Add spur at Consumer Unit

[EFLImpudence]

... moment

 

[EFLImpudence]

Quite so, but ....

Maybe the person(s) who invented Appendix 15 had it in their mind(s) that 433.1.204's minimum requirement of a CCC or 20A for the cable of a ring final circuit also applied to the cable of an unfused spur,

I would dispute that 433.1.204 applies to spurs. There is no reason for it so to do.

such that it might not be adequate for 26A, but would be adequate for what they regarded (as seemingly other do) as being the (20A) 'rating' of a double socket - hence their guidance that an unfused 2.5mm spur could supply one double socket but not two single ones (which I don't think anyone disputes would each be 'rated' at 13A)?

The same rule applies to the 32A radial in Appendix 15B so it cannot be because of the ring requirements.

 

[JohnW2]

I would dispute that 433.1.204 applies to spurs.

You're free to 'dispute', since your guess about 'intent' is as good as mine. As you know, what it says (in part) is;

433.1.204 Accessories to BS 1363 may be supplied through a ring final circuit, with or without unfused spurs, protected by a 30 A or 32 A protective device .......... Such circuits are deemed to meet the requirements of Regulation 433.1.1 if the current-carrying capacity (Iz) of the cable is not less than 20 A and if .....

I don't think it would be difficult for someone to think that "such circuits" was intended to include any spurs.

There is no reason for it so to do.

Probably not. Unlike cable of the ring itself, we re not talking about cable which, were it not a ring, would be 'under-protected'. However, again, we don't know what was in the mind of the person who wrote the guidance in App 15 - since they could, theoretically have given examples of a 1.5 mm² unfused spur supplying one single socket (but didn't).

The same rule applies to the 32A radial in Appendix 15B so it cannot be because of the ring requirements.

True (albeit guidance, rather than 'a rule') - but, again, for whatever reason they seem to be assuming that the CCC of 2.5mm² cable may be less than 26A.

Kind Regards, John