Melted socket and plug

Discussion in 'Electrics UK' started by richard_1234, 1 May 2007.

  1. richard_1234

    Joined:
    28 Apr 2007
    Messages:
    5
    Thanks Received:
    0
    Location:
    Leeds
    Country:
    United Kingdom
    Hi

    I have a washing machine pluged into a socket inside my kitchen cupboard. The washer went wrong so we got a new one, on removing the old washer we found that the face of the socket behind the plug had melted and turned brown and the plastic around the pins of the plug had melted including the black bands (safety plug) allowing the pins to wiggle.

    The socket looked perfectly normal until the plug was removed and could have been like it for months without realising.

    Just wondering what caused this?

    p.s. the socket has been replace and the wire behind was fine and the cause of the washer to go wrong was a faulty motor sensor.
     
  2. JohnD

    Joined:
    15 Nov 2005
    Messages:
    38,229
    Thanks Received:
    1,522
    Location:
    Hampshire
    Country:
    United Kingdom
    most likely a wire was not tightly gripped in its terminal. This creates a high-resistance joint which gets hot, as it gets hot it gets looser, so hotter, so looser. Eventually the junction between the wire and the terminal will burn away.

    This most often happens with heavily loaded connections, such as the switches for electric showers. For some reason it more often happens with the black neutral wire.

    The end of the wire that overheats is damaged by the heat and softened so that it will not form a good connection in future, so will overheat again. So the discoloured end needs to be cut off back to bright metal. Professional electricians have a tool to put a new end on if the wire is too short after cutting back (it needs great pressure to do it properly).

    Was it a single socket, or a double?
     
  3. Steve

    Joined:
    15 Apr 2005
    Messages:
    16,004
    Thanks Received:
    226
    Location:
    Yorkshire
    Country:
    United Kingdom
    another cause i've heard is the pins not being gripped tightly enough in their holes, creating a high-resistance connections between the plug and socket.

    Also corrosion and muck on the pins.
     
  4. DESL

    Joined:
    9 Oct 2006
    Messages:
    937
    Thanks Received:
    0
    Location:
    Essex
    Country:
    United Kingdom
    Ah that's why in the old days appliances like washing M/Cs were wired into a fused outlet. I was told by an old time served sparky that fixed appliances should never be plugged in as the design of the 13A plug and sockets cleans the contacts as you unplug and plug in.

    Cause of socket failure was put down to a certain amount of corrosion and weakening of the contacts which will eventually cause some minor arcing leading to a build up of carbon which then increases arcing and heat until one day they overheat to a point when thay fail.

    But these days as soon as you cut the plug off to wire into an outlet you invalidate the appliance warranty
     
  5. Steve

    Joined:
    15 Apr 2005
    Messages:
    16,004
    Thanks Received:
    226
    Location:
    Yorkshire
    Country:
    United Kingdom
    I took apart a 3-way adaptor block the other day. The pins are very brown, not shiny at all, because they haven't been inserted or extracted in so long.

    And the socket contacts inside have a very small surface area, I wouldn't say they are rated for 13 amps. Again very brown and dull. Whenever a plug is inserted, it sparks because of the high resistance.

    Its going in the bin, i've never liked 3 way blocks.
     
  6. nozspark

    Joined:
    24 Aug 2006
    Messages:
    1,062
    Thanks Received:
    34
    Location:
    Flintshire
    Country:
    United Kingdom
    3 way blocks are the devils work :evil: :evil:
     

Share This Page