Chris Pearson: 
Graham, what is the case law please?

and

and

Let's apply Occam's Razor to this problem.

If we take the view that a double socket-outlet should be rated at 26 A, then unfortunately it upsets some assumptions regarding the balance of loads on ring final circuits, and we'd have no choice but to prohibit ring final circuits.

However, we know that, in general, this is not the case that too many outlets are overloaded (as we don't have stacks of evidence showing mis-loading issues in these kind of circuits).

Given this fact, it's entirely unreasonable to expect a manufacturer to make a product to an elevated rating that it will never experience - and the cost of which would have to be passed on to customers, along with the wasted additional materials required. I think this is adequately covered in BS 1363-2.

In the mean-time, I will continue to recommend that two appliances both exceeding 1.8 kW are NOT connected to the same double socket-outlet (which in any case may upset the assumptions of balance of current in the ring final circuit).

Agree with the premise Grahame, but the problem is that the bean counters have value-engineered any previous durability out of the likes of the humble 13A socket these days. Having stripped a few from different brands and different eras, I can tell you that there is next to no copper or brass alloy inside today's accessories, merely cad plated steel.

MK used to warrant their outlets to stand a continuous 18A indefinitely but that applied to the old square edged 1980s style sockets with the chocolate brown plastic housing on the rear. Having stripped a number of these I can tell you that there are big copper strips present and solid brass screws and tunnel terminals too.

No wonder the things lasted well.

Contrast this with the ever failing MK Logic range - I've lost count of the numbers of sockets and light switches I have been called out to. Strip one of these and you find that there is a distinct paucity of non-ferrous metal present, and what there is can hardly be described as what I would term fit for purpose. There is a case for dedicated  4.00mm radials protected with 20A opds for appliances rated at 1.2 KW or more and connected via 20A outlet plates instead of Rings and 13A sockets in my view. 

whjohnson: 
 

Agree with the premise Grahame, but the problem is that the bean counters have value-engineered any previous durability out of the likes of the humble 13A socket these days. Having stripped a few from different brands and different eras, I can tell you that there is next to no copper or brass alloy inside today's accessories, merely cad plated steel.

If people want a double socket-outlet that retails for £1.00 inc VAT in ones, what can you do? Given the technical justification of point loading on the ring, and the abundance of low-power appliances predominating most of what we plug in at home, is there an actual problem?

There's no right answer to this, but the UK is criticised for over-engineered plug and socket-outlet solution around the world. I often wonder myself whether we should we keep holding on to this (undoubtedly great but) outdated solution of a fused (large) plug and ring final circuit?

Surely, with the exception of the shutter system, this solution's days are numbered given:

• Size and weight of plugs
• Energy needlessly lost in plug fuses
• Likelihood of safety issues in a 32 A ring-final vs 16 A or 20 A radial

I'd also like to see the number of accidents and extent of injuries from people treading on the UK plug, which always falls pins-up, than other solutions.
 

MK used to warrant their outlets to stand a continuous 18A indefinitely but that applied to the old square edged 1980s style sockets with the chocolate brown plastic housing on the rear. Having stripped a number of these I can tell you that there are big copper strips present and solid brass screws and tunnel terminals too.

No wonder the things lasted well.

Agreed … but in relative terms, how much were these products? I do have quite a few older accessories floating around, and yes they are definitely made from more sturdy stuff.

We say “better engineered” … but engineering isn't just “make it good”, there's always a budget.

Contrast this with the ever failing MK Logic range - I've lost count of the numbers of sockets and light switches I have been called out to. Strip one of these and you find that there is a distinct paucity of non-ferrous metal present, and what there is can hardly be described as what I would term fit for purpose. There is a case for dedicated  4.00mm radials protected with 20A opds for appliances rated at 1.2 KW or more and connected via 20A outlet plates instead of Rings and 13A sockets in my view. 

Agreed

I would be happy to defend double socket outlets in court, and the suggestion that 26A on a ring circuit is in any way unsafe. It is NOT reasonable to attempt to blame the electrician for using double sockets, or ring final circuits, or reasonable diversity. This whole point seems to me to be an attempt to re-engineer the whole wiring system based on scant or zero evidence. This is a trend that seems to be haunting every area of society, I have no idea why it should be happening except that certain political groups seem to have an agenda.

So, from the posts so far it seems that the evidence is that certain tumble driers have caused their plugs and socket connections to be somewhat burned, that certain sockets appear to be poorly designed, and that a lot of people “don't like the look of that”! The law behind “duty of care” also has an understanding that this duty goes with a “duty to control”, and this is important. BS7671 assumes the duty to control here, along with the customers' willingness to pay. It allows any accessories to BS??? to be used in most situations, at the reasonable choice of certain other characteristics (IP rating etc.), and sockets to be used with a ring circuit. It also suggests long-term cable ratings but recognises load diversity. All of these are bourne out as satisfactory in the almost complete set of installations, damage being really quite rare. Cases of fires caused by any of these are very rare indeed.

