UK Melted Plug and Socket cause

[zerozero7]

Hi all,
Washing machine plug and socket melted around Neutral pin. Whilst removing socket faceplate, noticed one brown wire was not in the terminal. May have come out of the terminal when pulling the socket forward or may have been out all the time.
Is this lose or disconnected live cable the 'definate' cause of the overheating on the neutral pin?
Thanks, Gary

 

[littlespark]

If the loose live wire was causing a problem, the heat damage would be showing around that terminal.

I think this has been caused be the neutral socket not having a good grip on the plug pins.
It can happen with older sockets, or ones that are plugged/unplugged constantly.
Can also happen if the sockets have had those plastic “child safety” shields fitted

 

[brianmoooore]

It's more likely indicative that the neutral terminal wasn't tight either. There appears to be slight thermal damage around the neutral terminal.

 

[littlespark]

There’s quite a bit of melting behind the live socket hole as well, meaning the live didn’t have a good grip either.

 

[Julie.]

That looks like the contacts between the plug and socket were not making proper contact.

It could be an undersized plug (cheap China incorrect size)

It could be oversized socket - poor quality socket (BG) or having an oversized plug inserted previously -- typically the ridiculous "child safety" things that reduce the safety, but the public uses.

It could be corroded contacts - usually the plug as the brass contacts get wet and go green, especially with stuff near washing machines, in garages etc.

Although the incoming connection may have been loose that actually wasn't the cause here - it does show that you probably need to get the installation checked properly though.

 

[telectrix]

cheap socket, limp wristed tightening of terminal screw/s.

 

[telectrix]

That looks like the contacts between the plug and socket were not making proper contact.

It could be an undersized plug (cheap China incorrect size)

It could be oversized socket - poor quality socket (BG) or having an oversized plug inserted previously -- typically the ridiculous "child safety" things that reduce the safety, but the public uses.

It could be corroded contacts - usually the plug as the brass contacts get wet and go green, especially with stuff near washing machines, in garages etc.

Although the incoming connection may have been loose that actually wasn't the cause here - it does show that you probably need to get the installation checked properly though.

why knock BG .I fitted loads, never any problems.

 

[Julie.]

why knock BG .I fitted loads, never any problems.

So have I

But it isn't the best quality, and I probably wouldn't use one where it was subject to large loads such as a washing machine/dryer or where it would be plugged in/out a lot.

I have them in my own bedrooms and living rooms etc - to be fair mostly the usb versions, but within the kitchen and utility where there will be kettles and fryers plugged and unplugged and for the dishwasher and washing machine, I have used more premium examples.

 

[telectrix]

we got kettle (3kW) and micro (1kW) in a double BG with usb. been in 6 years, no problems. in garage, washer, tumbler, 3 freezers all in 2 x BG doubles, extension lead for freezers.

 

[Petej999]

cheap socket, limp wristed tightening of terminal screw/s.

What Tel said

 

[Mark42]

Hi all,
Washing machine plug and socket melted around Neutral pin. Whilst removing socket faceplate, noticed one brown wire was not in the terminal. May have come out of the terminal when pulling the socket forward or may have been out all the time.
Is this lose or disconnected live cable the 'definate' cause of the overheating on the neutral pin?
Thanks, Gary

Hi Gary

Had the brown (Live) wire not been present you wouldn't have got much washing done ?.

The fact that it came out when withdrawing the front plate definitely indicates it wasn't tightened properly in the first place, and you have a cr@p installation.

So long as the wires aren't burned back beyond trimming distance this is no big deal. Just buy a decent quality new socket and replace it. Ditto a decent plug for the flex.

It might be worth gradually going round all your other sockets to check terminal tightness as well (switch off at the board first!). There's a bit of craft in getting the torque right - it should be firm, but not torqued down like the wheel nuts on a 44 ton truck! All that does is to strip the threads and/or cut through the copper cable.

Cheers and good luck, Mark.

 

[zerozero7]

Thanks all

Hi Gary

Had the brown (Live) wire not been present you wouldn't have got much washing done ?.

The fact that it came out when withdrawing the front plate definitely indicates it wasn't tightened properly in the first place, and you have a cr@p installation.

So long as the wires aren't burned back beyond trimming distance this is no big deal. Just buy a decent quality new socket and replace it. Ditto a decent plug for the flex.

It might be worth gradually going round all your other sockets to check terminal tightness as well (switch off at the board first!). There's a bit of craft in getting the torque right - it should be firm, but not torqued down like the wheel nuts on a 44 ton truck! All that does is to strip the threads and/or cut through the copper cable.

Cheers and good luck, Mark.

Hi Gary

Had the brown (Live) wire not been present you wouldn't have got much washing done ?.

The fact that it came out when withdrawing the front plate definitely indicates it wasn't tightened properly in the first place, and you have a cr@p installation.

So long as the wires aren't burned back beyond trimming distance this is no big deal. Just buy a decent quality new socket and replace it. Ditto a decent plug for the flex.

It might be worth gradually going round all your other sockets to check terminal tightness as well (switch off at the board first!). There's a bit of craft in getting the torque right - it should be firm, but not torqued down like the wheel nuts on a 44 ton truck! All that does is to strip the threads and/or cut through the copper cable.

Cheers and good luck, Mark.

