Author Topic: How To Wire a Plug  (Read 26790 times)

Offline Darren

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How To Wire a Plug
« on: July 20, 2009, 07:17:23 PM »
Usual disclaimers, this is how I do it and I never put the other end into the mains electricity supply. And I'm not suggesting you do either...
I just wire plugs up for the fun of it... :) :)


Ok, I bet you are all thinking "What the f***"

But the truth is not many people actually know how to wire up a simple plug properly, even though they may have done it many times. Even many electricians get it wrong..!!


This example is for a 3 phase lead, but the principles apply for ordinary domestic 13A three pin plugs that you use at home.

First you need to strip the insulation from the lead to expose the copper wire within. If you knick the copper, even if only slightly then you need to cut back and start again.

Do not knick the wire..... :poke:

If you have solid core then you can skip the next step. If you have multistrand as shown here then twist the strands between your fingers, flux and solder as shown.
This is because when you clamp the wire in the plug the fine strands can break thus reducing the capacity rating of the cable. The solder toughens then up into a solid mass.



Notice how the earth wire is much longer than the others.
This is very important and it is what most people get wrong. Making this mistake could cost you your life.  :zap:



The reasoning is this, and applies more in a domestic situation that anywhere else.

Cables get tugged regularly as part of their normal service. Be it a hoover, radio or whatever. Some items get well and truly tugged by their cords. Eventually the connections work loose and no matter what comes out first the earth should always be the last....!!

The earth won't come out cos the appliance will stop working first, but at least it's still earthed while that live wire is flapping about....!!!
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Offline John Hill

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Re: How To Wire a Plug
« Reply #1 on: July 20, 2009, 07:32:32 PM »
Ummmm.... did you remember to thread the cap on the cable before wiring the plug? :coffee:
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Offline Darren

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Re: How To Wire a Plug
« Reply #2 on: July 20, 2009, 07:41:30 PM »
 :lol: :lol: :lol: :lol:

Yep..... :thumbup:
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Offline Bernd

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Re: How To Wire a Plug
« Reply #3 on: July 20, 2009, 08:41:27 PM »
Darren,

I was told once to not solder the stranded wire because if there is any vibration it will crack and break eventually. How true this is I don't know but it does make sense.

Bernd
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Offline foozer

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Re: How To Wire a Plug
« Reply #4 on: July 20, 2009, 08:57:05 PM »
Not my favorite chore, only thing I ever remember for normal house wiring is "Black to Brass and Green to Ground." If I knew where the other went I could get rid of the candles.

Robert
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Offline Darren

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Re: How To Wire a Plug
« Reply #5 on: July 21, 2009, 05:18:05 AM »
Never heard of that one Bernd?

I doubt it's true as solder is soft. But what could happen is the strands break where the solder ends. But this is only if the cable is wiggled backwards and forwards. As it's held by the plug clamp this is not likely to happen.

If you don't solder or put a crimp on the wire the fastening screw breaks some of the fines wires as you tighten it. Not only reducing the amperage rating of the wire but you might also get some loose strands of wire floating about.

The real point of putting the post up was to highlight how the earth wire should be treated. That's the important bit.. :thumbup:

Earth is the most important wire in any circuit..... :zap:

« Last Edit: July 21, 2009, 06:32:32 AM by Darren »
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Offline John Hill

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Re: How To Wire a Plug
« Reply #6 on: July 21, 2009, 05:26:10 AM »
Darren, I was taught to strip twice the required length and to double it back so that there was twice the thickness in the clampy bit.

Too right about the earth, the same guy taught me exactly what you described and for the same reasons.
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Offline Darren

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Re: How To Wire a Plug
« Reply #7 on: July 21, 2009, 05:35:51 AM »
Hi John,

I was taught the same when I was an apprentice. One day I had a warning from an inspector on one job so I stopped doing it.

Another inspection much later I had another warning for not doing it.. :doh:

I don't think it really matters just so long as the wire is properly clamped... :scratch:
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Offline John Rudd

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Re: How To Wire a Plug
« Reply #8 on: July 21, 2009, 06:08:58 AM »
I also was told not to solder the wires.....Clamping down with the screw is fine but the soft soldered wire is likely to 'creep' and over time can work loose causing loss of contact..

I've never done this in practise so cant comment on the validity of what I was told...

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Re: How To Wire a Plug
« Reply #9 on: July 21, 2009, 06:17:58 AM »
Darren,

Many years ago when I worked for a computer peripherals manufacturer, we had a directive from the people on high to check every 240 volt 3 pin mains plugtop in the factory. The company had just been bought out from it's American parent company, and was now under UK engineering control, instead of American engineers being on the shop floor.

