones are worse - thinner filaments and tend ot be sized for 230V EU-standard voltage which is not necessarily true in the UK.

[Dave Plowman (News)]

It could, of course, be vibration from the fan as has been said - but low voltage tend to be more robust than mains in this respect. Think of the pounding car bulbs get.

[fred]

Oh, I think the LEDs might be worth a punt, you could run them from a little DC supply if the existing supply drops out due to underloading.

In the short term, how about wiring the lamp holders in series to undervolt the lamps, they may be a bit pathetic but as the filaments will be running cooler they should be less sensitive to vibration. Worth a try as it's zero cost and a few mins with a screwdriver.

[Dave Plowman (News)]

Presumably they are only switched on when needed to illuminate what's cooking? With your method you might as well just use a torch.

[Dave Liquorice]

Thought these where halogens, halogens don't like being under run, not particulary sure of the process but if they aren't hot enough the tungsten that evaporates from the filament deposits on the inside of the envelope, weaking the filament.

[fred]

Nothing to lose in the experiment though.

My own thoughts are that they'll be disproportionately dim too, say 30% of normal.

[Dave Plowman (News)]

I keep on reading this - but if it were always the case surely they'd recommend you don't fit a dimmer? I have some on a dimmer circuit and they seem to work as normal.

[Andrew Gabriel]

It's complicated and depends on lots of factors, but generally you don't need to worry about it.

The other thing is that lots (most) of the tiny capsule halogens are not really tungsten halogen cycle lamps. They are designed for use in open fittings, and so are low pressure lamps, so they are much less likely to explode when the filament fails.

For the halogen cycle to work, the pressure inside needs to be sufficiently high that if the filament breaks and an arc forms, the lamp will explode. So real tungsten halogen lamps either have an integral fuse, or have to be run in a fitting which will contain the hot fragments if they explode.

[Dave Plowman (News)]

Very true - quite a bang when it's a 2.5 kW studio luminare. ;-) But of course they are dimmed too.

MR16 have the actual bulb within a second glass envelope.

[john964lewis]