replacing bathroom extractor fan


I want to replace my bathroom extractor - looks quite old and is a strange size (I think) the front cover is, 160mm x 160mm. I can't see a
make on it but it is one of the type that switches on and off with the light and stays on a minute or so after switching it off. I want to replace it as its noisy but with a pull switch type so it doesn't come on with the light all the time.
Any ideas on replacement? I don't need to replace the outside wall louvre as it looks and works ok.
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further to last post, have taken the extractor off to look at it, it says 5927 timer model on it.
Notice that it has 3 wires - 2 red and one black, if I was replacing it with a switched type how many wires do they have - thought they had 2 wires? would it set any problems ?
Thanks
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The second live cable is for the timer. If you replace the fan with a non-timer it will just need one live and one neutral, so just use one of the live cables and make the other live cable safe. I had similar when replacing a timer bathroom extractor fan with a non-timer. Bathroom extractor fans are normally for a 15cm/6 inch duct/opening.
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Obviously the live cable needs to be connected via a ceiling switch and not be connected to a live cable that is continuously live.
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I was a bit quick in replying so I guess the L , N , SL
SL relates to Switched Live? so in that case the new extractor would use the wire from N and the wire from SL and then isolate the L - does this make sense?
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Presumably, the SL is coming via light switch - so if you use that, the extractor will only work when light is on. So unless you only want it to come on if the light is also on, you'll need to use the other Live. Don't cut either of them until you've tested it - in case they're wrongly labelled.
I'm not aware that the Live feed should also have a separate pull switch (assuming your new extractor comes with a pull-cord switch built in) but Codswallop may be more up to date than me.
And remember, if you dispense with the timer, the thing will often be accidentally left on.
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Martin

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Any device like a fan or other motor is required to have a means of disconnection for servicing. If this is a switch it must switch *all* connections and have at least 3mm separation when open. Three pole switches specifically made to fulfil this requirement for bathroom fans are readily available.
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Chris Green

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That's interesting - thanks. When did this rule come in, and does it apply everywhere or just wet rooms?
We're in a 40 year-old place, and will also want to swap a couple of extractors (which have no separate isolating switch) before long. Will this rule apply to such circumstances or just new-builds?
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Martin

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Everywhere. It relates to maintenance of appliances with moving parts, and is nothing to do with being in a wet location.

There's no requirement to bring up to current standards, unless you are modifying the installation. It would be a moot point if a fan replacement counted as modifying the installation.
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What happens if the fan needs to be a SELV model to meet current regs but the original fan is not?
Adam
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Everywhere, e.g. there should be isolation switches for hoods/extractors in the kitchen, for boiler electrics, in fact just about anything that's permanently wired as opposed to being plugged in. I'm pretty sure the requirement has been in place for quite a few editions of the IEE wiring regs., it's not a recent change.

Hmm, interesting question, I suspect that if you just change the fan and use the existing wiring then it's allowable. However since the IEE regs are not the law anyway it's questionable whether you have to conform to them at all. On the other hand an isolation switch is a big convenience when you want to clean the fan out etc.
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There is it L , N , SL are marked on the present extractor so I guess I just use one wire from L and one wire from N and isolate the SL wire is that correct?

The ducting is 4 inches so when I see 4 inch bathroom extractor (100mm) in for example screwfix then this relates to the ducting then and not to the actual size of the extractor then?
I have looked in the screwfix catalogue and they don't actually give the front plate size, only rate. Unless I am reading it wrong.
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No, on a non-timer fan the single live cable needs to be switched, not continuously live.

Yes, the size refers to the diameter of the fan blades and therefore the duct, not the front/inside grill. You need 100mm if that is the diameter of the duct, 150mm if the duct is 150mm diameter.
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wrote:

yea but hes going to have a fan with a pull cord on it so he *does* need to use the one wire from L.

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wrote:

Yes! Dont snip the SL incase it would be usefull in the future, just insulate it.

Yus
Is the front plate size vital? Screwfix only give bare bones information.
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marvelus wrote:

The front plate size is vital because the old one overlaps the tiles, just the way the installer did it I guess. I will take mine off and just go down to b&q or a diy place with it to get a similar size, guess they wont be more than a couple of quid difference between them and screwfix! Got all the info I need from this newsgroups - great and thanks.
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