Wiring a plug

[ebee]

I have looked on you tube to see what offerings there are for instructions on how to wire a UK plugtop.
Some seem ok but how many put the emphasis on getting the earthwire long enough to avoid pull out until last?
They all (most) seem to follow the rule of making the earthwire long but IMHO not always long enough.
I was taught to make them long enough to snuggly fit against the long curve portion of the space so that they would only pull out once the live conductors are well clear of the terminals.
Line should be short and no slack (or extremely little at best) N same or preferably ever so slightly longer , the E a good way behind .
That way Line comes out first , very closely followed by N (or even at the same time) the E once L & N are clear of terminals (hopefully).
Even that little card that manufacturers put on the plug don`t seem to help with decent dimensions.
I don`t think I`m being pedantic but merely this was how it should always be done.
It is second nature, for me, to do it this way and was taught at school back in my youth and retaught at most apprenticeships etc as far as I can see.
It does not always seem to be taught nowadays.
Of course there are often plugs put on (even sometimes by electricians) that are made off poorly in other ways too.
PS - when I`ve twisted the flex I often double it on the smaller conductors too, in order to make a decent mechanical and electrical join.

 

[ericmark]

Are school children still taught how to fit a plug? Since 1987 portable electrical items offered for sale in the UK need to have the UK BS 1363 plug fitted, if using an adaptor it can't be removed without a tool, so in the main people under 40 years old have never needed to fit a plug.

My children are a little older than that, and I remember the problem after teaching my children how to fit a plug and select fuse size, when they told the teacher at school they had got it wrong. Not as bad as when the teacher said there were two types of transistor does any one know what they are, and my son said field effect and bipolar, and was told wrong, and he did not correct the teacher but burst out laughing when teacher said they are PNP and NPN.

But this has always happened due to expecting teachers to teach outside their field of expertise, and not helped when the 'A' level book shows a fluorescent tube diagram without the ballast.

So the question is should things be taught in school which are wrong, and then the student has to try an remember which was the correct way? Even in industry people are taught what to do with electric leads on building sites and given the wrong heights for crossing walk ways and roads.

I know at work, the people I work with are not permitted to fit a plug, they have the ability, but health and safety rules mean they need to be on the data base as at least an instructed person before they can do anything with electric, it is the same with most other things, I have to do a course and test to use a lawn mower. Pain in the neck when I can sharpen a drill, but not allowed to use grind stone.

I do however see a problem where any tom dick or harry can publish a web page to show people how to do something which clearly they don't have a clue how it should be done. At least with a forum some one else can post after to say NO it should not be done that way. But also it changes country to country, and over time, so black is used for line in 120 volt countries, and neutral with 230 volt countries, one only knows where the black goes, after seeing the other colours, is it with a white or brown wire? Same with blue, if with a brown it goes to neutral, but with red and yellow it is another line.

We all know three core and earth single phase 230 volt should be three browns, but far easier to work with if brown, black, and grey, and I have yet to see yellow three core flex with brown, black, green/yellow, they seem always to be brown, blue, green/yellow, but there is no neutral with 110 volt site electrics. Why the brown, blue, green/yellow is even made with a yellow outer I don't know?

So how do you stop people giving out wrong info? I have enough problem when jumping in a car working out what speed I can travel at, is the 20 MPH sign repeated or the 30 MPH repeated, depends if in England or Wales, seems against the law to repeat the 30 MPH sign in England not a clue why, but has to be repeated in Wales. So I play safe, street lights with no sign I travel at 20 MPH it same with all things, when one changes the rules. But since plugs always fitted now, it hardly matters.

 

[SUNRAY]

Are school children still taught how to fit a plug? Since 1987 portable electrical items offered for sale in the UK need to have the UK BS 1363 plug fitted, if using an adaptor it can't be removed without a tool, so in the main people under 40 years old have never needed to fit a plug.

My children are a little older than that, and I remember the problem after teaching my children how to fit a plug and select fuse size, when they told the teacher at school they had got it wrong. Not as bad as when the teacher said there were two types of transistor does any one know what they are, and my son said field effect and bipolar, and was told wrong, and he did not correct the teacher but burst out laughing when teacher said they are PNP and NPN.

