Talk:BS 1363/Archive 1

This is an archive of past discussions about BS 1363. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page.

Archive 1

Archive 2

Spelling of the standard designator

I went to the BS site and saw they always put a space between "BS" and the following number, so I moved this article. — Chameleon My page/My talk 14:02, 5 Jul 2004 (UTC)

Why are British plugs fused?

This article claims that British plugs are the only ones that are fused - because of ring wiring opposed to linear wiring everywhere else. True or false? Secretlondon 03:36, 6 Jul 2004 (UTC)

Looks plausible to me. However, right next to me there is a power socket with a fuse in it, like all the sockets in this Spanish house. That would imply that we have ring wiring here, and this is continental Europe. Click on the pic for more pix.

Click here

— Chameleon My page/My talk 04:00, 6 Jul 2004 (UTC)

could be a ring could be a higher current radial. is it possible for you to find what fuse/breaker is protecting it what kind of cable is it and/or whether it is actually wired in a ring(plugwash)

btw the fising has nothign to do with the fact the cuircuits are rings it has to do with the fact that the cuicuirts are high rated (30A/32A ususally)

i only said it was limited to the uk as far as i knew. there may be other countrys that use it(plugwash)

American Christmas tree lights have a fuse in the plug. American portable air conditioners have a Leak Current Detection and Interruption (LCDI) circuit in the plug because they draw lots of power and are prone to short circuits (this looks like a British plug but has Test and Reset buttons on it). However, for the most part Americans don't need a fuse in the plug because most American circuits are limited to 120 volts 15 amps, which is 1800 watts compared to 7200 watts or more for the British ring mains. The British plug has a fuse because the socket can deliver enough power to the bedrooms to run an arc welder. They've designed an electrical system that is intrinsically dangerous and tried to compensate by overengineering the plug. RockyMtnGuy 05:51, 29 March 2006 (UTC)

The fuse in the plug protects the flex (connection between the plug and the appliance/equipment being powered) from overheating and causing a fire. It is not intended to protect the appliance. In general, domestic UK wiring allows the delivery of higher current at a higher voltage than US domestic wiring, while minimising the amount of wire actually needed. This is convenient, as it allows high power equipment, such as room-heaters or, if necessary, electric arc welders to be located at will withiin the premises. While the wires in the walls are rated to carry high currents, the flex to the appliance isn't, so the fuse is there to disconnect the appliance if a fault occurs and a continuous current higher than that the flex was designed for flows. Other countries use a different approach, using radial circuits, and limit the length of flexes such that the flex can carry enough power without becoming a fire hazard for the short period of time before the protective device protecting the radial circuit trips. The downside of this approach is that one faulty appliance or flex on a shared radial circuit will casue service to the entire radial circuit to be powered down, which can be inconveneient/dangerous. In the British system, one faulty appliance or flex only blows the fuse in its own plug, and all other equipment on the same circuit carries on working fine. WLD 10:49, 29 March 2006 (UTC)

I wonder whether one of the motivations behind the British 32 A ring circuit concept was that in the 1960s, some electricians' committees foresaw that soon all heating would be electric, in which case you would need such currents. Recall that when BS 1363 was introduced, it was the golden age of nuclear power, when people seriously believed that electricity would soon be so cheap that it will hardly be worth metering it, thereby making electrical heating the most attractive option. Markus Kuhn 12:53, 29 March 2006 (UTC)

For more info on how British wiring came to be the way it is, see Ring circuit. And if we don't reference that stuff in the article, we ought to.

Atlant 12:58, 29 March 2006 (UTC)

How many standards are there for British plugs and sockets?

"two standards to which the British electrical plugs and sockets are manufactured" - there are certainly more than two current standards covering UK electrical plugs & sockets... BS7671 mentions at least five. [e-mail] 15:17, 17 Jul 2004 (UTC)

BS 7671 Section 553-01-03 say "Except where Regulation 552-01-05 applies, in a low voltage circuit every plug and socket-outlet shall conform with the applicable British Standard listed in Table 55A" 'Low' voltage here is UK mains voltage. Table 55A give the applicable standards as BS 1363 (with BS 1362 fuses), BS 546 (with BS 646 fuses if any), BS 196 and BS EN 60309-2.