As you can imagine, over 1,000 employees, and any personal equipment they brought into the factory had to be checked as well, from tape players to hair curling tongues.

It took two of us, full time, over a month to sweep the whole factory clean. Separate every plugtop and cable, cut all the wires to correct length, so that if the cable was yanked, first to go was live, then neutral and finally the earth. Solder them up (or crimp, if we had any), reassemble, check continuity, and stick a safe to use sticker on it.

You wouldn't believe some of the plug wiring we found, especially as the American engineers never did manage to pick up our electrical safety regs. Luckily, the other maintenance guys did the machinery installations, and they were onto a loser before they even started. Most of them were nervous wrecks by the time they finished, purely because of some of the things they found. A lot of the main cable connections were made by twisting the bare ends together, and then putting a little twisty on cap over it, these joints were everywhere.

I think I could still wire a mains plug up correctly, in the dark, doing it behind my back, while fast asleep.

John

Offline Darren

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Re: How To Wire a Plug
« Reply #10 on: July 21, 2009, 06:20:25 AM »
All clamped wires creep,

It's the most common source of household electrical fires.

The electricity vibrations cause the screws to unwind, then they may arc and if enough heat is generated it can start a fire.
This is why all electrical connections should be accessible, (switches, wall outlets and fittings) If they get hot you can usually smell them due to the materials used. (designed that way)

If you make connections under the floorboards or hidden inside walls you are asking for trouble eventually.


To see this effect go around all your sockets and check the tightness of the screws. If they have been there for some time one or two are likely to be loose.
They should all be checked periodically, but rarely is this ever done.
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Offline Darren

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Re: How To Wire a Plug
« Reply #11 on: July 21, 2009, 06:25:31 AM »
The thing is, all those loose wires were most probably tight when originally fitted. Not really the fitters fault.

Those twisty on the end of bare wires were once common in the UK. Bad enough to give you nightmares... :(

I once had to rewire a hotel. In the attic where strips of wood with grooves in them with bare wires laid on top......!! Steel at that...

Oh and one or two dead mice and birds......well quite a few....


Scary....
« Last Edit: July 21, 2009, 06:27:52 AM by Darren »
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Offline John Rudd

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Re: How To Wire a Plug
« Reply #12 on: July 21, 2009, 12:05:36 PM »


Those twisty on the end of bare wires were once common in the UK. Bad enough to give you nightmares... :(


I remember them things..made of porcelain or plastic I think?
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Offline Darren

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Re: How To Wire a Plug
« Reply #13 on: July 21, 2009, 01:03:15 PM »
Both I believe...

oriible things they were...
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Offline Bluechip

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Re: How To Wire a Plug
« Reply #14 on: July 21, 2009, 02:58:42 PM »
The porcelain ones were called Scruit connectors, you can still get the plastic sort from Rapid I think.

You're right, gruesome little blighters ..

Dave

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http://www.rapidonline.com/products.aspx?tier1=Cables+%26+Connectors&tier2=Connectors+-+Single+Pole&tier3=Splices

« Last Edit: July 21, 2009, 03:06:19 PM by Bluechip »
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Offline rleete

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Re: How To Wire a Plug
« Reply #15 on: July 21, 2009, 03:14:28 PM »
Called wire nuts over here.  Still used, but only on solid wire.  Standard in most home wiring over here, I believe.  However, code requires all splices to be in sealed junction boxes of plastic or grounded metal.
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Offline Mr blindbird

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Re: How To Wire a Plug
« Reply #16 on: July 22, 2009, 05:24:36 PM »
Most interesting,good to know and makes copletely sence...about that ground wire...
luckely i dont have any over here......yep....all scratch your heads now...and i know it's not that safe but this house is 50 years old,all the electrical wiring is still the original,the kind that is insulated by some sort of fabric instead of the now used plastick like thingys.
There is absolutely none grounding in the intire house what soever :lol:
The minute i change anything about any wiring,i'll have to let safety inspectors in to check everything wich will end in an intire rewiring of the whole house :scratch:
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Offline Darren

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Re: How To Wire a Plug
« Reply #17 on: July 22, 2009, 05:29:46 PM »
Er.......


Please don't invite me over... :lol:

What country was it again....Belgium, isn't that part of Europe, or the EEC or both.....I'm sure you are supposed to have an earth.... :scratch:
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Offline John Hill

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Re: How To Wire a Plug
« Reply #18 on: July 22, 2009, 06:04:14 PM »
If nothing in the house is grounded that would be safe though it is difficult to see how things like plumbing could be relied upon to be non-grounded.  Of course if neither line is grounded I suppose that would be safe too as the entire house would be protected in the same way that before RCD breakers came available we used to use isolation transformers.