Thanks Mark...
"Had the brown (Live) wire not been present you wouldn't have got much wasting done ?"
It must have been using the other Brown ?
Not sure where the second lose brown looped to but the as far as I know all the other sockets were working so it was probably still in the terminal until I pulled the faceplate away although it was obviously poorly gripped.
Gary

 

[brianmoooore]

It's quite probably a ring final circuit (32A MCB?), so is intended to be fed power from both cables. On a well loaded circuit, this can cause damage to the fixed wiring, all the way back to the fusebox.

 

[zerozero7]

Thanks all for great prompt replies.
Only 1 year old good quality (?) BG socket with good quality (?) factory fitted washing machine plug. Permanently plugged in so socket has little use and located in a dry kitchen cupboard adjacent.
Seems to make sense that if it was a poor contact in the terminal there would be more heat damage in that location but as the damage seem to be around the socket and plugs prong, I am guessing it was a poor connection in there.
Got a very nervous homeowner who thinks her house is going to burn down and my ""probably a lose connection"" just isn't good enough.
Arranging for Spark who done the kitchen install to come back and give it the once over to reassure her.
Gary

 

[zerozero7]

It's quite probably a ring final circuit (32A MCB?), so is intended to be fed power from both cables. On a well loaded circuit, this can cause damage to the fixed wiring, all the way back to the fusebox.

That was my original thinking, lose or missing live overloading neutral?

 

[Lucien Nunes]

That was my original thinking, lose or missing live overloading neutral?

No, this isn't how electricity works!

The location of the melting / burning clearly shows that this was due to bad contact between the plug pin and socket contact, and unlikely to have been due to loose terminals. Granted the line terminal was apparently loose because the cable pulled out, and a loose terminal can cause a burnout, but in this case it was unrelated.

All contacts rely on tiny (almost invisible) areas of metal actually making contact, so the current density is high and at least some heat is dissipated in the resistance. Less effective contact leads to more heat, which accelerates oxidation of the surface and weakens the spring temper of the socket contact gripping the pin. . This further reduces the contact area and it goes into runaway, leading to a burnout.

Good quality contacts are less likely to suffer from this effect and the socket is the main player rather than the plug. But progressive failure can still be triggered by some random adverse situation like a layer of deposit on the plug pin before installation, and some combinations of plug and socket metal alloys make better contact together than others.

Plugs that are regularly moved have the advantage that any oxide buildup is mechanically scraped off so that fresh bare metal surfaces are exposed. The same is true of the socket contact although heavy use eventually wears out the contact. Again, quality counts and the devil is in the detail, although price is a guide there is no cast-iron guarantee that the most expensive socket will last the longest in a particular application.

 

[zerozero7]

No, this isn't how electricity works!

The location of the melting / burning clearly shows that this was due to bad contact between the plug pin and socket contact, and unlikely to have been due to loose terminals. Granted the line terminal was apparently loose because the cable pulled out, and a loose terminal can cause a burnout, but in this case it was unrelated.

All contacts rely on tiny (almost invisible) areas of metal actually making contact, so the current density is high and at least some heat is dissipated in the resistance. Less effective contact leads to more heat, which accelerates oxidation of the surface and weakens the spring temper of the socket contact gripping the pin. . This further reduces the contact area and it goes into runaway, leading to a burnout.

Good quality contacts are less likely to suffer from this effect and the socket is the main player rather than the plug. But progressive failure can still be triggered by some random adverse situation like a layer of deposit on the plug pin before installation, and some combinations of plug and socket metal alloys make better contact together than others.

Plugs that are regularly moved have the advantage that any oxide buildup is mechanically scraped off so that fresh bare metal surfaces are exposed. The same is true of the socket contact although heavy use eventually wears out the contact. Again, quality counts and the devil is in the detail, although price is a guide there is no cast-iron guarantee that the most expensive socket will last the longest in a particular application.

Now that, is what I call an answer!
Thank you.
I guess my concern is that I stubbornly refuse to accept that a nearly new good quality plug and socket can fail so badly/dangerously! How many dangerous sockets are out there!?!
Maybe I should sent it to BG for their comment.
Thanks again

 

[Lucien Nunes]

We can't assume it was 'dangerous' by design or manufacture, because we don't know the actual underlying trigger mechanism for the burnout. Once it starts escalating, any high-resistance fitting can turn into a lump of melted goo, and it has been happening since the first days of electricity. A century ago, when plugs were often made of wood, they would char rather than melt but the result was not very different to what happened to your washing machine plug.

 

[jace999]

I just had that.Tumble dryer stopped.plug and socket too hot to tougch.stank of that burning electrical plastic smell.turned off supply.got plug out.neutral pin had black residue.changed fused,cleaned pin and worked okay in another socket.socket took a very long time to cool down.sparky booked,though tempting to have a look.Q Why didnt the RCD trip?The heat generated indicated that the fault was taking place long enough for the disruption to have been detected.

 

[jace999]

i had similar.tumbler dryer stopped.socket and plug stank and too hot to touch.turned off elec.took out plug cleaned off black residue on neutral pin changed fuse worked okay in another socket.sparky booked though tempting to look inside socket.fake fuses were an issue on domestic appliances a while ago,but old fuse not burnt.As the fault must have been evident for a while to generate such extensive heat which didnt the RCD trip?

 

[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.