UK Melted Plug and Socket cause

[pc1966]

Q Why didnt the RCD trip?

RCD only trip if electricity goes "astray". Basically the look at the current going out on the L and coming back on the N, if they differ by more than a small amount (usually in the range of 0.015 to 0.030 amps) then they trip. As such they are intended to protect against electric shock, when often the person touches the L while in contact with the Earth and so some of the L current is not returning by the N as desired.

They can also protect against fires from partial cable faults when insulation is damaged and enough current flows to the CPC (earth wire, usually central in the flat "twin and earth" cable typically used in house wiring) to risk a fire starting, but not enough flows to trip the over-current protection device (these days normally a MCB = Miniature Circuit Breaker, but sometimes a fuse, when quick disconnection might need 100A or more fault current). Say crushed cable or rodent damage, even poor quality counterfeit cable.

Unfortunately they do not protect against overheating due to a poor connection. You can get AFDD (arc-fault detection devices) that are designed trip if the heating is caused by a tiny gap that is causing sparking (electrical arc) but they do will not pick up on a simple poor connection that is getting hot.

Quality parts and good workmanship, along with paying attention to any odd smells, sounds, or evidence of heating, are still the best defence for this particular problem!

 

[jace999]

RCD only trip if electricity goes "astray". Basically the look at the current going out on the L and coming back on the N, if they differ by more than a small amount (usually in the range of 0.015 to 0.030 amps) then they trip. As such they are intended to protect against electric shock, when often the person touches the L while in contact with the Earth and so some of the L current is not returning by the N as desired.

They can also protect against fires from partial cable faults when insulation is damaged and enough current flows to the CPC (earth wire, usually central in the flat "twin and earth" cable typically used in house wiring) to risk a fire starting, but not enough flows to trip the over-current protection device (these days normally a MCB = Miniature Circuit Breaker, but sometimes a fuse, when quick disconnection might need 100A or more fault current). Say crushed cable or rodent damage, even poor quality counterfeit cable.

Unfortunately they do not protect against overheating due to a poor connection. You can get AFDD (arc-fault detection devices) that are designed trip if the heating is caused by a tiny gap that is causing sparking (electrical arc) but they do will not pick up on a simple poor connection that is getting hot.

Quality parts and good workmanship, along with paying attention to any odd smells, sounds, or evidence of heating, are still the best defence for this particular problem!

Thanks for your clearly very knowledgeable reply.I am still shocked that the only safety feature that evaded a fire was my sense of smell and a small fuse in the tumble dryer plug.The safety regulations should be updated to include AFDD as a standard feature in new wiring installations and insurance premiums should reflect this in a reduction of premium.This wiring was only installed 4 years ago by a professional certified company.Even though the fuse disconnected current to the appliance,I can clearly see via the 3 plug pin entries that the internal housing of the socket is blackened and it is possible that a chain of events leading to a full blown house fire was already underway before all supply to the socket wiring was isolated.As we all leave several appliances on while we are away from home ,freezer etc why isnt this standard practice?The sparkys investigation will be revealing.I will get him to check all the other sockets too as the rewiring company blamed wiring difficulties on the age and location of my house . : ) : )

 

[pc1966]

Thanks for your clearly very knowledgeable reply.I am still shocked that the only safety feature that evaded a fire was my sense of smell and a small fuse in the tumble dryer plug.The safety regulations should be updated to include AFDD as a standard feature in new wiring installations and insurance premiums should reflect this in a reduction of premium.

While insisting on AFDD might seem like a good idea, in practice it is not necessarily so.

1) AFDD are not that good at stopping fires. They only add detection of an arc, and not overheating, and even the arc aspect is not that convincing (just search YouTube for John Ward doing some tests on AFDD). Also as I mentioned they do not stop fires from a simple poor connection or under-rated cable, nor would they stop fires from the likes of tuble dryers building up lint which as often classed as "electrical fires":

https://www.imperialclaimsconsultants.co.uk/faulty-whirlpool-tumble-dryer-recalls-increasing/

If they were a magic bullet to stopping fires, then why don't we see detailed analysis of what proportion of fires would be prevented?

