Four cables into one single socket

Itisonlyme · Oct 19, 2014

Hi all, I am continuing to replace all the sockets and switches in the house and as always the very last one is a bit of a headache.

Single socket on the landing to one side of an airing cupboard. On removing the faceplate in addition to the expected two cables for the ring there are two more runs of 2.5mm t+e. One of these cables has been fed in front of the back box rather than through the knockout which sets alarm bells ringing to me as it seems likely only a cowboy or homeowner with no pride would do this, this seems a later addition to the other 3 cables so could be diy.

i replaced the backbox with a deeper one to provide a better fit to the wall as its attached to a joist to the rear and a 25mm box isn't deep enough to reach the wall, added grommets as none fitted and run all four set of cables through knockouts.

I have a couple of questions:

1. Is this an acceptable arrangement in any event? As two cables are the ring and two others are feeding off it (assumed but not yet tested as had to pop out). Would need a trip into the loft to work out what they are feeding. If they are both spurs I believe only one is allowed and I would look to disconnect the other if not permitted. One may be a socket which is unused by us at least as it is inside the airing cupboard and would be no loss.

2. Assuming this is an OK arrangement trying to get 4 lots of wire into the terminals on the back of an MK single socket sounds a big ask, can I group the cables into 30amp connector block and then feed a single wire into the socket terminal? Don't like this idea much as I would think poorly if I took the socket off and found this arrangement.

Grateful of any advice.

Phil

Itisonlyme · Oct 25, 2014

Finally got around to chasing the wires down in the loft.

So, of the four wires running into this single socket :

2 are for the ring
1 is a spur running downstairs to a double socket running the broadband router and a NAS hard drive

These look to be the original install and seem reasonable enough.

Cable 4 runs up the wall into the loft into a junction box where it is then split 3 ways:

One running the loft light where live is run past the switch on the outside with the red wire only and the neutral into the switch. Don't understand why this wasn't run off the lighting cable less than 2 feet away.

Second runs to the an unused single socket 6ft plus off the floor inside the airing cupboard.

Third runs the full length of the loft and is run down conduit in the front bedroom to another socket which has a four way bar run off that.

All now disconnected and will remove once time allows.

p.s. Getting 3 wires back into the terminals of a single MK socket was a massive pain, I would have hated to try getting all four back in!!

Deleted member 9648 · Oct 25, 2014

You did the right thing disconnecting the fourth cable which was feeding more than one point. And yes,4x 2.5 solid core cables into a single socket is a pain,but possible.
The only point I wanted to make was that there are circumstances where two spurs off a single point on a ring would not require altering in order to comply with regulations.

Pete999 · Oct 25, 2014

wirepuller said:
You did the right thing disconnecting the fourth cable which was feeding more than one point. And yes,4x 2.5 solid core cables into a single socket is a pain,but possible.
The only point I wanted to make was that there are circumstances where two spurs off a single point on a ring would not require altering in order to comply with regulations.

Unfused spurs????

Richard Burns · Oct 25, 2014

Pete999 said:
Unfused spurs????

In parallel not series.

Pete999 · Oct 25, 2014

Richard Burns said:
In parallel not series.

Not sure I understand Richard

dingledong · Oct 25, 2014

Me neither

Pete999 · Oct 25, 2014

Pete999 said:
Not sure I understand Richard

If you mean two sockets taken from one existing, or one socket and another one from that one, both methods are non compliant,

Richard Burns · Oct 25, 2014

This diagram is what I mean.

[ElectriciansForums.net] Four cables into one single socket

There is nothing regulations wise to prevent multiple single cable spurs from one socket each cable to its own double socket.
The design of the cable terminals would limit this to two anyway, any more and you may risk overloading a point on the ring.
The recommendations are that the number of unfused spurs is equal to or less than the number of points on the ring and that the length of an unfused spur is less than 1/8 th of the ring length.

Pete999 · Oct 25, 2014

Richard Burns said:
This diagram is what I mean.
View attachment 26822
There is nothing regulations wise to prevent multiple single cable spurs from one socket each cable to its own double socket.
The design of the cable terminals would limit this to two anyway, any more and you may risk overloading a point on the ring.
The recommendations are that the number of unfused spurs is equal to or less than the number of points on the ring and that the length of an unfused spur is less than 1/8 th of the ring length.

So your saying that providing you take two spurs from the same socket it's OK? Sorry disagree with you on that one

telectrix · Oct 25, 2014

agree with richard. the left pic is permissible as each spur cannot be overloaded, where the right pic has 2 outlets on a single cable.

Simlec · Oct 25, 2014

Some socket outlets state on the back max 4x2.5mm (yes not all, but some)
The pic on the left is perfectly acceptable. How would you feel about the pic on the right with a 4mm to the first spured socket & 2.5mm to the next one?

Pete999 · Oct 25, 2014

Simlec said:
Some socket outlets state on the back max 4x2.5mm (yes not all, but some)
The pic on the left is perfectly acceptable. How would you feel about the pic on the right with a 4mm to the first spured socket & 2.5mm to the next one?

Lads show me where it states that Richards left hand scenario is acceptable and conforms to 7671

Richard Burns · Oct 25, 2014

Pete999 said:
So your saying that providing you take two spurs from the same socket it's OK? Sorry disagree with you on that one

No problem, you are entirely entitled to disagree, and from a practical point of view I would not want to do it.

Simlec said:
Some socket outlets state on the back max 4x2.5mm (yes not all, but some)
The pic on the left is perfectly acceptable. How would you feel about the pic on the right with a 4mm to the first spured socket & 2.5mm to the next one?

BS7671 does not give you the option of spurring from a spur without fusing down, however you could design it that way as a departure from BS7671, but again you would risk overloading the ring at the take off point and would be able to pull over the current carrying capacity of the 4mm from two double sockets, so would have to take diversity into account for the socket outlets which is hard to do (though obviously applied for general socket circuits in a very large way).

Far better to design circuits without messing about with calculations and pushing the limits, or am I just lazy?

Simlec · Oct 25, 2014

Pete999 said:
Lads show me where it states that Richards left hand scenario is acceptable and conforms to 7671

Should it be you showing us where it says it's the work of the devil .
Distrubted socket outlets are a way of conveniently plugging in temporary equipment, if it's likely to be over loaded then a dedicated circuit would be the way forward.

Richard Burns · Oct 25, 2014

Pete999 said:
Lads show me where it states that Richards left hand scenario is acceptable and conforms to 7671

This is not specifically prohibited by BS7671 therefore it is permitted.
433.1.5 gives overload requirements for rings and does not require that only one spur may be taken from a point on the ring.
The requirement not to overload the cables may prevent you from designing a ring with two unfused spurs off the first socket in the ring and designed to run fan heaters from those sockets as this could overload the short leg of the ring.