(Probably a simple) wiring question

Participant · 18 Jan 2014 at 09:51

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?):

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:

...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)!

Participant · 20 Jan 2014 at 19:03

Thanks both. Got banned shortly after I posted OP

. 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):

Reason I wasted 4 hours of my weekend

Participant · 20 Jan 2014 at 20:30

Nightglow said:
No earth sleeving.

Participant said:

I hadn't finished at that point, that was just WIP with me trying to get the thing working. It's all neat now.

Participant · 21 Jan 2014 at 13:28

JohnnyG said:
No FCU?

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.

Participant · 21 Jan 2014 at 15:13

I have no idea how to wire it up to a 3 core and earth arrangement

. Can I just fuse the two lives and let the neutral bypass the FCU?

Participant · 21 Jan 2014 at 17:27

Yeah, it comes on with the lights and remains on for however many minutes after the lights are switched off again.

Participant · 21 Jan 2014 at 19:12

Unfortunately not, those white wires go off to the rest of the upstairs lighting. The grey wires supply the bathroom downlights.