Reg 553-10-04 does say that BS 1363 is prefereable for housold and similar use, but doesn't preclude any of the others - in fact Reg 553-01-05 gives a few other allowable variations. 86.143.244.53 17:11, 26 March 2006 (UTC)([e-mail])

Maybe there's two main standards for domestic internal sockets? there could be one for external use plugs and maybe 110V industrial sockets and shaving sockets? that's five. I'm guessing the two standards in question are this one and whatever standars the old style round pin sockets were ( as seen in my grandda's house) colmd 11:00, 10 Sep 2004 (UTC)

well there are the european industril sockets (usually refered to as CEEs here) which are red blue or yellow depending on voltage (and some other colors but theese are much more rare) and come in single and phase and 3 phase and the 3 phase variety come with and without neutrals. current ratings availible are 16A 32A 63A and 125A

there is also an older british industrial style but i don't think it is seen much anymore

finally i think there is still a standard for two pin plugs although the only 2 pin sockets in the uk tend to be shaver sockets and theese are built to take a huge variety of plugs including europlugs

for normal domestic and commercial power in the uk now the 13A plug is almost exclusively used the peices on the 5A and 15A plugs mention the uk as this was their origian but they are no longer used for normal power applications here (the 5A is used in centrally switched lighting in some homes to avoid idiots overloading the lighting cuircuit and the 15A plug is used a lot in theatre lighting systems where it is prefered over the CEE industrial range because of its smaller size while still being unfused which is an advantage in such situations) --plugwash

BS5733/A is concerned with adaptors which enable BS1363 plugs to be used in Schuko sockets. 213.40.217.126 (talk) 19:25, 5 December 2008 (UTC)

What maximum combined current do double sockets allow?

"The double sockets are unfused, so it is theoretically possible to draw up to 26 amps, although this would not be safe." I don't think this is correct - why would a double socket not be able to safely supply 26 amps? Most ring-final circuits are protected at 32 amps. [e-mail] 15:17, 17 Jul 2004 (UTC)

Five? Wow, that's a lot. Do you have the text of BS 7671 there? If you have the information, incorporate it into the article. — Chameleon My page/My talk 16:22, 17 Jul 2004 (UTC)

double sockets are only required to be rated at 13A total although the decent brands like MK can take a bit more but im pretty sure no brand can take 26A for long periods this is a little known fact and most people i have spoken to agree it is extrememly stupid but it is true(plugwash)

Any twin socket meeting BS 1363 must be able to feed 26A total load continuously, otherwise it doesn't meet the standards - but I totally agree that it would be stupid to do so. 86.143.244.53 17:11, 26 March 2006 (UTC)([e-mail])

Nope, you give the BSI too much credit here. Read section 16 of BS 1363-2:1995 again very carefully: double sockets are only tested with 14 A through the first plug and 6 A through the second. That makes only 20 A test current for a double socket, not 26 A. Markus Kuhn 18:37, 26 March 2006 (UTC)

26amps would be the maximum on a double socket. when designing a circuit diversity is taken in to account ie not every socket is going to be used at the same time to full capacity eg in a domestic setting a ring main would have 100% of current demand on the largest point of utilisation + 40% of current demand of every other point of utilisation ( IEE on-site guide 2002). 26amps would give you a power output of 6.24Kw, far beyond the requirements of most domestic equipment. —The preceding unsigned comment was added by 86.135.226.188 (talk • contribs).

