Illegal mains plug?.....possibly lethal

[AndyID]

11 minutes ago, Enterprisingwestern said:

 

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

 

Mike.

 

 

 

Absolutely not. The UK ring can deliver 32 amps. A fault in the device can allow more than 7 kilowatts to dump into the cable which will melt and start a fire.

[Crosland]

24 minutes ago, Enterprisingwestern said:

 

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

 

NO! The fuse in an appliance plug is there to protect the lead to the appliance. An overloaded appliance would not necessarily trip the central MCB if the overload were too small (but still enough to cause a lot of damage within the appliance).

[phil-b259]

36 minutes ago, Joseph_Pestell said:

 

Certainly commonplace. But I am not sure if they are fully compliant.

 

Providing the appliance is double insulated (wrapped in plastic twice as it were) then UK regulations say it does not need to be connected to earth. Not sure whether there is a current limit on it though - the usual culprits tended to be phone chargers and suchlike which normally drawn small currents and only have a 3A or less fuse fitted.

[AndyID]

At least Gordon's plug doesn't pretend to have a fuse. There's a video on the web of a guy who bought a welder. The 13A plug had a fuse but when he removed it he discovered it had been "improved" with a piece of thick copper wire soldered neatly between the ends.

[Edwin_m]

3 hours ago, phil-b259 said:

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.

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.  

[Grovenor]

4 hours ago, mike morley said:

Not long before lockdown Eon nagged me into letting them fit a smart meter.  It came with a separate little display powered by a plug that has no fuse!

More likely that that is not just a plug but a switch mode Power Supply Unit, (aka wall wart) which don't have a mains fuse to protect the lead because the lead is low voltage just like phone chargers etc. The info should be on the PSU, it's moulded on the bottom of mine.

[andyman7]

18 hours ago, 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.  

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.

[Happy Hippo]

I'd complain,  but more importantly, I'd chop the plug off  the cable and replace it with a plug from one of the big DIY warehouses.

[Derekstuart]

23 hours ago, 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.

 

 

 

 

 

Phil, I read a story in a paper (so it must be true) where everyone's alarm clocks went off in the middle of the night, which was eventually traced back to the National grid having two out of sync. 50HZ, thereby turning it to 100Hz- thus making equipment relying on the electrical frequency for timing run at double speed. It might have been something to do with emergency generators rather than the main power station. It must have been 20+ years back.

 

So I can understand why they are so fixed on protecting the frequency now. Perhaps back then all that went wrong were a few alarm clocks, but given how everything is now computer controlled, God knows what the consequences of that could be now.

[Dagworth]

Transformers are designed to have a given rating for their size based on the frequency of the current they see, changing the frequency changes the power output. Being as the whole distribution system relies on transformers then keeping the frequency within the margins it is designed around becomes absolutely critical.

As the frequency drops then so does the output power of every transformer between the power station and the outlet socket on your wall. 

 

Andi

[smokebox]

54 minutes ago, Happy Hippo said:

I'd complain,  but more importantly, I'd chop the plug off  the cable and replace it with a plug from one of the big DIY warehouses.

 

And make sure the plug is not able to be plugged in to a socket.  Hitting it with a large hammer should do it and it's very therapeutic!

[gordon s]

1 hour ago, Happy Hippo said:

I'd complain,  but more importantly, I'd chop the plug off  the cable and replace it with a plug from one of the big DIY warehouses.

 

I did consider that Richard, but if they are prepared to cut corners to this degree, then God only knows what's going on inside. Needless to say I will return it once they give me a return address. If nothing is forthcoming then I'll claim a refund on eBay.

 

The last thing I need is a fire risk at home or worse still, risk of a shock to anyone.

[Grovenor]

1 hour ago, Happy Hippo said:

I'd complain,  but more importantly, I'd chop the plug off  the cable and replace it with a plug from one of the big DIY warehouses.

If you are talking about Gordon's original then the cable is probably no where near 10A rated so fitting a new plug would not help.

If you are talking of Mike Morley's you could be replacing a low voltage PSU with a mains plug and that would blow up the smart meter display for sure.

Gordon's just needs throwing after cutting the cable to stop someone else using it.

Mikes, If a PSU, as I suspect, will be fine.

[Clive Mortimore]

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.

 

 

 

 

 

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.

Edited November 17, 2020 by Clive Mortimore

[Crosland]

28 minutes ago, Clive Mortimore said:

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.

 

If they know in advance (ad break during corrie xmas special, perhaps?), and have the generators spinning, Dinorwig can bring 1800 MW on line in only 16 seconds. Otherwise it takes a lengthy 75 s 

[Clive Mortimore]

45 minutes ago, Crosland said:

 

If they know in advance (ad break during corrie xmas special, perhaps?), and have the generators spinning, Dinorwig can bring 1800 MW on line in only 16 seconds. Otherwise it takes a lengthy 75 s 

See taken all the fun out of the job.

[AndyID]

2 hours ago, gordon s said:

 

I did consider that Richard, but if they are prepared to cut corners to this degree, then God only knows what's going on inside. Needless to say I will return it once they give me a return address. If nothing is forthcoming then I'll claim a refund on eBay.

