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Overheated extension socket (UK) #109644
11/17/05 01:02 PM
11/17/05 01:02 PM
P
pauluk  Offline OP
Member
Joined: Aug 2001
Posts: 7,520
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:

[Linked Image]

[Linked Image]


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

[Linked Image]

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Re: Overheated extension socket (UK) #109645
11/17/05 04:03 PM
11/17/05 04:03 PM
I
IanR  Offline
Member
Joined: Dec 2004
Posts: 328
Palm Bay FL USA
I'd say, poor connection where the line conductor goes to the terminal. Was the screw loose?

Re: Overheated extension socket (UK) #109646
11/17/05 09:45 PM
11/17/05 09:45 PM
Y
yaktx  Offline
Member
Joined: Feb 2003
Posts: 288
Austin, Texas, USA
I'd be more inclined to suspect poor spring tension in the plug contact. That looks like a single-wipe contact.

Re: Overheated extension socket (UK) #109647
11/17/05 09:46 PM
11/17/05 09:46 PM
Trumpy  Offline

Member
Joined: Jul 2002
Posts: 8,250
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?.

Re: Overheated extension socket (UK) #109648
11/18/05 02:26 AM
11/18/05 02:26 AM
Lostazhell  Offline
Member
Joined: Feb 2004
Posts: 1,431
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 [Linked Image] ) Is there a photo of the plug prongs on the heater that was in use with this?

Re: Overheated extension socket (UK) #109649
11/18/05 11:29 AM
11/18/05 11:29 AM
S
SvenNYC  Offline
Member
Joined: Aug 2002
Posts: 1,691
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.

Re: Overheated extension socket (UK) #109650
11/19/05 01:31 PM
11/19/05 01:31 PM
P
pauluk  Offline OP
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Quote
cord cap.. (If thats what you call the ends over there


It would be called a trailing socket. [Linked Image]

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:

[Linked Image]
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:

[Linked Image]

A closer look at that prong:

[Linked Image]
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:

[Linked Image]


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).]

Re: Overheated extension socket (UK) #109651
11/20/05 02:07 AM
11/20/05 02:07 AM
Y
yaktx  Offline
Member
Joined: Feb 2003
Posts: 288
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!

Re: Overheated extension socket (UK) #109652
11/23/05 07:07 PM
11/23/05 07:07 PM
O
Owain  Offline
Member
Joined: Oct 2005
Posts: 19
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?

Re: Overheated extension socket (UK) #109653
11/23/05 09:03 PM
11/23/05 09:03 PM
Trumpy  Offline

Member
Joined: Jul 2002
Posts: 8,250
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??!!. [Linked Image]
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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