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Hi,

We have just taken a plug socket off the wall (electricity off) and found it in this interesting state. 
 

Does anyone know what causes this? Could this be a future problem? To us it looks like a fire hazard so it will be coming out.
 

No idea how old this socket is as it would have been installed before our time - potentially over six years. 
 

Thanks!

Gemma

 

pics attached

4F132085-0A52-4008-A76F-8EF1332B18E3.jpeg

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The 1st thing is it has been installed incorrectly, it should have a boot lace ferrule on the end of the wires - suggesst you remove all sockets and fit them before  the 'worst' happens.

 

If the boat has been built since 1998 It is a requirement, & the boat is non-compliant with the RCD.

 

The requirement is :

 

11.7 All conductors shall have suitable terminals installed, i.e. no bare wires attached to stud or screw connections.

 

Was the boat a self-build or a professional fit-out ?

Edited by Alan de Enfield
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Further to what @Alan de Enfield said. The socket was designed for domestic single core wire. On boats, we use multi strand wire, as it stands up to vibration a lot better. Unfortunately, this has problems when used with screw terminals, so a boot lace ferrule needs to be fitted to each wire where it goes under a screw. You can see heat damage where it has worked loose and formed a higher resistance joint. The ferrules are crimped to the wire. They need to be the correct size for the wire.

Jen

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2 minutes ago, Petalsnow said:

by the standard, diy. We are refitting her. That’s really useful thank you. We will make sure these are used. Really glad I checked.

 

It may be worth working your way thru' all the electric system to ensure it is safe, I can email you copies of the specifications / requirements for both 12v DC and the 230V AC systems if it helps. (send a PM - message rather than posting your email in public - avoids spamming)

 

Things like using 'domestic' (house) cable is not allowed.

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I know some others will disagree but if you can't easily get ferrules then light soldering is an alternative.  

 

That said CPC have a range of reasonably priced ferrules.  Some of these don't require special crimp tools just using the screw terminals to crimp the ferrule onto the wire.

 

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47 minutes ago, Alan de Enfield said:

 

Sent - let me know if they don't arrive. Some ISPs don't like my ISP.

 

47 minutes ago, Alan de Enfield said:

 

Sent - let me know if they don't arrive. Some ISPs don't like my ISP.

Worked a dream. Thanks again!

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That really has got hot. I would certainly check other sockets and fittings too. Is that on the 12 volt circuits or the 240 volt? The reason I ask is because it looks like the brass screw that holds the cable in seems to have 'de zincified' leaving just crumbly copper. Its the sort of thing that happens with electrolysis, battery terminals and other things leaving weak metal and in your case a bad contact, high resistance and a lot of heat. I think DC current is more susceptible. I'm not an expert but others will know more.

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16 hours ago, Alan de Enfield said:

 

The 1st thing is it has been installed incorrectly, it should have a boot lace ferrule on the end of the wires - suggesst you remove all sockets and fit them before  the 'worst' happens.

 

If the boat has been built since 1998 It is a requirement, & the boat is non-compliant with the RCD.

 

The requirement is :

 

11.7 All conductors shall have suitable terminals installed, i.e. no bare wires attached to stud or screw connections.

 

Was the boat a self-build or a professional fit-out ?

Which leads to an anomaly that if you have 240V wiring on the boat, the fixed wiring has to be multi-stranded and with a ferrule on the end of wires clamped under screw terminals in the socket, but you can then use land-based plug-in appliances, also fitted with a flexible cord but with no requirement for a ferrule on the wires clamped in similar screw terminals in the plug.

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4 minutes ago, David Mack said:

Which leads to an anomaly that if you have 240V wiring on the boat, the fixed wiring has to be multi-stranded and with a ferrule on the end of wires clamped under screw terminals in the socket, but you can then use land-based plug-in appliances, also fitted with a flexible cord but with no requirement for a ferrule on the wires clamped in similar screw terminals in the plug.

most plugs nowadays are moulded on but when i have bought bare lead devices such as spotlights there is generally some sort of ferule on the cable end,

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8 minutes ago, David Mack said:

Which leads to an anomaly that if you have 240V wiring on the boat, the fixed wiring has to be multi-stranded and with a ferrule on the end of wires clamped under screw terminals in the socket, but you can then use land-based plug-in appliances, also fitted with a flexible cord but with no requirement for a ferrule on the wires clamped in similar screw terminals in the plug.

Almost all 13amp plugs on appliances are now moulded so will be to standard, those that are not you will find that the cable ends are ferruled or tinned to prevent splaying.

 

If you remove the plug or shorten the cable then either ferrules should be fitted or the ends tinned. 

 

Sadly but unsurprisingly I do this every time I change a plug.

Edited by Loddon
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16 hours ago, jonathanA said:

I know some others will disagree but if you can't easily get ferrules then light soldering is an alternative.  

 

That said CPC have a range of reasonably priced ferrules.  Some of these don't require special crimp tools just using the screw terminals to crimp the ferrule onto the wire.

 

Others would indeed disagree because solder creeps under stress and runs away from the load, so the terminals work loose again -- in fact this is worse than using stranded copper wire...

 

I've seen this happen on multiple occasions with things like high-power speaker leads (where stranded wire works just fine, in an appropriate terminal designed for it), though I haven't seen anyone crazy enough to do it with mains terminals designed for solid single-strand wire...