But this has always happened due to expecting teachers to teach outside their field of expertise, and not helped when the 'A' level book shows a fluorescent tube diagram without the ballast.

So the question is should things be taught in school which are wrong, and then the student has to try an remember which was the correct way? Even in industry people are taught what to do with electric leads on building sites and given the wrong heights for crossing walk ways and roads.

I know at work, the people I work with are not permitted to fit a plug, they have the ability, but health and safety rules mean they need to be on the data base as at least an instructed person before they can do anything with electric, it is the same with most other things, I have to do a course and test to use a lawn mower. Pain in the neck when I can sharpen a drill, but not allowed to use grind stone.

I do however see a problem where any tom dick or harry can publish a web page to show people how to do something which clearly they don't have a clue how it should be done. At least with a forum some one else can post after to say NO it should not be done that way. But also it changes country to country, and over time, so black is used for line in 120 volt countries, and neutral with 230 volt countries, one only knows where the black goes, after seeing the other colours, is it with a white or brown wire? Same with blue, if with a brown it goes to neutral, but with red and yellow it is another line.

We all know three core and earth single phase 230 volt should be three browns, but far easier to work with if brown, black, and grey, and I have yet to see yellow three core flex with brown, black, green/yellow, they seem always to be brown, blue, green/yellow, but there is no neutral with 110 volt site electrics. Why the brown, blue, green/yellow is even made with a yellow outer I don't know?

So how do you stop people giving out wrong info? I have enough problem when jumping in a car working out what speed I can travel at, is the 20 MPH sign repeated or the 30 MPH repeated, depends if in England or Wales, seems against the law to repeat the 30 MPH sign in England not a clue why, but has to be repeated in Wales. So I play safe, street lights with no sign I travel at 20 MPH it same with all things, when one changes the rules. But since plugs always fitted now, it hardly matters.

One of the problems is teachersmay not know what they are teaching, they are trained to teach the curriculum from the documentation supplied to them as required. So, if the document says there are 2 types of transister then the pupils are taught there are 2 types of transister, however we all know transistors come in silicon, geraniums from the garden, FET, bipolar and in N & P versions of each... oh what about UJT's and... too?

A little while ago My grandson tried to tell me I was using an illegal extension lead as round pin plugs had been banned in the 60's and quite explicit with the details. I suggested he asked his science teacher to look at the stage lighting system and later I got into an email exchange originated by the teacher.

 

[ebee]

Yes i welcome those comments by Ericmark & Sunray, It is the age old teaching wrong, because a teacher is a teacher they are looked upon to know everything about everything they teach and sometimes their knowledge is not quite right, in fact sometimes quite wrong, this has always been the case and difficult to minimise in practice. I believe that, as a whole, teachers do try to get it right.

Then, traditionally, you have the written word. Very powerful in books and newspapers. In fact I used to often hear the statement " ... and it`s there in black and white!" as if being written it must be absolutely true, it can`t be wrong because it is written in a book.
Books and writings have been a great way for our authors to pass on some great theories, experiments, proofs etc and have contributed to our wealth of understanding. But, they can get things wrong, sometimes very badly.
A very few years back, I noticed someone coming up with incorrect statements and backing up those statements as valid because they were a published author in Electrics.
Well anybody can pay a publisher to publish their books and they can then give them away or sell them cheaply if they want to. It does not make them valid.

Then, in the modern era, we get tinternet, Folk putting their ideas out as fact, they become folklore.
It irks me that some of them have incorrect ideas and bad teachings and can be interpreted as facts and not challenged.
In fact, at least one tinternet author contributes on here on this forum, they do make some brilliant you tube teachings that are helpful for the ordinary person and electricians alike. Well done that man, I says, please continue with your excellent articles, many thanks for all of your hard work.
It`s just unfortunate that some of the other contributors, less correct, get their articles on you tube etc and some then some other folks follow them to the same extent as they follow the great and the good.

