(Probably a simple) wiring question

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Caporegime
Joined
13 May 2003
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Warwickshire
Hi

I'm trying to find the simplest way to take a permanent and switched live off my lighting circuit for an extractor fan. I was going to splice into the feed in the loft and use a junction box of some kind. However upon opening up my light switch I found an interesting arrangement, including a single core red wire and a twin and earth but with two brown cables (thinking about it, is this sleeving?):

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What's likely to be going on here? Have they used the light switch as a junction box to take a permanent live off to somewhere else?

I was going to base my wiring on this:

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...but why bother with a junction box when I can presumably take both switched live for the fan and permanent live for the fan run-on from the light switch? The only thing I'm struggling with is the neutral back from the fan, but presumably I can run single core flex from the fan neutral to one of the downlight boxes?

Thank you (again)!
 
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Have you got access above, loft etc? if so follow the cable from the pullcord to find the jb.

if not maybe the lighting jb is near one of the downlights, possibly the one closest to the switch or centre of the room where the original ceiling light would have been, maybe you can pull a downlight out and get to the jb?

Best to wire it from the jb with 3 core cable if poss, more elegant solution and will make more sense in future for whoever inherits your wiring.

If not you can take separate feeds for the fan, normally you see switch live and neutral with a separate perm live at fans.

What does the single core at the pullcord do? looks like someone has already taken a perm/switch live from the pullcord for something? is there an existing fan or was a fan fitted in the past?

Also if you dont need a overrun on the fan then you dont need a perm live, even if you have a timer model fan, just link the perm and switch lives out on the fan pcb to make it run

Ps. Just seen your post on DIYnot, looks like they have you on the right track, confirms you have loft access and just need 3 core from jb / redo jb if you cant fit the extra cable in etc
 
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Thanks both. Got banned shortly after I posted OP :p. The single core in the light switch goes off under the attic boards somewhere that I haven't yet managed to identify. Must be the landing light but goodness knows why they routed neutral and earth separately.

I found a junction box in the attic buried under loads of insulation. From this I took everything I needed...perm live, switched live, neutral and earth.

Fan didn't work at all initially, so I checked and re-checked everything assuming I'd buggered up the wiring. Turned out one of the wires had come loose from one of the choc blocks connected to the fan's PCB.

Some pics (to save words):

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Reason I wasted 4 hours of my weekend :o

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The text blended in, once you highlighted it, I spotted it.:o

Should still have sleeved it, especially with that poorly connected live on same cable, could easily come out & risk of electrocution.

Same applies to wiring on terminal blocks.

Trying to get the thing working, is no excuse for sloppy wiring, accidents can & do happen.

Seen a few electrocutions over the years, some avoidable if corners weren't cut...

Other than the wiring, it looks good, the vent in the soffit went well in the end.
 
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JohnnyG said:
No FCU?
Click to expand...

Nope, pointless complication to escape warranty claims. Manufacturer instructions state a 3A FCU, but lighting circuit is fused at 6A off the MCB, which is fine. If the fan fails it'll easily be able to handle 6A before it catches fire.

Plus the wiring is an absolute fanny for a timed fan off the lights. These guidelines are just getting unnecessarily strict. You're telling me I'm fine to use a light bulb designed for 40W at 6A, but not a commercial extractor fan? People are too afraid to question instructions like this.
 
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I'm an electrician, if the manufacturers state something if gets it, it's a requirement for me not a choice. Plus I'm then exonnerated should anything go **** up.
You can do whatever you want of course but for £3 and 10 minutes of work I can't see the point in leaving one out :)
 
Looking at that junction box the only thing fed from there is the bathroom lights and the fan.
If that's the case you could just take the supply L&N out of the box & put it in an FCU then from the FCU to the box, easy enough :)
 
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