Bathroom extractor fan question

Gaygle

Gaygle

Gaygle

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Hi all,

Currently got an extractor fan above my shower (comes on/goes off with the lights with the switch outside the bathroom and an isolator above the door) and it's a little noisy, so wanted to replace it with a quieter one and ideally with one with a timer built in too. The current fan is a 12v SELV one with a transformer in the loft above.

I understand I will need a permanent live connection (only have a switched live+neutral at the moment).

What would need to be done to get this to work?
 
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There should be a lighting junction box or similar in the roof above your bathroom with a perm live passing through for the light circuit. This should have everything you need, as it'll have the perm live to the light switch and the switched live to the downlights and the fan.

If necessary or easier you can just chop into the lighting circuit cable (should be 1mm2or 1.5mm2) to get a perm live, but I doubt this will be the best solution.

You would need to swap the twin and earth going from the junction box to the fan isolator for three core and earth, as you need live, switched live, neutral, and earth (though earth may not be required if double insulated) going to your fan. You may also need to change the isolator for a three pole isolator, assuming only a two pole was wired due to only needing to isolate switched live and neutral.

Either way, it will be easy.
 
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Thanks for the replies.

If I was to replace the axial fan with a mixed flow or centrifugal fan, would i get rid of the transformer altogether and just run 230v into it? Would there be any other complications with this such as fuses/RCD's/whatever?

I assume the mixed flow/centrifugal fan would be mounted in the loft, but have a length of ducting leading down into the grille (which would sit where the extractor fan used to be) above the shower?
 
You would have no need for the transformer. You'd run the fan from the same 240v mains circuit as the bathroom lights.

Some fan manufacturers state that a FCU must be used, some don't require it. In reality your lighting circuit is protected by the consumer unit so your fan would be too, and the main reason for down fusing a fan is so that a broken fan doesn't take out your lighting circuit also. However if it broke, you could isolate it and switch the lights back on, so really it's just another way for manufacturers to escape warranty claims!

Regarding ducting, simplest is as you say because you already have the hole. Remove ceiling fan, replace with vent from Amazon or eBay, run ducting through roof via in line centrifugal fan, venting through another plastic vent in the soffits.

Insulate ducting so condensation doesn't cause moisture problems in your expensive new fan.
 
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Excellent, thanks for this. I'm useless with electrician stuff. Could the power cable currently going into the transformer simply be used to power the inline fan in the loft instead?

I might even forget about the timer/humidistat if I just had a more powerful fan in the first place as it would get rid of the humidity quicker.
 
The switched live going to the transformer could be used for the new fan, yes. Forgoing the timing feature would save you having to run perm live and replace the isolator (if not already three pole being used as two).

When you install the fan, isolate it from the joists as much as possible. This will reduce noise perceived in the bathroom. I used a gardener's kneeling pad.
 
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The switched live going to the transformer could be used for the new fan, yes. Forgoing the timing feature would save you having to run perm live and replace the isolator (if not already three pole being used as two).

When you install the fan, isolate it from the joists as much as possible. This will reduce noise perceived in the bathroom. I used a gardener's kneeling pad.
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Fixing to the rafters instead of the joists will significantly reduce the perceived noise.
 
Yup. Replaced a £30 ebay special which was there before and its quieter and keeps the steam out much more effectively.

Install the fan as far away from the vent in the bathroom as you can as it keeps it quieter and the fans also work better "pulling" rather than "Pushing" if that makes sense.

Also save yourself a few bob on insulated flexi pipe (its a crazy price!), i just wrapped mine in some leftover loft insulation with some gaffer tape around it at intervals to hold it on, no issues with condensation dripping back through

edit - if they only have the timer one you can link the 2 live terminals together to put it back to a standard one, its still way cheaper than the one you posted.
 
Great cheers mate

The extraction pipe will be running under the loft board so I can drag a bit of wool over it.

Just ordered. Strangely a bit cheaper form their ebay shop
 
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