Toilet extract fan wiring question

[Chris Green]

This is as much a "how to do it neatly with minimum junction boxes" as it is about how the rules apply, but here goes anyway...

We are installing a new toilet cubicle downstairs for my M-I-L who is finding stairs increasingly difficult. It's in the corner of what is to become her downstairs bedroom. So far so good! :-)

To avoid chasing new channels in the (very hard) walls I'm using two Quinetic switches, one for the main bedroom light and the other for the toilet light which will also run the extract fan.

I have (reasonable but not *easy*, it's in the eaves) access to the existing 6A MCB protected mains feed for the downstairs lighting above the bedroom and toilet cubicle.

I'm using a Quinetic 'double' lighting receiver to handle the two Quinetic switches. The toilet light and fan are a combined unit but have the usual live/switched live/neutral connections which specifies that it should be run from a 3A FCU.

So, how do I fulfil the isolation requirement for the fan (among other things)? The Quinetic receiver has just live, neutral and two switched live connections.

Opinion genrally seems to be that the 3A protection is rather pointless when a toilet light/fan is run from a 6A MCB protected circuit. So, should I just put a 3-pole fan isolator to isolate the toilet fan/light and leave it at that? I don't really want to put a

3A FCU *before* the Quinetic receiver because it will then switch off the main bedroom light as well as the toilet.

Where should the isolator be, putting it anywhere in/around the toilet cubicle or bedroom gets us back into chasing hard walls. I guess a lockable one in the eaves reachable by opening a small door would be the 'right' way to do it.

Comments and ideas very welcome.

[Tricky Dicky]

Most fan isolator switches for bathrooms and WC are positioned outside the room above the entrance doorway. As far as I can see you only need to provide isolation for the fan the rest I would suggest is wired directly into the lighting circuit you describe. I do not know how you intend to create the cubicle but presume it will be a studded structure with a wall and doorway at right angles to each other. If so you should be able to wire in the isolator switch during its construction.

Richard

[Chris Green]

That is a good point, the cubicle will be a standard dry-lined construction so, as you say, I can put the isolator switch high up and out of the way somewhere there. Is there any good reason for the isolator switch being outside the cubicle?

The light is integrated into the fan, though in principle I can't see any reason for not wiring it such that it can be turned on even when the fan is isolated.

Another thought - would one 'service' the fan from the 'user' side or would it be more reasonable to expect whoever services the fan to want to access the back of it? That would affect where you'd want to put the isolator switch. ... and anyway, who ever services a toilet extract fan? :-)

[ARW]

They were usually placed outside because of misread 16th edition regs.

The OP is probably going to need RCBOs to meet the 18th edition regs.

[Chris Green]

Ah, a good point, this is I guess an addition rather than a replacement so I need to conform to 18th edition. I should be able to replace the existing 6A MCB with an RCBO I think, just need to check the space in the CU.

[Roger Hayter]

Not unless you have a bath or shower in your cubicle, which sounds unlikely. But I would put it where no-one is likely to touch it with wet hands. High up should do.

I have a similar appliance. That is I suppose ok if the fan *can* actually be serviced without risk of shock from the light circuit. Mine couldn't be, as the light needs dismantling to get at the fan.

[Chris Green]

No, no bath or shower, high up makes sense. I just thought it would be more out of sight inside rather than outside.

It's a 12v lamp with a transformer, I guess as long as the mains side of the transformer is inaccessible when servicing the fan then it would be OK. However I can't see how the lamp being on would help much so I think I'll drop the idea and isolate the whole thing! :-)

[PeterC]

From not-very-accurate measuring, it looks as if a miniature RCBO will replace an MCB. My board is a Wylex from about 1990 and a Wylex mini-RCBO seems to be OK.

[spuorgelgoog]

Or, if the CU can't take an RCBO, an RCD FCU fixed somewhere convenient.

Owain

[spuorgelgoog]

Especially if the toilet doesn't have a window, a £15 LED emergency light may be useful, both for fan maintenance and for emergency use.

Owain

[ARW]

Yes.