Additional sockets in the garage

16 Nov 2013
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Newcastle upon Tyne
United Kingdom

Looking for some help please. I have a detached garage which has a consumer unit powered from the consumer unit in the house. From the consumer unit in the garage is 1 light and one double socket right next to the consumer unit at the door. The socket has 1 cable coming directly from the consumer unit. I want to add 2 double sockets at the back of the garage and then at a later date an outside socket from one of the new sockets. As there is only 1 cable to the current socket this is, I suppose, acting as a spur from the CU. Can I make this into a ring by running the new sockets from this socket and then doubling back to the CU? Eventually creating a spur to an outside socket from one of the new ones.

Thanks in advance
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You need to know size of cable and size of protection device.

With a B32 MCB and 2.5mm² cable you are right you can't extend however.
With a B20 MCB and 2.5mm² cable there is not really a problem.
With a B32 MCB and 4mm² cable there is not really a problem.

Likely protected by a B16 MCB and with 2.5mm² cable there is not really a problem. The only real problem is RCD protection nearly all sockets now need RCD protection there are many ways to do it all depends what you already have and supply type.

Thanks for the response. Yes it is a B16 with 2.5mm cable. The consumer unit in the house is RCD protected so I'm assuming as this feeds from there it will also be RCD protected. If so it's just a case of completing a ring main as per my first post if my thinking is correct?
You don't need a 'Ring'.

Just connect the new sockets to the existing one in parallel or to the CU, the same as the existing one- whichever route is easier.
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Just remember that the maximum TOTAL load on teh sockets will be limited to 16amp. But that will be fine for most applications - unless you want to run a MIG welder or an engine hoist.
You must check you have 30mA RCD protection though, so if this is not integrated to the garage CU. Then at the house CU press the test button of RCD and then check for power-loss in garage.
fair point prentice.

Is there any compliant earthing. Is it TNS or TNCS or TT?

What is the cable installation method, what is going on in the garage?

Who is certifying the work?

Is there a water supply in the garage?

and as a moot point, I was asking if any body was asking. I was not asking.
Hi guys

Thanks for all the responses.

In terms of the first question the sockets will be earthed from the cable but I 'm guessing your question is more complex than that

There will be nothing major in the garage, general power tool use

As it's an extension to an existing circuit it doesn't need certification(except for the outdoor socket which will be done at a later date)

There is no water unless there is a roof leak.
It would need either an electrical installation cert or a minor works cert.
The main questions concerns conformation of RCD protection, for new sockets.
When was this circuit to garage, garage CU and circuits from there installed and do you have the documentations?
The garage has it's own breaker on the house cu which has 30ma RCD protection.

We bought the property about 18 months ago and I can't say when the circuits were installed but nothing was raised in any of the surveys or by the mortgage company, they asked about pretty much everything else so will have to check the pack to see if there is anything in there with regards to documentation.
Do not take it for granted that the RCD on the house CU protects the garage, this needs confirming as does it's rating. If you have not received any documents on purchase of the property regarding the safety of the electrical installation, I would suggest that you have an electrical installation condition report made on it.
If you do have the documents this will confirm a number of things, regarding RCD protection, impedance and earthing arrangement.

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