Sure thats the most you can draw but that doesn't mean the sockets are required to be able to stand that safely for long periods. Plugwash 01:24, 20 April 2006 (UTC)

Unswitched sockets

The regs require an adjacent switch where this is not incorporated into the socket

are you sure about this and do you know of any online sources that confirm it? Plugwash 22:58, 17 Nov 2004 (UTC)

Don't know about online source but section 537-04 of BS 7671 requires a 'means of means of interrupting the supply for the purpose of emergency switching' , 'not a plug and socket-outlet' which must 'be installed in a readily accessible position where the hazard might occur'. [e-mail] 15:08, 18 Nov 2004 (UTC)

i've brought this up over at http://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?board=Diy;action=display;num=1100734083;start=0#6 where there are quite a few uk electricans

don't have a definitive answer yet and I don't personally have a copy of the regs which also makes things hard for me to confirm.

feel free to join in the discussion over there if you wish Plugwash 16:31, 18 Nov 2004 (UTC)

The fact that the plug can be removed from the socket provides adequate switching for emergency purposes. The regulations apply to permanently wired appliances (such as cookers, immersion heaters, and storage heaters) where the lack of a removable plug requires a switch to be in place. WLD 14:16, 24 May 2005 (UTC)

There is no regulatory requirement for a switch on a BS1363 socket at all. It has simply become the expected norm. Switches were used on much older pre-BS1363 sockets way back when some areas had DC supplies, because DC doesn't stop flowing when you pull the plug out — it's quite happy to bridge the gap between the socket and the pins with an arc, so you needed to be able switch off the current before withdrawing the plug. This switch became the expected norm, and remains today, although no longer required for its original purpose. There is one place where you shouldn't used a switched socket — that's the electrical supply for a gas appliance. The reason for this is that the appliance must be fully isolated when being serviced — a switch might only disconnect the live side and its presence might encourage a service engineer to fail to properly isolate the appliance. Either an unswitched socket should be used, or a Fused Connection Unit with double pole switch. --81.187.162.107 20:10, 2 August 2005 (UTC) (Andrew Gabriel)

what about a socket with a double pole switch? Plugwash 20:27, 2 August 2005 (UTC)

I regularly observe the risks of socket switches in lecture theatres. Speakers plug in their laptop power supply to make sure that they will not run out of battery during the talk, but forget to check the position of the socket switch (and the power supply LED). They realize that the switch was off only half-way during the lecture, when the operating system suddenly goes into hibernation near the climax of their presentation and they have to reboot in front of over a hundred people. I believe there is a market for unswitched sockets at places where laptops are likely to be plugged in. Actually, lecture theatres should generally use multi-standard sockets (already commonly used in Asia) that also accept europlugs and US/Japanese plugs, because convenience to international travelers with 100–250 V switched power supplies is there much more of a requirement than paranoid child-safety worries. The BS 1363 designers were too worried about domestic safety concerns and the shutters and deliberate incompatibility with other systems can be quite a nuisance elsewhere. Markus Kuhn 10:44, 17 February 2007 (UTC)

I don't think any reputable british electrician would even consider fitting one of those sockets with irregular holes and probablly not compliant with the actual standard for any of the plugs.

There is also the problem (this also manifests itself with travel adaptors) that it would be virtually impossible to make a socket that accepted and correctly earthed both british plugs and those of our closest neighbours. Plugwash 19:49, 17 February 2007 (UTC)

Fuses and misconceptions about appliance protection

As far as I'm aware, the fuse in a BS 1363 plug is NOT for appliance protection. This seems nonsensical, but is actually quite logical.

An appliance that needs fused protection will incorporate this into the appliance itself. These can be low current rating specialised fuses, or thermal cut-outs or circuit breakers. However, the fuse in the plug is there to prevent the cord attaching the appliance to the socket from overheating and becoming a fire risk. Different cords have different current ratings, so a thin and flexible cord will be protected by a lower current rating fuse than the heavy duty cords used for kettles and irons.

The fuse is also not there to protect people from possibly fatal electric shock - it doesn't fail quickly enough in most situations. WLD 10:37, 24 May 2005 (UTC)

edit to fusing section

This edit to the fusing section seems to greatly oversimplify the case. It has always been normal the world over (including in the uk prior to the BS1363 system) to connect say a 3A flex to a considerablly higher rated (15A or similar) socket system. I think the crucial reason for using a fuse with the BS1363 system was too allow for such high rated socket cuircuits to be used safely but your edit implies that all flexes must be protected by a fuse/breaker of same/lower rating than the flex which is grossly misleading (also think of things like pendant drops in lighting etc). Plugwash 11:55, 24 May 2005 (UTC)

I can't speak to the exact question you're addressing here, but I think that the rationale for allowing (say) 15 amp mains circuits but only using a (say) 18 gauge line cord on an appliance is that you really don't have too much need to protect the appliance line cord against a mere overcurrent; faults within the appliance are assumed to be more "short-like" and will blow any reasonably-sized fuse or breaker on the branch circuit (and in many appliances where that might not be true, they have an internal fuse or over-temperature cut-out). By comparison, it's very easy to create an over-current on the branch circuit wiring, simply by plugging in a few too many appliance loads.

