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An image of an opened AC plug, with three wires

The red copper wire was burned so I took out the burnt part of the wire and reinserted all the wires by myself.

ThreePhaseEel
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Nilamber
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    Why is the bare part of the red wire sticking way out and through like that? Why isn't it like the others? – Harper - Reinstate Monica May 13 '20 at 23:31
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    Please provide a picture of the finished result. There are currently three serious errors which need to be confirmed as having been corrected before it can be deemed safe. – Tetsujin May 14 '20 at 07:56
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    For safety reasons make sure the ground (yellow/green wire) is longer than the other two. In case someone pulls on the cable the ground wire should always be the last one which fails. – Michael May 14 '20 at 10:57
  • @mrpursit There are 3 variants of the BS546 standard, rated at 2A, 5A, and 15A. The 15A variant is in use in South Africa and India – CSM May 14 '20 at 14:14
  • @Mackavity Do we know this plug is being used in the UK? If not, should the UK tag be removed? The BS546 plug is still regularly used in both South Africa and India and not often used in the UK. – mpursuit May 14 '20 at 14:30
  • Uncommon but still used in the UK. – user_1818839 May 14 '20 at 14:39
  • Isn't this called a plug or socket rather than an outlet or receptacle? A plug or socket goes into an outlet, and an outlet or switch or light etc are fitted onto a receptacle. – Carl May 14 '20 at 16:42
  • Apart from the points about strain relief, cutting the extra length of copper wire sticking out of the clamp and the ground wire not being the longest, I would add that you should put a wire ferrule over the end of the red wire (the other two wires seem to have one). Otherwise the individual strains of copper wire could get squeezed out of the clamp, reducing the wire gauge at that point and causing it to overheat at higher amperages, potentially causing a fire. – user149408 May 14 '20 at 17:46
  • it looks like the groiund wire has solder on it. This can flow under the screw force and loosen the contact. Cut off any solder so the terminal screws down onto bare copper. – Neil_UK May 14 '20 at 18:00
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    @Carl I'd say it's a plug, since it's on the end of a wire and appears to have prongs rather than holes (I assume - not familiar with UK electrical and we can only see the back of this one.) To me (US English) a socket is interchangeable with outlet or receptacle - it's a hole that something goes into, not something that goes into a hole. (Think "eye socket", "ball and socket", "socket wrench", etc.) – Darrel Hoffman May 14 '20 at 18:57
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    I'm sorry to have to point this out, and if you need to ask the Question then you must assume that no, it's not safe. Test this be asking everyone here who thinks otherwise to warrant their suggestions… ie, to put their money on the line, not their opinions and your life! – Robbie Goodwin May 14 '20 at 22:47
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    You should also make sure you know why the wire burned in the first place and make sure the situation cannot repeat. – Jeffrey May 15 '20 at 03:21

4 Answers4

44

That plug needs redoing. Urgently. It is unsafe.

Make sure the clamp is on the covering for the cable not the individual wires

This is a correctly wired UK plug... different live & neutral colours and there's a fuse, but you get the idea that the cable grip goes over the outer covering of the cable and is properly tightened. The exposed power wires (red and black in your picture) should be only as long as they need to be to reach the plug pins, no longer. The earth/ground wire (green & yellow) should be a little longer, so it gets pulled out last if the cable grip fails. The bared copper should also be the minimum length needed to get under the screws, which should be fully tightened.

