Dangerous 13A Plugs

[GoingUnderground]

Exactly. I was surprised to see the "afterthought" plug, which may mean goods have been made for one country, then exported to UK markets with a revised plug...

 

My wife bought a kettle 2 weeks ago from a well known chain, and it had the traditional 'screw on' plug. What both it and Nigel's electric fire have in common is that they are both high current appliances with the lead permanently fitted to the appliance itself.

 

The tendency seems to be that both ends are moulded fittings, the 13 A plug on one end and a 3 pin 'kettle' or 'clover-leaf' or 'figure 8' 2 pin line socket on the other. But those tend to be for lower current devices, e.g. desk top PCs, battery chargers, radios, laptop PC power supplies, etc., or the item comes with its own dedicated 'wall wart' integrated plug and transformer..

[Penlan]

I know it's probably a daft question, I'm just curious. Dave.

Dave, No it's not a daft question, it's sensible, because if you don't know, you don't, so then ask.

 

For some people certain topics are done subconsciously,

there can be no doubt to some that a sequence of words/actions come together, like 2 added to 2 equals 4...........

 

But how on a PC etc.,

can I do 3 x (times) 3, divided (because on this posting I can't find the divide sign) by 2, to equal 4.5,

when the proper arithmetic signs can't be found or work, apparently on a PC you need to write =sum((3*3)/2),

I wasn't taught * and / in maths lessons and if you don't know when you start using these keyboards, you don't know,

you ask (or when all else fails, read the manual).

PS - The brackets are per BODMAS = Brackets,Order*, Division, Multiply, Add and Subtract - the sequence you should use to work out the final Sum.

* Order actually means Power, but BPDMAS is not such an easy acronym, - look here for more confusing details.

 

I've just looked in the 'Symbol' drop down menue's etc of my various word and spreadsheet etc., packages and none have a good old fashioned (School Cert.,) divide symbol.

 

So, for some/a lot, electrics is a mystery too, or soldering

[Edwin_m]

I've an idea it's because we use ring mains in the UK that can supply enough current to cause a lot of damage if a fault occurs. Others have their wiring in a star so each socket has its own wire back to the distribution board and I assume its own circuit breaker.

[max]

One should mean that the fuses protecting the circuit of socket(s) in use are sufficient protection,whether they are NFB or wire type? Why do other countries not use fused plugs,I doubt their regulations regarding appliances are less strict than in the UK?

Just curious.

 

Max

[Jenny Emily]

 

I've just looked in the 'Symbol' drop down menue's etc of my various word and spreadsheet etc., packages and none have a good old fashioned (School Cert.,) divide symbol.

 

 

 

÷ appears if you hold down the ALT key and then type out the number 0247 on the keypad.

[Oldddudders]

÷ appears if you hold down the ALT key and then type out the number 0247 on the keypad.

Is that what they mean by a "Shortcut"?

[Suzie]

This problem is not always the result of a faulty plug. Some appliances when faulty can draw a lot more current than they are supposed to, but not enough to blow the fuse - but just enough to make the fuse glow nice and warm - warm enough to melt a new, cheap, thermoplastic plug. Plugs in the olden days used to all be of the thermosetting plastic type which could easily withstand this type of heating with nothing more sinister than a bit of discolouration of the plastic in the fuse area.

 

The new cheap plugs appear to have come about when the law changed to require appliances to be supplied with a fitted plug, and plugs were made to a price by people abroad unfamiliar with their use rather than to a quality standard by people who understood their use (MK etc.). I guess that British Standards never predicted that plugs would be made from unsuitable materials - materials that are perfectly suitable for other countries where fuses are not used in the plugs (USA, Europe etc. - pretty much everywhere other than the UK.)

 

In tests it would appear that you can usually get about 25A through a 13A fuse if you treat it carefully with nice resistive load (i.e. a faulty electric heater). I once had a 3kW kettle that stopped working after a few years - the 5A fuse in the plug had blown!

 

I would not be inclined to worry too much about the use of these cheap plugs on table lamps and other low powered items in non-hostile environments (with the correct 3A or smaller fuse!), but for anything drawing more than 5A or something used in a hostile environment think about replacing a cheaper plug with a quality one - they really are not that expensive and can of course be reused many times and last for decades. 

 

 

[bertiedog]

To get special symbols you can also simply call up the windows character map, copy the symbol and paste it ÷ or Ω № ♪ Φ ® © .....any on the letter map

[Jenny Emily]

This problem is not always the result of a faulty plug. Some appliances when faulty can draw a lot more current than they are supposed to, but not enough to blow the fuse - but just enough to make the fuse glow nice and warm - warm enough to melt a new, cheap, thermoplastic plug. Plugs in the olden days used to all be of the thermosetting plastic type which could easily withstand this type of heating with nothing more sinister than a bit of discolouration of the plastic in the fuse area.

 

The new cheap plugs appear to have come about when the law changed to require appliances to be supplied with a fitted plug, and plugs were made to a price by people abroad unfamiliar with their use rather than to a quality standard by people who understood their use (MK etc.). I guess that British Standards never predicted that plugs would be made from unsuitable materials - materials that are perfectly suitable for other countries where fuses are not used in the plugs (USA, Europe etc. - pretty much everywhere other than the UK.)