Atlant 12:36, 24 May 2005 (UTC)

It may be normal to connect a 3A flex to a socket that is designed to be able to deliver 15A - but it is certainly not safe. If the appliance demands more than 3A but less than 15A, the flex will overheat, causing a fire hazard, and possibly melt the flex's insulation, presenting a shock hazard. BS 1363 'assumes' that the appliance can/will/should look after itself, but overcurrent protection for the flex is the fuse in the plug. Pendant drops do not attach to BS 1363 sockets, but are directly wired to the lighting circuit, which is installed with a heavy enough gauge of wire to carry the rated current. The typical lighting circuit is protected by a 5A fuse at the consumer unit.

WLD 13:43, 24 May 2005 (UTC)

well if its not safe to connect a 3A flex to a socket that is designed to be able to deliver 15A how come practically every country in the world does it as normal practice?! Plugwash 16:31, 24 May 2005 (UTC)

Because they have deemed the risks associated with overheating flexes to be small enough such that the economic cost of changing their electrical systems is considerably greater than the value of the lives saved and property damage avoided by using safer systems. Just because lots of people do something does not make it safe. A good example is the risk of unprotected promiscuous sex compared to the prevalance of AIDS. Anyway, I think your revert of my text has made the meaning incorrect again - a swift search of the Google Usenet archives gives the below article, which explains the situation quite well. The fuse is not there to protect the appliance. If it does manage to protect the appliance, it is incidental to its job of protecting the flex.

WLD 16:58, 24 May 2005 (UTC)

 From: [e-mail] (Andrew Gabriel)
 Subject: Re: Incandescent Lamp Industry Trivia
 Date: 1998/02/11
 Message-ID: <6brl98$[e-mail]>#1/1
 X-Deja-AN: 324042435
 References: <6bg07b$[e-mail]> <[e-mail]> <6bqh7b$[e-mail]><[e-mail]>
 X-NNTP-Posting-Host: cucumber.demon.co.uk [158.152.58.86]
 Organization: home
 Newsgroups: sci.engr.lighting
 .
 In article <[e-mail]>, [e-mail] (Oxyura) writes:
 >In article <[e-mail]>, [e-mail]
 >(Andrew Gabriel) writes:
 >
 >>No. The fuse is there to protect the appliance flex, so that a thin flex for
 >>a table lamp can be safely protected at 3A say, whilst a 3kW heater with a
 >>thick flex would have a 13A fuse.
 >
 >Right on!  Now, as a practical matter, where in the USA can such protection be
 >purchased, either as a plug or as a separate unit for use at the wall outlet. 
 .
 A fuse for this purpose needs to be linked to the flex it's
 protecting, hence we put it in the appliance plug.
 .
 .
 >I have had electronic test equipment damaged because it had to absorb the full
 >15 amps before the main fuse blew.  It is absurd to expect a 15 amp fuse to
 >protect a 20 to 50 watt piece of test equipment.
 .
 Ah - our plug fuse is _not_ to protect the appliance, only the
 appliance flex. If an appliance needs fusing, it must include
 an appropriate fuse on the incoming mains. (Of course, the plug
 fuse cannot fail to provide some protection to the appliance,
 but that's not its purpose.)
 .
 Sometimes, this can cause an appliance to have to have a thicker
 flex than you might think it requires. An example is a fridge or
 freezer which might consume only 90-130W. However, the switch-on
 surge of the compressor requires that it's plug has a 13A fuse,
 and this in turn requires that it have a 13A flex (for fault
 current though, not continuous). I don't think there are any
 other examples like this in normal domestic use though.
 .
 -- 
 .
 Andrew Gabriel
 Consultant Software Engineer

As you all consider this, you also have to consider the introduction of Arc-fault circuit interrupters; they address this very concern about "not-quite short circuit" faults in lamp cords and the like. (They still don't address overcurrent faults, but given the fact that lamp sockets only accept lamps up to a certain maximum wattage, I have a tough time seeing how an "overcurrent" fault can arise in such devices.) I don't know how widespread AFCIs are in European or British practice, but here in the U.S., they're now mandated for a lot of new work (bedrooms, etc.) by the National Electrical Code.

