Mystery: One pin on plug overheating

[cheeryble]

Hi 

 

Why would one pin on a three pin plug (though cable to 3 pin socket is not earthed) get overheated?

If there was some sort of overload in the microwave it would burn both sides.

A friend said he had the same issue on a two pin and he untried it round it was ok

IS there a polarity issue with the socket?

 

 

[bankruatsteve]

It's probably loose and arcing inside.  Most likely not from over-current.

[Crossy]

4 minutes ago, bankruatsteve said:

It's probably loose and arcing inside.  Most likely not from over-current.

 

Yup, that looks like a poor connection inside the moulded plug.

 

Cut it off and replace with a new plug, you'll probably want to replace the outlet too as it's likely been damaged internally.

 

[cheeryble]

Thanks Steve and Crossy

yeah I thought of poor connection in socket first hadn't thought of plug.

 

Anyway no need for correct polarity + and neutral inside socket?

[bankruatsteve]

No.  AC circuits (almost) always don't care "polarity".  Otherwise, plugs and sockets would be shaped so they only fit one way.  The US actually had a plug like that for certain appliances did want neutral on a particular pin.  But, that's long gone now (I think).

 

Edit: Now that I think about it... There was (is?) a configuration for appliances needing up to 20 amps where it would only fit in a receptacle capable for that.  (Using a right-angle pin.)  Whatever.

Edited September 9, 2016 by bankruatsteve

[cheeryble]

Hmmm Steve 3 pin they only do fit one way.....but question of the wiring in the socket.

Still i take your point ...not an issue

 

Thanks again

[bankruatsteve]

Yeah, I'm a bit fuzzy on it now.  But, I do recall that 20 amp sockets had one of the slots as a right angle.  IE: normal plugs would fit into it but a 20 amp plug with the right angle blade could only fit into a 20 amp socket.

[manarak]

aaaah... polarity questions with AC current

[Crossy]

1 hour ago, manarak said:

aaaah... polarity questions with AC current

 

No + or - but there is Live and Neutral.

 

Normally not an issue with modern appliances, but still important when single-pole switches (lights) and breakers are employed.

[bankruatsteve]

I have an oven that has blue and brown wires and, at the time I installed it, I didn't know which was for live.  So, I guessed wrong and connected the blue to live, brown to neutral.  The oven would not turn on.  Where's the manual?  IMPORTANT... the brown must be connected to live and blue to neutral.  So did that and the oven turns on.  I suspect for the same reason Crossy mentioned: that internally it must be using single pole switches.  

[cheeryble]

Apart from changing the plug I obviously need to open the socket, check for loose pin-gripper, and may as well be sure live and neutral are right way round.

Stay tuned gotta find time

[Crossy]

Cheery, replace the outlet, it is almost certainly damaged.

[cheeryble]

6 hours ago, Crossy said:

Cheery, replace the outlet, it is almost certainly damaged.

 

OK Crossy I'll open it up when I get there and most likely it will need replacing.