Illegal mains plug?.....possibly lethal

[DCB]

1 hour ago, Captain Cuttle said:

I always check the feedback, in this case sixteen negatives in last month says it all.

 

Alan

Check the positive feedback as well,  " Total waste of space," "Absolte;y f'ing useless" are two "Positive" feedbacks I have read.   You can post what you want under "Positive " feed back but have to jump through hoops to leave negative feedback.

However back to the plug. I can't see any way one could reach the metal section of the plug while it is still actually in contact with live or neutral contacts within a socket.  It may well be entirely safe and legal. The old plugs had solid brass pins with no insulator which meant you could touch the live as you extracted the plug if you tried hard enough. Later ones kept the same architecture but added the insulation to the pins.

The old type pins are much better for making stuff out of....

Lack of a fuse is the real lethal bit. Fuse should be there to protect the lead, or maybe its got a non replaceable fuse?  Another step towards a throw away society?

Edited November 18, 2020 by DavidCBroad

[gordon s]

I normally check the feedback, but for some reason missed this time. There are two issue re the pins. The earth pin is sleeved which is a no straight away and when I was involved in connectors many years ago, I seem to recall there were a set of dimensions that controlled the distance of the pins from the edge and a minimum distance between the back of the plug and the front face of the socket plate. This was specifically to stop small children being able to touch live pins when inserting a plug.

 

Either way, it's all academic now. They have refunded my money immediately and I've sent the product back. We each make our own choices in this world and the safety of my family and my home are paramount.

[Edwin_m]

3 hours ago, gordon s said:

I normally check the feedback, but for some reason missed this time. There are two issue re the pins. The earth pin is sleeved which is a no straight away and when I was involved in connectors many years ago, I seem to recall there were a set of dimensions that controlled the distance of the pins from the edge and a minimum distance between the back of the plug and the front face of the socket plate. This was specifically to stop small children being able to touch live pins when inserting a plug.

 

Either way, it's all academic now. They have refunded my money immediately and I've sent the product back. We each make our own choices in this world and the safety of my family and my home are paramount.

I would guess the sleeving on the live and neutral pins is long enough that the metal part of the pin has disappeared into the socket before it makes electrical contact inside.  So even someone pushing a knife between an almost-inserted plug and its socket should be safe.  But I don't know this for certain, so don't try this at home folks...

[gordon s]

The whole issue of sleeving on the earth pin is the reverse. You could have earth contacts in the socket that are near the front face such that when the earth pin is inserted it goes past the contacts and then you have them mating with the sleeved area and not the metal part.

[John M Upton]

I just took a look at that ebay listing and interestingly, the last picture shows a inset pic of the plug which looks to be a correct domestic UK type and not that narrow unsafe pile of poop that it was actually supplied with.

 

Buyer beware....

[BokStein]

14 minutes ago, gordon s said:

The whole issue of sleeving on the earth pin is the reverse. You could have earth contacts in the socket that are near the front face such that when the earth pin is inserted it goes past the contacts and then you have them mating with the sleeved area and not the metal part.

 

Agreed!

 

During my apprenticeship, it was instilled firmly that the earth wire is longer than the live and neutral so that 'it pulls out last'! The same applies to the pins of the plug; the earth pin should always be in contact with the contactors in the socket and it should be the last to disconnect!

[Nearholmer]

You will find this interesting http://bs1363.fatallyflawed.org.uk

 

All the plugs a nightmare could ever conjure-up, including yours, I think.

[AndyID]

7 hours ago, Edwin_m said:

But even if you have a separate feed to each socket, that would have to be capable of supplying enough current for a kettle or fan heater, so risks burning out the sort of flex that would be used for a table lamp.  So I think you still need the fuse.  

 

The alternative is separate high and low current sockets, as we used to have with the old round pin ones that came in small and large sizes.  

 

You could use a circuit breaker with a much lower trip current. They are usually 20 A here and electric kettles work reasonably well, even on our wimpy 120 V. (US houses are supplied with 240 V. Neutral connects to a center-tap at the transformer.)

[Edwin_m]

10 minutes ago, AndyID said:

 

You could use a circuit breaker with a much lower trip current. They are usually 20 A here and electric kettles work reasonably well, even on our wimpy 120 V. (US houses are supplied with 240 V. Neutral connects to a center-tap at the transformer.)

A partial short in a low-current appliance causing it to draw 19A could still cause a lightweight cable to catch fire.  

[AndyID]

1 hour ago, Edwin_m said:

A partial short in a low-current appliance causing it to draw 19A could still cause a lightweight cable to catch fire.  

 

That's true but I think the minimum appliance wire here is supposed to be 18 gauge. Even at 20 A that will dissipate 5 watts per foot (2.5 watts in each direction). I don't think that will melt the insulation but I'm not going to try it

[Guy Rixon]

On 16/11/2020 at 16:56, phil-b259 said:

 

Thus is true - but its only really in the past couple of decades where switch mode power supplies have become common.