Atlant 16:46, 24 May 2005 (UTC)

Actually, to answer the question "if its not safe to connect a 3A flex to a socket that is designed to be able to deliver 15A how come practically every country in the world does it as normal practice?!" more fully, the thinking is as follows: In continental Europe, the typical domestic electrical distribution is via a branched network from the incoming supply to the sockets in the house. The root of each branch is at the supply, and the overcurrent protection will either be between the branch and the supply, or at each socket. The overcurrent protection is typically a 16A fuse or MCB. If we use a 3A flex to connect an appliance to a socket, the important point is whether, under fault loads, the flex will become unsafe before the fuse blows or the MCB trips.

Flexes are rated conservatively, and a 3A flex can carry subsantially more than 3A for a short period of time, which will (should) be longer than it takes for the fuse to blow or MCB to trip. However, this is only true if the flex is short enough. If it is too long, it will become dangerously overheated before the fuse blows - which is why high-power appliances will typically have short flexes in continental Europe, or have their own heavy-duty supply. So the european practice is to restrict the length of the flex, whereas UK & Ireland practice is to provide overcurrent protection for the flex in the plug. This latter method allows longer flexes and allows higher power distribution via the efficient (in materials use) 32A overcurrent-protected ring main.

WLD 18:10, 24 May 2005 (UTC)

I think we need to distinguish between why the fuse was put there in the first place and the other advantages of having it there.

I don't have sources handy but from what i have read the practice in the uk BEFORE the 13A plug was introduced was very similar to that in the rest of the world, that is in many cases thin appliance flexes would be protected only by a 15A fuse (and often a 15A rewirable at that!). The british ring main wiring system was designed to allow 2 3KW heaters in any two locations plus some leftover capacity for small appliances whilst using as little cable as possible (iirc there was a copper shortage at the time). In order to achive this the cuircuit had to be on a 30A fuse and that in turn meant that fusing at the point of use was needed to avoid a significant reduction in the level of protection offered to appliance flexes. Plugwash 16:42, 27 May 2005 (UTC)

since the system of fused plugs was introduced the practice of choosing the right fuse for the appliance and its flex has been drilled into peoples heads to the point where many think it is vital even though the normal practices in the rest of the world clearly show that its not really needed. Plugwash 16:42, 27 May 2005 (UTC)

I guess it depends on what you mean it's not really needed. My understanding of the above is the British system is somewhat different from the much of the rest of the world and the correct fuse+flex is needed in the British system. Now whatever the reason the fuse+flex design was originally chosen, it appears there are arguably some advantages Nil Einne 01:33, 2 October 2006 (UTC)

the FUSE IS TO PROTECT THE CABLE!!, that is clearly outlined in the standard, and gives local protection to different sizes of cable, something a central fuse cannot do. Also be aware that the fuse does not always blow, if you can form an arc between the L&N , what happends is that the PVC cable burns off and starts an electrical fire, this is why you must use the corerct size of fuse.

Pin insulation

I have some old plugs which state BS 1363 on them, but the pins are not insulated, thus I presume pin insulation was added later to th standard. Pic soon. boffy_b 14:59, July 19, 2005 (UTC)

Yes, I've noticed this too on products up to around the early/mid '80s - I've never seen plugs that old with insulated pins. --Zilog Jones 14:27, 18 August 2005 (UTC)

I've also noticed this.