The 'MEN', 'PME' systems deliberately introduce an earthed environment so that most fault conditions will cause a fuse to blow or breaker to trip.  That is one way to get a safe (enough) system but it is not the only way.
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Offline Darren

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Re: How To Wire a Plug
« Reply #19 on: July 22, 2009, 06:11:24 PM »
So what happens when you grab a live whilst standing in the shower then?

Tell you what, how about you disconnecting your earth John and giving us a demo, be sure to video it though.... :lol:

Earth systems were developed for a reason.
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Offline John Hill

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Re: How To Wire a Plug
« Reply #20 on: July 22, 2009, 06:23:05 PM »
So what happens when you grab a live whilst standing in the shower then?

Tell you what, how about you disconnecting your earth John and giving us a demo, be sure to video it though.... :lol:

Earth systems were developed for a reason.

If there was no circuit between the shower and the supply I would be quite OK,  that is the point.  Isolation is isolation.  

In the PME and MEN systems one of the 'lives' is connected to the shower already!  Back at the transformer one of the secondary taps is connected to earth but if it was not there would be no potential between either and earth and that is the priciple of protection we used to get from an isolation transformer.

Earth systems were developed to protect against the case where one leg may have been accidently connected to earth, a situation that would go undetected but at the same time make the other leg lethal to the touch of anyone in an earthed situation.  So, they deliberately earth one leg which halves the problem and provides a mean for a protective fuse to blow if the other leg gets grounded too.

In the PME and MEN systems it is still not safe to touch the ungrounded leg (phase) in the shower as it WILL BE THE PRESENCE OF THE EARTH CONNECTION THAT KILLS YOU!

As far as standing in the shower goes it is quite possible that Mr Blindbird's house is actually safer than yours!
« Last Edit: July 22, 2009, 06:25:26 PM by John Hill »
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Offline Darren

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Re: How To Wire a Plug
« Reply #21 on: July 22, 2009, 06:39:13 PM »
The simple fact is that power stations do now earth one phase at source.

But even if they didn't there is still potential between two phases as they are "out of phase with each other"
Otherwise nothing would work on electricity.

Grounding one phase simply gives the safety devices something to work with.

But I know what you mean by isolation, it's why birds can sit on high voltage wires as live to squawk the tale... :lol:
Linesmen are also safe up there, they sometimes even have carts to pull themselves along from one pylon to the next to save climbing up and down constantly.

It doesn't matter how you look at if, electricity and living tissue do not mix very well if you give it a path, which is what earth does so I guess you have a very valid point.
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Offline Mr blindbird

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Re: How To Wire a Plug
« Reply #22 on: July 22, 2009, 07:24:44 PM »
Yes,we're supposed to have grounding...since a while,but in fact,all the old houses(like mine that dates from before there were made regulations about grounding),are allowed to stay in orriginal shape,on one VERY strickt condition;nothing of any wiring may be changed,i gues that's got to do with the change from this old and till some point safe system to a half new system where the grounding is only in a part of the house.
As soon as i would change a single socket with a new one and let them know,that would be the most expensive socket nown to man,cause it would result in a forced by law completely rewiring the house :zap:
That was also the reason why i couldnt get me a lathe so easy,it had to run on 220,if i wanted the company to place 380,i'd have to rewire the house :bang: and it was up till resent that i discovered they make these chinese lathes for a fair price that run on 220.By the way...i was clever enough to make sure no wires are in the neighberhood of my shower :lol:and even if there would be one i sure wouldnt tuch it :zap:
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Offline Darren

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Re: How To Wire a Plug
« Reply #23 on: July 23, 2009, 03:34:34 AM »
Sounds like a very difficult position's to be in, I bet you have extension leads everywhere !!!
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Offline Mr blindbird

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Re: How To Wire a Plug
« Reply #24 on: July 23, 2009, 04:59:34 PM »
That's ok,I'm used to it as i been living here all my life,moving is realy not my thing and yes,there are a LOT of extention leads...behind the sofa's,under the carpet,hell,there are even extension wires comming from extention wires  :lol: but i always make sure i dont overload the lot.
That wouldnt be possible either as the main breaker in my cirquit box is 20 amps  :scratch:.
the minute i put on 2 apliances the same time,the main will jump  :lol:
But never the less,i think your tip is verry handy,as when in the future i need to fix a plug at work or anywhere else,i'll make sure the ground will be longest,i had seen it before but never questioned it why,now thx to you i understand why.
Hey wayt...what's with my plug of my pc here...??looks like it came loo  :zap:  :zap:  :zap: sssssee  :bugeye: o dear...do i smell burned pork meat here?  :D

Danny
If force doesnt solve the problem,you're not using enough...
If aditional force still doesnt do the trick...you should have checkt if it's a right or left thread first...