Only one spur from a socket?

[ericmark]

I have always been under impression one spur only per socket. I only have the original BS7671:2008 so it may have changed now, but when I looked for the regulation, appendix 15 shows only one spur from each socket, but I could not find any regulation as such to say that.

433.1 does have exceptions for the ring final in that cable rated at 20A or above can be feed from a 30/32A fuse/MCB but very little 433.1.5 says may be supplied with out without unfused spurs.

As an example I looked at MK Logic Plus which gives terminal capacity 3 x 2.5 mm² 3 x 4 mm² and 2 x 6 mm² with RCD types the 2 gang is reduced to 2 x 4 mm² even with the filtered socket which gives 3 x 1.5 mm² 3 x 2.5 mm² 3 x 4 mm² and 2 x 6 mm² it is noted even the 1.5 mm² still only has 3 cable capacity. But a 2A BS 546: 1950 socket has 7 x 1mm² and the German socket also has 4 x 1.5mm² so it would seem the limit of three cables is unique to BS 1363: Part 2: 1995 sockets. While looking at the technical data I note although the current for simple 1 and 2 gang is 13A per socket that 3 gang and sockets with RCD and Filters built in are only rated 13A total latter two resistive.

So it could be said 134.1.1 electrical equipment shall be installed in accordance with the instructions provided by the manufacturer of the equipment means only 3 wires in a BS 1363 socket. One thing I did note with the appendix 15 although in a junction box it shows a mixture of cables sizes in sockets in all cases the three cables are always the same size. That includes both ring and radial.

434.2.1 does seem to limit an unfused spur to 3 meters and with 433.4 there is a “does not preclude” statement for ring final circuits so if there is a special case for a ring final it is stated. Same with 433.4.1 and 523.8 I am not worried about high integrity sockets.

Amendment 12 does state “An unfused spur should feed one single or one twin socket-outlet only. An unfused spur may be connected to the origin of the circuit in the distribution board” but that does not actually say you should not have two spurs from the same point.

Years ago the Regulations included the on-site guide with information like distance from sink and where a cooker isolator should be located but many of the regulations have been now dropped in resent times we have seen the bonding regulations change. Today near every electrician keeps the BS7671 handy and refers to it on a regular basis but years ago if an electrician asked to look at the regulations it was a “What do you want to see that for” and we lived on rumour control some one said “Your not allowed to do that” so we stopped doing it without actually checking.

I am not saying we should take two spurs from one socket all I am saying I can’t find a regulations that said you should not. Yes implied with diagrams and manufacturers data but does no actually say you shouldn’t.

So what have I missed? Clearly for this thread regulation numbers will need to be quoted as the idea is to confirm or rebut a myth.

 

[JohnW2]

I am not saying we should take two spurs from one socket all I am saying I can’t find a regulations that said you should not. Yes implied with diagrams and manufacturers data but does no actually say you shouldn’t. ... So what have I missed? Clearly for this thread regulation numbers will need to be quoted as the idea is to confirm or rebut a myth.

As I am always saying, I don't think that you have missed anything, since I do not believe that any regulation explicitly forbids two spurs originating at the same point on a ring final.

However, as you've said, in the case of sockets, you probably won't find one which the manufacturer says has a terminal capacity for 4x2.5mm² conductors (although some, like MK, say 2x6mm² is OK) - so that might have been said to preclude two spurs from on socket (but discretion in relation to MIs is now allowed under Amd3). However, if the spurs were originating at a JB, you could certainly find one that had capacity for four (or even more) conductors, so there then would certainly be no regulation explicitly forbidding two or more spurs originating at the same point.

Of course, particularly if one is talking about a point fairly close to one end of a ring, then the designer has to be satisfied that "under the normal conditions of use, the load current in any part of the circuit is unlikely to exceed for long periods the current-carrying capacity (Iz of the cable" (433.1.101). However, as I've said more times than I care to remember, that issues is essentially the same whether several spurs originate from a single point (socket, JB or whatever) of from a number of points (.g. sockets) a few inches apart.

So, I suppose the short answer to your question is that, AFAIAA, the alleged 'prohibition' of two (or more) spurs originating at the same point (socket or whatever) on a ring finally is, per se, essentially a myth.

Kind Regards, John

 

[EFLImpudence]

I have always been under impression one spur only per socket. I only have the original BS7671:2008 so it may have changed now, but when I looked for the regulation, appendix 15 shows only one spur from each socket, but I could not find any regulation as such to say that.

I don't think anything relevant has changed except the regulation numbers.
Appendix 15 is not exhaustive and other methods may be employed - I think everyone would consider a lollipop circuit acceptable, for example.

