garage cu

18 Jan 2007
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United Kingdom
Hi Guys, have been asked to install a garage / shed CU. I have never had to do one!!

I can't find anything in the ref. section.

I need to draw power from the house cu to the garage cu to install lights and sockets.

Does anyone have a wiring diagram for connecting the cu. What cable should I employ for bringing power to the garage cu.

Would 4mm T&E be suitable? It is through wall not requiring running externally.

Have bought a starbreaker Garage kit 63A, 30mA RCCB with 6A and 32A type B MCB's

Cheers any help would be greatly appreciated
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Asked by whom?

Not someone paying you money, I hope....

Do you plan to notify the work?
Hi Ban

Asked by a friend, no he isn't paying me and yes he has notified LABC.

Now, any help please?
I've been looking to do an almost identical job myself. 4mm T&E, to my knowlage is rated at around 32A. As the max you can drawer from the local breakers before they trip is 38A, I would look at using 6mm minimum. I've opted to go straight for 10mm as it allows me to add additional load in the future.

How are you drawing power from the CU? via a breaker? if so, what rating on the breaker?

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I have thought about 10mm as well, I intend to use a 40A breaker, there is spare way in the cu.

I need to talk with my friend about what he intends to place in the garage, I've a feeling he will be putting the dryer and freezer in there, I intend to install a ring final rather than a radial.
There is nothing wrong with correctly specced radials. They are not inferior to ring finals.
damn, dryer and a freezer. Don't know what there ratings would be, but I know there power hungry things. the drier especially.

Do double and tripple check your ratings.

4mm is too small for a 40A breaker, 6mm is ok provided no insulation or grouping factors are involved. Unusually long cable runs may also require larger cable.

a 40A breaker in the house feeding through appropriate sized cable to a garage CU containing a 32A breaker for a ring and a 6A breaker for lighting is a perfectly accepable arrangement.

You should use the non-rcd side of the house CU to avoid chaining RCDs.

Be aware that the 17th edition wiring regs require non RCD protected cables that are concealed, less than 50mm deep and are part of an installation that is not supervised by an instructed person (exactly what that entails is somewhat open to debate) to be either mechanically protected, in earthed conduit or of an approved type that incorporates an earthed metal layer (unfortunately split con was removed from the list of approved types). While it is currently still acceptable to work to the 16th edition it would probablly be wise to ensure all new work is compliant with this requirement.

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