"BS 1363:1984 (Incorporating Amendmend Nos. 1,2,3,4,5, and 6)", which I have here in PDF, came into effect 31 August 1984. The foreword mentions that is was prepared to make the standard comply with a new IEC plug and socket standard (presumably IEC 884). The 1984 edition describes already a plug with insulating sleves around the live and neutral pin, including an abrasion test for these sleves. Shamefully, British Standards (unlike Wikipedia articles!) do not contain in their very elaborate but not very informative front matter an adequate revision history. Unfortunately, I don't have easy access to a copy of BS 1363:1363, the original specification, to compare. Markus Kuhn 18:15, 17 December 2005 (UTC)

Plug abuse

From the article: Should the cable be tugged from the plug, the designed lengths of the internal wires should mean that the live wire is disconnected first, followed by the neutral and finally the earth. This ensures that an abused plug will fail safely. Isn't the wire with the least amount of slack going to come out first? If the live wire is a smidgen longer than it needs be, then it won't be the first to come out. And the cable grip might take the strain instead - in which case who knows whether the cable will break before the socket gets pulled out of the wall! Jll 11:38, 15 March 2006 (UTC)

Properly wired with all wires routed neatly and not stretched the longer wires should end up with more slack. of course if someone forciblly wires it with equal length wires (i've been guilty of this myself before) the opposite will happen. Plugwash 22:38, 26 June 2006 (UTC)

Disputed section (Criticism of design) Misinformation?

There are 2 points id like to raise. Firstly "continuous running at 26 A will result in a damaged socket" even if sockets are only required to be rated at 13A, this statement is in practice simply not true. The internals of a 2 gang socket are akin to the busing in the old 2 way fused consumer units rated for (if memory serves me) 42 A. It is perfectly legal to have a radial circuit with overcurrent protection rated at 20A served by a conductor of size 1.5mm^2 (MIMS) to suggest any but the most archaic and poorly built sockets will ever be damaged by 26A is simply wrong IMHO.

Secondly "the use of flat, rather than round pins is regarded as a design flaw by some as being inadequate for heavy duty applications" Is it me or is pretty much all busing at pretty much all duties is either flat or rectangular, and I'm no maths wizards but i think that a circle offers the least surface circumference to area ratio of any shape. Flat pins offer a greater surface area for lover impedance contact, and the conductor size, even with poor internal terminations, is more than adequate for handling well in excess of the rated 13A.

Any counterpoints / criticisms or can I remove the offending text?--Pypex 18:07, 5 February 2006 (UTC)

the above is nonsence, if you take apart a plug & socket and LOOK AT THE PHYSICAL AREA OF CONNECTION, yes many plugs have round pins ,but the sockets have a blade used as a connection to them!!, so the area of connection is SMALLER than a B.S plug pin which contacts on atleast 2 FLAT surfaces.

While I'm having a moan. "The at so and so voltage 3Kw will draw in excess of 13 amps" is either intentionally misleading (in the context of the article) or just shows a poor understanding of electronics. If you drop the voltage through a simple load then the power output will decrease exponentially (at 220 volts a 3kw heater rated for 240 will output only 2.5Kw) The same is true of pretty much everything that will draw anywhere near 3Kw (heaters, motors etc) the only exceptions that come to mind things like switch mode PSU's and light bulbs, which could only ever tip the scale near 3kw in an industrial setting. Or in short, resistive loads at a lover voltage draw less power. I've given it a few days now so I'm going to put it right.--Pypex 22:53, 8 February 2006 (UTC)

I dunno about the second one but i'm pretty sure the first one is true dispite being highly surprising. Plugwash 23:26, 8 February 2006 (UTC)

Ive no doubt that the BSI would do something as daft as allow 13 amp double sockets, but to state that drawing 26 A will damage a socket is just nonsense. If there was a double socket on the market not capable well in excess of 26 A I'd be very surprised.

