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Old 14th Jun 2022, 1:54 pm   #41
GrimJosef
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Default Re: Tin Foil - makes you weep

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Originally Posted by Craig Sawyers View Post
... Anyone observing that all other mains plug standards are fuse-less will feel justified in using a length of pot shaft, or whatever in place of a regular fuse.
... and slowly but surely Darwinian evolution will weed that gene out .

Cheers,

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Old 14th Jun 2022, 2:53 pm   #42
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Default Re: Tin Foil - makes you weep

Well said, GJ!
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Old 14th Jun 2022, 3:02 pm   #43
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Default Re: Tin Foil - makes you weep

Why do all other mains plug systems, from European Schuko to Australian standard - both 230/240 systems - manage without a fuse in the plug?

Actually I can be easily convinced that the Schuko plug/socket is safe. But the Australian one looks pretty lethal!

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Old 14th Jun 2022, 3:48 pm   #44
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Default Re: Tin Foil - makes you weep

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Why do all other mains plug systems, from European Schuko to Australian standard - both 230/240 systems - manage without a fuse in the plug?
Because their final circuits have protection rated at 16A, which is sufficiently low to trip safely and protect wires down to 0.75mm sq (actually, maybe 0.5mm sq) in all likely fault conditions. That means that a house, for example, has a much greater number of final circuits, and they're (in my direct experience) much more prone to nuisance tripping with loads like big transformers and motors, but there's no need for fuses in the plugs.

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Old 14th Jun 2022, 3:55 pm   #45
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Because their final circuits have protection rated at 16A, which is sufficiently low to trip safely and protect wires down to 0.75mm sq (actually, maybe 0.5mm sq) in all likely fault conditions. That means that a house, for example, has a much greater number of final circuits, and they're (in my direct experience) much more prone to nuisance tripping with loads like big transformers and motors, but there's no need for fuses in the plugs.

Chris
I have to agree with the nuisance tripping. The supply to my garage is a single circuit with a 16A breaker. Extremely irritating when a welder, grinder or saw can all trip it on startup and also take out the lights. I have a battery backup light in there.
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Old 14th Jun 2022, 4:22 pm   #46
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Default Re: Tin Foil - makes you weep

Somewhere, I can't help thinking, there must be a village idiot with just a tiny patch of foil missing from his hat...

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Old 14th Jun 2022, 5:05 pm   #47
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Default Re: Tin Foil - makes you weep

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Why do all other mains plug systems, from European Schuko to Australian standard - both 230/240 systems - manage without a fuse in the plug?

Craig
Possibly because the whole question of socket outlets in the UK was carefully considered by a committee, which unlike many seems to have known how to design a horse. (Post War Building Studies No. 11, 1944).

You may not agree with their conclusion that a ring circuit, necessitating a plug fuse, would allow a large number of sockets and save copper, but if you care to study what they published, it would be diffilcult to argue that all foreseeable aspects of domestic electrical installations were not thoroughly considered. Several existing plug types, including some with fuses, were considered before it was decided it was better to have a new design. The committee anticipated a great increase in the number of appliance which would be used in the average home, although still underestimated what we use today.

It might be a little cynical to say that they had to come up with something better because the situation in the uK then was so chaotic at the time, but at least it eventually led to virtually complete national standardisation.

Who would care to argue that the US and quite a few other plugs were given the same degree of thought? Whatver you think of the plug chosen, you have to give them marks for effort.

If you've ever tested your home ring main, you may well find that socket outlets near the distribution board have an prospective fault current of over a thousand amps - surely that justifies a properly design HBC fuse? It would be interesting to see what happens to the various IED fuses.

PMM
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Old 14th Jun 2022, 5:42 pm   #48
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Default Re: Tin Foil - makes you weep

Personally, I've always thought the UK ring-main-and-13A-fuse-in-the-plug is rather over-engineered; it assumes that _any_ potential load needs to be provided with an earth-connection and be able to draw 3Kw - meaning bulky, expensive plugs/sockets.

I like Schuko - I also like the little cheap-and-simple 2-pin "Europlugs". I get on well with the US 117/234V two-phase-center-tapped approach too.

In times-past I pondered about the idea of something like an IEC309 'kettle-lead' socket as a successor to the BS1363 plug/socket: You could fit 5 of them into the profile of a dual back-box, even if you include an in-box fuse in the profile.

