More wiring Qs - multiple metalcad sockets in a workshop.

[Andy Dingley]

A quick bit of repair the other day - Contactum dual sockets getting all arcy and sparky owing to crap plug pin contacts, so I had to swap them out for new (CED) ones. The workshop bench wall was wired with conduit drops at intervals to pairs of metalclad sockets, i.e. 4 sockets in two boxes. Boxes were bolted together with a conduit nipple and locknuts. Standard stuff.

One thing I noticed though was that the ring went up and down the conduit to each pair of boxes, but one dual socket was wired as a spur from the other, not a ring across all the sockets. One of them was also a triple (6 sockets), wired as two in a spur.

What does the team think? Acceptable practice / Shoddy work / Run away! or Get a life, it's only 6" of cable?

[Dave Osborne]

OK.

One of them was

Not sure what this means.

I wouldn't have done it that way, although it is acceptable to have one spur for each socket on the ring.

It is the same amount of work to do it "properly", so the extra sockets may have been added as an afterthought (or as a "bugger I've (or the apprentice has) cut the cables too short to loop through to the second box).

[ARWadsworth]

If it is not a spur off a spur then there is no problem. I am not sure what "One of them was also a triple (6 sockets), wired as two in a spur." means. If it is two 3 gang sockets with the 1st one on the ring and the 2nd a spur from the 1st then it sounds fine.

[Terry Casey]

A typo, perhaps, for "wired as two AND a spur" i.e 2 (on the ring) + a spur?

[Andy Dingley]

Three double metalclad sockets. I think the ring went to the centre one, then a spur left and a spur right.

[ARWadsworth]

Ahh, I see. That is allowed, although there are supposed to be no more unfused spurs on the ring than there are points on the ring (eg if you have

10 sockets on the ring then you can have 10 spured sockets and it need not matter what point on the ring these spurs come from - all 10 spurs can in theory come from one of the sockets).

It also does not matter if the sockets are singles or doubles. You could have 10 single sockets on the ring and 10 doubles fed from spurs.

[John Rumm]

Slightly lazy given how easy it would have been to ring them all, but in general ok.

The six socket one, depends on what you have - one socket with two unfused spurs, each feeding one socket, is ok[1]. One socket with one unfused spur, feeding another socket and it in turn then feeding one further socket is not ok[2].

[1] for certain values of "ok". If you knew in advance that you wanted a number of big heavy loads on these sockets, then its not ideal since you will concentrate a very high point load current on one set of terminals. [2] Not ok in the sense that you are theoretically capable of overloading the short bit of cable at the head of the spur. In reality it may not be much to worry about since the chances of drawing a sustained 30A from two double sockets is fairly small - especially now you know how they are wired!

[Andy Dingley]

I think it was probably a legacy issue. They might have originally installed single double sockets at each point, then realised there weren't enough sockets and doubled up the boxes. In that case one of the existing drops would have been just 6" too short to do it right.

[John Rumm]

Perhaps, although if you have conduit, then a few insulated crimps would solve the cable length problem. (crimp happy me!) ;-)

[ARWadsworth]

It's a workshop John. The only heavy often used loads are the kettle and electric heater:-)

[Andy Dingley]

Wood steaming for bending. Three electric wallpaper strippers all on the go together.

(When I'm there though, at least I don't run them all from one extension lead with a nail in the fuse)

[John Rumm]

Kettle - that's what mine is missing... (could do with running water and a loo as well!) ;-)