Something interesting happened this morning.

I had a severe short caused by a cable being dammaged on my laptop power supply (it was squashed by a filing cabinate drawer)..

Simple 2 core cable, and due to the type of flooring there was obviously no leakage to ground so the RCD wasn't activated. (It was squashed between a plastic foot and plastic flooring so was fully insulated and there was no ground cable to cause a ground fault)

Noticed a slight burning smell and my desktop computer, printer etc went off as there was no power at the socket the 20amp MCB on the panel tripped out.

Worryingly or interestingly, im not sure which but the 3amp fuse in the plug was still in perfect working order!!!

Dud fuse? or just slow blowing?

Seems very inadequate protection on a 35 amp ring!!!

djk,
Does your laptop power supply have a box with a Transformer in it, to step down the voltage?, sometimes there is also a 3AG type fuse in this box, that protects the Primary side of the Transformer, but it sounds like if there was one, it never blew either.
It sure sounds strange how that 3A fuse never blew, mind you, the MCB at the Panel may have had a better Time/Current characteristic than the fuse, which I assume was an HRC type?.

Some of the BS1362 fuses do seem to be rather reluctant to blow. I assume your MCB was a type B curve?

I've done a quick search to see if there are any time/current curves for BS1362 fuses online, but I couldn't find them. Here are the curves for BS1361 Fuses , the type used in British consumer units.

Has anyone tested this on a ring circuit?

Yeah, it's a B type MCB (Siemens to be precise)

Unlike an equivilant house in the UK this one has 9 X 20A radials rather than a couple of rings.

Wonder would that have blown a ring MCB?

If a 3A fuse stays in working order on a 20A MCB, what would happen to a 5A fuse on a 32A MCB? Or a 13A fuse?

From Panelcomponents:

The fuse installed in all British plugs conforms to BS 1362 ("General purpose fuse links for domestic and similar purposes…"). The size of this fuse is 6.3 x 25.4mm. It has a breaking capacity rating of 6000A and is constructed with a sand-filled ceramic tube. The time-current characteristic on this family of fuses is not necessarily consistent with any other international standard, but it appears to have most of the characteristics of a fast acting fuse.

Here is an experiment: Does a 13A fuse blow on a modern ring?

By the way, why are the fuses 3A? The smallest wire size is 0.5 mm² which is good for twice that.

[This message has been edited by C-H (edited 08-17-2003).]

Hmm.. I see another experiment for ECN testing labs, British branch coming up!

I don't know why the committees decided upon 3A as a standard rating, except that it's convenient for most small appliances up to around 750W.

These days, to simplify things for householders the recommended BS1362 fuse sizes are just 3 and 13A, even though many other sizes are available (most commonly 5A in general stores).

The original scheme, however, recommended that plugs be fitted with a 2, 5, 10, or 13A fuse as appropriate.

Paul,

I remember seeing 16amp fuses to that spec on sale here in the 1980s !

They subsequently disappeared!

3KW appliences can pose problems here with 13Amp fuses particularly where the voltage is very definitely 220V.

I've also seen people simply wrap the live wire around the live pin by-passing the fuse.
Solder it onto it.

or even open up the fuse and replace the fusewire inside with a 16amp type instead!

I've also seen plugs with a peice of heavy guage cable saldered into the fuse carrier as the fuse kept blowing with appliences like tumble dryers.

Bypassing the fusing over here would generally only expose you to 20Amps though. so not quite as dangerous as in the UK.

Ideally here 3KW appliences need to be connected to a schuko or BS546 plug as 13amps is only barely enough.

It's become less of a problem as newer appliences are rated for 13amp max ( at 230V)
Older ones were designed around 16amp 220V so the maximum wattage is a little lower than it was 10+ years ago.


[This message has been edited by djk (edited 08-17-2003).]

[This message has been edited by djk (edited 08-17-2003).]

A few strands stripped from a piece of flex and wrapped around the fuse clips is another trick.

