cable current rating

[dartnell]

can some please advise what is the current- carrying capacity of 2.5mm cable used in a standard ring main power circuit. Is it double of a radial circuit?

 

[BR]

It is 27A MAX. Take into account locational issues. e.g insulation coverage etc.

 

[ban-all-sheds]

Anything from 18.5 to 27A, depending on where it is, see here. There is a later table in the regs which gives slightly higher ratings, but TLC don't have it online. You won't go wrong though with the ones above.

But the current carrying capacity of the cable is the same whether it's in a radial circuit or a ring, as ye cannae change the laws of physics. But the current carrying capacity of the circuit is higher for a ring because, of course, there are two cables supplying each socket, which is why a ring using 2.5mm cable can be on a 30/32A breaker. Is that what you meant?

 

[dartnell]

Thanks guys.

Yes B.A.S that is what confused me.
I can't understand how you can have have circuit breaker with a higher amp than the cable capacity.

 

[ban-all-sheds]

Because in a ring final circuit there are two cables carrying the current to each socket...

so in a perfectly balanced situation, no length of cable is carrying more than half the total load on the ring, which is protected at 30/32A, and it would take either a serious imbalance or a break close to the CU for one segment to get to more than 27A.

 

[securespark]

as ye cannae change the laws of physics.

I didn't know ye were frae the lan' o' Scots?????

 

[ban-all-sheds]

Not me guv - but I am old enough to remember the original Star Trek...