Garage Power

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sb2

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I have a Garage and Out Building (next to the garage) I what to get power to.
Currently I have a new full RCBO consumer unit in main house.
With a 40A RCBO attach to 16mm2 3 core cable to the Garage.

Looking to put a consumer unit in Garage and one in Out Building.

Question:
1. Is do I need to put RCBO / RCD in Garage / Out Building or just MCB?
2. Is there any safety averaged the having in RCBO or RCD in Garage / Out Building as the has a RCBO in main house?
 
There's no point having two RCD/RCBOs in series unless the upstream one is Time delayed. It's better to have localised RCD/RCBO imho.

Does the Outbuilding actually need a consumer unit is a question I'd be asking, what will be used inside it power wise?

I agree with the above comment(s) though unless you can thoroughly test the installation prior to energising and on energising.
 
Thanks for your reply.

I am trying to find info on cascading RCBO and selectivity problem.
 
In the main, they go x3, so 10 mA, 30 mA, 100 mA, and 300 mA, etc, and not seen above 30 mA used in domestic. Some cables and installation methods do not need RCD protections, like SWA for example, but test equipment is required, and the result is it costs too much to DIY.
 
So i just need to use MCB in Garage / Out Building CU as will be RCD protection from the RCBO in main consumer unit?

That will save a chunk of money fitting MCB, if it is unnecessary to fit RCBO in Garage / Out Building CU, without any extra safety averaged.

Dose that sound OK?
 
The circuit from the house CU has an RCBO. This provides 30mA earth fault protection and 40amp over current protection.
You do not need a second 30mA RCD in the outbuilding.

IF you decide to install a consumer unit in the outbuilding then it will be a NEW consumer unit. Any circuits you add to this will be NEW circuits.
Under Building regulations, new CUs and new circuits are both NOTIFIABLE events. You would need to go through a whole lot of expense and pain if you raise a building notice with your LABC and then try and presuade to them that you are competent, know BS7671 inside out and have the (required) set of calibrated test equipment that you will need to produce the necessary Electrical Installation Certificate.

You only option is to find a registered electrician to do this for you. Dont even think of doing the job and then trying to find an electrician to "sign it off". That isn't going to happen.
 
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