I've never seen a 16A fuse designed in plug size (1 x 0.25"). Such a device would certainly be non-compliant with BS1363, which specifies 13A maximum.

Coincidentally, some friends of mine had a chip fryer blow out a fuse yesterday. The socket was only on a 15A radial circuit, but the BS1361 consumer unit fuse opened leaving the 13A plug fuse intact.

There's not a big enough difference to guarantee discrimination there, of course, but it does point toward rather different curves for BS1362 fuses.

Note for our friends who aren't familiar with the British Standards:

BS1361 specifies the fuses used in distribution panels, rated 5, 15, 20, 30A and in increasing physical size to prevent overfusing.

BS1362 is the specification for the ceramic-bodied fuses used in our 13A plugs.

BS1363 is the specification for the 13A plugs and sockets themselves.

This has always a worry to me,, here in the uk the flex that supplies electric lawn mowers is always 2 core.. if the blade slices thru the flex with out any contact to earth the RCD will remain on, it is unlikley that the fues would blow because of the speed of the blade,,

the worst that could happen is the gardner with his wellies on could place his finger on the bare flex and recive an electric shock, straight across live and neutral,, rcd would still not trip..

i feel for the cost differance manufactuers should use 3 core flex,,

Thoughts??

I agree Paul, but what has always concerned me is that there is no guarantee the mower is on an RCD in the first place. Further, excessive dampness ingress can bypass the double insulation !

ermm never thought of that..

but your right we forget about dampness.. the only good thing these days,in most new houses the ring mains are rcd protected..

One thing which concerns me is the way that the RCD is marketed here.

Obviously its use is a good thing when outdoor power tools are involved, but I've run into many people who have been given the impression that with an RCD there is no way they can receive a dangerous shock.

They seem genuinely surprised when I've explained that in certain situations it would still be quite possible for somebody to be electrocuted even with an RCD in line.

Blame Esther Ranson..

i remember when she did her programme (thats life) she pushed RCDs or in those days ELCBs,,the electrician i served my time with rang the BBC to say that these may not prevent you having a shock in every instance..

they said thanks for the call

by the way,,, how do keep you pc to remember your pass word and user name.. i have to keep typing them in

PaulC -- Under 'preferences' at the page top under the 'post new topic' button, you are given the option...

"Store Username & Password in browser memory for 1 year (otherwise you will have to type your username and password once per browser session)" yes no

Ah yes.... They probably weren't able to squeeze in anything more about the subject, otherwise they would have had to cut out something like the beer-drinking snail or the water-skiing dog.....

RCDs are GFCIs?

Karl

Yes. RCD=Residual Current Device, which is equivalent to the GFCI.

I'll post a more thorough description in the Earthing Systems thread.


[This message has been edited by pauluk (edited 08-29-2003).]

2 core flex for lawnmowers????? Ugh!
In Schukjo countries there aren't any 2core extension cords any more, so people are simply forced to use a 3core cord with Schuko plug and trailing socket.
Still there are ugly stories about cut cords. The neighbour girl at my aunt's (guess she was about 14 back then) was mowing the lawn (probably lazy 'cause she didn't want the job) and cut right through the cord. My aunt said she flew right through the air from the shock. What I don't know though is how the current got into the handle of the mower, since they're usually plastic covered.

Just to let you know, that one of the discount supermarkets in my area, according to the promotional leaflet dropped through my letter-box, will next week be selling extension leads for heavy duty use, with the following comment!!!
"with 16amp fuse for use with appliances up to 3.5kw"
The picture clearly shows a BS1363 type plug!
Comments any one ?

Hmm..... I don't doubt that the well-engineered BS1363 plugs and sockets (e.g. MK) would carry 16A without any problems, but I don't sede this as a good path to be taking. Let's face it, some of the "el cheapo" contract-range stuff gets warm with a 10A load on it due to poorly designed contacts.

Have you thought about writing the supermarket and explaining that the BS1363 specification doesn't cater for over 13 amps?