You could come up with special cases like a ring + spur with a plastic patress and a low quality double socket all pushing the limit on the breaker then it could possibly overheat. If people feel it could do with a mention then fine, but it would have to be heavily qualified rather than the original scaremongering.--Pypex 02:11, 9 February 2006 (UTC)

Read section 16 of BS 1363-2:1995 for the temperature-rise limits for double sockets. In a nutshell: No part of the socket must heat up more than 50 K over 4 h during the test. Single sockets are tested with 14 A through one plug, double sockets are tested with 14 A through the first plug and 6 A through the second. The standard obviously does not specify which current will damage the socket, it only specifies which current a socket must survive before type approval can be given. Which current damages a socket depends very much on the individual product (materials used, exact design of contacts, heat conduction, ventilation, etc.) and how/where it is installed. I am sure that it would be possible to construct BS 1363-2 compliant sockets that remain well below the permitted 50 K temperature rise at currents of 30 A or more. You'd have to check the manufacturer's data sheet for the upper safety limits of a specific product, not the standard. Markus Kuhn 15:07, 11 February 2006 (UTC)

Comments by 87.113.11.20

220 volts was (until recently) standard in both Northern Ireland and the Republic of Ireland and yes 220 volt 3kw electric heates were widely available and in many case sold fitted with BS1363 plugs. These heaters would have drawn more than 13 amps on a 220 volt supply (which in any case had an official tolerance figure of +/- 6% and an even greater actual tolerance) And considerably more than 13A when the supply voltage changed to the new European 230 v standard. Its a fact of common experience (in Ireland anyway) that 13 amp plugs on heaters, tumble driers etc often overheat and need replacment. The problem with flat v's round pins is probably more down to wear (in frequently inserted/removed) plugs than considerations of resistivity due to surface area (only speculating on this last point) ?

I was wondering if it would be possible to get some definitive consensus on the disputed section of this article. My points of contention are:

• Non-round conductors provide a larger surface area with which to make contact, thus decreasing resistance.
• Large round conductors are wasteful in AC applications due to the Skin effect
• Decreasing the voltage will also decrease the current drawn through a load, hence a 3kw appliance rated for 240v will output less than 3kw at less than 240v, hence the 13 Amp rating is not exceeded.

--Pypex 00:18, 24 April 2006 (UTC)

Forget about the skin effect in 50 Hz plugs: it is negligible to start with, and certainly so compared to the cable. The voltage/current relationship for the appliance that you give holds only for a simple resistor, not for anything that is actively controlled (e.g., heater with thermostat, centrifuge motor, etc.). Finally, the contact area achieved is more a function of the design of the socket contacts, rather than of the plug pins. There is not much inherent advantage of one pin shape over the other, except perhaps that very flat pins are mechanically less stable. Markus Kuhn 20:46, 24 April 2006 (UTC)

It is my understanding that most loads, especially those drawing anywhere near 3kw are either simple resistors, or can be closely approximated to them. This basically covers all heaters (thermostatically controlled or not), kettles and to a great extent motors. Non linear loads tend to be such things as light bulbs (for which varying voltage is a great source of trouble for manufacturers) and things such as switch mode PSU's, these things don't really ever come close to drawing 3kw. A bit of control gear doesn't suddenly negate ohms law.--Pypex 22:16, 24 April 2006 (UTC)

On a lower voltage, a heater with a thermostat will draw a higher average current but a lower peak current as when its on it will draw less like any other heater but it will be on for a greater proportion of the time. Plugwash 23:02, 24 April 2006 (UTC)

The major issue with the BS1363 plugs when compared to Schuko CEE 7/7 is that Schuko is recessed i.e. you cannot touch the pins at all on the 16A plugs while you're inserting them. BS1363 sockets are flush, so the pins are exposed as they're being inserted. To make the plug safe, the original design didn't use sleeved pins, but rather minimised the contact surface area to just around the tip of the pins themselves. This mean that the pins were not live until the plug was almost fully inserted. The drawback is that the pins can become rather warm under full loading, particularly if the socket's springs have become a little loose with wear and age. Schuko sockets, can have a much larger area of contact, because users cannot come into contact with the pins. Only the small 2.5A flat 'Europlug' has sleeves and this is because it does not have the round front that would prevent you from touching the pins as you're inserting the plug. Overall, the Schuko system is safer from that point of view. It's a bit like an industrial plug, i.e. pins totally kept out of harms way! So, I would agree with the criticism. Also, on 220V in Ireland they do overheat quite regularly. I've seen plenty of evidence of burned sockets. However, they do the exact same on 240V in the UK if the socket is even slightly loose.