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General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
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31st Mar 2017, 7:11 pm | #1 |
Dekatron
Join Date: Oct 2003
Location: Southport Lancashire, UK.
Posts: 3,221
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Hot 13A plug pin
Not really "vintage" and I hope this isn't a daft question, but I have always wondered why only the live pin of a 13A plug gets warm if run near its limit. If the current flows through the neutral as well why doesn't that get equally hot?
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Paul |
31st Mar 2017, 7:17 pm | #2 |
Dekatron
Join Date: May 2008
Location: Derby, UK.
Posts: 7,735
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Re: Hot plug pin
Because the live pin is not solid brass, but split to accept the end cap of the fuse. So it has a smaller cross-sectional area, therefore a higher resistance.
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31st Mar 2017, 7:26 pm | #3 |
Dekatron
Join Date: Oct 2003
Location: Southport Lancashire, UK.
Posts: 3,221
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Re: Hot plug pin
Thanks Julie, I wondered whether it was something to do with the fuse
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Paul |
31st Mar 2017, 7:30 pm | #4 |
Heptode
Join Date: Dec 2010
Location: Barnstaple, N.Devon, UK.
Posts: 556
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Re: Hot plug pin
Hi Paul. It's more to do with the fuse than the actual pin. Often there is a screw or a rivet on the top of the pin securing the fuse holder and these can get loose with age. The fuse will also become warm if run close to it's full rating.
I used to run a disco and the lighting supply plugs would need to be checked and the fuse holders cleaned occasionaly to keep them from getting hot at times of full loading. I've seen plugs on large appliances (3kw fires etc) where the plug has gone brown on the fuse area. Quite often because the screws / fuse holders are not tight enough and then the resulting resistance makes the matter worse. David. |
31st Mar 2017, 10:26 pm | #5 |
Dekatron
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 5,549
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Re: Hot plug pin
When I worked in a calibration lab the engineer who worked next to me got a whole day worth of power meters with 1Kw RF dummy loads to check.
By lunch time a burning plastic smell was being traced to a power socket. You could see the shape of the plug in black charcoal on the socket face-plate. |
1st Apr 2017, 6:42 pm | #6 |
Dekatron
Join Date: Jan 2012
Location: Brentwood, Essex, UK.
Posts: 5,316
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Re: Hot plug pin
In the 1960's my aunt had a red rubber plug from Woolworths on her 3kW electric fire that used to get so hot that the rubber went very soft indeed. On one visit I noticed that the rubber had perished so badly that a piece had come away, exposing the brass top of the fuse-retaining clip, and immediately went and got her a new plug. In the "hot" plug, the fuse cap was located in a groove in the end of the pin and held in place by a fairly rigid clip, rather than between two springy split ends of the pin or two springy fingers attached to the end of the pin.
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1st Apr 2017, 10:01 pm | #7 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,527
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Re: Hot plug pin
I never liked any rubber plugs at 3kW. Nor any cheapo hard plastic ones either. MK ones with binding screw wire connections were good and seemed to run cooler than any other make.
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2nd Apr 2017, 7:55 pm | #8 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,952
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Re: Hot plug pin
The 13A fuse itself is a "resistor" that heats its end-clips, causing oxidisation and elevated resistance (and so higher losses and more heat) in the plug.
To be Honest, I've never really liked the BS1313 fused-plug and "ring" wiring; separately-fused radial circuits with a 15A fuse at the head-end and BS546 15A unfused plugs/sockets at the end-points make more sense to me: such a circuit can deliver the rated current indefinitely without needing to worry about other loads introducing themselves.... |
3rd Apr 2017, 10:51 am | #9 |
Octode
Join Date: Mar 2006
Location: Co. Durham, UK.
Posts: 1,111
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Re: Hot plug pin
My thoughts precisely. The fused plug is for convenience, the ring-main for economy.
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3rd Apr 2017, 1:41 pm | #10 |
Dekatron
Join Date: Oct 2003
Location: Southport Lancashire, UK.
Posts: 3,221
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Re: Hot 13A plug pin
I suppose that when radial circuits were the norm there were far fewer sockets in the average house. Wouldn't a separate circuit for each socket be rather unwieldy these days?
Having said that, my son has been doing some electrical work at his house and found that the neutral at one end of the upstairs ring was not connected at all at the consumer unit.
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Paul |
3rd Apr 2017, 4:26 pm | #11 | |
Nonode
Join Date: Oct 2008
Location: Warsaw, Poland and Cambridge, UK
Posts: 2,669
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Re: Hot plug pin
Quote:
Give me a 32A ring main and fused plugs any day! Chris
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