Extractor Fan Query

[Stu777123]

Hi all

want to install an extractor fan which works of the from the lighting circuit but not the light switch

It would also have a timer fitted

want to meet all the regs so was first going to run power from bathroom light to Double pole isolator switch outside the bathroom.

I then wanted to run this to a pull switch before running it to the exractor fan which has a timer fitted

I'm guessing i'm going to have to activate the pull switch twice to start it again if left to shut off automatically on the timer. does anyone know a way around this?

also does this meet with the regs and could i just get away with a double pole pull switch as an isolator?

cheers

stu

 

[bernardgreen]

Use a momentary pull cord switch

http://www.tlc-direct.co.uk/Product... cord switch&gclid=CIzho6yHosACFW3JtAodX00A2w

has a red cord which you can change to a white one.

 

[JohnW2]

... was first going to run power from bathroom light ...

You will only be able to do that if the bathroom has a 'loop-in' wiring system, because you will need a 'permanent live' (and neutral) feed.

... to Double pole isolator switch outside the bathroom. ... I then wanted to run this to a pull switch before running it to the exractor fan which has a timer fitted

The instructions for your timer fan will probably require it to have a 3-pole isolator switch (permanent live, switched live and neutral). That being the case, you would theoretically need to take the supply feed (from light or wherever) to the pull switch (see below) and thence take the perm live, switched live and neutral through a 3-pole isolator to the fan.

I'm guessing i'm going to have to activate the pull switch twice to start it again if left to shut off automatically on the timer. does anyone know a way around this?

As Bernard has said, if you use a 'momentary action' pull-cord switch, you'll just have to pull it once.

Kind Regards, John

 

[ban-all-sheds]

If he's using a momentary switch to trigger it he need only take L/N/E to the fan, and therefore only need a 2-pole isolator. Although apart from guarding against the possibility of the fan failing permanently on, I don't see why isolators are particularly necessary in a bathroom with a window.

You never see one installed for the light.

 

[JohnW2]

If he's using a momentary switch to trigger it he need only take L/N/E to the fan...

Eh? The fan will need a permanent live to enable it to run, and a switched live to trigger it.

However, on reflection, you're right that it would need only a DP isolator (not that it really needs an isolator at all!), as the OP suggested, since the momentary pull switch can/would be downstream of the isolator. - so my apologies for unnecessarily confusing that issue!

Kind Regards, John

 

[ban-all-sheds]

The fan will need a permanent live to enable it to run, and a switched live to trigger it.

Yup.

L/N/E to the fan, switch wired across L & SL terminals.

 

[JohnW2]

The fan will need a permanent live to enable it to run, and a switched live to trigger it.

Yup. L/N/E to the fan, switch wired across L & SL terminals.

Fair enough, but it's become a bit semantic! - the 'switch wired across L & SL terminals of the fan' will be providing the fan with a S/L (and the feed from the isolator will be providing the perm L and N)

Kind Regards, John

 

[Stu777123]

Thanks a lot guys

just to make sure i've got it right, is this what your talking about or compatable with regs?

View media item 81401
hopefully my wiring diagram has been displayed

 

[JohnW2]

Thanks a lot guys ... just to make sure i've got it right, is this what your talking about or compatable with regs?

Yes, that would work. However, it would be simpler/tidier (one less cable) if you connected both the L and S/L (and earth) of the momentary switch to the fan - then you would need just one cable from switch to fan, rather than one to fan and one to isolator.

Kind Regards, John

 

[ericmark]

want to meet all the regs

To start with this work may need registering under Part P it depends exactly where all parts are and country you live in.

The Part F is the other thing here we need to know if there is a window and if so does it open. If a fan is required rather than just being something you want then there are extract rates and run on times to consider.

Also one has to consider Part L if you home is electric heated or heating uses a balanced flue then no problem but the word open flue also covers things like gas fires built into the wall with what would seem no access to the flue if it draws air from the room that is called an open flue.

Using heat recovery units it's not a problem as it pumps air both in and out of the house but simple extractors with wood burners are a real problem.

Many seem to think it does not matter if in another room but clearly all air pumped out must get in from some where so question has to be where is the air replaced from. Again Part L details this.

Even a simple tumble drier could fall fowl of Part L.

What I have not worked out is if the 15 minutes time is from entering or leaving the room I would have thought the latter but unless one uses a PIR can't quite see how it could be done.

The main reason for the isolator is fans are not that good and often do fail so to be able to continue using lights when a fan fails you need an isolator. Depending on the size of fan H&S could require it to be visible from the position of the fan but unlikely the fan will exceed 370W so likely isolator is just so lights can be used should the fan fail.

Using a pneumatic timer switch and non timed fan or a momentary switch and timed fan is the easiest way to comply but also you can consider humidity control and PIR.

The Approved documents are here do remember Wales and England use different Part P and so does Scotland not sure about Ulster etc.

I see not point in trying to explain exactly how to do it until we know exactly what is required. And of course how to the letter of the law you want to go. To me recovery units are far too expensive and even though I have a open flue fire I still use my tumble drier but I am just careful not to use the two together.

I know you have Essex down but you may be talking about a house somewhere else so worth saying the rules do change.

 

[JohnW2]

want to meet all the regs

To start with this work may need registering under Part P ... The Part F is the other thing here ... Also one has to consider Part L if ...

This is a little difficult/sensitive ... I cannot criticise, since everything you say is, of course, strictly true, but ......!!

What we have been discussing with the OP would be fully compliant with the Wiring Regulations. As for notification, if, as seems to be the case, the property in question is in England, the work would not be notifiable (which I presume is what you mean by "registering under Part P"), provided the ceiling height is not less than 2.25m (which would be unusual).

Kind Regards, John