Radial final circuits in garage

[sharpener]

You can have a maximum of one spurred socket per socket on a radial or ring. It is acceptable to spur straight out from the breaker, but what you've essentially done is spur out twice.
BS7671 refers to sockets being wired in a ring final, radial final, or spurred from either of those. What you've got is more of a 'spider' type arrangement which BS7671 makes no reference to.

To be exact, the configuration _as inspected_ had only one of the spurs actually installed at the time, even so they wouldn't accept it.

IIRC the On-Site Guide says that one spur per socket or item of fixed equipment (i.e. two, which can be from the breaker) is acceptable on a radial cct with 4 sq mm cable and a 30A breaker (A2 radial cct) but makes no mention of spurs for a final radial circuit with 2.5 sq mm cable and a 16 or 20A breaker (A3 radial cct). However it doesn't say (except by omission) that they are not allowed either.

Regarding the discrimination issue, the 16A breaker in the main CU protects the 2.5 sq mm cable out to the garage. The breaker in the garage unit is therefore not strictly necessary *at all*. but it would surely look a bit odd just to have the 6A mcb on the lighting circuit and nothing at all on the power circuit, also it is handy as an isolating switch. I agree that ideally in the event of an overload on the power cct it would be nice to be sure that the 16A mcb in the garage unit would be the one to trip (thus leaving the garage lights on), but I am not certain that making it a 20A breaker in the house would provide sufficient discrimination as I recall that the I squared t ratings of the two are both the same.

The sub-contract inspectors could not tell me the next step i.e. they do not know if they are going to be sent back to re-inspect or if I will be given written notice of their findings or what (some rigorous process this!), but as and when I hear anything further I will as Murdoch suggests ask what regs are being contravened.

Probably the easiest thing is for me to change my mind about having the two double sockets, as the only thing that is essential at right now is the spur box for the garage door actuator(!) They cannot prevent me from using a portable extension lead/4-way distribution board from the single socket outlet, even though common sense suggests that to have permanent wiring in trunking would be preferable.

Thanks for all the helpful comments.

 

[Guitarist]

You could have mounted a 4x4 adaptable box under the CU and brought your socket cables into this, all connected to wago connectors fed from the CU.
The other option, as your 2.5mm from the house CU is already essentially a radial, would be to dispense with the garage CU altogether and radial socket to socket then sfcu for lighting and sfcu for door circuit in 2.5mm.

 

[Adam W]

I'd go with post #8 - ask the person who has a problem with your work what their problem is with your work.