Wiring bathroom fan/light combo

[sergeantash]

Hi all,

Pre-cursor, I'll of course obtain necessary Part P certification and building regs prior to any work...

I'm planning on adding an extractor fan-light combo unit within my bathroom - I want it to turn on and off with the main bathroom pullcord light switch (powering the 12v low voltage spots that I am fitting) BUT I also want the ability to switch the fan/light on and off exclusively via my fan isolation switch outside the bathroom above the door.

Excuse my crude diagram drawn into the plastered wall but is this a fair representation of how the circuit would flow?

Untitled

• sergeantash
• 3 May 2010
• 1

The upper circle is the main light circuit looping in/out of a junction box from which I will spur a 1.5mm cord to the bathroom pullcord switch - from which L2 will feed into another junction box, splitting to the 12v low voltage lights, the other to the fan isolation switch and onwards to the fan itself. The neutral/com and earth will also feed through respectively.

The fan/light unit does NOT have a timer and so doesn't require a permanent live.

Is this the best/right way to wire what I need? The junction boxes are 30amp 250v rated.

Many thanks!

 

[ColJack]

define "exclusively" in respect to turning the fan on and off..

do you want to be able to turn the fan on without turning the lights on or just to be able to turn the fan off when the lights are on?

if the latter then your drawing is fine.

 

[sergeantash]

Sorry for the confusion, I mean't exclusively if the main lights are on (via pullcord). In which case, I'm good to go?

One more problem I seem to have caused myself is the confusion of L1, L2 and COM within the pullcord, I assumed L1 and L2 were the live continuity i.e. each side of the switch with COM being neutral and unswitched, is that correct?

 

[ColJack]

no.. com is switched between L1 and L2.. live into COM, live out of L1 or L2..

neutral in a terminal block.

 

[ban-all-sheds]

Pre-cursor, I'll of course obtain necessary Part P certification and building regs prior to any work...

How can you get work certified before it's done?

powering the 12v low voltage spots that I am fitting

12V is not low voltage. The IEC definitions of voltage bands are:

• Extra Low Voltage: AC below 50V and DC below 120V
• Low Voltage: 50 - 1000V AC or 120 - 1500V DC
• Medium voltage: 1kV - 35kV
• High voltage: 35kV - 230kV
• Extra-high voltage: >230kV

This is not some pedantic technical point - if you start getting involved in doing your own electrical work, and start learning about regulations etc you'll come across references to "Low voltage", and it'll be no good you thinking that that means 12V...

I assumed L1 and L2 were the live continuity i.e. each side of the switch with COM being neutral and unswitched, is that correct?

I don't know whether to laugh or cry. How you think you can put forward a convincing explanation of the way that you'll make reasonable provision in the design and installation of your electrical installation in order to protect persons operating, maintaining or altering it from fire or injury beats me.

I don't suppose it will do any good to urge you to get an electrician, and not attempt electrical work yourself until you know something about it, will it....

 

[sergeantash]

Sadly every forum has a troll such as yourself - whilst I appreciate a minor element of your post (even if put forward in an incredibly arrogant manner) please consider that posters submit to this forum for help and assistance, not for a patronising talking-down and 'better than thou' response.

Thank you to ColJack for his very helpful information.

Everyone makes mistakes, I'm here asking questions because I want to get this right, clearly some are better are providing a friendly and helpful response than others.

 

[geraint]

superb... it is supposed to be a helping site... not a site to be abused or full of regulations,, and the clever ones are not even in any trade...

 

[ban-all-sheds]

Pre-cursor, I'll of course obtain necessary Part P certification and building regs prior to any work...

That could easily indicate that you are helplessly muddled about how what the Building Regulations require, how notification works, what Part P certification means etc.

Getting those things wrong could land you in a mess which you would rather avoid, so why was I being a troll, or arrogant, or patronising to ask you what you meant?

Feel free to be rational, logical and objective in your answer.

12v low voltage spots

If you look at P1 it will tell you

The requirements of this Part apply only to
electrical installations that are intended to
operate at low or extra-low voltage and are...

so if someone thinks that 12V is low voltage, what might they think 230V is, and what might they decide about the applicability of P1?

Why was I being a troll, or arrogant, or patronising to point out the correct definitions of the terms?

