Outside socket installation

[JohnW2]

I think you mean there is a separate terminal for each leg of a ring circuit. Just connect the three wires as normal and see if both sockets work.

That is certainly possible, maybe something like this...

Untitled

• JohnW2
• 29 Oct 2011
• 6

What we really need is for the OP to explain exactly what he's got (ideally with a photo). If it is something like the above, then all the discussion about 'two single sockets on an unfused spur' is really just an unnecessary distraction.

stuali10 ... would it be possible for you to post a photo of the back of your socket?

Kind Regards, John

 

[DetlefSchmitz]

If it is something like the above, then all the discussion about 'two single sockets on an unfused spur' is really just an unnecessary distraction.

To be fair it's an unnecessary distraction anyway.

Unless double sockets come marked on the front with '20A max', then it is completely academic how they are wired behind.

It's just an anomaly caused by trying to dream up logical rules for an illogical wiring practice called a ring final.

 

[riveralt]

I came across this a little while ago when I fitted a Timeguard 'double' IP55 outside socket.
http://www.timeguard.com/products/safety/powerseal-outdoor-power/outdoor-twin-gang-socket
Like any good electrician I gave the installation instructions to the customer - who promptly lost them - unfortunately the customer was me.

In this particular case I was planning to run this socket as a spur from the ring final circuit via a FCU. Unfortunately when it came time to fit the damn thing I noticed that there were two sets of terminals and the instructions required a bridge from one to the other.
I ended up running the rfc to one of the set of terminals and use the second of terminals as a spur from the first with a 2.5mm² T&E bridge.
Quote from instructions:

2.3.1 Sockets In spur configuration we recommend feed cable of 1.5 sq. mm for
the single socket and 2.5 sq. mm for the double socket. If the unit is
to form part of a ring then incoming and outgoing cables must
both be 2.5 sq. mm (with the double socket we recommend that
the incoming and outgoing cables can be connected to one socket
each with a 2.5 sq. mm bridging cable between the two sockets.

 

[EFLImpudence]

All this does depend on the definition of a 'twin socket' (Appendix 15 wording).

I would say riveralt's example is more of a 'twin' than is the usual 'two-gang'.

 

[JohnW2]

To be fair it's an unnecessary distraction anyway. ... Unless double sockets come marked on the front with '20A max', then it is completely academic how they are wired behind. ... It's just an anomaly caused by trying to dream up logical rules for an illogical wiring practice called a ring final.

In common sense terms, you're right. In fact, there is another much-discussed anomoly - namely that it is 'allowed' to produce double sockets which cannot safely carry 2x13A loads, given that virtually no end-users will be aware that this is the case.

However, I don't think the actual issue is an 'unnecessary distraction'. I think it would probably be difficult to find an electrician who would be 'happy' (or, at least, who would regard it as compliant) to wire two single sockets to an unfused spur from a ring final - because of the (admitetdly only 'Informative') App 15 of the regs - even if they were mounted on a dual backbox. If the socket the OP has does have separate terminals for the two sockets (hence the need to link them with a cable), then I suspect that many would regard that as 'two sockets', as far as App 15 is concerned. As I've already written, if they choose to ignore the guideline in App 15 (compliance with which would probably be a 'pretty good defence'!), they will be left with having to produce their own argument for having a 2.5mm² cable protected by a 30/32A OPD.

Kind Regards, John

 

[JohnW2]

All this does depend on the definition of a 'twin socket' (Appendix 15 wording). I would say riveralt's example is more of a 'twin' than is the usual 'two-gang'.

I agree - really not much different from having two single sockets on a dual back box.

However, as you say, Appendix 15 actually uses the word 'twin' (rather than 'double' or 'two-gang'), thereby really confusing the question of what they are talking about (I assume they really mean 'standard double').

Kind Regards, John

 

[DetlefSchmitz]

I agree - really not much different from having two single sockets on a dual back box.

However, as you say, Appendix 15 actually uses the word 'twin' (rather than 'double' or 'two-gang'), thereby really confusing the question of what they are talking about (I assume they really mean 'standard double').

And as you keep saying Appendix 15 is informative.


Clearly what they had in mind (apart from legacy installations) was that it is very unusual to use a double socket to draw 26A. It is much more a convenience to be able to plug in more than one item.

Plugging a kettle into each socket of a garden extension and running them continuously is just not a likely scenario.

So it is surely a case of common sense, and it seems that there are not regulations to say any different.

 

[ericmark]

First sorry to the Welshman even if the wrong end of Wales I did not expect this result.

To be fair it's an unnecessary distraction anyway. ... Unless double sockets come marked on the front with '20A max', then it is completely academic how they are wired behind. ... It's just an anomaly caused by trying to dream up logical rules for an illogical wiring practice called a ring final.

In common sense terms, you're right. In fact, there is another much-discussed anomoly - namely that it is 'allowed' to produce double sockets which cannot safely carry 2x13A loads, given that virtually no end-users will be aware that this is the case.

