Ring main and spurs

Extend the ring.

Only one spur can be run from a socket on a ring. It's trivial to check, but are you certain that the socket of interest is on a ring? My place has a mix of rings and multi-socket radials from under-floor JBs. I've sorted-out the ones I've encountered but have put 20A MCBs on everything that may not be a simple ring.

Cliff Topp expressed precisely :

Thanks very much guys.

The regs gave a guide as to no more spurs than points on the ring - it never said you could not have two spurs from the same point on the ring (note that does not mean a spur off a spur).

However 4 x 2.5mm T&E into a socket terminal is hard work and depending on the manufacturer/make it is impossible.

Unless the OP is lifting floorboards/chopping into walls then he is also going to struggle with 5 x 2.5mm T&E cables in a 2g back box if he extends the ring.

I like your "stick every socket circuit I am not sure about on a 20A MCB" solution. Very neat.

The classic problems of ring circuits.

You can't always tell easily if a socket is 'on' a ring or not.

If it is on a ring you are quite limited in how you can extend it.

All my new circuits are simple multi-branch circuits with 20A MCBs, much more straightforward.

I have to agree with Adam about trying to stuff 4 x 2.5mm2 cores into socket terminals especially with many modern sockets. Some of the older versions of better makes like MK it is just about possible and you would need a 35mm deep box too.

Richard

Ooops, thanks for correcting my misunderstanding.

Have you considered the voltage drop when using 2.5mm T&E on a 20A radial circuit? The maximum length is only around 30m.

A friend of mine is going to wire his place up with radials and I have suggested he uses 6mm for the first leg from the CU and then continue with 2.5mm.

Scolmore/Click sockets are pretty good in accepting 4 x 2.5mm cores.

And yes the back box depth is very important in this case.

Now if the OP is lifting floorboards and chopping in for the new socket then he can use a MF JB and extend the ring properly.

We have so few heavy consumption devices that voltage drop really isn't an issue. The kitchen *is* a ring, it was there when we came so oven and such are on a ring. My radial circuits all serve things like my study which is full of computers, routers, etc.

I have installed quite a lot of separate radials, each dedicated to quite small areas. This also helps when isolating faults and/or making changes as turning a circuit off only affects a small area.

As a matter of interest, why is one solution better than the other, if they are only short runs?

Brian

Electrically there is not much between them, however extending a ring might make further future mods a bit simpler.

The trick using crimps in the back box to add extra terminal space or an independent connection point can be handy for extending a ring when you can only easy join it at one socket position:

A ring is easily tested. Spurs can't. Hence I would prefer to extend a ring rather than add a spur if possible. You can also break into the ring at a place of convenience too.