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taylor105728 4th Apr 2014 11:52 am

Re: Another unusual plug and some other questions
Tractorfan, G6Tanuki, AC/HL (220, 221, 222)...

Many thanks for the suggestions. Our landlord in the 1950s was never anxious to modernise - we still had Victorian fireplaces and a cast iron cooking range when we left the house in 1969 - and he had family links to both coal mining and railways, so an industrial origin for the plugs and sockets sounds very likely.

The sockets were star wired back to one of two cast metal quadrant lever boxes above the kitchen sink (the other being for lighting). The sockets had no earth provision, despite the fastening screw on the plug case, which 'captured' the appliance earth wire.

I will now investigate industrial connectors!

factory 17th Aug 2015 6:53 pm

Re: Another unusual plug and some other questions
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Originally Posted by Tractorfan (Post 522875)
You may be interested in these radio interference suppressors I've accumulated over the years. They were made by Belling-Lee, Aerialite & Dubilier plus an anonymous 2pin example.

I bought a few small catalogues last week, in a Dubilier one from 1954 I found this page with the range of radio interference suppression plugs they offered.


winston_1 19th Aug 2015 12:41 am

Re: Another unusual plug and some other questions

Originally Posted by broadgage (Post 603028)
Must be a limited market for these Crabtree outlets since they are not allowed in the USA nor likely to be used in the UK. Possibly used in the Middle East ?

Not allowed in the USA? Maybe so, but on a recent trip there I was surprised to see these installed in a coach (Megabus) for the purpose of passengers charging their phones and tablets.


Originally Posted by emeritus (Post 603071)
A hotel I stayed in near Gatwick Airport last year had UK, Schuko and US mains sockets in the room.

Charging points at Heathrow and Gatwick have UK and Schuko next to each other nowadays.


Originally Posted by broadgage (Post 604558)
The convention seems to be
12 volt DC=USA type mains plugs
24 volts DC= old type UK round pin plugs, 5 amp or 15 amp according to load.
240 volts AC but of restricted capacity= MK non standard 13 amp plugs

Rather dangerous thing to do. There are still homes with 5 amp round pin sockets often for portable lightning all controlled by a single switch. Nothing to stop someone plugging in one of their 24v DC appliances.

There was a similar problem in Australia where portable generators were being sold with a 12 volt 2 pin socket with the same outline as the 2 business pins of their standard 240 volt socket (I've seen them here as well). The authorities soon put a stop to that with a recall and generators there now have the standard Australian low voltage (ELV here) 2 pin socket which has the 2 pins at right angles to each other.

broadgage 20th Aug 2015 12:59 pm

Re: Another unusual plug and some other questions
I would consider it foolhardy to use old style UK round pin sockets for 24 volt DC if they were already used in the same premises for AC mains.

For relatively new or re-wired premises though, the old round pin 5 amp and 15 amp outlets are ideal for 24 volt DC supplies.
I have seen the 15 amp sockets used for intermittent loads of a lot more than 15 amps, not best practice but they never even got warm.

Refugee 20th Aug 2015 2:00 pm

Re: Another unusual plug and some other questions
The pins on 15A plugs are quite heavy and will be able to absorb quite a bit of heat over a short period but the user must make sure enough time elapses before the next load is applied.

emeritus 20th Aug 2015 2:44 pm

Re: Another unusual plug and some other questions
As the standard US flat pin plugs are rated at 15A, a UK 15A plug should be capable of carrying currents far in excess of its nominal 15A.

My GEC catalogue of 1911 explicitly says as much about its range of 2 pin plugs that correspond with the old UK standard 2A 5A and 10/15A 2 pin plugs: "The terminals are of ample dimensions, and the complete plugs are guaranteed to permanently carry currents far in excess of their rated capacities".

Herald1360 20th Aug 2015 11:15 pm

Re: Another unusual plug and some other questions
The current limitation is more likely to be the integrity of the limited area contact between the socket and the pin than the csa of the pin itself, especially when old springy bits relax.

IanBland 23rd Aug 2015 1:37 pm

Re: Another unusual plug and some other questions
I did a rewire (back in the 90s) in which the client wanted their table lamps on a special circuit on a dimmer switch (anyone remember incandescents? :) ) and I installed the circuit for that as 5A sockets, so they couldn't inadvertently plug anything else into it. Needless to say, in this domestic dwelling they didn't use 5A sockets for anything else.

Also, it's a bit off topic but worth noting in discussions of actual current capacities that twin 13A sockets are not rated for 26A continuous and will, after sufficient use with a 6kW load, Halt And Catch Fire.

emeritus 13th Nov 2015 1:14 am

Re: Another unusual plug and some other questions
Following on from #228, last week we had a midweek break at Warners on the IOW. Our bedside lights were connected via the old style 3 pin 5A plugs and sockets. I have previously found these used in hotels to allow standard lamps to be controlled via wall or bedside switches, but in this case the (unswitched) sockets were not controlled by wall switches, the lamps being switched by in-line flex switches. No fuse box in the chalet, so I couldn't check the fusing arrangements!

We could have done with a couple of incandescents: the bedside lamps were fitted with base-down ES-base GLS LED lamps, made by BELL. No problem with RFI on any band until my radio got closer than 4" (Spain came through loud and clear on medium wave), but as bedside lamps they were dire. This type of lamp is evidently designed for burning base up in a ceiling light fitting as light is only emitted from the hemisphere opposite the base. As a consequence, while the light reflected from the ceiling made the room bright enough, very little light came down where it was needed to read in bed. Rough measurements with the exposure meter of my camera indicated the downward illumination was less than 20% of the upward. Must remember to bring a couple of my own tungsten lamps in BC and ES bases with me next time we go away.

unabridged 12th Jan 2016 1:10 pm

Re: Another unusual plug and some other questions
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Sorry to go back a few pages, but something of interest in this day and age:

Just this minute made this on my desk at work! Was surprised to find we still have a live Walsall ring in our TV studio area. I'm currently tasked with converting an old cupboard to a recording suite. Just a couple of Walsall's on the wall so this will provide temporary power for my tools / radio whilst I work; until rewired further down the line.

Herald1360 12th Jan 2016 1:20 pm

Re: Another unusual plug and some other questions
Is what trickles out of them normal mains? Walsalls and the like were often used when there was something "odd" about the supply connected to them. Backup, different voltage, clean, or whatever.

unabridged 12th Jan 2016 2:47 pm

Re: Another unusual plug and some other questions
Yeah; the room hasn't been used for TV stuff for at least 20 years, but back when it was put in in the early 70's it was there to provide some kind of clean supply and forced seperation from domestic circuit for certain bits of kit - on a seperate phase i think.

As the room changed and was no longer used for TV stuff (this is a college so it changes a lot) the supply for these was removed, and at some point it has just been tagged onto an MCB in the domestic board.

Tractorfan 13th Jan 2016 11:04 am

Re: Another unusual plug and some other questions
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I've got a Walsall gauge plug & socket like that. The socket is actually made by Walsall and the plug is marked 'Sainsbury's' but carries no maker's name. The plug also contains some kind of suppressor or vdr in the cover connected between all three pins via springs. It may be intended for EPOS use (Electronic Point Of Sale). The base of the plug is moulded in such a way that it could accept another fuse holder on the neutral side if used for another variant.
Cheers, Pete.

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