I want to fit a shavor socket (with isolating transformer) in my bathroom. On the other side of the wall is a light switch so, at the risk of being shot down!, can I simply wire it into the back of this switch?
I think you'd better get someone to do this for you. Sorry, but the question indicates that you really don't understand the function of the wires in nearly all light switches...
Unlikely, because most UK light switches will only have a live feed, switched live to the light and earth wires in them.
You need live, neutral and earth - so you'll have to run back to somewhere else - via a fused spur.
Alan.
Does it need a fused spur ? the (professionally) installed one in my bathroom is fed straight off the lighting circuit.
If a "ceiling rose" style approach is used. Depends on how it was wired.
There are often live and neutral going straight into the switch ... neutral & live going out to next switch and neutral & swtiched-live going out to light. All earthed as required etc etc.
Alex
Wouldn't this be a job you aren't allowed to do anyway, due to Part P and it being in a bathroom and all
Indeed. OP should probably read other recent threads on this thorny issue and make an informed decision on how to get the work done.
Google groups for Part P or Part Pee in uk.d-i-y might help here.
Alex.
Not if on the lighting circuit. Probably a good idea if it's on a ring circuit, as otherwise it will only be fused at some 30A. I've never seen any claim of what the max supply feed rating is before you need extra protection. The isolating transformer type all have a 25W slow acting thermal trip inside them, and you won't get any more power out than the transformer can pass anyway.
I think that should read "there are sometimes [...]" rather than "often." Although this 'switch-feed' lighting wiring system is sometimes encountered, the loop-in method is far and away the most common, IME, IMHO, YMMV.
N.B. If the added shaver point is within the zones then the CPC of the cable feeding it will need adding to any supplementary bonding in the bathroom, unless the CPC of the relevant circuit is already bonded.
No spur needed if off the lighting circuit - which is the common way to do it since there's not usually any ring wiring into the bathroom. And shaver sockets are usually nearer the ceiling anyway.
OK ... small point, easy to find out in practice ... a couple of electricians I know use it wherever possible. You will often find it where they have worked, or so they tell me.
Alex.
It makes sense if you think you may want to add table light circuits in the future. But wiring every switch like this is rather wasteful of cable, as well as more work.
A few uninformed comments in this thread I fear. I just happen to have one of these upstairs waiting to be installed. The instructions inform me that it is doubled insullated and designed to be connected to the lighting circuit. As one poster pointed out, you don't get 13 amps in bathrooms.
Of course. But *very* rarely to a circuit at a light switch.
Why significantly more work? I did my ground floor like this and upstairs with roses (mainly due to light fitting styles) there didn't seem to be much in it for me. Admittedly this was a first fix situation so access etc was not a problem.
Alex.
Because you'll have two lots of TW&E going to every switch. And extra JBs to spur off the feed. Much more work on a standard lighting radial than using normal ceiling roses.
Nothing wrong with either method - but I'd be surprised at a pro using it as a norm.
There are pro's and pro's........
Dave
But you get 45A in the shower cubicle :-)
Owain
No extra JB's are required in its pure form.
The switch box is fed with the main feed which is then fed to the next switch box and so on and so forth. In that sense the switch box becomes the JB (rather than the rose or actual JB).
This means that all the main feeds are inside the switch box this has 2 advantages:
Some extra cable is true, 1 drop per switch + overhead of feed going around perimiter of area not through centre, second point is a bit variable on layout of lights etc.
Using the method I *think* you were suggesting would also surprise me and is indeed more work and is the worst of both worlds.
FYI: The guy who originally suggested this to me as the best approach wiring my house has circa 30 years domestic exp. The other guy I discussed it with (briefly) is an industrial electrician who had (Part Pee) a sideline.
Alex.
Yes. See reply to previous post.
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