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Old 6th Aug 2021, 7:22 pm   #61
Graham G3ZVT
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Default Re: Mains plug restoration

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Originally Posted by winston_1 View Post
I wonder whether this sleeving of pins is another matter of safety gone mad.
No. It was a very sensible, and fully "backwards compatible" enhancement to the standard.
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Old 6th Aug 2021, 7:43 pm   #62
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Default Re: Mains plug restoration

Backwards compatible maybe, but it must have added to the fabrication cost, and it also thins down the brass in the pin over the insulated length. This must make it more fragile. In principle it will make it a bit more resistive too, and therefore more prone to heating, but I suspect that that's negligible compared with other, thinner, elements in the current path inside the plug and the socket.

However if it saves a lot of injuries and deaths then it's obviously worthwhile. If it saves none then it isn't. I wonder if anyone knows whether it does ?

Cheers,

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Old 6th Aug 2021, 7:58 pm   #63
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Default Re: Mains plug restoration

Doubt if many lives are saved. 240v across a finger won't kill, it will just be very uncomfortable.

They did this exercise in Australia with their thin pins and found the pins tended to break off and remain in the sockets. How safe is that? Not sure if they have fixed that problem.
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Old 6th Aug 2021, 8:26 pm   #64
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Default Re: Mains plug restoration

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Backwards compatible maybe, but it must have added to the fabrication cost, and it also thins down the brass in the pin over the insulated length. This must make it more fragile. In principle it will make it a bit more resistive too, and therefore more prone to heating, but I suspect that that's negligible compared with other, thinner, elements in the current path inside the plug and the socket.

However if it saves a lot of injuries and deaths then it's obviously worthwhile. If it saves none then it isn't. I wonder if anyone knows whether it does ?

Cheers,

GJ
One thing the MK style shutter and and sleeved pin plug achieved, both separately and particularly when used together, was to put an end to the practice of trapping a pair of wires behind the plug to obtain a temporary supply. Actually it's still possible, but it's very difficult.

I did this countless times in customers houses to connect my soldering iron.
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Old 6th Aug 2021, 9:59 pm   #65
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Default Re: Mains plug restoration

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Originally Posted by Lucien Nunes View Post
BS7671 is chiefly about electrical installations of buildings rather than portable appliances. It refers to the use of plugs mainly to describe the requirements they pose for the use of sockets. Some parts are worded in slghtly ambiguous ways; for example the reference in post #32 to one pin being engaged while another is fully exposed, is basically a prohibition on any kind of socket where pins of a plug could be engaged individually, e.g with the neutral pin in the line socket and the line pin overhanging the side of the socket body.
Lucien I have said it before on here, that you have people with a limited subset of knowledge that are trying to apply one set of standards (that they very well be familiar with) trying to apply that knowledge to another set of standards that they are not familiar with.

Yes there is a large degree of overlap between the rules, and yes the laws of physics still apply, however the different standards each have their own rules and caveats, and not many people know with any depth of certainty any of the rules that apply to maybe two standards if they are lucky! This is where problems arise, urban myths start to spring up and mistakes start to be made.
People whom are otherwise intelligent (and even experts in their own field) start to stray into unfamiliar territory and make big mistakes in the belief they are correct.
This is not a dig at anyone in particular btw.
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Old 6th Aug 2021, 10:08 pm   #66
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Default Re: Mains plug restoration

Sleeved pins are a good idea. They make an unlikely electric-shock scenario even more unlikely.
Pretending that unsleeved pins are suddenly somehow 'lethal' is not such a good idea.
THAT is 'safety gone mad'.
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Old 6th Aug 2021, 10:27 pm   #67
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Default Re: Mains plug restoration

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Originally Posted by rambo1152 View Post
... the practice of trapping a pair of wires behind the plug to obtain a temporary supply. Actually it's still possible, but it's very difficult.

I did this countless times in customers houses to connect my soldering iron.
I did it once at CERN. I'd turned up for a meeting there having forgotten my BS1363-to-Swiss mains adaptor and needing to use my laptop, which had a flat battery. We couldn't find a lead with the right plug at one end and socket at the other to run into my power block. So I took the (removable) plug off my lead and wedged the (long, thin) bare wires into a 220V outlet. The Swiss/French/German engineers looked on with a mixture of amusement and horror . They didn't need telling not to put their fingers into it.

Cheers,

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Old 7th Aug 2021, 1:44 pm   #68
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Default Re: Mains plug restoration

Interestingly, the modern MK cooker control unit in my kitchen (pic 1 - installed new last year) has those rotary shutters.

The previous larger CCU (pic 2 - installed new in 1980) had earth pin operated shutters, while all the other MK wall sockets in the house had the rotary ones.

I very much prefer the new understated white switches to the red ones of the previous CCU - although they're still the same size.
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Old 7th Aug 2021, 10:33 pm   #69
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Default Re: Mains plug restoration

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Interestingly, the modern MK cooker control unit in my kitchen (pic 1 - installed new last year) has those rotary shutters.

The previous larger CCU (pic 2 - installed new in 1980) had earth pin operated shutters, while all the other MK wall sockets in the house had the rotary ones.

I very much prefer the new understated white switches to the red ones of the previous CCU - although they're still the same size.
Until 2007 my parents house had a larger version of the right hand cooker switch. I've seen a version with neon indicators for the switches.

