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#109644 - 11/17/05 09:02 AM Overheated extension socket (UK)
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
This extension was found feeding a 2kW heater (240V) which apparently had been running on it for several hours per day for the last two years or so:






Although not obvious from this photo, the PVC insulation on the hot conductor has gone quite brittle with the heat:


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#109645 - 11/17/05 12:03 PM Re: Overheated extension socket (UK)
IanR Offline
Member

Registered: 12/06/04
Posts: 326
Loc: Palm Bay FL USA
I'd say, poor connection where the line conductor goes to the terminal. Was the screw loose?

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#109646 - 11/17/05 05:45 PM Re: Overheated extension socket (UK)
yaktx Offline
Member

Registered: 02/19/03
Posts: 286
Loc: Austin, Texas, USA
I'd be more inclined to suspect poor spring tension in the plug contact. That looks like a single-wipe contact.

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#109647 - 11/17/05 05:46 PM Re: Overheated extension socket (UK)
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
I'd say there was a bad connection between the pin on the heater plug and the contact on the cord connector.
Paul,
Is that a shuttering device just above your thumb in the 2nd pic?.
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#109648 - 11/17/05 10:26 PM Re: Overheated extension socket (UK)
Lostazhell Offline
Member

Registered: 02/21/04
Posts: 1248
Loc: Bakersfield, CA (Originally Or...
The left part of the burnt contact looks a bit thinner than the opposing contact in the same place.. I'm going with Yaktx on this one as overheating/arcing from a worn contact in the cord cap.. (If thats what you call the ends over there ) Is there a photo of the plug prongs on the heater that was in use with this?

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#109649 - 11/18/05 07:29 AM Re: Overheated extension socket (UK)
SvenNYC Offline
Member

Registered: 08/19/02
Posts: 1685
Loc: New York City
Yeah, that seems like a really cheap and bad-quality connector.

You can just tell by the cardboard strip that's being used as a cord grip.

Most of those only have single-wipe contacts.

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#109650 - 11/19/05 09:31 AM Re: Overheated extension socket (UK)
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
 Quote:
cord cap.. (If thats what you call the ends over there


It would be called a trailing socket.

 Quote:
Is that a shuttering device just above your thumb in the 2nd pic?.


Yes, all BS1363 sockets, including trailing types for extensions have a shutter. My thumb was keeping it open in order to get the picture.

 Quote:
Was the screw loose?


No, it was quite tight.

 Quote:
Is there a photo of the plug prongs on the heater that was in use with this?


Your wish is my command....... You can see that the line pin has certainly been getting warm:


You'll quite often find marks around the live pin on BS1363 plugs due to the heat buildup around the fuse and clips, especially on the cheap types where they've been run on higher currents. For those unfamiliar with BS1363, here's the inside of the plug where you can see that the top of the prong goes straight to the fuse:



A closer look at that prong:


The bright mark does line up with the contact on the socket (the plug was being withdrawn regularly to turn off the heater).

The socket looks like the type which would have been intended for garden tool extensions originally -- The orange color being a giveaway. Although BS1363 is normally rated for 13 amps, this one being part of such a low-power set was clearly never intended for such use:




I did run the heater on a known good socket for a while and noted the normal heat around the live pin after a half hour. It didn't seem unusually warm though, so I think given the evidence the best bet is poor prong/socket contact on a socket which was never really intended to run on 8 amps for extended periods.

The usual backtracking of heat down from the fuse could well have contributed to the problem after a few hours use though.



[This message has been edited by pauluk (edited 11-19-2005).]

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#109651 - 11/19/05 10:07 PM Re: Overheated extension socket (UK)
yaktx Offline
Member

Registered: 02/19/03
Posts: 286
Loc: Austin, Texas, USA
Oh, now I see the "max 3 amp load" label!

We have 3A in-line switches, but not plugs! I thought those contacts looked flimsy!

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#109652 - 11/23/05 03:07 PM Re: Overheated extension socket (UK)
Owain Offline
Member

Registered: 10/26/05
Posts: 19
Loc: Scotland,UK
The cord-grip is a sort of fibre composition, not cardboard, and was the usual material used for cord-grips before plastic became commonplace.

AIUI the socket *must* be rated to 13A to comply with BS1363 but it's possible it was originally manufactured with the 3A MAX marking for use on extension leads rated at 3A only.

Is the heater plug cracked or was that a hair on the lens?

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#109653 - 11/23/05 05:03 PM Re: Overheated extension socket (UK)
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
 Quote:
AIUI the socket *must* be rated to 13A to comply with BS1363 but it's possible it was originally manufactured with the 3A MAX marking for use on extension leads rated at 3A only.

A 3A Extension lead??!!.
Why such a small rating?.
Most lighting circuits have a higher current rating than that.
Is the other end (that plugs into the wall socket) fused at 3A?.
Is this a case of wrong connector or wrong sized ext. lead all round?.
I would have thought that a UK ext. lead would have to have a current rating of 13A, to match the connector?.
Or are there different ratings for different things?.
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