433.1 does have exceptions for the ring final in that cable rated at 20A or above can be feed from a 30/32A fuse/MCB but very little 433.1.5 says may be supplied with out without unfused spurs.

Not sure what you mean regarding "without unfused spurs".

As an example I looked at MK Logic Plus which gives terminal capacity 3 x 2.5 mm² 3 x 4 mm² and 2 x 6 mm² with RCD types the 2 gang is reduced to 2 x 4 mm² even with the filtered socket which gives 3 x 1.5 mm² 3 x 2.5 mm² 3 x 4 mm² and 2 x 6 mm² it is noted even the 1.5 mm² still only has 3 cable capacity. But a 2A BS 546: 1950 socket has 7 x 1mm² and the German socket also has 4 x 1.5mm² so it would seem the limit of three cables is unique to BS 1363: Part 2: 1995 sockets.

We don't know why.
Room for 2 x 6 and 3 x 4 would clearly be big enough for 4 x 2.5.

While looking at the technical data I note although the current for simple 1 and 2 gang is 13A per socket that 3 gang and sockets with RCD and Filters built in are only rated 13A total latter two resistive.

3 gang sockets have a 13A fuse.

So it could be said 134.1.1 electrical equipment shall be installed in accordance with the instructions provided by the manufacturer of the equipment means only 3 wires in a BS 1363 socket.

It could if we knew the reason for it.

One thing I did note with the appendix 15 although in a junction box it shows a mixture of cables sizes in sockets in all cases the three cables are always the same size. That includes both ring and radial.

Another anomaly.

434.2.1 does seem to limit an unfused spur to 3 meters regulation

Only when the down-stream device is protecting against fault current.
This does not apply to the equivalent overload protection position or omission when the CPD is providing the fault protection.

and with 433.4 there is a “does not preclude” statement for ring final circuits so if there is a special case for a ring final it is stated. Same with 433.4.1 and 523.8 I am not worried about high integrity sockets.

Irrelevant.

Amendment 12 does state “An unfused spur should feed one single or one twin socket-outlet only. An unfused spur may be connected to the origin of the circuit in the distribution board” but that does not actually say you should not have two spurs from the same point.

Ergo.

Years ago the Regulations included the on-site guide with information like distance from sink and where a cooker isolator should be located but many of the regulations have been now dropped in resent times we have seen the bonding regulations change. Today near every electrician keeps the BS7671 handy and refers to it on a regular basis but years ago if an electrician asked to look at the regulations it was a “What do you want to see that for” and we lived on rumour control some one said “Your not allowed to do that” so we stopped doing it without actually checking.

Very true. Old wives tales and folk lore.

I am not saying we should take two spurs from one socket all I am saying I can’t find a regulations that said you should not. Yes implied with diagrams and manufacturers data but does no actually say you shouldn’t.

Does your knowledge tell you it would be safe?

So what have I missed? Clearly for this thread regulation numbers will need to be quoted as the idea is to confirm or rebut a myth.

Perhaps you are not missing anything but are looking for "You may do this" instead of "I know it is safe to do this".

 

[JohnW2]

Of course, particularly if one is talking about a point fairly close to one end of a ring, then the designer has to be satisfied that "under the normal conditions of use, the load current in any part of the circuit is unlikely to exceed for long periods the current-carrying capacity (Iz of the cable" (433.1.101). However, as I've said more times than I care to remember, that issues is essentially the same whether several spurs originate from a single point (socket, JB or whatever) of from a number of points (.g. sockets) a few inches apart.

In an attempt to turn that into some practical advice by adding some numbers ...

Even if the CCC of the cable is only 20A (unlikely, but allowed for a ring final), if one is more than about 37.5% (just over one-third) of the way around a ring, then (with an assumed maximum total load of 32A) it is impossible to "overload any part of the cable" (even for short periods), even if one draws the full 32A design current at a single point on the ring.

If, much more commonly, the CCC of the cable is 27A (Method C), if one is more than about 15.6% (about one-sixth) of the way around a ring, then (with an assumed maximum total load of 32A) it is impossible to "overload any part of the cable" (even for short periods), even if one draws the full 32A design current at a single point on the ring. It is probably quite common that the distance from the CU to the first socket is at least 15.6% of the total ring length, so that it is then impossible to overload any part of the circuit, even if the full 32A is drawn from the first socket (and spurs attached thereto).

Kind Regards, John

 

[ericmark]

I see a big difference between not doing something myself to condemning something done by someone else.

So although I will not try to stuff four wires into a terminal myself if I am doing an electrical installation condition report I can't really fault it when others have taken two spurs from the same point.

