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Garage wiring

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Garage wiring

Postby Worstcombi » 31 May 2015, 21:27


I'm formulating my plans for May workshop (20' x 20‘ double garage), and have some questions regarding 16amp sockets.

The garage power is fed from the main house CU and 32A MCB with SWA cable. There is a second CU in the garage with plenty of spare breaker slots and also a 30mA trip.

I'm getting my electrician out to do some wiring in our bathroom and would
Inke him to install two 16amp sockets and isolators for me. My question is, should I have these done on a ring with a 32A type C breaker, or two separate radial circuits with smaller breakers?

There are also 4 double sockets (not enough), fed on a 20A radial, think there was only one socket when it was built. Want to have a few more installed. Should I have a 32A ring installed or a couple of 20A radial circuits. In the event of an overload, I don't want the MCB to disconnect in the house before the garage one.

I want to fit all the boxes and conduit ahead of the electrician - he's a good sparky, but can't install anything level or plumb :lol:

Cheers in advance
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Name: Simon

Re: Garage wiring

Postby 9fingers » 31 May 2015, 22:11

The best thing is to ask your electrician.

My understanding is that 16amp sockets are connected on individual radials. A socket rated at 16a cannot have breaker greater than 16amp.
If you think you might need more current, you can go up a size to a 32 amp socket and choose breakers up to 32 amp to protect the wiring to it.
I would install type C breakers on those breakers just in case you get nuisance tripping on starting big motors.

you might as well up the breaker in the house feeding the garage supply to a type C too.

I also think that any more than two 13amp sockets need to be on a ring - again your sparky will be the est person to advise because you need his signature on ticket at the end of the day.

good luck

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Old Oak
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Re: Garage wiring

Postby Robert » 31 May 2015, 22:32

Nothing to add to bobs answer but was just thinking... 20' x 20' for a workshop...wouldn't that be nice..

Enjoy the project. Sometime sorting a workshop is more enjoyable than actually making stuff in it!
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Re: Garage wiring

Postby Worstcombi » 31 May 2015, 23:02

Thanks Bob,

Will definitely seek my electricians advice, just trying to get my head round it first. Had a nose on the IET forum and there was some disagreement regarding installation of 16A sockets. I might as well have them on separate radials as there's plenty of spare ways on the CU and I want one socket on each side of the workshop.

I think the number of sockets on a radial is governed by floor area as many as you like under 50m2 I think, or at least it used to be - as long as it's fused down to 20A with 2.5mm cable. I think i'll have a ring installed anyway as my DX is 2 kW run it at the same time as a big tool or machine and I guess that's getting a bit close to tripping a 20A breaker.

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Joined: 29 May 2015, 14:48
Location: Stowmarket, Suffolk UK
Name: Simon

Re: Garage wiring

Postby TonyT » 14 Sep 2015, 15:54

Two radials more useful than one ring.
16A on each radial.
C type breakers on everything.
If I understand correctly you have a 30mA RCD in the garage Consumer unit? If this is the case then it should not be fed from an RCD in the house.

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