Extending a ring circuit

Since it is already enclosed in a back box there is no actual requirement for additional insulation. (it is no more vulnerable that the connections on the socket itself)

However you can get ready made enclosures for chock block strips:

If it's inside a backing box with either a socket still in place or a removable cover a choc block will be fine. As regards insulation just make sure the wires are dressed so they can't be nipped - or a short occur. A choc block is really no different to a socket terminal so needs no extra protection. Personally I always overlap the wires so both terminals grip them even when feeding from both ends - and make sure no bare wire projects beyond the brass bit. Wrapping in insulation tape will do no harm

- but I don't bother.

Thanks Dave (and John) I'll do just that.

Use a good quality nylon choc block where the screws don't bear directly down on the conductors.

There's a lot of crap ones about on market stalls and in pound shops, and in such as Half Frauds.

DG

================================== Can you be a bit more explicit or give an example of the type you describe. How are the wires held if not (directly) by screws?

Cic.

Some have the screws pressing on springy bits of metal that press on the cable. I'm not sure that I'm convinced that they're any better given that virtually every socket, switch and CU I've ever touched has the screws bearing on the cable.

================================== Understood, but it seems less secure to me.

Cic.

Why? Connectors in wiring accessories aren't usually of this style. This type is better for flex, though.

experience of those. Usually those bits fall out and the screw works fine on its own. The cable clamping is top-notch, however.

They are on the better stuff... (look at the connections on a MCB for example). Less chance of breaking the wire by over tightening, and a larger contact surface area.

Hmm. Most of these strips aren't attached to anything so the contact to them still depends on the screw. But the housing provided the larger contact area anyway. So two more surfaces to cause possible problems. Oh - I've yet to break a wire as found in TW&E - far more likely to break the screw through overtightening.

What make sockets etc use this idea?

Not so much a problem on the phase and neutral, but I have seen CPC connections where the installer has tightened the screw right through the wire - leaving it effectively disconnected.

The TLC Ultimate range, and IIRC the current MK Logic range, plus many others probably.

They tend to be particularly good when you have several wires to accommodate since there is more terminal space, and unlike a screw on its own there is no possibility of "missing" the wire and it ending up beside the screw rather than under it. Another nice feature is captive screws, so they can't fall out if you undo them too far.

IME, you tend to see this style terminal on the accessories with an "inline" layout of the connections - which also makes wiring easier.

Except I've just taken a look behind the double socket I was going to extend from and it's a spur...

I'm wanting to run 5 doubles from it (all intended to be low load such as audio equipment, phone chargers and table lamps) so it looks like I need to add a fused spur. Unless someone knows otherwise.

Always the way ;-)

Check it really is the only socket on the spur if you can, and then add a FCU before it and any further extensions. Obviously the total load on all sockets will be limited to 13A, but that sounds like it ought not be an issue given the intended use.

Thanks.

It's either that or break into a ring in the bedroom above and come down the wall (ground floor is a concrete slab). I really don't like the idea of this as it means gaining under-floor access in really limited space next to some built-in wardrobes.

An alternative (hopefully).

The original socket I wanted to use is in an extended part of the room in question. At the other end of the room, in the 'original' part of the building, there is another 13 amp double socket which also turns out to be a spur. Would it be acceptable to run a cable from one of these spurs, incorporate the 5 new sockets and then connect the other end into the other spur? Both existing sockets are on the same fuse on the consumer unit.

No, because rings must be "circular" rings, or spurs off the ring. You'd be creating a sort of figure-eight layout, which isn't allowed (and will make future testing and fault-finding unneccessarily complicated)

Owain

On Sat, 03 Nov 2007 15:28:15 +0000 someone who may be F wrote this:-

A ring final circuit should be just that, a ring of cable starting at the consumer unit and returning to it. A limited number of spurs may be run from the ring. What you are proposing is to short both sides of the ring across the middle, which might cause a number of problems.

At the existing socket you may want to fit one of these

But, depending on the topology, it might be possible to remove a section of the ring to restore the integrity. It depends on what exists on the ring between the points where the spurs are connected.