enter image description here

Michael Harvey
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    & +2 for actually bothering to cut each wire to the correct length. I've even seen factory-made ones with all the same length, crammed in. – Tetsujin May 14 '20 at 07:52
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    Actually, for a UK plug, I think that while the live and neutral (brown and blue) wires should be no longer than needed, the earth (green/yellow) should have a little slack.  (As the picture demonstrates.)  That way, if the cable is pulled strongly enough for the clamp to fail, the live and neutral will disconnect _before_ the earth. – gidds May 14 '20 at 10:26
  • The plug looks more like, the relatively unused, BS 546 which is unfused than a fused BS 1363 which is much more common. – mpursuit May 14 '20 at 12:50
  • The wire colours are the old red live/black neutral as well. I wonder if this is even a UK plug? – Michael Harvey May 14 '20 at 13:19
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    I think it is a BS546 plug which are rarely used in the UK now. Sometimes they are used for sockets connected to the central lighting circuit which are controlled by the main light switch. It is most likely a 5A plug though. I'm wondering if the burning was caused by the plug being put on a device which draws higher current (eg 13A heater) – mpursuit May 14 '20 at 13:43
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    The OP's plug is very probably an Indian Type D, not a UK plug at all. https://www.worldstandards.eu/electricity/plugs-and-sockets/d/ The Type D is, in fact, the old UK BS 546. – Tetsujin May 14 '20 at 13:45
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    Indian Type D are BS546 which were standard in the UK till 1947 when the square pin (BS 1363) was introduced. They are still used rarely in the UK. – mpursuit May 14 '20 at 13:49
  • The other consideration which says it's Indian is… how many people in the UK have *both* aircon and a BS546 socket to try plug it into? ;) …and, yes, plugging aircon into 5A isn't all that wise in the first place, so even with the plug correctly wired, it's still probably unsafe. – Tetsujin May 14 '20 at 13:52
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    I shall refrain from quoting Prince Philip. – Michael Harvey May 14 '20 at 14:27
  • Reading the edited history I now realise this is connected to a aircon and the UK tag was added by someone else. I agree it is more likely this is being used somewhere that Indian Type D are still regularly being used – mpursuit May 14 '20 at 14:27
  • UK also never had [afaik] red, black & striped. Striped came in with brown/blue. I claered the UK tag - but I've almost no rep on this stack, so it went in the queue :\ – Tetsujin May 14 '20 at 14:48
  • In fixed wiring, green & yellow striped was used between 1977 and 2004. However in appliance flex it switched in 1977 from red, black and green straight to brown, blue and green/yellow striped. – mpursuit May 14 '20 at 15:03
  • @Tetsujin doesn't the wisdom if the plug size depend on how big the AC is? A small window unit should be comfortably under 5A at 240V. – Dan Is Fiddling By Firelight May 14 '20 at 20:38
  • I have never seen red, black and striped on flex in the UK, you do see red/black/bare cable with green/yellow sleeves in fixed wiring though (fixed wiring cable in the UK stayed red/black for decades after flex changed to brown/blue). – Peter Green May 15 '20 at 02:23
  • guys thank you for the responses. Also i am from india so does that change your answer and also the air conditioner is working fine with no problems. – Nilamber May 15 '20 at 11:47
  • @Nilamber - The answer applies to any country. The point is not whether the air conditioner works, it is whether the plug is safely wired. – Michael Harvey May 15 '20 at 12:31
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You should trim the extra copper off it will not help to have it hanging out there. You also need to make sure when you put things back together the clamp is on the covering for the cable not the individual wires but other than those items I would say it looks safe. A proper torque would be needed to be 100%.

Ed Beal
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    make sure all the clamps are tight. chances are the red one came loose, thus the reason it arced. – Scott May 14 '20 at 00:27
  • It looks like there was some solder on the other wires - never seen a setup like that (screw terminal + solder) - maybe it helps hold it in place? – htmlcoderexe May 14 '20 at 08:02
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    If the wires have solder on them, then they should be trimmed back to bare wire. Solder + screw joints is a very bad idea because the solder will (slowly) flow, thereby loosening the joint over time and allowing arcing. In fact as the remaining wires appear to possibly have solder on them, this is probably what caused the fault in the first place. – SiHa May 14 '20 at 11:10
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It would be a cleaner installation to not allow the wire to stick out very far on the far side (looking at you red wire). Make sure that there is only copper under the clamp for the red wire and no insulation under the screw and cramp (it looks like it's pushed in too far)

Ack
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  • The comment about insulation seems to contradict the other answers – Kai May 14 '20 at 13:37
  • People may be using ‘clamp’ to mean different things… The screw-down strip at the bottom of the plug that holds the whole cable in place (which is what I'd call the clamp) should go over the white outer insulation, not the separate coloured insulation on each wire.  But the terminal pins and their screws should hold only bare wire, not insulation (and, as someone else pointed out, not even solder). – gidds May 14 '20 at 14:51
  • yes thanks @gidds for clarifying the words I used, I do mean that bare wire should be under the terminal pins – Ack May 14 '20 at 14:57
  • @gidds - "The screw-down strip at the bottom of the plug that holds the whole cable in place (which is what I'd call the clamp) - called the 'cable grip' in this context in the UK – Michael Harvey May 14 '20 at 20:31
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The wires are way too long, they need to be shortened and the sheath of the flex needs to be secured under the cord grip. The stripped section at the end of the wire should be long enough that the screw can properly clamp down on it but not excessively long.

Ideally the live wire should have no slack the neutral wire a medium amount of slack and the earth wire should have the most slack. This way in the unlikely event that the cord grip fails and the cable gets ripped out of the plug the wires should become disconnected in the safest possible order.

Also personally I would not reuse a plug that had shown signs of heat damage.

Peter Green
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