2) They add a lot of cost. Sure that will no doubt drop in time, but today you could be looking at £2000 extra on the cost of a rewire or new CU. Now if you have paid off your mortgage and earn £50k/year that might not trouble you, but for the majority of folk that is going to make them think twice.

The unintended consequences of that are either poor electrical installation going unfixed, instead of being brought up to date with at least RCDs, or them going to some dodgy character a mate at the pub knows, and probably getting a far less safe job done (maybe with fake AFDD off eBay, etc, as well)

3) For a given budget, you would be better spending the extra AFDD money on a proper linked-up fire/smoke alarm. Why? Well because only around 12% of fires are due to the wiring that might be protected by the AFDD but your smoke alarm should give to a chance to escape all of them:

UK house fire statistics & common causes of fires | Morgan Clark

Updated for 2023/24, the following fire statistics have been compiled to draw attention to the risks of house fires in the UK.

www.morganclark.co.uk

This wiring was only installed 4 years ago by a professional certified company.Even though the fuse disconnected current to the appliance,I can clearly see via the 3 plug pin entries that the internal housing of the socket is blackened and it is possible that a chain of events leading to a full blown house fire was already underway before all supply to the socket wiring was isolated.As we all leave several appliances on while we are away from home ,freezer etc why isnt this standard practice?The sparkys investigation will be revealing.I will get him to check all the other sockets too as the rewiring company blamed wiring difficulties on the age and location of my house . : ) : )

Overheated plug/socket combinations can be due to either the socket, which would be your electricians responsibility, or the appliance plug, which is another issue. To me "wiring difficulties on the age and location of my house" sounds very suspicious, but without full details and someone interdependently looking at it I could not say any more.

 

[jace999]

While insisting on AFDD might seem like a good idea, in practice it is not necessarily so.

1) AFDD are not that good at stopping fires. They only add detection of an arc, and not overheating, and even the arc aspect is not that convincing (just search YouTube for John Ward doing some tests on AFDD). Also as I mentioned they do not stop fires from a simple poor connection or under-rated cable, nor would they stop fires from the likes of tuble dryers building up lint which as often classed as "electrical fires":

https://www.imperialclaimsconsultants.co.uk/faulty-whirlpool-tumble-dryer-recalls-increasing/

If they were a magic bullet to stopping fires, then why don't we see detailed analysis of what proportion of fires would be prevented?

2) They add a lot of cost. Sure that will no doubt drop in time, but today you could be looking at £2000 extra on the cost of a rewire or new CU. Now if you have paid off your mortgage and earn £50k/year that might not trouble you, but for the majority of folk that is going to make them think twice.

The unintended consequences of that are either poor electrical installation going unfixed, instead of being brought up to date with at least RCDs, or them going to some dodgy character a mate at the pub knows, and probably getting a far less safe job done (maybe with fake AFDD off eBay, etc, as well)

3) For a given budget, you would be better spending the extra AFDD money on a proper linked-up fire/smoke alarm. Why? Well because only around 12% of fires are due to the wiring that might be protected by the AFDD but your smoke alarm should give to a chance to escape all of them:

UK house fire statistics & common causes of fires | Morgan Clark

Updated for 2023/24, the following fire statistics have been compiled to draw attention to the risks of house fires in the UK.

www.morganclark.co.uk

Overheated plug/socket combinations can be due to either the socket, which would be your electricians responsibility, or the appliance plug, which is another issue. To me "wiring difficulties on the age and location of my house" sounds very suspicious, but without full details and someone interdependently looking at it I could not say any more.

Thanks.My nose went off without the fire alarms even activating.The company that did the original wiring were all industry acredited.They also cut floorboards between joists,broke a door frame by throwing a drill down in temper and the main engineer sent sat in his van for an hour before work on his phone outside our house as the boss had trackers fitted to vans but not employees boots and lefyt our home unlocked for over an hour while he went to the pub.The company changed their name a couple of years later.These types discredit the profession thats why Im not having them back and will send the socket to the NICEIC.

 

[telectrix]

for over an hour while he went to the pub.

bloody lightweight. pub visit should be at least 3 hours, 8pints, and a meat & potato pie.