I've just noticed that this leaflet has two pictures, one for a extension socket with surge protector, and the CE and BSI kite-mark symbols next to image (No mention of "16amp" on this item).
The other image, for the 2 "16amp" items, shows a picture for a 4 way/15mtr cable item, and a picture of a 1 way/25mtr cable item. However, the symbols next to these are the CE and the German GS symbol, not the BSI symbol.

[This message has been edited by Plugman (edited 03-20-2004).]

It's possible that their information is incorrect and that they've quoted schuko stats.

I wouldn't trust BS1363 with 16A loads I've seen far too many slightly burned sockets despite the sturdy pins the sockets contacts don't appear to give a lot of surface area and the pins can get warm, particularly on cheapo sockets where they loosen up with use.

Regardless how high quality the plug is no one can be sure what kind of socket it's being plugged into.

I also suspect that as schuko 16A plugs are fully recessed and do not need sheathed pins that the surface area of the pin used to make contact could be signifigantly larger than BS1363 which has most of the pin shrouded in plastic and only makes contact when the plug is inserted very deelply into the socket.

Keeping the pins completely out of reach has a lot of advantages. The smaller Europlugs only carry tiny loads so the shrouding doesn't really matter. I notice that many heavier class II appliences, eg vacuum cleaners use contour plugs that keep the pins out of reach while inserting too... same as schuko just witout the ground contacts.

Similar principle used by Ceeform (CEE 17) too except the plug is "recessed" rather than the socket allows for quite a lot of contact area on the pins.

Recessing BS1363 at this stage would be impossible as there is no standard plug shape. They're all slightly or even substantially different ranging from square to contoured.



[This message has been edited by djk (edited 03-20-2004).]

Thanks to Plugman for scanning and sending me the ad in question, which is from the Lidl supermarket:




[This message has been edited by pauluk (edited 03-20-2004).]

djk, you may be interested to know, that this supermarket has branches in Eire and N.Ireland and is now offering this item as a special offer at Euro 11.99, on it's Irish website.
The wording is a little different from the U.K. website version, but the following comments are made:-
"16A,250V,max 3500W - Intertek/GS certified"
I hope you're right about it possibly being incorrect info attached to the relevant pictures, otherwise these "16amp" items will be on sale all over U.K./Ireland !

[This message has been edited by Plugman (edited 03-20-2004).]

I suspect they've accidently posted / printed Schuko details.

Where would you even get a 16A fuse to BS1362 specs?


I will go take a look later


[This message has been edited by djk (edited 03-21-2004).]

I hate to point out the obvious, but there is no fuse in a shucko plug. Makes a simple typo less likely. The Lidl ads for schuko extension I've seen only have the CE mark.

Good point C-H. Maybe Lidl is just trying to get Brits used to seeing 16A in an attempt to introduce Shucko here.

LOL!

It could also be that Lidl has made a version of the British plug that can be used in Germany, intended to replace schuko

Intertek is connected to Semko and now have offices in the UK. As I understand it they issue the GS mark and maybe the S mark for British products. Someone had an example of a Nemko-marked BS1362 fuse some time ago. On Interteks website you can search for S and ETL-listed products, but not GS.

[This message has been edited by C-H (edited 03-21-2004).]

Article about testing of British wiring accessories, like plugs and sockets.
http://www.uk.etlsemko.com/en/popup_about.asp?page_id=71&type=fa

Given the fact that Intertek are headquartered on Savile Row, one would expect them to tailor a solution to suit you needs. Sorry, couldn't resist...

[This message has been edited by C-H (edited 03-21-2004).]

Euro plugs are designed for a max. load of 2.5A. Anything heavier has to be fitted with a contour plug. However, some el-cheapo (mostly Italian market) hairdryers are fitted with Euro plugs. I've got a 1800W hairdryer with Europlug at home, it even has the "250V, 2.5A" embossed.

I thought that Italy has a higher rated 2-pin Europlug-like connector too ? 10 A ?