Feel free to be rational, logical and objective in your answer.

I assumed L1 and L2 were the live continuity i.e. each side of the switch with COM being neutral and unswitched, is that correct?

You don't even know how a simple switch works.

Think about that. Your knowledge of electrics is so limited that

you don't even know how a simple switch works.

Do you know what would happen if you did wire one up on the basis of your assumption?

I'm here asking questions because I want to get this right, clearly some are better are providing a friendly and helpful response than others.

The problem with that is that you'll only ask questions about what you think you don't know, not what you actually don't know.

You came here because you had a question about connecting up a fan. If you hadn't had that, if it was just putting in a light switch which you assumed you knew how it worked you wouldn't have asked here, you'd just have gone ahead and done it. And then what?

I quite understand how it's not what you want to hear, but carrying out electrical work on the basis of assumptions when in reality you have a huge lack essential knowledge is extremely inadvisable - it is dangerous and irresponsible.

• //www.diynot.com/wiki/electrics
  
  
• //www.diynot.com/forums/viewtopic.php?p=75416#75416
  
  
• http://web.archive.org/web/20080213151445/http://www.kevinboone.com/electricity.html
  
  
• http://web.archive.org/web/20080213151445/http://www.kevinboone.com/domesticinstallations.html
  
  
• //www.diynot.com/forums/viewtopic.php?t=7553[/list]

 

[sergeantash]

Putting to one side the persistantly arrogant style of your posts, I do understand how a switch works although hadn't until now encountered a need to wire a ceiling pullcord type. I wouldn't have at any stage proceeded to wire up any electrical element for which I had doubt and in such a case would refer to instructions, reference books or otherwise - I happened to be online at the time and was 'thinking out loud'.

The point you fail to miss is your post style, your failings in basic friendly interaction and the need to belittle those you respond to throughout your past posts. To a point, you would do yourself justice in simply not bothering as your posts show a real lack of real any enthusiasm to really help.

If you really do genuinely know what you're talking about and work professionally in the electrical industry, why not try and gain a little respect by becoming the kind of mentor that users of this forum register to find - sadly your opening post in response to my OP suggests to me and others that you're a cock, I would like to think that in real life you're really not, although I am happy to be corrected.

Back to the original topic, I do have another question - the fan installation instructions suggest a 3amp RCD to protect the fan, should I splice into a socket/backbox style RCD after the fan/light combo isolation switch within the loft?

 

[holmslaw]

..

 

[bongos]

If the circuit you're connecting the fan to does not already have RCD protection then you will need to use something like this to connect your fan. It should be fitted with a 3A fuse.

If the circuit already has RCD protection then you could just use a standard FCU fitted with a 3A fuse.

 

[sergeantash]

Thanks for your reply holmslaw - the isolation switch that I bought doesn't have a built in fuse, here's a link to the exact unit:

http://www.diy.com/diy/jsp/bq/nav.j...refview=search&ts=1273057546941&isSearch=true

Do I either buy a new switch frontplate to incorporate a fuse or loop into a fused spur box in the loft, then onto the fan-light?

 

[bongos]

As your fan doesn not have timer overun you do not need a three pole isolator. You need a two pole isolator (the earth is never run through the isolator).

Have a look at the one I linked to above. If you do not require a FCU with RCD protection because that circuit already has it then you could use a standard FCU like this.

 

[sergeantash]

As your fan doesn not have timer overun you do not need a three pole isolator. You need a two pole isolator (the earth is never run through the isolator).

Understood, from the shelf they only had 3-pole units. I assume I can use just the L1 and N out from the fan isolation switch that I have with L2 as a redundant unwired pole should I change the fan to a timed unit in the future? Regarding the earth,

Have a look at the one I linked to above. If you do not require a FCU with RCD protection because that circuit already has it then you could use a standard FCU like this.

Lovely, I'll grab one of those tonight. I'll put together a schematic just to check that all is planned correctly and post it here a little later if I get chance.

Another question (sorry!), I intend to install a shaver socket into the bathroom - I have read that it is fairly common to install these via the lighting circuit - could I run this unit from the same FCU or does it require it's own?

Thanks very much for your help!

 

[holmslaw]

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