However, I don't think the actual issue is an 'unnecessary distraction'. I think it would probably be difficult to find an electrician who would be 'happy' (or, at least, who would regard it as compliant) to wire two single sockets to an unfused spur from a ring final - because of the (admitetdly only 'Informative') App 15 of the regs - even if they were mounted on a dual backbox. If the socket the OP has does have separate terminals for the two sockets (hence the need to link them with a cable), then I suspect that many would regard that as 'two sockets', as far as App 15 is concerned. As I've already written, if they choose to ignore the guideline in App 15 (compliance with which would probably be a 'pretty good defence'!), they will be left with having to produce their own argument for having a 2.5mm² cable protected by a 30/32A OPD.

Kind Regards, John

I think John has highlighted the real problem here. It's not if allowed or not allowed but would an electrician sign it off.

If the South Wales poster is willing to break the law and do the work without it being notified to the LABC as still required in Wales then classing a a double socket is not a problem.

If however he wants to abide by the law and get the original electrician to connect then he may have a problem. But also that electrician has a problem having done half a job to start with.

I have many times asked why the appendix should be included in the BS7671 C&G 2382 exam but it is so I suppose we must regard it as part of the regulations.

I was rather surprised it has the connections for caravan wiring which has been changed many times but I think that should be moved to another thread if discussed.

 

[DetlefSchmitz]

I have many times asked why the appendix should be included in the BS7671 C&G 2382 exam but it is so I suppose we must regard it as part of the regulations.

It is declared to be informative and is therefore not part of the regulations.


[Well, what else would I be doing on a lovely sunny afternoon?]

 

[JohnW2]

And as you keep saying Appendix 15 is informative. Clearly what they had in mind (apart from legacy installations) was that it is very unusual to use a double socket to draw 26A. It is much more a convenience to be able to plug in more than one item.

With respect, I don't think any of us can conclude what they 'clearly had in mind'!

So it is surely a case of common sense, and it seems that there are not regulations to say any different.

In general, protection of a 2.5mm² cable with a 30/32A OPD is clearly neither acceptable nor compliant with the regs. As I've been saying, although 433.1.103 'authorises' unfused 2.5mm² spurs from a ring final, there appear to be no ('normative') regulations in relation to what can, or cannot, be fed by such an unfused spur - which (unless one wishes to use the 'guidelines' in App 15) leaves one with the 'usual' regulations relating to any circuit (i.e. not specifically ring final spurs).

In terms of those 'usual regulations', 422.2.2/434.2.1 would, as I read them, probably allow two single sockets (the fuses in the associated plugs not possibly having a combined rating of more than 26A) to be supplied by a 2.5mm² cable (if clipped direct) which was protected by a 30/32A OPD if it's 'length' did not exceed 3m and various other conditions were satisfied. One can debate what 'length' means in the context of a spur, but one could certainly argue that it is the length from the point of connection to the ring which matters. Is this what you had in mind? If not, what regulation(s) would you be using to justify protection of a 2.5mm² cable with a 30/32A OPD?

Kind Regards, John

 

[Bluehair]

If the South Wales poster is willing to break the law and do the work without it being notified to the LABC as still required in Wales then classing a a double socket is not a problem.

Stupid laws are there to be broken.

 

[Spark123]

422.2.2 is something to do with emergency evacuation

Fault current protection is already dealt with by the 32A or 30A OCPD hence 434.2.1 is not really an issue.
It is one of our daft rules that doesn't allow two single adjacent sockets as opposed to a double as a spur off a RFC. Saying that, it is a good idea to have an outside socket supplied from a 13A double poled Fused Spur unit anyway as if it gets water in it then you can switch off and isolate it, allowing the circuits RCD to be reset and the Mrs doesn't miss Corry!

 

[DetlefSchmitz]

And to prevent malicious externally caused internal disruption.

 

[JohnW2]

422.2.2 is something to do with emergency evacuation

OK OK - don't your typing fingers ever let you down? Try 433.2.2

Fault current protection is already dealt with by the 32A or 30A OCPD hence 434.2.1 is not really an issue.

Good point.

It is one of our daft rules that doesn't allow two single adjacent sockets as opposed to a double as a spur off a RFC.

Essentially agreed - although, as has been said, that's a 'guideline (Appendix 15), not a regulation or rule. Nevertheless, as I said, I don't think many electricians would be happy to go against that guideline. I suppose it's just possible that, as I suggested, someone may have thought that (perhaps based on perceptions of 'ratings') two single sockets represent a greater potential load than does one double socket.

Saying that, it is a good idea to have an outside socket supplied from a 13A double poled Fused Spur unit anyway as if it gets water in it then you can switch off and isolate it, allowing the circuits RCD to be reset and the Mrs doesn't miss Corry!

True - but all that could be achieved with just a DP switch - so it is, in itself, not a reason for having a fuse and thereby theoretically restricting the total load to 13A.

Kind Regards, John

 

[Spark123]

Don't know if you are allowed to use a DP switch on a RFC, I think they are built to a different British Standard number as to those allowed by reg 433.1.103 or any given in appx 15