 

In any case the importance of frequency is demonstrated by the way the National Grid stick rigidly to 50Hz - if it wasn't a big deal then it would be allowed to drift far more.

 

The limits for mains voltage are quite big - it can easily be allowed to drift down to 220V but if the frequency moves by more than 1Hz then stuff gets automatically cut to stabilise it.

 

It is important to note that the big power outage in the South East that left class 700 trains stranded all over the place actually occurred because the National grid automatically cut off areas to preserve the 50Hz mains frequency after a power plant went offline.

 

 

 

 

 

Phase errors arising from frequency drift are annoying in single-phase systems as they stuff up clocks, but more serious in multi-phase installations where they can, apparently, cause overloads and fires. Buffer sets connected to supplies with drifting phase are a particular problem.

 

Many years ago, an engineering colleague was invited to inspect the local power station of which his facility was a leading customer; this was on an island that only had the one power station. All seemed well and good, until he noticed that the station's wall-clock was showing the wrong time. Reasoning that the clock was mains-powered, and wrong because the frequency was drifting, the visitor got rather stressed and angry with his hosts. Eventually they got him calmed down and fetched the clock off the wall to show him. It was battery powered.

[Edwin_m]

8 hours ago, AndyID said:

 

That's true but I think the minimum appliance wire here is supposed to be 18 gauge. Even at 20 A that will dissipate 5 watts per foot (2.5 watts in each direction). I don't think that will melt the insulation but I'm not going to try it

That probably explains it then.  Anyone know the standard for wiring on things like lamps with fused plugs in the UK?  

[Nearholmer]

I'm well out date on the IEE Wiring Regs (even that tells you I'm well out of date!), but this is the guide from B&Q, who I would be confident wouldn't publish it if it wasn't well-founded.

 

https://www.diy.com/ideas-advice/how-to-understand-electrical-cables-flexes-fuses/CC_npcart_400277.art

 

This area is also subject to dangerously sub-standard cr*p, especially at this time of year, when very dodgy illuminated Christmas decorations are freely available. Even now there are some on the market (literal markets are a "good" source) that have a re-wireable 13A plug, often fitted with an over-rated fuse, on the end of pathetically small and non-robust bits of un-sheathed single or two-core "bell wire", which is really vulnerable to pinching-damage, and to tiny children or pets biting it.

[DY444]

On 16/11/2020 at 20:07, Edwin_m said:

The power went off in a few places but I believe it quickly recovered.  I understood the problem with the 700s was a direct result of the frequency change caused by the reduction in supply.  The 700s were programmed to shut down if they detected a small drift away from 50Hz, but unfortunately the units with the latest software didn't automatically come back into use when the power went back into tolerance.  They needed a technician with a laptop to intervene.  

 

On 17/11/2020 at 14:55, andyman7 said:

None of the units came back on automatically, but Siemens were part way through a software update. Software in updated 700s removed the ability for the driver to reset the unit in case of shutdown due to loss of AC frequency, because a risk analysis had shown that this might be due a fault compromising signalling immunisation. They had therefore decided that local override was a potential hazard and therefore a reset should require a technician. The risk analysis had not factored loss of frequency from the national grid because such a situation had not previously occured. The law of unintended consequences - the software 'upgrade' supposedly fixed other bugs and removed a perceived risk, but then created a new one.

 

The real problem was that the 700s and 707s were not compliant with the UK standard for tolerance of frequency drift in the traction supply.  Had they been then they would not have shut down in the first place.

[gordon s]

Cut off the plug and stripped the wire just for the hell of it....

 

The input cable is marked Soundtec Electronics AVV 70°C 250v/300v. The cable is twin core and appears to have 16 strands (possibly more) of 0.06mm copper.

 

The low voltage side is again copper with probably 24 strands of 0.09mm copper. Off to check out the rating specs.

 

[roythebus]

On 16/11/2020 at 17:06, Enterprisingwestern said:

 

Isn't a fuse on aa appliance connected to a MCB/RCD circuit redundant?

 

Mike.

 

 

Yes. If you plug the appliance into an extension lead, that is also fused. why have 3 fuses in a circuit when 1 will do? Which one will blow first? Not the lowest rated, but probably the RCD in the cupboard under the stairs.

[Nearholmer]

An RCD will operate very rapidly for a fault to earth, but it won't operate for a direct line-to-neutral fault, which is one of the key risks with an appliance with a trailing lead, because the lead itself is so vulnerable to damage that can cause just such a fault and potentially lead to fire. There are other possible causes of L-N faults within many appliances too, especially if the appliance gets knocked/bashed/dropped.

 

Depending upon the rating of the lead and appliance, and the set-current of an MCB, without a fuse at the plug, sufficient current may be let-through to a L-N fault to cause sustained burning after the breaker trips. 

 

 

Edited December 7, 2020 by Nearholmer

[roythebus]

Reminds me of an incident many years ago with my first mrs. I had a home-made extension lead with a single 13 a plug on one end and a 13 a socket on the other. This was wound onto a metal and cardboard cable reel for storage.

