DIY Doctor

Extraction Fan Advice

Postby pbp » Fri Dec 19, 2008 10:47 am

I have a new extraction fan with a 140w motor with twin lights at the back which are 2x 40 wats max.

The other day I switched on the lights and there was a pop and the housing circuit tripped out. I reset it and checked the bulbs in the fan. One bulb had blown and now I have replaced both bulbs the lights will no longer work.

The extraction fan still works okay but can anyone help me on this one as we need to have the lights working

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Simply Build It

Postby stoneyboy » Sat Dec 20, 2008 11:56 am

Check the bulbs in another fitting.
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Postby pbp » Sat Dec 20, 2008 5:31 pm

Urrrm Yes I did that! and have new bulbs that work in everthing else expcept the fan....

thanks for the technical advice
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Postby ericmark » Sat Dec 20, 2008 11:01 pm

You say housing circuit tripped so I would assume that is in consumer unit? Normally a 6 amp B type would be used so up to 30 amp may have flowed before it tripped. Many fans have manufactures instructions to use 3 amp fuse without this protection it may have blown a printed circuit track if cheap bulbs without internal fuses are used.
When a bulb blows it can caused ionisation which means the gas inside the bulb becomes conductive. Good quality bulbs have built in fuses which will blow if this happens. When this does happen the glass often goes a black/blue colour and the bulb seems to flash as it blows. Without the built in fuse to current can go very high a MCB will normally trip in under 40ms but a B6 MCB will take between 18 to 30 amp to trigger the magnetic part of the trip even higher in first 40 ms which is why electronic equipment is often protected by a fuse rather than a trip as with a short circuit a fuse will often rupture quicker than a trip can open.
I hope I am wrong and this has not happened in your case. But with no details on fitting or exactly what opened due to fault only a general answer can be given. Although even if you did give more manufactures do not tend to give out details on how the fan is made so likely could not be more specific even if more was known.

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