It would therefore seem that the components and cables are satisfactory, used to the guidelines of BS7671, and do not require derating by electricians on a whim. In fact, I seriously worry about some of the comments because they do not reflect reality, and whilst rings may not be entirely free of theoretical criticism, based on unlikely loading scenarios, finding any visible result from such seems to be impossible. I must have looked at thousands of installations in domestics, I have seen almost zero damaged cables from internal heating. I have seen some burnt sockets (well a bit brown around one of the pins, almost exclusively the live) but none that have actually caught fire. This is hardly surprising, to catch on fire they need to be heated to 500-600 degrees C, basically red hot, as do most common materials even paper.

Therefore I deduce that there is not a significant problem with double sockets or rings, and would need a great deal more evidence to reconsider my opinion. There are many more subjects covered in BS7671 that need more consideration than this, particularly electric vehicle chargers. It is extremely dangerous to charge batteries at a very high rate when in a vehicle, and resulting fires cannot be put out in the conventional way. The Earthing is very dubious, yet we carry on, and even the economics of such vehicles appears to be beyond consideration. The whole supply system is in danger of failure, yet the Government considers at least doubling the overall load by law. Why not worry about these much more important things.

davezawadi (David Stone): 
 

It would therefore seem that the components and cables are satisfactory, used to the guidelines of BS7671, and do not require derating by electricians on a whim. In fact, I seriously worry about some of the comments because they do not reflect reality, and whilst rings may not be entirely free of theoretical criticism, based on unlikely loading scenarios, finding any visible result from such seems to be impossible. I must have looked at thousands of installations in domestics, I have seen almost zero damaged cables from internal heating. I have seen some burnt sockets (well a bit brown around one of the pins, almost exclusively the live) but none that have actually caught fire. This is hardly surprising, to catch on fire they need to be heated to 500-600 degrees C, basically red hot, as do most common materials even paper.

In a place of work, a fire need not occur to prove a breach of legislation. Evidence of burning as you describe is all that's needed to prove a risk of injury existed (Regulation 5 of the Electricity at Work Regulations 1989). Where such damage leads to exposed live conductive parts, the proof is even more readily available.

If children could be at risk in a home from overheating sufficient to cause “blackening”, then I, for one, am happy to continue to point that out.

I perfectly agree with you that not every case of 2 no. “heavy loads” will damage a double socket-outlet, but I've seen it too often to just let this go without saying anything.

No-one is “derating” the double socket-outlet here, its rating is clearly stated, and I worry about finger-in-the-air science being used to say “well, just ignore that, it'll be OK”. Yes, often it is … but not always, and not always as infrequently as might be claimed.

Sadly, I've yet to invent the crystal ball that will tell me which particular installation might be a risk, and which one might not be.

Well Graham, I think that the blame should rest with the manufacturer and sale of goods act. It is illegal to sell something which is not fit, and this appears to be the case here. This is not changed in any way by a supposed specification, this is itself clearly not fit for purpose if a specified item burns (or goes black). The problem often appears to be the plug/fuse assembly as someone else stated above. Both are supposed to be made as compatible items, clearly, this in a few cases may not be true. But to suggest this is any way the installers fault seems very unsatisfactory. If you apply this to Grenfell tower, the cladding is entirely the fault of the installer, which is very far from true. It is very likely that the law will be changed as a result of the inquiry, which has found endless problems with the standards process as much as anything else.

It seems to me that the suggestion that we change to single-socket radials for everything, and unfused plugs, is much worse than our present system. In my house I would need a 1000m of cable and 50 breakers for such a system, clearly, it is not fit for purpose, yet might save one fire per year according to your view. I doubt it as more equipment is bound to mean more risk.

In my experience (40+years) it is very rare indeed for this “burning” to occur. If the EAWR is going to work in the way you suggest, there would be NO electricity in any workplace, because it is impossible to be SURE that this burning (slight colour change) will not happen. The answer is a proper maintenance regimen, not an outright ban. I note that you would ban soldering irons as a serious safety risk, that is perhaps why most electronics are made in China, and almost all our steelworks have closed! The EICR is such a regimen, it would be unnecessary if nothing could ever go wrong!

davezawadi (David Stone): 
 

Well Graham, I think that the blame should rest with the manufacturer and sale of goods act.

Perhaps … see below, although consider the intended use vs Appendix 15 of BS 7671.

 

 It is illegal to sell something which is not fit, and this appears to be the case here. This is not changed in any way by a supposed specification, this is itself clearly not fit for purpose if a specified item burns (or goes black).

That would perhaps need some more explanation or elaboration. I'm not sure I agree on this point.

The problem often appears to be the plug/fuse assembly as someone else stated above. Both are supposed to be made as compatible items, clearly, this in a few cases may not be true. 

