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Garage consumer unit connection

Postby Bianchi9 » Tue Jan 25, 2011 6:56 pm

I have recently moved house. The detached garage electrics are fed by a suspended cable from the house (consumer unit with trips). The cable in the garage is into an FCU then onto a single 13 amp socket. The flourescent light is supplied from the back of the socket.
I have a new consumer unit ( 125Adouble switch + B16 & C6 switches.)
I would like to add 2 additional double 13amp sockets and possibly a larger flourescent.
Can I fit the consumer unit my self and will it need certification?
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Postby ericmark » Wed Jan 26, 2011 12:46 am

When is a consumer unit a distribution unit? The problem is the Part P regulations do not follow the definitions laid out in BS7671:2008 and they on one hand say for a new circuit you must pay the LABC and register the work and yet it also says other than in special locations you can fit a FCU without informing them yet under BS7671:2008 that is considered as a new circuit.

They also say you can replace like for like but to define what they mean for example if you replace a 8.5kw shower with another 8.5kw shower of an upgraded design is this still like for like?

Personally I would say first ask yourself can you do the work to comply with BS7671:2008 and only after you are satisfied you have the knowledge and skill consider if you need to inform the LABC.

So let us look at what the work will involve.
1) The earth loop impedance and prospective short circuit current will need measuring and you will need to compare the readings with what is required to operate the automatic disconnection devices you are going to fit.
2) Unless already protected with a RCD likely you will need to fit a RCD and of course test it works which involves measuring the point at which it trips both on positive and negative half cycles and for a 30ma trip it must hold at 15ma and trip at 30ma and trip within 40ms at 150ma.
3) You will also need to check the insulation on cables ect. This needs to be done at 500 volts.

So step one is to buy or hire the meters even to hire you are looking at £75. You of course need to be able to use the meters and to complete either a minor works cert or an insulation cert.

Do you know what B16 and C6 means? For the magnetic part of the trip to work and to disconnect within 0.1 seconds it does need to work then a B16 MCB will require 80A to flow. The C6 will require 60A to flow.

If after all that you still think you can do the work required then we have the problem in getting the LABC to accept you can do it all without causing danger. Likely they will want to see something which at least on paper shows you have some skill.

My son with C&G 2391 (Shows he is qualified to inspect and test) was not accepted by the LABC as being able to sign the paperwork. (They didn't know what a C&G 2391 was!) Only when I showed them my degree did they relent and let me test the work.

In theory once you pay the LABC their fee they are then responsible for site safety so have the power to get outside contractors in to test the work. At first they could not charge for this testing but now they can. So it is down to the local guys as to what they will let you do.

Some can be very helpful and will guide you through the hoops. But sadly not all. And because the regulation is so poorly written as to what you can do is down to case law. So if some one has fitted a consumer unit in a garage before and was fined for not informing LABC then that will be quoted if you try and do the same.

So if the house is yours and you have no intention of selling or renting then it may be worth the chance in same way as doing 40 in 30 limit in dead on night. But if there is the chance of anyone getting injured, or reporting, or solicitors asking for paperwork. Then not really worth taking the risk.

As to if permitted likely you are not permitted but it would be for the courts to decide and personally I would prefer not to have the hassle.
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