Extractor fan - loop at switch

[emmamason]

Hi,

I'd like to install an inline timer extractor fan in my bathroom so that it comes on with the bathroom light. The wiring diagrams I've seen are for circuits that loop at the ceiling rose, but mine loops at the switch. At the light in the bathroom I just have a twin core and earth, so no permanent live. What do I need to do in this situation?

Thanks,
Emma

 

[riveralt]

I did a wiring diagram for a similar scenario which is outlined below - you might need to adapt it to accomodate your shower manufacturers instructions. This was for a wall fitted extractor fitted with a timer overrun

Extractor fan circuit

• riveralt
• 3 Dec 2010
• 2

This was a small bathroom with an accesible walkthrough loft above. I put both the FCU and the three pole isolator up there.
The switch cable was plastered in and the customer didn't want the plaster/wallpaper removed.

 

[Luckyphil]

Or .... if you have access via the Switch to the Loft Space or underfloor , Take a 3 Core & earth from the Switch . Brown fom the Live Side of the Switch (ie permanent live) Black (Sleeved Brown) from the Switched Side of the Switch , Grey (sleeved Blue) crimped or connected to the Neutrals which are presumably in the Switch Box , then Earth connected (and G/Y Sleeved) with the others , The Three Core should then go to a Triple Pole Fan Isolater then onto the Fan

At the Fan - the Brown is your Permanent Live
the Black (Sleeved Brown) is your Switched Live
The Grey (Sleeved Blue) is your Neutral
The Fan may have no Earth Connection , Do NOT cut the
Earth cable out - sleeve it G/Y and put a Cnnctr Block on it
and tuck it out of the way in the Fan.


Lucky

 

[emmamason]

Thanks very much for your replies

Riveralt, if I was to do it that way am I right in thinking that the neutral and live loop you have from the light wouldn't exist in my scenario since they are going from the switch? Actually, come to think of it you also have a live from the switch to the light - I don't think I have that either. I found a diagram of my circuit method:

Untitled

• emmamason
• 8 May 2011
• 1

Lucky, I thought about doing it this way but it's very crowded in the switch back box - there are 4 cables and I think I'd struggle to fit in another one. Maybe the only way though!

Thanks!
Emma

 

[riveralt]

Given the circumstances as you describe then you are going to have to replace the twin and earth (switch live and neutral to lamp) with a three core and earth - as suggested by luckyphil.

The additional core should be used to take a permanent live up to the extractor fan through a three pole isolator - however I'm not sure how you will introduce an FCU into the wiring - as this will more than likely be required by the manufacturers.

 

[Luckyphil]

What I was suggesting was to run an extra 3C & Earth from the Switchbox , onto a 3 Pole Isolater and then to the Fan , You can then pick up all you need at the Switchbox ..... subject to access and getting that Cable in there !!

Lucky