 

 

Interesting. I always thought that plugs were required by legislation to be made from thermosetting rather than thermosoftening plastics. I didn't realise it wasn't actually enshrined in any legislation.

 

I can't think of anything sillier than using a plastic that can soften and distort when exposed to heat, used in a thing that can get warm.

[Bernard Lamb]

Interesting. I always thought that plugs were required by legislation to be made from thermosetting rather than thermosoftening plastics. I didn't realise it wasn't actually enshrined in any legislation.

 

I can't think of anything sillier than using a plastic that can soften and distort when exposed to heat, used in a thing that can get warm.

You would have thought so, particularly as they bear the BSI Kite Mark. Any thing that I was involved with at work, that carried a Kite Mark, had a very tightly toleranced specification for the material used.

Bernard

[n-gauge]

Bring back Bakelite! Twas all the rage - phones, radios, plugs, well sockets and switches. I don't recall there being any problems with it.

 

George

[mike50001]

abit more to add to the why dont other countries use fuses in plug tops.

 

england is one the very few countries to use ring wiring for sockets, where most countries use radial circuits.

this means the wiring for the ring is protected at 32 amps, where the radial is protected at 16/20 amps.

 

so theres quite a difference in the supply to the socket protection in other countries to here.

[bertiedog]

abit more to add to the why dont other countries use fuses in plug tops.

 

england is one the very few countries to use ring wiring for sockets, where most countries use radial circuits.

this means the wiring for the ring is protected at 32 amps, where the radial is protected at 16/20 amps.

 

so theres quite a difference in the supply to the socket protection in other countries to here.

 

Not quite right, as the distribution trips, (or fuses), are best set to the lower distribution values, not to such high amperages as 32 amps. The ring could deliver such a maximum in theory, but in practice it does not. The main trips and fuses protect the wiring to the plug, and the plug fuse protects the cord and device. The main household mains "in fuse" protects the distribution board, especially in the case of a house fire. The only high ampage supply run would be to the electric cooker supply, separately fused at high value.

Ring mains were considered safer than radial when the change was made from round pin 15 amp to 13 amp square pins, in effect doubling up on fusing, especially compared to the then common US un-fused plug system.

Stephen.

[CUTLER2579]

Bertie Dog said:-

Not quite right, as the distribution trips, (or fuses), are set to the lower distribution values, not to such high amperages as 32 amps.

 

I am slightly unsure what you mean by this,are you saying that in the Consumer Unit the Ring Main Circuit Breakers although marked at 32 amps will trip at less than 32 amps.

Regards.

[bertiedog]

Bertie Dog said:-

 

I am slightly unsure what you mean by this,are you saying that in the Consumer Unit the Ring Main Circuit Breakers although marked at 32 amps will trip at less than 32 amps.

Regards.

 

You are absolutely correct if the ring is set to 32 amp breakers, but they can be set to lower values and really should be in practice. This is one of the reasons I do not like ring mains, They are really being fused to too high a setting, albeit within the regulations. If I had my way all plugs would be fed by a fully fused ( RCD etc.,in practice), spur supply set at the max value for just the one fused outlet socket and plug, and wired in a fully insulted conduit system as well.

[mike50001]

You are absolutely correct if the ring is set to 32 amp breakers, but they can be set to lower values and really should be in practice. This is one of the reasons I do not like ring mains, They are really being fused to too high a setting, albeit within the regulations. If I had my way all plugs would be fed by a fully fused ( RCD etc.,in practice), spur supply set at the max value for just the one fused outlet socket and plug, and wired in a fully insulted conduit system as well.

 

 

the only adjustable breakers ive seen are big industrial ones, an mostly rated way over 32amp.

 

but domestic ones are not adjustable, but you could fit a lower rated one, 32 amp is standard on ring circuits or you wouldnt be able to boil the kettle an put a heater on without tripping it out.

[Jenny Emily]

Bring back Bakelite! Twas all the rage - phones, radios, plugs, well sockets and switches. I don't recall there being any problems with it.

 

George

 

The problem with Bakolite was that it went brittle with age. I think heat also accelerated this process. I recall the plug on my old Hornby Dublo A3 controller shattering when plugging it into the wall, leaving a rather worried child looking at a live pin poking through the débris.

[bertiedog]

There should really be no single items drawing 32 amps on a ring circuit, a kettle, (average domestic) only draws 2 kw's etc., about 8 amps, and a water heater that is anything beyond a 10 amp type should really be on a devoted high ampage spur of it's own. I know fully it is often allowed in the regulations , but that's partly why we still have troubles with fuses and supplies, just not enough protection.

Ring mains makes assumptions about the average use of the sockets, which individual spur fusing allows for, overload that spur and it blows, where as the same excess current drawn on a ring will indeed not trip the 32 amp breaker, (It should blow the plug fuse of course).

 

It may not blow the ring, but it may cause a fire that the spur fused type would not have caused. This is where we came in, the 13amp plug that had overheated, which on a ring main is potentially fed by a 32 amp supply, rather than a spur at 13 amp.