 

I got home and found she'd used it for something like the washing machine. The cable reel had started to melt as the tin inner of the reel acted as a core for the coil and had caused it to overheat. Luckily the only damage was to the cable, but 10 minutes more could well have caused a fire. Think before you use an extension cable, completely unroll it first if you're going to use a high current thing for a continuous period.

[AndyID]

1 hour ago, roythebus said:

 but probably the RCD in the cupboard under the stairs.

 

That's a snag with a ring mains. The RCD has to be at the point that feeds the ring and it has to apply to all the outlets on the ring. With a radial system you can have individual RCD protected outlets, protect the entire spur by putting an RCD outlet at the first outlet in the spur or only the outlets "downstream" from an RCD outlet.

[bradfordbuffer]

On 17/11/2020 at 17:16, Clive Mortimore said:

A side story nothing to do with Gordon's unsafe plug.

 

As an apprentice with the GEGB I had a short period of time working in the control room of the power station I was working in. A generating set was going to be added to the grid and they asked me to switch it on. Generators are not switched on to the grid until the frequency equals that of the grid and as Phil says as close to 50Hz as possible. Switching involved turning two handles at the same time and the control room staff told me if I got it wrong I blow the whole grid, well at sixteen you believe people. I was so nervous as the two needles on the dials reached the same frequency.

 

Today I imagine the fun of scaring an apprentice has been taken out of this procedure by a computer, and they call it progress.

All the fun of scaring a apprentice has been removed by equal opportunities diversity litigation and the possibility of kissing  pension good buy!.....body could out side snowflakes falling! 

[AndyID]

3 hours ago, roythebus said:

The cable reel had started to melt as the tin inner of the reel acted as a core for the coil and had caused it to overheat.

 

I wonder if it was the tin inner that caused the heating. The current flowing in the line would be cancelled by the current flowing in the neutral so it's not so much like a typical coil winding which has a single conductor. It might just have been resistance heating in the cable and the heat had nowhere to go because it was tightly wound on a coil.

 

Ether way it's not a good idea to do that!

 

I've tried to educate my wife about the dangers of high current devices like hair dryers, toasters and room heaters etc and how they should never be plugged into any sort of adapter or extension cable but I'm not entirely convinced she really gets it.

[TheQ]

9 hours ago, AndyID said:

 

That's a snag with a ring mains. The RCD has to be at the point that feeds the ring and it has to apply to all the outlets on the ring. With a radial system you can have individual RCD protected outlets, protect the entire spur by putting an RCD outlet at the first outlet in the spur or only the outlets "downstream" from an RCD outlet.

If you want individual RCD protected sockets you can have them, there are 20 double sockets within 15 feet of me all with indvidual RCD built it.

RCD07MAVN | Theben / Timeguard 30A, BS Fixing, Active RCD Socket, Plastic, Surface Mount , Switched, 230V ac, Twin Metal | RS Components (rs-online.com) RS price is extortionate, you can get them for below £15 quid..

 They do after all recommend an individual RCD on the input of electric mower cables 

Edited December 8, 2020 by TheQ

[Nearholmer]

Andy

 

not sure why you have such reservations about ring mains. They’re electrically very efficient, and in the U.K. context if standards are properly followed the whole protection arrangement works perfectly safely.

 

I can appreciate that in a commercial/industrial setting where some quite small loads can actually have high importance then fully radial can be helpful to minimise nuisance tripping, but not really necessary in a domestic setting.

 

Kevin

[Joseph_Pestell]

12 hours ago, roythebus said:

Reminds me of an incident many years ago with my first mrs. I had a home-made extension lead with a single 13 a plug on one end and a 13 a socket on the other. This was wound onto a metal and cardboard cable reel for storage.

 

I got home and found she'd used it for something like the washing machine. The cable reel had started to melt as the tin inner of the reel acted as a core for the coil and had caused it to overheat. Luckily the only damage was to the cable, but 10 minutes more could well have caused a fire. Think before you use an extension cable, completely unroll it first if you're going to use a high current thing for a continuous period.

 

My ex-wife broke several extension leads this way.

[Michael Hodgson]

34 minutes ago, Nearholmer said:

Andy

 

not sure why you have such reservations about ring mains. They’re electrically very efficient, and in the U.K. context if standards are properly followed the whole protection arrangement works perfectly safely.

 

 

Quite so. 

 

My only doubt about ring mains is that they work on the principle that a fully loaded 30A ring carries 15A on one lead from the fusebox and 15A on the other so that it won't exceed the rating of 2.5mm T&E cable.  But you have no way of knowing if the ring somehow becomes broken (eg one wire accidentally disconnected from one of the sockets) unless there is also some other fault which causes the fuse to blow.  Surely you can't even prove that the ring is complete when you first connected it to the fuse box?  If 30A of appliances happens to be running all on one side of the break, that cable is then carrying double its rated load but still won't bother the 30A fuse.  So why isn't there a fire risk in the cables buried in the wall?  Are we relying on a theoretical safety margin in the rating of cables?