Most 'domestic' loads are only tens/hundreds of Watts; why always design for the worst-casr?

[Can you still buy a full 3Kw-rated radiant/convector-heater/tumble-drier?]
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Old 14th Jun 2022, 6:01 pm   #49
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Most 'domestic' loads are only tens/hundreds of Watts; why always design for the worst-casr?

How many members of the general public really understand the load rating of appliances such that they could choose the correct socket if there was a choice of rating; that is without a variety of socket types? And if there were such a choice, how long would it be before unsuitable adaptors started appearing?

[Can you still buy a full 3Kw-rated radiant/convector-heater/tumble-drier?]
Have a look at "Fast Boiling" kettles, i.e. 3 kW models.

PMM
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Old 14th Jun 2022, 6:11 pm   #50
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Default Re: Tin Foil - makes you weep

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Have a look at "Fast Boiling" kettles, i.e. 3 kW models.

PMM
Given the duty-cycle I'm happy to run such a kettle on a 16A radial and feeding it through flimsy 1.0mm-squared flex.

[Why does a kettle need an earth?]

My electric cooker - if I turned every element on at the same time - could draw a theoretical 47 Amps@240V but I'm happy to power it via a 16-amp "Commando' plug-and-socket...

Designing for 'worst-case' is sometimes silly.
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Old 14th Jun 2022, 6:20 pm   #51
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Default Re: Tin Foil - makes you weep

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Given the duty-cycle I'm happy to run such a kettle on a 16A radial and feeding it through flimsy 1.0mm-squared flex ... Designing for 'worst-case' is sometimes silly.
Designing so that everyday equipment is unsafe unless it's operated by a genuinely competent person doesn't have a lot to recommend it either.

My late mother-in-law had dementia. While she was still living alone she was quite capable of putting water into her electric kettle and switching it on without closing the lid. The open lid meant the boil trip didn't function. Worst cases do happen.

Cheers,

GJ
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Old 14th Jun 2022, 6:54 pm   #52
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Default Re: Tin Foil - makes you weep

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Quote:
Originally Posted by pmmunro View Post
Have a look at "Fast Boiling" kettles, i.e. 3 kW models.

PMM
Given the duty-cycle I'm happy to run such a kettle on a 16A radial and feeding it through flimsy 1.0mm-squared flex.

[Why does a kettle need an earth?]

My electric cooker - if I turned every element on at the same time - could draw a theoretical 47 Amps@240V but I'm happy to power it via a 16-amp "Commando' plug-and-socket...

Designing for 'worst-case' is sometimes silly.
Until comparitively recently, only metals were a practical material for the body of kettles and metal-bodied kettles are still about.

Ancients like me can remember when "plastic" - meaning thermoplastic - was considered a cheap material in the derogatory sense. There were probably thermoset, e.g. Bakelite, kettles later, but I would expect some age-related embrittlement with those.

Metal remains the most suitable material for element sheaths and I certainly wouldn't want that unearthed. Apart from the conductive nature of water it's not at all inconceivable that some people might use a metal spoon or ladel to stir the contents of a kettle. There is also a risk of someone stirring the contents of a mug while adding hot water from a kettle such that there could be a conductive stream back to the element. Think of accidents caused by people sticking metal knives into toasters, not stopping to think the knife is conductive - or perhaps they imagine the element ribbon is not live?

We're considering people using all sorts of IEDs instead of fuses; if they can do that, what won't they do?

PMM
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Old 14th Jun 2022, 8:43 pm   #53
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Default Re: Tin Foil - makes you weep

My late brother-in-law's house in France had been built in the late 1950's. Each radial circuit was protected by double-pole fuses at the distribution board and in addition, each socket and light switch incorporated its own 6A or 10A fuse. The original fuses were disposable, resembling ceramic-bodied 2 pin plugs with the fuse link sealed within the body. Later replacements were bakelite, with a replaceable fuse link consisting of a strip of printed circuit board with the fusible element consisting of a thin copper track running between two pads which had through holes for screwing the fuse link in place using the pins. To access the fuse you had to unscrew the switch or socket cover and carefully pull out the fuse link without touching any of the live metal parts (unless you removed both the fuse links at the distribution board first) .
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Old 14th Jun 2022, 11:08 pm   #54
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Default Re: Tin Foil - makes you weep

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I'm sure I have seen one of those. Were they red in colour?
Yes they were red, and fitted with a larger cord grip so as to accept larger than 1.5mm flex.
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Old 14th Jun 2022, 11:18 pm   #55
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Default Re: Tin Foil - makes you weep

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Quote:
Originally Posted by G6Tanuki View Post
Most 'domestic' loads are only tens/hundreds of Watts; why always design for the worst-casr?

