Where's best to put the extract fan in a bathroom?

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oldbutnotdead

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Prepping the current house for renting out so putting an extract fan in the bathroom (it gets steamy in there). Plenty of headroom (ceiling is at 2800) so planning to core through the wall to outside.
Physics tells me the best place to put the fan would be at the tap end above the bath (where the shower is as well)- that way all the vapour generated by shower can be sucked straight out the room.
Safety makes me wonder if 400mm vertical and minimal horizontal clearance between the shower head and the fan is good enough- in the 25 years I've lived in the place that bit of wall has never got wet when I've used the shower but it would be possible.
Layout- the long wall where the bath is is the outside wall, radiator is not at the tap end. There's a window (opeanble) above the bath in the middle of the room, there's enough clearance above window and lintel and masonry etc. to put fan above it.
I really don't want to disturb the roof by venting through the ceiling and out that way- natural slate and not in the best condition.
Ta for assistance
 
What type of fan you have, and where it can go is detailed in the WIKI at http://www.diynot.com/wiki/Electrics:bathroom_zones

One thing to remember is that, if you have a 4" hole extracting from the bathroom, you need an equivalent space for air entry, otherwise the fan will be trying to create a vaccuum in the room and will not work efficiently.

ALso, if the fan is to be ducted, consider if the fan is powerful enough. Some cheapo fans are barely able to push air through a 9" cavity wall, let alone through a metre of corrogated ducting.
 
Ta both. TheVictorian- not the biggest bathroom in the world (1700 wide x 2400 long), door is opposite the outside wall so pretty much as far away as possible. Taylortwocities- the fan is wall mounted going through the (9") wall, it'll be at minimum 2400 above floor level so outside the zones. Wiring from fan to lighting circuit will be in flex on the surface through the ceiling (which will be about 6 mm above the fan) so no extraneous requirements to do with buried cable. It has one of those rubbish backdraught preventers (2 flaps on tiny wee springs)- fitted a similar one in the utility room at the House of Pain, I cored the hole slightly downhill (so any moisture buildup in the duct would go outside rather than inside), as a result the poxy little springs aren't strong enough to hold the flaps when the wind blows. So this one is going in level.......

I had a Google after making the post- everything came back with 'stick it above the tap end if you can' so that's where it is going- subject to limitations with poo pipe outside, half brick wall turning into full brick wall, little fun bits like that :)

As an aside, I was quite surprised to see the zone is measured from floor level rather than from surface of shower tray/bottom of bath- makes my life easier so not complaining....

EDIT Oh yeah TTC, thanks for that reminder- there's a sliding door on the room with a 10mm gap under it, if that isn't enough I'll stick a vent in the thing :)
 
oldbutnotdead said:
As an aside, I was quite surprised to see the zone is measured from floor level rather than from surface of shower tray/bottom of bath- makes my life easier so not complaining....
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It doesn't matter; fans are allowed in zone 1 (subject to suitability).
 
oldbutnotdead said:
As an aside, I was quite surprised to see the zone is measured from floor level rather than from surface of shower tray/bottom of bath- makes my life easier so not complaining....
Click to expand...
If it's any consolation, you are by no means the only one to be surprised by that! Like a good few of the regulations, it does not look as if it was intended to make sense :-)

Kind Regards, John
 
stillp said:
The bottom of my bath, and shower tray, are sloped so the water can drain.
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I'm not too clear as to how "finished floor level" is defined. A family member has a 'raised bath', with two steps ups to it. There is no visible 'floor' at the top of the steps (only under bath, and therefore not 'finished'). If one takes 'finished floor' level as relating to the actual floor (below the steps), zones 1 and 2 would end only about 1.8m (probably less) above the bottom of the bath.

Kind Regards, John
 
JohnW2 said:
zones 1 and 2 would end only about 1.8m (probably less) above the bottom of the bath
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In such cases the person doing electrical work has to use some of that rare commodity, common sense. BS7671 is a standard, not a text book or a recipe book!
 
stillp said:
In such cases the person doing electrical work has to use some of that rare commodity, common sense. BS7671 is a standard, not a text book or a recipe book!
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One would certainly hope so (although I'm not holding my breath in relation to all people 'who do electrical work'!).

However, I would think that it's much more difficult for, say, someone doing an EICR, since (although they can 'mention things') I presume that they cannot really 'fail' or 'code' something which, even if a violation of common sense (which they personally feel is 'unsafe'), appears to be compliant with BS7671.

Kind Regards, John
 
What are you discussing?

Fans are allowed in zone 1 - are you saying, regardless they should not be placed there?

They are like showers.
 
EFLImpudence said:
What are you discussing?
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The general concept of Zones 1 and 2 ceasing at 2.25m above 'finished floor level' (even if the bottom of the bath/shower is significantly above that level.
EFLImpudence said:
Fans are allowed in zone 1 - are you saying, regardless they should not be placed there? They are like showers.
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Indeed, but, as you know, both fans ('if suitable') and electric showers (and a few other things) are specifically allowed in Zone 1 and Zone 2 by 701.55. However, other things (e.g. FCUs) are not allowed in those zones, so it would seemingly be 'compliant' (albeit not very consistent with common sense) in some bathrooms to install, say, an FCU on wall or ceiling appreciably less then 2.25m above the bottom of the bath (i.e. possibly easily touchable by someone standing in the bath).

Kind Regards, John
 
EFLImpudence said:
Oh, I see - not the OP - ok.
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For what it's worth, it actually was a point raised by the OP (if 'OP' means 'original poster', rather than 'original post'!!)....
oldbutnotdead said:
As an aside, I was quite surprised to see the zone is measured from floor level rather than from surface of shower tray/bottom of bath- makes my life easier so not complaining....
Click to expand...
EFLImpudence said:
I suppose that is a good point.
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Glad you agree. It is, of course, a point we have discussed previously.

Kind Regards, John
 
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