I feel if I can't quote a regulation breached then I can't consider it as a fault?

 

[JohnW2]

So although I will not try to stuff four wires into a terminal myself if I am doing an electrical installation condition report I can't really fault it when others have taken two spurs from the same point. ... I feel if I can't quote a regulation breached then I can't consider it as a fault?

It's not just a case of what you consider. If you accept what EFLI and I have said, then no regulation has been breached, so there simply IS NOT any 'fault' (non-compliance). Simples!

Kind Regards, John

 

[deadshort]

If you are stuffing four 2.5mm cables into the back of a socket then you are breaching the regs, one spur per socket is the rule per socket on a ring i.e. 3x 2.5mm cables at the back of the socket. Simpler still

This subject has been flogged to death


DS

 

[ericmark]

If you are stuffing four 2.5mm cables into the back of a socket then you are breaching the regs, one spur per socket is the rule per socket on a ring i.e. 3x 2.5mm cables at the back of the socket. Simpler still

This subject has been flogged to death


DS

The question is what rule by whom and when. As I said at start you need to quote the rule as I can't find it.

 

[EFLImpudence]

This subject has been flogged to death

That doesn't stop us.

Would you agree that it is allowed on a radial circuit?

If so, then the argument is that it is not allowed on a ring solely because it is a ring.
In which case, would you like to state why and what is the difference?

Also, if you replace "stuffing" with "terminate satisfactorily" does it seem less unacceptable?

 

[JohnW2]

... one spur per socket is the rule per socket on a ring

As several people are asking, what 'rule'?

This subject has been flogged to death

I don't know about 'to death', since there clearly are still dissenters. The discussion will undoubtedly recur so long as people make assertions which they cannot (or do not) back up with regulations.

As I keep saying, electrically speaking, if four conductors can be terminated satisfactorily in the terminals of a socket (or JB), that's not significantly different from terminating three in each of two sockets (or JBs) just a few inches apart on a ring.

Kind Regards, John

 

[ericmark]

A 2A BS 546: 1950 socket has 7 x 1mm² and the German socket also has 4 x 1.5mm² from manufacturers data

But it seems it's the socket not the being a ring which limits it to one spur (if it does) going by number of wires one can put in each terminal. Not even a British thing as BS 546 socket says 7 x 1mm² so if there is a rule then it must be in BS 1363 not BS 7671 and I don't have a copy.

 

[stillp]

A 2A BS 546: 1950 socket has 7 x 1mm² and the German socket also has 4 x 1.5mm² from manufacturers data

But it seems it's the socket not the being a ring which limits it to one spur (if it does) going by number of wires one can put in each terminal. Not even a British thing as BS 546 socket says 7 x 1mm² so if there is a rule then it must be in BS 1363 not BS 7671 and I don't have a copy.

"11.5 Line and neutral terminals in fixed socket-outlets shall permit the connection, without special preparation, of one, two or three 2.5 mm² solid or stranded or of one or two 4 mm² stranded conductors."
"11.6 Earthing terminals in fixed socket-outlets shall permit the connection, without special preparation, of one, two or three 1.5 mm² or 2.5 mm² solid or stranded or of one or two 4 mm² stranded conductors."

Those are the minimum capacities of the terminals, and there is no statement as to how many conductors may be fitted to the terminals.

 

[JohnW2]

But it seems it's the socket not the being a ring which limits it to one spur (if it does) going by number of wires one can put in each terminal.

As most people are saying, there does not appear to be any regulation which imposes any such restriction, whether the circuit be a ring final, a radial or anything else.

Kind Regards, John

 

[EFLImpudence]

"11.5 Line and neutral terminals in fixed socket-outlets shall permit the connection, without special preparation, of one, two or three 2.5 mm² solid or stranded or of one or two 4 mm² stranded conductors."
"11.6 Earthing terminals in fixed socket-outlets shall permit the connection, without special preparation, of one, two or three 1.5 mm² or 2.5 mm² solid or stranded or of one or two 4 mm² stranded conductors."

Those are the minimum capacities of the terminals, and there is no statement as to how many conductors may be fitted to the terminals.

Thank you.

So, would anyone interpret that as meaning NO branches/spurs are allowed on 4mm² 32A radial circuits?

 

[JohnW2]

So, would anyone interpret that as meaning NO branches/spurs are allowed on 4mm² 32A radial circuits?

Certainly not me. As stillp pointed out, the Standard appears to specify only minimum terminal capacities, and says nothing about maximum capacities, nor anything about how many conductors "may" be terminated in a socket terminal.

Kind Regards, John