Does adding a 16A MCB to a spur meet regs, or do I need a 13A fuse?

[ericmark]

... and the 20A MCB protecting the feed to the garage will eventually trip if the total load on garage sockets is markedly above 20A.
Did you mean 27A (ie. 2.5 mm² Method C), rather than 22A?

Quite honestly, in the case of a 2.5 mm² Method C ring, I think that 27A is so close to 32A that, except in exceptional circumstances (knowledge about likely very large long-term loads) that my feeling is that all this concern about overloading the short leg of a ring with a load applied close to one end of the ring is probably not really necessary.

Kind Regards, John

I would assume at some point the cables are buried in plaster, in a ceiling void and using other installation methods as the poster says he can't assess under a floor, so to be on safe side I would rate at 22A unless sure otherwise.

 

[JohnW2]

I would assume at some point the cables are buried in plaster, in a ceiling void and using other installation methods as the poster says he can't assess under a floor, so to be on safe side I would rate at 22A unless sure otherwise.

Fair enough - although the two methods you mention would also be Method C, and nothing the OP has said suggests that it is in insulation or conduit anywhere (although I suppose it's not impossible).

In any event, with a 20A OPD, things would be OK even with your 22A figure.

Kind Regards, John

 

[ericmark]

As to if an electrician would actually do the calculations is questionable. If you plug in the PSCC meter and find it is well within the limits, then no point in calculating.

I know limit is in the regulations, however I have some LED lights rated 85 ~ 250 volt, as long as you select a light which will work with volt drop even if it does not comply, can't really see a problem.

But some one on the site can make a judgement, and decide where it is OK to break the regulations, it was a consideration of mine, if I test and know as a result some thing does not comply and don't note it, could I be asked to pay for it's correction latter? So I was careful, however I know many do a EICR and don't include what I would and also include what I would miss out, it is a professional option not a hard and fast pass or fail.

 

[JohnW2]

As to if an electrician would actually do the calculations is questionable. If you plug in the PSCC meter and find it is well within the limits, then no point in calculating.

I'm not sure what you are think/talking about 'calculating' - I thought we were talking about cable CCC?

I know limit is in the regulations, however I have some LED lights rated 85 ~ 250 volt, as long as you select a light which will work with volt drop even if it does not comply, can't really see a problem.

I presume you're talking about voltage drop. If so, it would only be non-compliant with regulations if the voltage were such that the attached equipment "did not function safely". Everything else 'in the book' about VD is only guidance in an 'informative' Appendix.

Kind Regards, John