One thing I had noticed, and the reason I started this thread, was we are not taught how to wire a plug like we used to be . Is this progress or not? As Eric pointed out, perhaps we do not need to be as much as we used to because most things come ready fitted nowadays.

 

[ericmark]

Unless some thing goes wrong, I would not open a plug at home, of course I have not wired them all up, and if some one has swapped brown and blue likely I would not know.

What we need is an easy fast way to test, unlikely I am going the remove the plug top to view inside. Out of interest I tried with my non contact voltage tester which shows 4 levels of voltage detected to see what it did when items were switched on/off, with the idea it would show very easy if line - neutral were reversed, however it showed a wall as being line, and also all the 5 volt DC supplies to my Nest Mini speakers.

On an extension lead switched on at the wall 4 bars, but switched off still on bar, because it does show one to four bars, one can see a change, but this with no indexation as to how strong the signal is, must be next to useless. OK my tester at £35 was not expensive, it is a handy quick to use tool, and testing an extension lead it does show 3 bars near neutral or earth and 4 bars near the line, but still rather a hit and miss method to test for line - neutral reversal.

Socket tester would be better, but when I did a google to get the picture, this one priced at £61 that's a silly price. And the instructions

really? Even before the 5% extra for safety a ring final was 1.44Ω at 1.8Ω it is about right for a 25 amp type B with 2% for safety. I see nothing in the instructions about being only valid for 20 amp radial circuits using a B20 MCB clearly designed to test 15 or 16 amp sockets not for BS 1363 type.

I remember being told to write out detailed instructions on how to make a cup of tea as an exercise in programming a PLC, OK clearly we would not in real terms use a kettle which needs lifting up, and repositioning before tilting it to poor, but to write instructions is very hard, which can't be miss understood.

As a young lad my son saw this sign and said see I told you dad it's a cycle track, I said that means no bikes, he said not this sign means no bikes, I could see his logic, how can the two signs mean the same? As to this answers on a post card. But my point is how can one write instructions in British language which are not ambiguous. Beware of the man eating haggis etc.

I am sure everyone has been asked how to do something, and when one has seen it done you have said that's not what I meant. If the red circle means no, and a line through it means no, then this is a double negative so means bikes are allowed, rather a stupid sign. But when we shout NO NO don't do that, do we mean you should do it?

OK I do it with my wife, you don't want a cup of coffee do you, to which she would answer yes, so I would not make one, but she has got wise to that now, so it is no I want one.

Can you imagine trying to translate BS 7671 into Welsh!

 

[JohnW2]

I was taught to make them long enough to snuggly fit against the long curve portion of the space so that they would only pull out once the live conductors are well clear of the terminals. .... Line should be short and no slack (or extremely little at best) N same or preferably ever so slightly longer , the E a good way behind .
That way Line comes out first , very closely followed by N (or even at the same time) the E once L & N are clear of terminals (hopefully).
..... I don`t think I`m being pedantic but merely this was how it should always be done.

As you say, that's what is taught, and I therefore wouldn't class your comments as 'pedantic'.

However, as we know, being 'what has always been taught' (or 'what has always been done') is never a guarantee that some is rational or necessarily even sensible 'correct' - in some cases, it may transpire that one is just dealing with a long-established and perpetuated 'myth'..

At first sight, the concept of trying to ensure that the earth ';always pulls out last' sounds very reasonable and I think that (probably just like you) I have always accepted that concept without questioning it.

However, now that you have raised the issue, I've tried to actually think about this and, probably maybe because I have 'missed something', I'm currently trying to think of any scenarios (even very improbable ones) (at least 'single fault' ones) in which a significant hazard would arise even if the earth didn't 'pullout first' ... what scenarios am I missing, and how common are they?

Kind Regards, John

 

[JohnW2]

If the red circle means no, and a line through it means no ....

Unfortunately, to add to the potential confusion, although a red circle usually means that, it doesn't always - unless, that is, you believe that, say, this one means that one is not allowed to drive at 40 mph ...

 

[ericmark]

This shows the problem even better.

