Plug socket circuit question

[ebee]

I reckon it`s to j
help prevent at very uncmmon practice two singles from being converted to twins later on so you`d would end up with 3 or 4 sockets on the same spur from the ring which is a situation best avoided

 

[EFLImpudence]

They still sell long pieces of rope even though people might hang themselves later - not worth avoiding I suppose.

 

[ebee]

No I think back in the day a few folk did start converting singles to twins so it might have some merit though. agree about the rope. gotta stop manufacturers making knives too sharp - someone might cut themselves

 

[Harry Bloomfield]

I reckon it`s to j
help prevent at very uncmmon practice two singles from being converted to twins later on so you`d would end up with 3 or 4 sockets on the same spur from the ring which is a situation best avoided

A twin outlet, is unlikely to have two 3kw fan heaters plugged into it, but two single outlets, not adjacent to each other (possibly in different rooms) might need heat in both areas/rooms.

 

[JohnW2]

I reckon it`s to j ... help prevent at very uncmmon practice two singles from being converted to twins later on so you`d would end up with 3 or 4 sockets on the same spur from the ring which is a situation best avoided

Maybe - I've heard that suggestion before. More commonly, those who believe that a double socket is only 'rated at 20A say that such is therefore OK for a cable only required to have a CCC of 20A, whereas 2 x 13A (single sockets) represents a potential load above that CCC.

If someone is aware of the guidance (that an unfused spur should serve only one, single or double) socket would understand that changing that to 'two double sockets" would be in contravention of that guidance - and, of course, if they were unaware of the guidance, it would matter what it said!

In any event, as EFLI has implied, I think there is a limit which one (or regs, or 'guidances') should attempt to anticipate silly things (in contravention with regs and/or guidances) that people might do in the future - after all, someone could decide to wire a 10.5 kW shower to the ring circuit!

In fact, I'm not sure that any of this has got anything to do with actual regulations (as opposed to the 'informative guidance' of App 15). The actual regs (433.1.204) appears to say that a 2.5mm² cable with a CCC of at least 20A, protected by a 30/32A OPD, may be used for a ring final "with or without unfused spurs" (without any comment about, or restriction of, what may be connected to those unfused spurs) and appears to say that such an arrangement w deemed to satisfy 433.1.1, which would otherwise requre Ib < In < Iz for any/all of the cable (which it clearly wouldn't if Iz=20A and In=30/32A).

If that is the correct interpretation of 433.1.204, then it seems that all we are talking about is 'guidance', not actual regulations/requirements.

Kind Regards, John

 

[JohnW2]

No I think back in the day a few folk did start converting singles to twins so it might have some merit though. agree about the rope. gotta stop manufacturers making knives too sharp - someone might cut themselves

Same problem with ('dangerous') 'hot coffee' as well, I believe !

Kind Regards, John

 

[Murdochcat]

As I've said Per the diagram (which is 'guidance', not a regulation) one can spur one (double or single) socket in that way). If you wanted to know why the guidance does not seem to 'allow' two single sockets, you would have to ask the person who wrote it!

Kind Regards, John

I have always been under the impression that 2 x single sockets are not permitted because they later could be changed to 2 x 2G sockets , meaning the load on the spur cable could be up to 40 or 52 A

 

[JohnW2]

I have always been under the impression that 2 x single sockets are not permitted because they later could be changed to 2 x 2G sockets , meaning the load on the spur cable could be up to 40 or 52 A

As I said, that's one of the theories that people have. However, as has been said, I think the original guidance (maybe even a regulation?) said "one double or two singles".

However, as I also said, if people are aware of that guidance, they would/should realise that they'd be contravening it by changing it to two doubles- and if they were not aware of the guidance, it wouldn't really matter what it said!

 

[plugwash]

In any event, as EFLI has implied, I think there is a limit which one (or regs, or 'guidances') should attempt to anticipate silly things (in contravention with regs and/or guidances) that people might do in the future

There clearly is a limit, the question is where should that limit be drawn.

One thing to keep in mind is that most electrical installations (and this isn't just true of domestic installations) suffer from a lack of good record-keeping. If I see a socket on a spur how am I supposed to know what else is on the same spur without dismantling the whole installation?

 

[JohnW2]

There clearly is a limit, the question is where should that limit be drawn.

Indeed, and I can't really see how that can be down to anything other than individual opinion/'judgement'.

One thing to keep in mind is that most electrical installations (and this isn't just true of domestic installations) suffer from a lack of good record-keeping.

Agreed.

If I see a socket on a spur how am I supposed to know what else is on the same spur without dismantling the whole installation?

It wouldn't be trivial. However, if you found a socket with two cables connected to it, you wouldn't know whether it was 'on the ring' or a spur, with another spur coming from it, without doing at least some 'dismantling'. I'm nor sure that this, in itself, is a likely explanation as to why the guidance suggests a maximum of one single socket on an unfused spur.

Would you perhaps be more comfortable if the guidance suggested "one double socket or two physically close single sockets"?

Kind Regards, John

 

[ebee]

We haven`t mentioned unfused "death cubes" yet have we?

 

[bernardgreen]

This is a sold down the big river as a 10 way stack. Stacks with even more sockets are available

 

[Murdochcat]

Would you perhaps be more comfortable if the guidance suggested "one double socket or two physically close single sockets"?

Kind Regards, John

No. The guidance needs to simply say a single accessory is the spur. As it stands is far to open to interpretation - which is mainly done to bend rules or just install non compliances.

K
I
S
S

 

[EFLImpudence]

The cable is the spur.

 

[EFLImpudence]

Two single sockets on a 2.5mm² spur is clearly electrically satisfactory; that someone might do something stupid in the future is irrelevant.