Only separating here to draw a line between points …

But to suggest this is any way the installers fault seems very unsatisfactory. If you apply this to Grenfell tower, the cladding is entirely the fault of the installer, which is very far from true. It is very likely that the law will be changed as a result of the inquiry, which has found endless problems with the standards process as much as anything else.

Sorry … the limitations of the ring final circuit are very clear.

If it's not recommended to place a 2 kW oven on the ring final, then it's certainly not recommended to put two heavy current-using appliances on an individual double socket-outlet … this is specifically covered in Appendix 15 of BS 7671 item (iii) … so, what are you actually saying?

It seems to me that the suggestion that we change to single-socket radials for everything, and unfused plugs, is much worse than our present system. In my house I would need a 1000m of cable and 50 breakers for such a system, clearly, it is not fit for purpose, yet might save one fire per year according to your view. I doubt it as more equipment is bound to mean more risk.

No, I said perhaps ditch the ring final for radials, NOT single socket-outlet radials.

That would address the situation with 2 no. point-loaded appliances with rating > 2 kW though.

In my experience (40+years) it is very rare indeed for this “burning” to occur. If the EAWR is going to work in the way you suggest, there would be NO electricity in any workplace, because it is impossible to be SURE that this burning (slight colour change) will not happen. The answer is a proper maintenance regimen, not an outright ban. I note that you would ban soldering irons as a serious safety risk, that is perhaps why most electronics are made in China, and almost all our steelworks have closed! The EICR is such a regimen, it would be unnecessary if nothing could ever go wrong!

I'm sorry David, but I have to disagree. This has nothing to do with banning soldering irons, but overloading of a device that clearly states its rating.

The only thing I will concede, is that the rating is concealed from the user … which could be considered indefensible if it were not covered by a British Standard !

I see your points Graham, but I think you are being misguided as to the possible levels of risk. Whilst Appendix 15 does suggest a degree of care is required it is NOT a regulation and is not usually up to the electrician anyway. From your comments, I would infer that you think that double sockets should not be permitted, or possibly they should only be fed via a 13A FCU. You also imply the 2.5mm cable size is inadequate, whereas I suggest that it is not, and is proven by 10s of millions of installations that it is perfectly satisfactory.

I also see that your comment about a washing machine and tumble drier is generally factually incorrect, in that the washing machine heat time is severely limited to perhaps 10 or 15 minutes. This is essentially contrary to Fig 15A (ii) because the load profile is not a “space heating type profile" which may be continuous for many hours. It is necessary to understand that the power dissipation in a length of 2.5mm cable is 18 Watts per metre at 32 Amps, and the heat loss by convection is approximately this at 20C ambient. The heating time is therefore very considerable to get to 70C, more than 15 minutes or so, and if it gets to 71C does this actually matter?

I mentioned soldering irons because you suggested that a socket at a temperature similar (enough to go black) to an iron (300 C) is contrary to the EAWR, and therefore an electric soldering iron is similarly so. I realise that the situations are slightly different, but both require a similar level of care from an employee. The center of the point is that sockets do not normally burn up when loaded to 13 or even 20A (about the fuse blowing fairly quickly current). Only poor or faulty sockets might blacken, or ones mated with a poor plug. It is not reasonable to suggest that this is normal, or similarly, certain FSUs on immersion heaters sometimes suffer in the same way, usually due to poor fuse contact should not be used. Good ones do not suffer in this way.

Ultimately this discussion about ring circuits (again) is not reflective of real installations. There are bound to be a few problems, and maintenance is obviously required. However, realistically it is impossible to prevent any faults with anything. If you apply the same standard of zero faults, garages would endlessly be in court. Cars are quite reliable now, much better than 40 years ago, but there are still not zero problems and such is impossible. Poor quality products should be eliminated, but in the bigger picture that is not controlled by a standard. Standards rarely say anything about reliability, and this is always designed in, not tested in, and not under external event controls.  We might think that we can control usage, but we cannot. We also should not attempt to make things completely “idiot-proof”, it is an ideal that cannot be achieved. Fixed wiring systems are extremely reliable, even with fairly extreme abuse.  Remembering the loose tails fiasco, it could have been foreseen by a reasonable person, and the “controls” on meter installers make a problem inevitable. Double sockets are occasionally problematic, but it is easily detected and corrected with a new socket. Faults and improper usage are much more common with appliances, tumble driers where the filters are not cleaned are a case in point.

I suggest that a single socket and a two-way adaptor is much worse than a double socket, but that would be the result of removing double sockets!

gkenyon: 
Man on the Clapham Omnibus

and

Wells v Cooper (1958) 2 All ER 527

I am not at all sure how they are relevant.

TMOTCO is simply an ordinary person and some allowance is made for a house-holder as opposed to a tradesman in respect of standard of care.