Shower extractor fan cable question

[MasterAbacus]

Hi all,

Just a quick one...

A shower extractor fan, or should i say bathroom extractor fan, wired to the shower pull switch, so it comes on with shower...

What size cable should be used?


Rgds

MA

 

[securespark]

Personally, I would not.

 

[MasterAbacus]

well thats a really informative answer....

I did ask this question sometime last year, but due to delays, ive only just got round to doing it. and cant seem to locate my post.

The wiring is already in situ from the old fan, but it looks like 1mm cable, and the earth wire is cut back, so as part of my Bathroom bonding I want to re-establish this earth.

I just want to know prior to installing replacement unit if i should leave existing cable or replace to 1.5mm, 2.5mm cable.

 

[securespark]

well thats a really informative answer.....

Yes, it is. It tells you that I would not add any other circuitry to a shower. IMO, it is not right to. For what it's worth, the NIC feel the same, too.

It is not against the regs to add to a radial circuit of this ilk, however the OSG states a water heater should have its own dedicated circuit. IMO, a shower is a water heater.

If you did go ahead, you would have to take a feed off the shower switch in the same size cable.

There has been stuff on here before. Search using keywords and Ban, or Ban-all-sheds.

 

[MasterAbacus]

so basicaly what you are saying is that th existing is wrong....

everything is already in place and i asked this question before, and recieved an answer, after searching I cant find my prev post.

From what you tellin me is that the 10mm that is used for the shower should be used to feed the fan...LOL.... i think not.

the existing fan has failed after many years use, hence my question, im just going to do a like for like replacement. But wanted clarification about the cable size.

Im sure someone on here will give me the answer im after... HOPEFULLY.

 

[RF Lighting]

so basicaly what you are saying is that th existing is wrong....

Yes

everything is already in place and i asked this question before, and recieved an answer, after searching I cant find my prev post.

//www.diynot.com/forums/viewtopic.php?t=62527&highlight=

From what you tellin me is that the 10mm that is used for the shower should be used to feed the fan...LOL.... i think not.

Yes

the existing fan has failed after many years use, hence my question, im just going to do a like for like replacement. But wanted clarification about the cable size.

10.0mm² to feed an FCU from the shower switch, then onto the fan.

Why not do it properly, and feed the fan from the lighting circuit?

You could then install a fan to come on with the lights, or one with an integral pull switch, a humidistat or even a PIR movement detector.

Im sure someone on here will give me the answer im after... HOPEFULLY.

We will give you the correct advice. It might not necessarily be the answer you want though.

 

[securespark]

Saved me th bother, RF.

 

[RF Lighting]

Are you feeling all redundant again?

 

[securespark]

[Sobs quietly in corner..]

Yes.

 

[philrosenberg]

From what you tellin me is that the 10mm that is used for the shower should be used to feed the fan...LOL.... i think not.

This is because the circuit is fused (or MCB'd) assuming 10mm cable, if you use smaller and a fault occurrs then the smaller cable could potentially catch fire before the fuse blows. The only way to do it would be as RF says you would need to take 10mm to a fcu with a smaller fuse in, then the appropriate cable on from there. Your fan instructions should tell you what the fan is rated to in order to determine what size fuse you need. Bear in mind the fcu must be accessible (so the fuse can be replaced if needed) and also I presume a regular fcu cannot be inside any of the bathroom "zones" these roughly extend directly above the bath to the ceiling and for 3 metres around the bath to the ceiling or 2.25 metres, whichever is lower.

I'm telling you this so you're not tempted to just leave it as is with 1 mm which would be dangerous, but you'd be much better taking securespark's advice and not running it from the shower circuit, even if only because the fan should continue running after the shower is switched of to clear the remaining steam.
If you want automation then perhaps a humidity sensor would be better such as http://www.tlc-direct.co.uk/Products/BGREMHM.html

Also bear in mind this work is notifiable to building control under part P