At the risk of making myself look a bit of a.......

[Sparky83]

....Pratt!

I was having a disscusion with a mate of mine and radials (like you do)

and we disagreed on on feeding a 2.5mm t&e from the 32a mcb of a ring ciruit.

I thought that you could only spur off the ring from a point on the ring itself like a socket, but he said you could take it straight from the mcb itself. To me this then becomes a radial circuit sharing a mcb with a ring main?

What would happen if the ring was removed and the radial circuit left, on a 32amp breaker, that would be right, so what makes it ok when a ring shares the mcb?

I've had a look about and even on this forum but some say its ok some dont. Im happy to admit im wrong, which is how it would seem it is but i would like a good explenation as to why its ok.

Cheers
Shawn

 

[Jimmy Boy]

If you look at appendix 15 page 362 of BRB it shows various arrangements including using 1.5mm for sockets using a FCU ! Would I no, but it's there as table 6F page 134 of OSG shows the CCC of 1.5mm to prove it

 

[WayneL]

Thanks for the P362 note - its clearly states that an unfused spur can be connected "to the origin of the circuit in the distribution board" which means that there would be 3 cables running into the protector (2 x 2.5 and 1 x 4.0). Thats how I read it!

Looks like I need a length of 4mm to add the double socket my customer wants.

No, no no

An unfused, 2.5mm spur off a 'Ring Final' can feed one single or one double S/O, even from the origin (MCB) of the circuit.

You don't need to use 4mm!!

 

[Octopus]

Many thanks WayneL, I was ering on the side of caution!

 

[WayneL]

Many thanks WayneL, I was ering on the side of caution!

Of course, if you want to use 4mm it isn't a problem - it's your choice