Garden office/Shed Electrics

[ashtraywasp]

I am building an outbuilding with a garden office and a shed, and I need to know how to wire it.

The consumer unit in the house seems to have RCDs feeding MCBs for each subcircuit. I'm planning to have four subcircuits in the building, one for the outlets in the garden office, one washing machine and dryer, one for the lights on both sides, and one for the radiator in the garden office.

From research it seems that the best approach is an MCB in the main consumer unit and an RCBO per subcircuit with an SPD for the sub consumer unit in the outbuilding, using SWA cable run from the house to the subunit.

I don't know if that is overkill and I can use an MCB at the house unit and an RCBO feeding MCBs per subcircuit, although an SPD sounds good to protect my PC and other expensive equipment.

Any advice?

 

[ericmark]

Clearly new circuits, so step one is to consider which route, a compliance certificate (using scheme member) or completion certificate (using LABC) if the latter, the more detailed to application the better, as I found if you don't they may ask for something latter, which is harder to do when you have not planned to do it, in my case they wanted an extractor fan.

So the first question, is if it is possible to take a non RCD protected feed from the existing consumer unit. With washing machine, tumble drier, and radiator looking at least 32 amps, so at least 6 mm² SWA as a feed, but a 100 amp would need too large of a cable, so it will need some overload device in the main consumer unit.

Rather naughty, but even if you intend to DIY, I would get one quote for the work, A) as it may be cheaper than you think, and not worth DIY and flouting the law. B) as he will likely tell you how he would do it.

With a high integrity CU in the house, then a 32 amp MCB feeding the shed feed, without that, then looking at second mini CU in the house or renew the existing.