More garage wiring

[memphis32]

Morning y'all,

I've spent quite some time searching here and elsewhere, but it seems every garage in the country is wired differently and needs a different answer!!

I have a new-build with a separate double garage, which has a light and double socket. I'd like more of both, and had been under the impression that I could add to that circuit without any input from a sparky. It seems I'm already wrong on that count!

Currently the garage has it's own 16A breaker in the house CU. The cable comes out of the house in a junction box (where I'd like an external double socket as there are none yet), goes under the garden path, back up the garage wall and then through it, to a plastic backbox with what looks light a light switch on it. There are four terminals in there, so I'm guessing at double-pole.

A cable then goes up to the actual light switch, which appears to have a fuse in it, and splits there to the light fitting and a double socket.

Should the fused switch not be the first box in that sequence, with the cable splitting there and the light switch being just a switch? And can I daisy-chain more double sockets from the one that is there? Also, can I fit LED panels or battens myself, or does that require a pro? And If I can, are they just daisy-chained as well?

In terms of my competence, I'm an electronics technician by trade, but mains wiring legislation seems to be a completely alien language to me!!

 

[MickCheese]

i would probably look at running a few sockets from a 13amp fused spur and doing it myself.

But

That doesn't make it right.

Mick

 

[novocaine]

To do it correctly (in the eyes of most sparkies anyway) you'd want to fit a consumer unit at the end of the incomer (a 3 way is typical with a 63a RCD) then take 1 ring (note, ring not spur) for 13 amp sockets in 2.5mm (normally 32a MCD,) and 1 for lighting (6a MCD) in 1.5mm. 32a should let you have 2 separate sockets sets, as you are unlikely to be running all machines at once. this depends on the cable coming in though, as if it's just a 2.5mm spur from the main CU you maybe overrating the incomer and you'll want to get it replaced with 4 or 6mm armoured cable. which is why you really need a sparky to look at it.

you should have a sparky do the work or at the very least final connection and certification (in the eyes of Part P of the building regs anyway) which then covers your arse with your insurance company too.

EDIT:
just noticed you said 16a breaker in the house, so that'll be 2.5mm, time to call a sparky and hope the cable is in conduit not just an armoured cable under the patio.

 

[HappyHacker]

As the circuit is protected at 16A in the house and presumably has an RCD in the main consumer unit you can add as many 13A sockets as you like in the garage. The fuse in the garage is I assume for the lights to protect the lighting circuit at 3 or 5 Amp. This is a quite normal and acceptable way for it to be installed and saved the builder the cost of an additional consumer unit in the garage.

The limitation is the 16 A breaker for the circuit if you intend to run large or a number of appliances at the same time. e.g. A decent table saw and extractor may well exceed the 16A especially on startup. A 16A MCB will run with an overload for some time before tripping but it is not good practice.

If you want to run heavy loads get an electrician in to look at your installation as there may be a number of ways to satisfy your requirements which it is impossible to comment on without much more information including the load requirements and supply characteristics which would probably need measurement. It would only be part Pee certifiable if it is a new circuit or in a bathroom, it may be notifiable if you change the MCB in the house but I would have to get the document out as I can't remember all of the most recent changes.

I have to add Part Pee is different in Wales, they did not make the most recent changes, and they have a different scheme in Scotland