 

[pc1966]

for over an hour while he went to the pub.

bloody lightweight. pub visit should be at least 3 hours, 8pints, and a meat & potato pie.

Missing presumed fed.

 

[jace999]

for over an hour while he went to the pub.

bloody lightweight. pub visit should be at least 3 hours, 8pints, and a meat & potato pi

 

[jace999]

Sparky appearing tomorrow.Meanwhile..have tried the tumbledryer which was in use at time of socket meltdown in a different socket on a different circuit.Clean pins and new fuse .It got the socket extremely hot very quicly there too before I pulled it.Apart from possibly crap sockets fitted is there any way, somehow the dryer could be pulling too much voltage through by a defect in the actual dryer or causing another issue leading to extreme heat in the socket?

 

[littlespark]

I don’t know if it was mentioned earlier, but is this a moulded on plug, or one that’s been put on?

It may be that the connections inside the plug are loose, rather than the wall socket.

 

[Avo Mk8]

It may be that the plug or its internal wiring is now damaged due to the heat it had experienced, in fact I think it likely, even if it wasn't the cause in the first place. - update - just looked at the pic of the plug - needs changing (and the cable cutting back a bit as the copper will probably be affected)

It's also possible that the appliance is taking excessive current due to a fault.
Both could be dealt with by the electrician.

 

[freddo]

You have replaced the dryer plug haven't you? You're not still using the old damaged one?!!

 

[jace999]

I don’t know if it was mentioned earlier, but is this a moulded on plug, or one that’s been put on?

It may be that the connections inside the plug are loose, rather than the wall socket.

Its a moulded plug on the dryer.The actual dryer plug didnt get hot it was plugged into an extension cable.It was the feed into the extension plug ,the plug and socket ,that got very very hot.That was why I asked if the dryer itself can disrupt voltage flow somehow.Excuse non tech terms.just an unqualified bod trying to work it out.The extension cable itself is a mega tough bit of kit.Not from b and q.?

 

[Avo Mk8]

Its a moulded plug on the dryer.The actual dryer plug didnt get hot it was plugged into an extension cable.It was the feed into the extension plug ,the plug and socket ,that got very very hot.That was why I asked if the dryer itself can disrupt voltage flow somehow.Excuse non tech terms.just an unqualified bod trying to work it out.The extension cable itself is a mega tough bit of kit.Not from b and q.?

Two possibilities
1) The extension cable is not adequately rated (despite its claims!) - or maybe faulty. It does look the part, but can't really see the csa of the conductors.
2) There is a fault with the dryer, though if there was, you might expect the dryer plug itself to also be getting hot (eg if the fuse was warming up), but you say it was OK.

 

[jace999]

Two possibilities
1) The extension cable is not adequately rated (despite its claims!) - or maybe faulty. It does look the part, but can't really see the csa of the conductors.
2) There is a fault with the dryer, though if there was, you might expect the dryer plug itself to also be getting hot (eg if the fuse was warming up), but you say it was OK.

You are right to consider all possibilities. Maybe the heating up this time was unconnected with the original issue.All will be revealed tomorrow.A sparky will come galloping over the hill with assorted tech stuff and will sort it out.It was terrifyingly swift and potentially deadly whatever happened.Left unattended it would have been a house fire.

 

[Avo Mk8]

Left unattended it would have been a house fire.

There I would disagree with you, I don't believe there would. To get their product approvals to be sold legitimately, the materials of both the plug, and the socket on the wall, will have passed a glow-wire test to demonstrate they won't support combustion. So although there may be loads of melted plastic and a horrible smell, there shouldn't be flames to create a house fire.

 

[telectrix]

There I would disagree with you, I don't believe there would. To get their product approvals to be sold legitimately, the materials of both the plug, and the socket on the wall, will have passed a glow-wire test to demonstrate they won't support combustion. So although there may be loads of melted plastic and a horrible smell, there shouldn't be flames to create a house fire.

unless there's flammable material/s close to the socket.

 

[Lucien Nunes]

It's possible but unlikely that the dryer is taking too much current. If it did, because it would be producing proportionately more heat, the most likely symptom would be that the dryer overheated, not the plug. And it has various thermal cutouts and limit stats to prevent that happening.