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.

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.