6 minutes ago, Tracy D'arth said:

I do understand the use of ferrules on flex cable connections but have ever did we survive a whole century not using them?

By using solid wire instead of stranded? By using terminals designed for stranded wire (which surround it) not ones designed for solid wire (single hole with a screw)? By having houses/boats catch fire because of bad connections? (used to be acceptable but isn't any more, like boys up chimneys)

Edited by IanD
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I do understand the use of ferrules on flex cable connections but have ever did we survive a whole century not using them?

 

 

A good tight screw will grip on anything, solder, brass, copper. even aluminium. Its the guy doing the job that makes the difference, not the material or the tools.

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21 minutes ago, Loddon said:

Almost all 13amp plugs on appliances are now moulded so will be to standard, those that are not you will find that the cable ends are ferruled or tinned to prevent splaying.

 

If you remove the plug or shorten the cable then either ferrules should be fitted or the ends tinned. 

 

Sadly but unsurprisingly I do this every time I change a plug.

Tinning -- meaning, coating each strand with a thin layer of solder to prevent the copper oxidising -- is not so bad but isn't usually recommended (or sometimes banned).

 

Partly because it's tricky to do properly (I assume you do, of course...), and careless people often end up soldering all the strands together into a single big copper/solder strand, which is not safe.

 

It's why crimped-on (or solder-filled) ferrules are the recommended way to get stranded cable into a connector designed for single-core i.e most mains connectors.

 

If the connector is designed for stranded cable (e.g. signal/mains Speakons which surround and compress the cable) then just bare copper strands are the best solution, but most mains connectors aren't made like this.

13 minutes ago, Tracy D'arth said:

I do understand the use of ferrules on flex cable connections but have ever did we survive a whole century not using them?

 

 

A good tight screw will grip on anything, solder, brass, copper. even aluminium. Its the guy doing the job that makes the difference, not the material or the tools.

The problem with solder is that it creeps under stress; it might be tight when you first make the connection, but it doesn't stay that way.

 

Anyone who works in the electrical or electronics fields is aware of this, tightening down a connector onto squishy soldered things is a no-no. Plated is fine, a bunch of strands soldered together isn't.

6 minutes ago, Keith M said:

What happen when do up a screw type fixing and you only manage tighten down on a 1/3 of the stands? 

That's the problem with mains terminals (usually just a hole with a screw) designed for single-strand cable. Stranded might be OK if it fills the entire hole before you tighten the screw down, but this is rarely true. It's why ferrules are recommended.

Edited by IanD
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I try to get the strands well twisted together and then double them back on themselves so that the connection is as full of wire as possible before tightening the screws. Then go over the screws again before you finish.

Never had a burnt connection like the one shown doing it this way, or with solder.

 

 On heavy stuff when not using crimp lugs we used to wrap the bare conductor with copper wire or thick copper tape to fill up the connector before clamping down. Did thousands of 300A and above terminations like this without any problems. Telephone exchange battery supplies mostly.

 

I remember when copper was in short supply, after Rhodesia became independent I think, and we had to use aluminium cables for mains wiring. The existing accessories with one screw were not good at getting a solid connection and the aluminium  was brittle, snapped off easily where the screw bit into the conductor if stressed.

A range of accessories with clamp plate connections were made, like CU MCBs are now, much better connections.

 

 

Edited by Tracy D'arth
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28 minutes ago, Loddon said:

Almost all 13amp plugs on appliances are now moulded so will be to standard, those that are not you will find that the cable ends are ferruled or tinned to prevent splaying.

 

If you remove the plug or shorten the cable then either ferrules should be fitted or the ends tinned. 

 

Sadly but unsurprisingly I do this every time I change a plug.

True most appliances come with moulded on plugs these days, but I remember when bare wire ends were the norm, and if you were lucky the shop might fit the plug for you.

 

I have just googled "wiring a plug UK" and got dozens of hits. A quick look at a few didn't find a single one suggesting the use of a ferrule. Just twist the ends, maybe fold double, insert into the terminal and tighten the screw down on the wires. Even the BBC.

 

Edited by David Mack
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20 minutes ago, IanD said:

Tinning -- meaning, coating each strand with a thin layer of solder to prevent the copper oxidising -- is not so bad but isn't usually recommended (or sometimes banned).

 

Partly because it's tricky to do properly (I assume you do, of course...), and careless people often end up soldering all the strands together into a single big copper/solder strand, which is not safe.

 

It's why crimped-on (or solder-filled) ferrules are the recommended way to get stranded cable into a connector designed for single-core i.e most mains connectors.

 

If the connector is designed for stranded cable (e.g. signal/mains Speakons which surround and compress the cable) then just bare copper strands are the best solution, but most mains connectors aren't made like this.

Most people don't know what Speakons are 😱

I had to go and look at one in the workshop to remind myself of the clamping arrangement the flange makes all the difference 😷

MK used to produce 13amp plugs that could be considered suitable for stranded cable (pic below) but they are a pain to wire neatly, not sure if they still do.

Tinning is a last resort.

 

ETA I started in the Audio industry in the days when the  EP series were the standard speaker connections before Speakon was invented😎

 

 

MK-BS1363_13_Amp_White_Fused_plug_inside.jpg

Edited by Loddon
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