 

[ebee]

However, now that you have raised the issue, I've tried to actually think about this and, probably maybe because I have 'missed something', I'm currently trying to think of any scenarios (even very improbable ones) (at least 'single fault' ones) in which a significant hazard would arise even if the earth didn't 'pullout first' ... what scenarios am I missing, and how common are they?

Hmm, not common but the concept of whatever is disconnected the earth must not be unless all others are , would prevent any unearthed metal on a live appliance sort of situation. I think we would rather that our unearthed fridge/washer had no L or N connected if earth wasn`t. So I suppose it makes sense. Like you I had just accepted it but without thought to likelihoods

 

[ebee]

Before speed cameras the red circle number meant do not travel less than 10mph above that number or everyone else will tailgate you and honk the horn.
Oh and those 20mph signs still mean 30 mph target or above.

I used to have a little habit of not exceeding the speed limit for a while, oohh it did annoy folk!

 

[JohnW2]

Hmm, not common but the concept of whatever is disconnected the earth must not be unless all others are , would prevent any unearthed metal on a live appliance sort of situation. I think we would rather that our unearthed fridge/washer had no L or N connected if earth wasn`t.

Sure, hence my caveat about 'a single fault'. Conductors being pulled out of plugs and cases of appliances 'becoming live' are both very uncommon events, so that for both those faults to be present simultaneously would presumably be ;extremely improbable'

So I suppose it makes sense. Like you I had just accepted it but without thought to likelihoods

Indeed - but it does illustrate how we can 'just accept things', without perhaps thinking enough about the "why"? Two oft-quoted examples are 1.5mm² cables in lighting circuits and 6mm² (or even 10mm²) cooker circuits - in both cases (certainly the former) seemingly for no better reason than "that's what we've always done"!

 

[morqthana]

Since 1987 portable electrical items offered for sale in the UK need to have the UK BS 1363 plug fitted,

Doesn't have to be moulded though, does it?

 

[morqthana]

A little while ago My grandson tried to tell me I was using an illegal extension lead as round pin plugs had been banned in the 60's and quite explicit with the details. I suggested he asked his science teacher to look at the stage lighting system and later I got into an email exchange originated by the teacher.

An interesting tale of "teacher says" interaction

 

[ebee]

Sure, hence my caveat about 'a single fault'. Conductors being pulled out of plugs and cases of appliances 'becoming live' are both very uncommon events, so that for both those faults to be present simultaneously would presumably be ;extremely improbable'

Indeed - but it does illustrate how we can 'just accept things', without perhaps thinking enough about the "why"? Two oft-quoted examples are 1.5mm² cables in lighting circuits and 6mm² (or even 10mm²) cooker circuits - in both cases (certainly the former) seemingly for no better reason than "that's what we've always done"!

Yes I do 6.0 T & E for cookers
Rewireable fuses aplenty, then on 30A MCBs then 32A MCBs.
Years ago 4.0 was not much less than 6.0 , sometimes more expensive because less common so that`s one reason.
One more reason is less different sizes to keep in stock too.
4.0 was not well favoured for radial circuits by lots of us although some did use it.

1.5 was pretty common many years ago on lighting circuits then copper costs went sky high so 1.0 became norm to many if the circuit allowed it (most domestic lighting circuits did) and it`s easier to use so 1,0 eventually became quite common.

Result, the common sizes I bought by the 100m reel and always made sure I had plenty were 1.0, 2.5, 6.0 T & E and 1.0 3c & E and bonding was 6.0 then became 10.0 later on, even later 4.0 earth wire for supp bonding.
Keep stock down whilst keeping plenty of what I needed.

 

[ebee]

An interesting tale of "teacher says" interaction

Reminds me of when we were taught x/x = 1 then I threw a spanner in the works and asked "what if x=0?" I concluded that 0/0 = anything on the basis of an object moving at 0 miles in 0 seconds could be moving at any speed 1mph, 1000mph or speed of light and 0/0 is correct for all speeds.
However a number divided by 0 is anything and everything in other words infinity which is an impossibillity.
Remember the early calculators , Sinclair Cambridge, you tried to divide any number including zero by zero and the display tried to go round and round on every digit, great fun at the time.