Lighting circuit - loop through in switch

[Dan Sloane]

I've recently started changing normal switches to dimmer switches in my 1 ear-old home and noticed a very strange wiring technique....

Each of the switches I've changed so far have had the 'loop-through' wiring done inside the wall switch. Most rooms are fitted with LV halogen downlighters, so there's no ceiling rose - but surely the looping should have been done in junction boxes.

Annoyingly, this means there's very little space in the back box for the extended depth of a dimmer.

Can anyone please give me guidance whether this conforms to 16th Edition regs, or if I should get another qualified electrician to inspect.

Regards, Dan

[John Watson]

Hi John,

This is sometimes done, especially in older properties where there may not be a ceiling void.

This can be a real pain - as I'm sure you've found out. You may find you need to fit deeper back boxes. They usually need a deeper back-box than the

16mm ones often used for light switches.

Yes it does conform. Debatable whether it is good practice. In your case I'd say it is good practice, as any joints are more easily accessible to inspect etc. than ones hidden away in the ceiling void.

Interestingly this months "Professional Electrician" mag, Nov 03 p61 has an NICEIC article that covers (more-or-less) this point.

[Christian McArdle]

I don't think of any reason why it wouldn't conform, provided that the correct terminals are used. It seems sensible, given that with downlighters there isn't an obvious ceiling rose location to do the wiring.

Christian.

[John Southern]

This is known as the "switch feed" method of wiring common in industrial and commercial wiring. Also good for domestic and the the method i prefer because hopefully all connection are in the switch back boxes.

Jon.

[Andrew Gabriel]

Also allows replacing the switch with a device which needs a permanent live and neutral supply, like an X10 wall switch for example.

[Dan Sloane]

So - it's annoying, but safe and has a useful side effect.

Thanks for the posts. Dan