plug set alight!

[real1314]

hi, newbie here, reasonably experienced in diy incl electrics, but a mate who's just moved into a new house today has had a problem - plugged his washing machine in, and the plug smouldered and eventually set alight - he switched off at mains (it's got mcb's but they didn't trip?) and disconnected plug which is a charred mess, with the fuse almost completely burnt to nothing at one ond, completely charred at the other.
question is, is it likely to be the socket at fault or the machine?
hard to actually get to the socket in question, but all other sockets are fine.

thanks in advance

 

[Adam_151]

At a rough guess I would guess maybe the cable got snagged when the machine was moved, and the live wire almost all pulled out, but not quite, leaving a fairly high resiatance section which still was low enough resiatnce to let a sizeable current through, which heated up the section which set light to the plug. This is by no means the only possible explanantion though

So to be on the safe side, replace the plug (cut the cable back) the fuse, and the socket, when doing so, inspect the ring main wires for damage, if they are then there could be a problem.

MCBs and Fuses are unable to detect this kind of fault

 

[plugwash]

either the plug or the socket or both but extremely unlikely to be a problem with the machine itseld. both plug and socket will need to be replaced. for the plug just cut back to undamaged flex and fit a new flex. the socket may be harder depending on how much damage was done to the wiring and how much slack cable there is.

i'd strongly advise keeping the whole cuircuit turned off until you have dealt with the socket in question (power equipment using extention leads from other cuircuits in the meantime).

 

[mapj1]

If it was a moulded plug, it is quite possible this is indeed just the result of the cable being tugged, the wires inside are just trapped under folded 'blades' of metal formed as part of the terminals. This is a form of crimping, which usually reliable, but being completely unable to be inspected, a defect is only found like this.
In many situations a re-wirable plug, which can be opened and inspected is preferable, unless one wishes to inspect all plugs with infra-red camera, in operation there is very little early warning. The compounding problem is that at full- load a 13A fuse will dissipate about a watt when operating normally, and in many of the overmoulded designs there is precious little metal to carry this heat away (no big chunky screws) Once the springs have reached tempering heat (about 180- 250c depending on the alloy used) they can lose their spring, exacerbating the heating by making a poorer contact. Result a viscous cycle of oxidise, poor contact heat, more oxidation, poorer contact.....meltdown.
As advised by others, cut back the cable until the cores look undamaged (no melting of plastic, nice shiny metal cores ..), and re-fit new plug and new socket. On re-using, keep an eye on it!
PS this is a very common cause of tumble drier fires, mainly as these are often left unattended, and unlike washers, the heater is on pretty much non-stop in operation.

 

[plugwash]

remember to deal with any damaged insulation on the socket side as well.

since you are less likely to be able to cut this cable back this may mean using something like heatshrink (preferablly adhesive lined) to replace destroyed insulation (plain sleeving has the disadvantage of being able to easilly slip araound and is bloody bulky too) .

 

[real1314]

....cut off plug as advised, seems to be fine - have opened the plug to check for any signs of a problem - nonthing at all wrong. Currently have it plugged into an alternative socket that's been checked with a socket tester. The socket that was used is behind a base unit, only accessible from the side via a cut-out hole - what a great location!!

will be fitting a new kitchen soon, so should be able to check out socket thoroughly then.

thanks for the advice