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Fitting extractor fan

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Merlin | 11:58 Sun 07th Nov 2004 | Home & Garden
8 Answers

I'm planning the next job - fitting an extractor fan in the bathroom. The house is 1930s and the bathroom has a vent that is just a hole through the wall with a wood grill on the inside and a 'concrete' grill (or grill brick) on the outside. I happy with the idea of wiring from the light fitting (in the loft) and removing and making good the inside and outside vent covers. I'm a reasonably competent DIYer and can get the necessary assistance for the electrics - but if anyone's done this before, I'd appreciate some tips and advice on what nasties to look out for.




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Don't wire from the light! And get a proper bathroom extractor, insulated and earthed

contrary to the previous posting, it is standard practice to wire from the light fitting. That way the fan comes on when you switch on the light. However, you must fit a fan isolator switch in series to the light and the fan which should not be within arms reach of either a bath, shower or sink. Also, if the fan is directly overhead of a shower or bath then it must be of a low voltage type. Hope that helps, but please consult a registered electrician to be safe.

You can wire from the lighting circuit. The fan has a low load.

Considering the age of your house, the first thing to check would be the capacity of the circuit you intend to use.  Realizing that voltages are different in the UK than in the US, I would want to see how many items are on that circuit. In the US the circuit would most likely be 15 amps for a 120 volt system.  Additionally, the exhaust "grill" you describe would probalby need extensive reworking to make it weather proof, unless you intend to exhaust out of the ceiling/roof... Luck!
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Thank you all for your contributions. Clanad! - it's nice to hear from you again.

Off the top of my head, circuits in the domestic supply in the UK are 30 amp, 250 volt, 50 Herz. In the bathroom there is only the light fitting (40 - 60 Watt bulb) operated by a pullstring.

The existing vent is directly above the bath taps, about 4 feet up from the bath - ideal for extracting the worst of the steam. Is this too close to the bath/shower occupant according to UK regs?

And to keep it simple, I would have the fan come on when the light goes on. And as there is a well-used (battery-operated) radio in the bathroom, a quiet model is required.

I shall, of course, consult competent electricians. As for the hole through the wall - it seems to be common practice when installing an extractor for the first time, for one to just make a hole through the wall, stuff the ducting through and make good with the weatherproof outer fitting. Fortunately, I have a ready-made hole.(!!)

Well! Merlin... I didn't pay any attention to the posting signature, just focused on the question.  It would seem that unless the existing grill through the interior wall is the correct size, you'll be required to build a frame inside the wall to hold the fan mechanism.  I don't want to add unneeded work, but in addition, the fan housing on the ones I've installed are somewhere around 6 to 8 inches in heighth.  If your wall is only the standard (for that era) 4 inches, there won't be enough room.  I've only installed such fans in the ceilings and vented through the roof. Again, luck with the project!

Merlin, one final suggestion after giving this more thought.  Since you only have the pull-string light in the room, wouldn't it make more sense to install a combination light/fan where the existing light is now?  I don't know if the attic above the light is accessible, but I've installed a number of these units and it hasn't been that big of a job. The exhasut through the roof is fairly easy as well. 

If you install the fan only in the wall you'll have to route electricity to it, probably from the existing light anyway.  One can also get a combination fan/light/heat unit, but this would draw more amps so be concerned about the capacity of the circuit breaker/fuse for the line.  Good luck...

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Clanad et al

Thanks for all the advice. That was a useful reminder about having a switch to isolate the extractor fan. Routing the electrics from the light fitting through a new switch to the fan will be fairly straightforward in the loft above the bathroom. The existing archaic vent hole is ideally placed through about 10+ inches of wall. I think the weather may have beaten me for this year - I don't fancy being up a ladder for the exterior work at this time of year - not even for a couple of one-hour jobs. Just gives me so much longer to 'plan' the job!

Thanks all.

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