 

The last thing I need is a fire risk at home or worse still, risk of a shock to anyone.

 

I suspect the manufacturer sells that device in lots of markets without any problems but the supplier of the cable does not appreciate the finer points of the UK domestic mains distribution system which is unique and, in restrospect, not a very good idea.

 

You'd probably be fine if you replace the plug and use a 3 amp fuse. If there is a problem in the unit the 3 amp fuse will provide plenty of protection. But I can see why you probably don't want to do that.

[AndyID]

2 hours ago, Derekstuart said:

Phil, I read a story in a paper (so it must be true) where everyone's alarm clocks went off in the middle of the night, which was eventually traced back to the National grid having two out of sync. 50HZ, thereby turning it to 100Hz- thus making equipment relying on the electrical frequency for timing run at double speed. It might have been something to do with emergency generators rather than the main power station. It must have been 20+ years back.

 

 

According to what I remember being taught (it was a long time a go) that would not be possible. The weaker generator would become immediately cream crackered.

 

What might have caused it was a defective or overloaded generator that was not connected to the rest of the grid.

 

IIRC the problem with frequency drift is that the overloaded generators are still synchronized with the grid but they are not quite in phase and that sucks large currents through the distribution system where they are not supposed to be going.

[PatB]

8 hours ago, Grovenor said:

If you are talking about Gordon's original then the cable is probably no where near 10A rated so fitting a new plug would not help.

 

Why would the cable need a 10A rating? With an output of 72W, even allowing a very conservative 50% efficiency, I make that a max 0.6A input current. 

 

If 10A is a generic UK requirement for all flexes (I confess I'm now probably 30 years behind on UK regs), I would suggest that 99% of low current consumer appliances, judging by eyeball measurement, are undercabled. 

[AndyID]

22 minutes ago, PatB said:

Why would the cable need a 10A rating? With an output of 72W, even allowing a very conservative 50% efficiency, I make that a max 0.6A input current. 

 

If 10A is a generic UK requirement for all flexes (I confess I'm now probably 30 years behind on UK regs), I would suggest that 99% of low current consumer appliances, judging by eyeball measurement, are undercabled. 

 

I'm a bit out of touch too but I think that's why there are 3 amp fuses. There used to be all sorts of fuse sizes but maybe they are no longer available. Gordon's PSU would run happily with a 1 amp fuse if there still is such a thing.

 

Mind you, most cables, even if they are not rated for 10 amps continuous, will pop a 13 amp fuse quickly enough to prevent a fire in the event of a dead-short. The worst case is when some lowish resistance fault develops in the equipment and it keeps drawing a lot of current but not enough to pop the fuse. That can seriously overheat an underrated cable.

[Edwin_m]

5 hours ago, AndyID said:

 

I'm a bit out of touch too but I think that's why there are 3 amp fuses. There used to be all sorts of fuse sizes but maybe they are no longer available. Gordon's PSU would run happily with a 1 amp fuse if there still is such a thing.

 

Mind you, most cables, even if they are not rated for 10 amps continuous, will pop a 13 amp fuse quickly enough to prevent a fire in the event of a dead-short. The worst case is when some lowish resistance fault develops in the equipment and it keeps drawing a lot of current but not enough to pop the fuse. That can seriously overheat an underrated cable.

Yes, as I tried to explain to my mother-in-law a few years back after I discovered she'd put 13 amp fuses in table lamps etc because if there was a fault it was easier to reset a tripped breaker in the "fusebox" than to replace a fuse in a plug.  

[AndyID]

2 minutes ago, Edwin_m said:

Yes, as I tried to explain to my mother-in-law a few years back after I discovered she'd put 13 amp fuses in table lamps etc because if there was a fault it was easier to reset a tripped breaker in the "fusebox" than to replace a fuse in a plug.  

 

I think you just summed-up the problem with with ring-mains system in one short sentence. When they came up with It probably seemed like a good idea at the time and they had me fooled but.....

[Edwin_m]

5 hours ago, AndyID said:

 

I think you just summed-up the problem with with ring-mains system in one short sentence. When they came up with It probably seemed like a good idea at the time and they had me fooled but.....

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.  

Edited November 18, 2020 by Edwin_m

[Captain Cuttle]

On 16/11/2020 at 12:51, gordon s said:

Thought I had seen it all, particularly with product from China, but this surely cannot be legal. I ordered one of these purely to test an old Lionel locomotive. I'm always wary of ordering from China, but the mains plug on this device surely can't be legal....

 

https://www.ebay.co.uk/itm/363109269512

 

The main plug is the smallest I have ever seen and cannot meet specs re finger access and spacing to the edge. There can't possibly be a fuse in the plug, so surely this must break every UK safety regulation on mains plugs. Is it legal to supply electrical goods in the UK with a plug that doesn't meet BS1363?

 

Need to check my facts, but reporting to both eBay and Trading Standards is certainly an option if they are illegal.

 

 

 

[Captain Cuttle]

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

 

Alan