Could anyone please advise me how to wire an extractor fan with run-on
timer in a bathroom? It needs to be wired into a wall mounted light.
The instructions say that switched live, permanent live and 3 AMP
double pole fused spur are needed. The pull cord switch and the wall
light are run from a junction box in the loft. I'm a complete amateur
so please be as detailed and descriptive as possible.
Usually there is a lighting 'ring' that runs (red, black, and earth) from
the main box round the lights. From this ring are dropped a black to the
light, and a live ("permanent live") to the switch. From the switch comes
the "switched live" which then goes to the light. If you draw it on a bit
of paper it will make more sense.
The "3 amp spur" is probably saying that the live and neutral to the fan
should both be switched, and have a fuse in the live wire. You should be
able to get a suitable socket from Homebase or B&Q - but switches need (I
think) to be outside the bathroom where you can't touch them with wet hands.
safety safety safety. Assume that complete idiots will be in the bathroom
without you there to tell them to not electrocute themselves !!!!!
If you (carefully with the mains off and using a torch) look at the wiring
in the ceiling rose of the light you should find the following connections :
1) "permanent live" ring in, linked to permanent live ring out, linked to
permanent live going to switch
2) neutral ring in, linked to neutral ring out, linked neutral going to
3) "switched live" from switch, linked to live going to light
4) earth from ring in, earth from ring out, possibly earth from something
So by tracing where the cables go physically, you should be able to work out
where's the best place to "tap in" to each.
You can get junction boxes from B&Q which have four screw teminals inside
and are used for joining the live, neutral, switched live, and earths. Or
use a ceiling rose if the wires are small (but's that not really a
"professional" way of doing it!)
If you include the switch, then you could always wire in a standard
three-pin socket in the loft as power to the fan, and put a three pin plug
on the wire coming from the fan, and put a 3 amp fuse on the wire from the
fan. This won't be "standard" but as long as you clearly label the socket
as "switched supply fan only" it should be ok - and might be the simplest
and safest for a 'complete amateur'. Make sure the wires won't be trodden
on or pulled inadvertantly.
hope this helps
You'll have more wires than terminals in a standard JB. I'd suggest using a
loop-in light fitting and taking everything from there.
Yeah, but it's good practise to use 3+E (as suggested by Owain) and to leave
the earth unused and safe in the fan. Connect the other end in the fitting -
doesn't hurt to have earth for when you drill thro' the cable ;-)
Besides if you've been following some of the other threads you'll have
noticed how the IEE change their requirements everytime there's a new set of
regs so for the 17th edition you'll need to earth double insulated equipment
and will only be allowed 6 volts in a bathroom.
Permanent live from the loop - lives, switched live from the return to the
light from the switch, neutral from loop - neutrals. Hope that makes sense.
| "Nearly Done!" wrote
| > Thanks for your help so far fellas! What I'm thinking of doing is
| > taking a feed from the circuit (which is a junction box circuit) into
| > another junction box and have the light fitting, fan and switch all
| > converging in there (wired up as the last ceiling rose on a ceiling
| > rose circuit). Would that be OK or would it be better for everything
| > to be wired together at the light fitting?
| You'll have more wires than terminals in a standard JB. I'd suggest using
| loop-in light fitting and taking everything from there.
Only 4 terminals (L SwL N E) and that's standard in a 4 terminal 6A box.
Much easier doing it there than at some wall light.
| > An isolating switch will be fitted between junction box and fan. The
| > fan doesn't require an earth as per the wiring instructions.
| Yeah, but it's good practise to use 3+E (as suggested by Owain) and to
| the earth unused and safe in the fan.
Specifically required by the regs in fact.
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