Failed switched plug socket

[Milleniumaire]

Seasons Greetings.

I was asked to check out my in-laws failed microwave a couple of days ago. Although only a couple of months old, it has stopped working as though it wasn't getting power.

I checked the 13amp fuse in the plug and replaced it, but no luck. I then plugged the microwave (with the original fuse re-fitted) into a different wall socket and it worked.

I then started to unscrew the front of the wall socket and heard a "sizzling" sound, so stopped. I located a spare single gang, switched plug socket, then isolated the power and removed the socket, so see the following:

20211225_152944

• Milleniumaire
• 28 Dec 2021

20211225_153139

• Milleniumaire
• 28 Dec 2021

The wire connections into the socket were solid - I had expected one of them to be loose. As you can see there's a sign of scorching on the neutral, and possibly a little on the live also. I noticed the neutral socket connection had a crack in it.

The house was built in around 1984 and as far as I know it hasn't ever been rewired, so I was a little surprised to see two types of cable, although I guess it is possible kitchen fitters may have done some wiring!

Although the new switched plug socket is working, I'm concerned about the signs of scorching on the cables.

Any idea why this might be happening? I assume this is a sign of the cable being overloaded, but could a "faulty" socket also cause this?

 

[sparkwright]

Those brown and blue wires are very very likely to be more recent than circa 1984, so that tells me that someone has spurred off that socket in the last 15 years, and probably made a pig's ear of it.

It is likely the connections were poorly terminated when this was done, perhaps by some chancer, and that's why it's all burnt.

The overheating can cause a loose connection to appear tight, but it's still a poor connection.

Alternatively, a worn out socket or heavy load cause this, but my money is on loose connections.

All black copper needs cutting back, or cleaning up with wire wool, so you have clean shiny copper.

All damaged copper that is on the verge of breaking off needs cutting back and re-stripping.

All heat damaged insulation needs cutting back, or in some cases, stripping back and sleeved with heat shrink insulation, shrunk on.

 

[Harry Bloomfield]

Some of those cables look very much like aluminium, installed during the copper shortages. Aluminium was a source of constant problems with poor connections due to oxidation forming and subsequent overheating at terminals.

 

[Milleniumaire]

Those brown and blue wires are very very likely to be more recent than circa 1984, so that tells me that someone has spurred off that socket in the last 15 years, and probably made a pig's ear of it.

It is likely the connections were poorly terminated when this was done, perhaps by some chancer, and that's why it's all burnt.

The overheating can cause a loose connection to appear tight, but it's still a poor connection.

Alternatively, a worn out socket or heavy load cause this, but my money is on loose connections.

All black copper needs cutting back, or cleaning up with wire wool, so you have clean shiny copper.

All damaged copper that is on the verge of breaking off needs cutting back and re-stripping.

All heat damaged insulation needs cutting back, or in some cases, stripping back and sleeved with heat shrink insulation, shrunk on.

Thanks for the quick response.

I did think about cutting back the wires to good copper and sleeve when fitting the replacement socket, but there is barely any spare cable to play with, although I guess it would be possible to remove a centimetre or so.

Some of those cables look very much like aluminium, installed during the copper shortages. Aluminium was a source of constant problems with poor connections due to oxidation forming and subsequent overheating at terminals.

Yes, I noticed the brighter wires, all of which come from the same cable and these seem to have more damage than the copper wires.

 

[sparkwright]

If you really are struggling for length on the wires, and you cannot pull any slack through the wall, you could consider joining them in 30amp connector blocks, with some new 2.5mm2 cable going to the socket.

This way each connector block contains 3 wires.

***

You could consider extending only the short wires with connector blocks, but the trouble is you may end up with too many connector blocks which can make pushing the socket faceplate back impossible.

 

[Milleniumaire]

If you really are struggling for length on the wires, and you cannot pull any slack through the wall, you could consider joining them in 30amp connector blocks, with some new 2.5mm2 cable going to the socket.

This way each connector block contains 4 wires.

***

You could consider extending only the short wires with connector blocks, but the trouble is you may end up with too many connector blocks which can make pushing the socket faceplate back impossible.

Thanks. I'll have another look at the wiring and clean it up/trim it as you suggest. The back box isn't very deep, so as you say, adding connectors may result in an issue.

 

[sparkwright]

You can get a spacer, which is about 10mm thick, which can go between the wall and the socket, which may help you.

 

[Harry Bloomfield]

Yes, I noticed the brighter wires, all of which come from the same cable and these seem to have more damage than the copper wires.

Try a little test - try scrapping those silver coloured wires to see if the scrapping reveals copper under the silver or not, but be careful - aluminium cable is much more brittle than copper.

 

[ericmark]

Looking at when Ian Smith was in power it is possible aluminium has been used, seem to remember cables exploding when used with motor vehicles, the problem is any heat expands the aluminium at a different rate to brass so it squashes the aluminium and it becomes loose.

 

[Alec_t]

Looks like the bottom grommet isn't fitted in the back-box.

 

[crystal ball]

Looking at when Ian Smith was in power it is possible aluminium has been used, seem to remember cables exploding when used with motor vehicles, the problem is any heat expands the aluminium at a different rate to brass so it squashes the aluminium and it becomes loose.

What did it have to do with Smith?

 

[Harry Bloomfield]

What did it have to do with Smith?

We had a falling out, which reduced the copper imports, which sent copper prices through the roof.

 

[crystal ball]

We had a falling out, which reduced the copper imports, which sent copper prices through the roof.

Rhodesia was not a major exporter of copper

 

[Harry Bloomfield]

Rhodesia was not a major exporter of copper

It's exports to the UK were large enough to cause a massive price increase, when they were stopped.

 

[crystal ball]

It's exports to the UK were large enough to cause a massive price increase, when they were stopped.

Looking at some archive material and it does not indicate any major imports from Rhodesia, the price was rising certainly but other factors were cited for this, I lived there for a number of years and copper mining was not a large industry