How many members of the general public really understand the load rating of appliances such that they could choose the correct socket if there was a choice of rating; that is without a variety of socket types? And if there were such a choice, how long would it be before unsuitable adaptors started appearing?

[Can you still buy a full 3Kw-rated radiant/convector-heater/tumble-drier?]
Have a look at "Fast Boiling" kettles, i.e. 3 kW models.

PMM
It is now very hard to find space heaters or clothes dryers with a full 3 kw loading. I suspect that this is due to a de facto admission that cheap modern 13 amp plugs and sockets are not able to reliably handle a continual 13 amp load.

Fast boiling electric kettles do use a full 13 amps and seem fine in practice due to the short term use.

Screwfix used to sell, and might still sell a true 3 kw fan heater. It was described as being for "industrial use" and did not include a plug.
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Old 14th Jun 2022, 11:28 pm   #56
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Default Re: Tin Foil - makes you weep

My grandmother lived in a 1930's semi in North Manchester.
It had a large metal-clad double-pole fuse box with radial wiring to Wylex sockets.

I don't know the reason for the DP board, I'm sure it was never a DC supply, I imagine it was a case of what was available.

She moved out in the early '80s and I suppose the place was rewired, but sometime before then I put heavy gauge wire in the neutral fuses and marked them NEUTRAL LINKS DO NOT REMOVE.
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Old 14th Jun 2022, 11:43 pm   #57
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Default Re: Tin Foil - makes you weep

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It is now very hard to find space heaters or clothes dryers with a full 3 kw loading. I suspect that this is due to a de facto admission that cheap modern 13 amp plugs and sockets are not able to reliably handle a continual 13 amp load.
To be fair I doubt it. That would suggest that producers are considering the UK market separately from others. They won't be.
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Old 15th Jun 2022, 11:59 am   #58
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Default Re: Tin Foil - makes you weep

I was doing work in a small unit where they had one of those ‘industrial’ heaters. I think it came from Machine Mart. It was plugged into the standard mains system and one day I noticed that the cable was warm. I never ran it on its full setting when I was in there, even though the place could be darned cold. Fortunately, I was moving around a lot and wore extra layers.
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Old 15th Jun 2022, 12:11 pm   #59
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Default Re: Tin Foil - makes you weep

There is a wide spread in the power taken by different appliances.

Something properly engineered for a high power and heavy use item will appear over-engineered for a light appliance. This is not a problem in itself. You don't want anything to be under engineered because that will create problems.

So, if things are planned and built properly, ALL applications will appear either exact or over-engineered. Nothing should be under-engineered.

If some 13A plugs and sockets aren't capable of surviving continuous use, then they are inadequate and better types should be used.

The idea is that the fixed system is well enough engineered that any valid appliance can be plugged in anywhere. In this way there are no niggling extra rules which have to be remembered. If it's a 13A socket, it will work properly as a 13A socket.

A light appliance can have a light mains cable and the right fuse in the plug will protect it. The full-size plud is the interface into the beefy fixed installation.

It has all been quite well thought out, the only iffy area being diversity.

If you want to use IEC distribution strips, or masterplugs or whatever, then that works, just power it from one 13A plug, and fit it with an appropriate fuse.

David
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Old 15th Jun 2022, 12:57 pm   #60
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Default Re: Tin Foil - makes you weep

Going back to the the start of this thread, I was given a Fluke 70 series meter years ago. the case near the sockets was partially melted, the fuse inside having been covered in tin foil. The meter was ok with the top off and a new fuse. It was never repaired. The reference to NASA power supplies was IIRC "battle short" from the US Navy. A warship is safer if it continues to maneuver and fight rather than stop, even if something burns out. A violent shock from an explosion will often open mechanical contactors and relays momentarily.
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