 

I have always thought that ring mains design was more to save the consumer from fuses blowing so often, but this way round it does not increase the protection, it smacks of protecting the wiring, rather that the consumer. In my opinion you simply cannot have too many fuses, RCD , breakers etc. in the system. I am not a domestic electrician, but a trained qualified industrial electrician, where standards had to be somewhat higher than I still see in domestic installations, some practices which apply there really worry me. The use of 32 amp is by the way the recommended practice as a maximum figure, a lower trip may always be substituted on a ring.

[Suzie]

The US uses a ring main system, it would be impractical to do otherwise since they have rules requiring sockets be fitted all the way around rooms a minimum of six feet apart! presumably to eliminate any need for regular use of extension leads.

 

I am not sure that replacing the ring main with a star system would be very practical, my house has about sixty wall sockets without including those in the garage, sheds and garden. Running separate wires for all of them to an individual breaker would result in a lot of wiring and a huge consumer unit. Perhaps for a new build it could all be factored in with a more industrial approach to installation. I believe that it is now possible to use European wiring in the UK now if you are keen, at least all the colours match now.

 

Including a 16A breaker in each socket would be a very good idea. You can already buy sockets with an RCD fitted, it is not rocket science. Resettable breakers are a lot more reliable than fusible links and can be set a lot closer to the desired trip point.

 

Clearly what will really make a difference is making the plugs out of a proper material. I cannot see why the relevant standards cannot be updated in the light of the experience of the failure of unsuitable materials.

 

 

[Grovenor]

I am not sure that replacing the ring main with a star system would be very practical, my house has about sixty wall sockets without including those in the garage, sheds and garden. Running separate wires for all of them to an individual breaker would result in a lot of wiring and a huge consumer unit.

Where star type wiring is used you are not limited to one socket per circuit, the number of sockets allowed on each circuit will depend on the size of cable used and the usage of the rooms supplied hence likely loads and resulting diverstiy factor.

Regards

Keith

[max]

Not quite right, as the distribution trips, (or fuses), are best set to the lower distribution values, not to such high amperages as 32 amps. The ring could deliver such a maximum in theory, but in practice it does not. The main trips and fuses protect the wiring to the plug, and the plug fuse protects the cord and device. The main household mains "in fuse" protects the distribution board, especially in the case of a house fire. The only high ampage supply run would be to the electric cooker supply, separately fused at high value.

Ring mains were considered safer than radial when the change was made from round pin 15 amp to 13 amp square pins, in effect doubling up on fusing, especially compared to the then common US un-fused plug system.

Stephen.

 

 

Stephen, you say 'the fused plug protects the cord and device'......is this really necessary or is it an additional protection at extra cost? Correct circuit fuse ratings

ought to be sufficient to protect devices and their cables plus lots of devices have their own built in protection like thermo fuses,etc.Apparently using a ring main system seems not to be the reason for using fused plugs, since it is also used in the US.

 

Max

[Edwin_m]

I have always believed that lamps etc in the UK were able to us a much thinner flex due to being fused at 3 amps. Is this correct and if so do lamps in other countries have to have a flex carrying the full rating of the circuit? Do they use a thinner flex and rely on the quick operation of the breakers (and minimal voltage drop, shades of the DCC coin test!) to trip out before any fault overload can cause dangerous overheating?

[meple]

Where star type wiring is used you are not limited to one socket per circuit, the number of sockets allowed on each circuit will depend on the size of cable used and the usage of the rooms supplied hence likely loads and resulting diverstiy factor.

Regards

Keith

 

 

A star system can be used in the UK and is compliant with IEE regs. They are fused at 20amps for 2.5mm cable.

[GoingUnderground]

I think I'm correct that the old round pin 15A sockets were all on a star distribution pattern, and in those days there was only one socket in each room and a single pendant light fitting.

 

The ring main was introduced to allow lots of smaller loads to be plugged in without a significant increase in wiring costs. It was also supposed to be safer by reducing the need for adaptors which ran the risk of overloading the old 15A spur system., and allowing a lower fuse rating to each appliance.

 

As has already been said, putting every single socket on its own fused/MCB'd spur would result in much more expensive domestic wiring and probably 20, 30 or even 40 way consumer units. Just count up the number of sockets you have these days in your house and garage plus the lighting circuits, immersion heater, cooker, electric shower, etc..

 

I don't share others reservations over ring mains, but then I'm not a professional electrician. However do we really want to have to change the MCB in the consumer unit just because we've unpligged a table lamp and plugged in an electric fire into the 13A socket in a star pattern system. I think not. And you can be certain that before long, every MCB in the box would be 13A no matter what the load. Ring Mains and fused plugs are not perfect, but they are a reasonable compromise provided the appropriate fuse and MCB are used. But I do support replacing the fusible links in older consumer units with plug in replacement MCBs because of their greater sensitivity, not to mention protecting some folks from their own stupidity in using ordinary wire instead of fuse wire.

[meple]

You can have as many outlets as you want on any spur of the star so there would not be any more MCBs/fuses as there are in a ring main system. The difference is that they are fused at 20amp and not 32amp.

 

Lighting circuits are always star wired.