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Author: Subject: Garage wiring...
computid

posted on 5/7/16 at 12:48 PM Reply With Quote
Garage wiring...

Hi All,

Since this forum is basically the font of all knowledge I thought I'd ask here

So I've recently been re-organising my garage to accommodate my new lathe (wa-hoo!) and I started looking at the wiring, now this was put in by the previous owners or perhaps the ones before them so I had nothing to do with it but I need some advice.

There seems to be a spur off of the kitchen ring main going out to the garage (External building) which is then fed into a fused switch. There is a lighting circuit spurred off of this into a light switch and then to two double tube strip lights. There is also a double socket spurred off the fused switch as well.

This means there is a lighting circuit plus a double socket on the spur. What I'd like to do is wire a fused switch in which is then wired to an emergency stop button which is, in turn, wired to the lathe. This is my first real folly into house electrics bar the usual swapping sockets and adding ceiling lights.

As I understand it, you're not allowed to spur from a spur? Or can you if the cable rating exceeds the maximum load (e.g. 2x13amp sockets = 26amp on a 32amp spur is fine, but 13*3 = 39a (double socket plus lathe switch) isn't ok because it exceeds the maximum load of 32 amps)? And this is without adding the lighting circuit in. Then again, as I understand it the double socket is only rated to 20amps so if I use a 12amp fuse in the lathe switch then 20+12 = 32amp and I should be ok? Could well be talking complete rubbish here!

Part of me says I should rip the current wiring out and extend the kitchen ring into the garage for the lighting and the double socket and then run a separate spur for the lathe, but this seems like an awful lot of work and I don't much fancy ripping the kitchen apart to try and find an appropriate place to take the ring from (can you even extend a ring to an outside structure?).

I mean ideally the garage would be on it's own ring but the consumer unit is in the middle of the house and it would be almost impossible to wire a new circuit to without tearing the house apart.

In all honesty, if the lathe is running and the lights are on I doubt I'll be using anything else so the load will never exceed the maximum BUT I would ideally like to stay on the correct side of the regs.

Any advice is appreciated! Cheers.






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cliftyhanger

posted on 5/7/16 at 02:52 PM Reply With Quote
what size is the cable from the house to the garage? if single 2.5mm stuff that carries 20A max....(usually fused at 16A)

If you want a 32a supply to the garage, then add another 2.5mm cable to add it as part of the ring. But remember the whole ring has max capacity of 32A, so if a waching machine etc is on as well.....

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coozer

posted on 5/7/16 at 03:19 PM Reply With Quote
Mines on spur from somewhere upstairs. In have a consumer unit with a 16amp breaker in it for the sockets. I have a lathe, compressor, mad saw table all running 3 HP motors. Lathe is plugged into a 13amp socket, runs ok,. The others plus my big mig are on blue 16amp fittings. I only have one 16amp wall socket so can only run one at a time.

6 strip lights on the lighting circuit. Been like that for over 25 years and it hasn't burnt down... yet...😁





1972 V8 Jago

1980 Z750

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daniel mason

posted on 5/7/16 at 03:46 PM Reply With Quote
And what size cable is the garage lighting?
As I'd imagine there's a 13a fuse in the spur

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daniel mason

posted on 5/7/16 at 03:47 PM Reply With Quote
Also is it using the pme Earth?
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prawnabie

posted on 5/7/16 at 06:06 PM Reply With Quote
Ive just done the same thing..

We we moved in we had 3 sockets in a detached garage (badly wired) and a strip light. this was connected to a fused connection unit then swa to the house and that went into t+e and into the back of one of the kitchen sockets. Sparky said it was fine as it was fused down in the garage (apart from the dodgy wiring!)

The problem was our house was built when playstation and xboxes etc didn't exist and we have one ring main top and bottom. I run two welders, and compressor and various power tools so the decision was made to upgrade it all!

I had the sparky fit a ring of sockets in the garage with 5 strip lights connected to a small garage consumer unit. The electrician took the power from a box in the meter cupboard into a KMF? switch, then swa cable from there to the garage CU. The SWA had the earth connected at the house end incase i put a spade through it, but as we have a PME supply the earth wasn't connected at the garage end, I had to have an earth spike installed for that.

Simple enough to do, the main problem was because it was PME, we couldn't export the earth to the garage as it was out of the bonding zone for the house.

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