Contour plugs don't normally fit italian sockets as the pins are too fat for the lower rated sockets and not spaced far enough apart to fit into a 16A outlet.

I have seen schuko/italian comination outlets in italy though. Quite a smart design. It's basically a normal schuko socket with a hole at the centre that accepts the ground pin on the 10A italian plugs.

I really can't see the non-CEE 7/7 systems, other than the UK/Ireland (because of the ringmains quirk) surviving. With the addition of various Eastern European countries, all of which use Schuko or French sockets, the non-CEE 7/7 countries are in a total minority. CEE 7/7 is well established as the defacto European standard. The Danish, Swiss and Italian systems really don't offer any advantages. If Switzerland or Denmark for some reason wanted to keep polarised outlets they could always adpot the French UTE / CEE 7/V system rather than the unpolarised German VDE CEE 7/IV.

I honestly can't see why the UK and Ireland can't simply use fused schuko outlets either. There's no reason why companies like MK etc couldn't produce sockets that conform to CEE 7/7 and also maintain the safety features of a British outlet. Manditory shuttering, built in switches, even little neon lights to tell you that they're on Just put a 16 amp fuse into them on the live side.

UK wall boxes are an unusual, non-European, design anyway so only BS CEE 7/7 outlets would fit and non-fused imposters would be very easy to spot. Just insist that they have some clearly identifiable moulding like "For use in UK & Ireland" visible on the inside of the outlet.

There would be no reason to phase out ring mains nor to have fused and non fused outlets.. Just like today, we use fused plugs regardless of wheather they're plugged into radial or ring circuits.

Electricians are not going to start installing unfused sockets on ringmains and DIYers can already install a whole variety of unfused outlets directly onto ring mains should they be stupid enough (BS546 or just make a trip over to callais and buy a French outlet or two... or as I've seen here once or twice; blue CEE 17 sockets with no fuse on a ring main in a shop!) So I can't see why there would be any increased risk.

The vast majority of UK appliences are not properly fused anyway. From what I can see, 13A fuses are popped into many plugs for TVs, VCRs, Radios etc.. which isn't really a huge problem as they're all designed to be plugged directly into 16A sockets anyway.

----

[This message has been edited by djk (edited 03-22-2004).]

[quote]I thought that Italy has a higher rated 2-pin Europlug-like connector too ? 10 A ?[|quote]

Obviously they don't. All "ungrounded 10A plugs" I've seen were actually Euro plugs instead, with the 2.5A max. In fact they'd only need to make them rectangular instead of the weird Euro design and they wouldn't fit Euro sockets any more, but for some reason they don't.
However, Euro outlets are pretty rare.
And considering what rubbish is sold openly today... I've seen lots of taps that convert a Schuko socket into 3 Euro sockets. However, the face of those adaptors is more or less flat, so it also takes 2 ungrounded plugs, or with some brute force probably even Schuko plugs! No approval marks visible, manufactured by Kopp.

Ragnar,

look here http://www.feller-at.com/English/Feller-UP-E.htm

It seems it does exist

I never found anything particularly wrong with the Italian way of doing things provided you you don't try to force a schuko or contour plug into one of their 10A sockets

It does seem as though in the long term, CEE7/Shucko will become the de facto standard across Europe.


Hence the simplification of the specified fuse ratings for the public. The original specs told people to use a 2, 5, 10, or 13A fuse as appropriate. These days, instructions just say to fit a 3A or a 13A fuse.

It has never been helped by the fact that for many years BS1363 plugs were sold with a 13A fuse already fitted. Plugs with a 3A fuse pre-installed are on sale now, but so many people have no idea what size fuse to use anyway. "It's a 13A plug, so it needs a 13A fuse" seems to be the most common view.

Fused sockets would certainly be a way to introduce Shucko with U.K. rings, although I think that new construction would probably be better just going with radial circuits anyway (yeah, I know, I'd like to see rings disappear! ).