The socket was rarely used, possibly only when my Mum needed to use a hand mixer for something being heated in a pan.
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Old 8th Aug 2021, 12:17 am   #70
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Default Re: Mains plug restoration

Shortly after the sleeved plug requirement came in, I ordered some stuff from one of the advertisers in one of the hobby magazines (Practical Wireless or Television), and included a couple of 13A plugs in my order. Well they did have sleeves, but the sleeving consisted of rather thin-walled plastic tubing that had evidently been pushed (or shrunk) over the pins of Hong Kong-manufactured unsleeved plugs, as the metal of the pins was of uniform cross-section over their entire lengths. The sleeving soon split and broke off, but as the plugs were cheap it wasn't worth complaining. I just bought some proper UK-made ones from a local high street shop.

When my son modernised his kitchen some 5 years ago, I replaced the original bulky (and not properly recessed) cooker point and 13A socket with a compact MK one (with neons), the size of a conventional double socket. I was disappointed by the quality: the neons didn't line up with their transparent red windows, there was complete absence of any means for positively keeping them in position, and the act of pushing on their leads to position them, made the red windows ping out: the windows were simply snapped into position and were only retained by ridiculously-small detents. A bit over-value-engineered methinks.

Last edited by emeritus; 8th Aug 2021 at 12:24 am. Reason: typos
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Old 8th Aug 2021, 7:57 am   #71
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Default Re: Mains plug restoration

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Originally Posted by winston_1 View Post
Doubt if many lives are saved. 240v across a finger won't kill, it will just be very uncomfortable.
240 across the fingers would make it very difficult to let go of the plug.

What happens when your other hand or another body part is touching an earthed conductor?

I have first hand experience of this, in my first job I was using a 240v scroll saw, the plug was the older type, socket not switched, system, (customers), not protected by an RCD.

I wasn't killed, obviously, but did sustain a dislocated shoulder.

Many pundits have said since what should have been done regards the work equipment, environment etc. But all it needed to prevent the accident was a fifty pence shrouded pin plug.

I didn't put two fingers round the plug body onto the pins, my little finger on my right hand touched the live pin and my other hand was flat on an earthed stainless worktop.

Very few people are ever electrocuted, but a lot die from secondary impact, falling from a ladder for instance, that is the real danger of electric shocks.

So what the question is, is what number of avoidable injury's or deaths are acceptable, not if this kind of regulation actually saves lives: these sorts of rules are made for better or worse as a reaction to a problem, the unshrouded pins of old 13A mains plugs were obviously causing significant footfall at hospital AE departments for the regs on plug top designs to be ammended.

A lot has been written about the safety of vintage equipment, an old valve radio that is properly maintained for instance, is safe because the user is protected from casual contact of live parts, it is not the case with these unshrouded plugs.

Display them as curios, or bin them.
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Old 8th Aug 2021, 11:41 am   #72
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Default Re: Mains plug restoration

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Originally Posted by Red to black View Post

.......

People whom are otherwise intelligent (and even experts in their own field) start to stray into unfamiliar territory and make big mistakes in the belief they are correct.

......

Just so
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Old 8th Aug 2021, 12:33 pm   #73
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Default Re: Mains plug restoration

There is a story that shrouded pins were introduced primarily to stop children and malicious individuals from using a coin to short out the pins, which is otherwise very easy to do with a BS1363 plug. Switching the socket on would produce an impressive bang and shut down the ring main.
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Old 11th Aug 2021, 7:46 am   #74
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Default Re: Mains plug restoration

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Originally Posted by paulsherwin View Post
There is a story that shrouded pins were introduced primarily to stop children and malicious individuals from using a coin to short out the pins, which is otherwise very easy to do with a BS1363 plug. Switching the socket on would produce an impressive bang and shut down the ring main.
That may have indeed happened, but the cynic in me would expect something like that to be cited as a reason for changing the regulations, in preference to inviting litigation in acknowledgment that the design was, (to the young and careless user at least!), dangerously flawed.
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Old 11th Aug 2021, 2:41 pm   #75
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Default Re: Mains plug restoration

A 1p piece under a BC lamp does much the same thing, so they should have banned BC lamp holders and lamps in favour of those foreign ES items.

Oh wait, they didn't need to ban them, they are slowly disappearing anyway, through attrition / commercial forces.
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Old 11th Aug 2021, 3:27 pm   #76
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Default Re: Mains plug restoration

But of course ES bulbs introduce their own problems, given that the metal collar is connected to one side of the mains, so it's vital that the socket is wired with this side connected to neutral.
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Old 11th Aug 2021, 4:29 pm   #77
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Default Re: Mains plug restoration

I wonder if, like me, Paul and Rambo were unfortunate enough to read "Calling Base 10" by Douglas Castle, (1943) in the Blackie's books for boys and girls series at junior school, in which the juvenile hero does indeed employ the coin in the light fitting trick to evade his Nazi captors?

Also, thanks to Winston for the info on the Malaysian plug key and link to that comprehensive document - very informative. At least the Plasplugs tester version has the text "remove after testing" and identifies L and N correctly!

Cheers
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Old 13th Aug 2021, 7:12 pm   #78
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Default Re: Mains plug restoration

My mother still has the butter knife, with two chunks missing from the blade, with which, back in the early 1970s, my younger brother, then a toddler, removed a plug from a socket. Shrouded pins are probably a good idea.
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Old 13th Aug 2021, 10:29 pm   #79
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Default Re: Mains plug restoration

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But of course ES bulbs introduce their own problems, given that the metal collar is connected to one side of the mains, so it's vital that the socket is wired with this side connected to neutral.
Which is damn near impossible given how European lamp plugs can go both ways in a Shuko socket.
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Old 13th Aug 2021, 11:53 pm   #80
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Default Re: Mains plug restoration

I think it was mentioned on another thread some time ago that the current UK regs do not require the threaded part of ES sockets to be connected to N.
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