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Reversed live and neutral (Read 5522 times)
plugwash
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Re: Reversed live and neutral
Reply #22 - Jan 11th, 2005, 4:23pm
 
aparently in some parts of spain the polatiry at the intake point swaps every few weeks but i digress Wink.

some parts of europe also have installations that are supplied from 220V line-line services.

It is perfectly possible to design stuff to be safe with live and neutral either way round and most portable appliances are designed this way to make them safe accross europe (where nonpolarisaed plugs are the norm). It is possible to do the same for fixed wiring and the caravan regs essentially require this.

the fact is we brits seem to get upset at people trying to suggest that the IEE regs are anything less than gods commandments. We won't for example adjust our sockets to take europlugs (all it would involve would be adding a fuse and adjusting the shutter design nothing more) even though the whole of the rest of europe and most other countries that use the same voltage band have made sure thier sockets can take the things.

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Re: Reversed live and neutral
Reply #21 - Jan 11th, 2005, 3:53pm
 
The Gov't don't spec it, it's BS, oh yes those very same ones who run such a reasonably priced scheme for Domestic Installers. All Part P says is do it to B$7671 and pay us the dosh. So if the IEE can be wangled into requiring pink fluffy outlets in kitchens then that'll go in. BSi may then change the standard if the others are seen to be obsolete.

However it's not going to make a reverse polarity safe to use, just safe when switched off.

I'll shut up now as my name appears way too often in this post and I'm getting bored with the sound of my own keyboard.  Kiss
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Re: Reversed live and neutral
Reply #20 - Jan 11th, 2005, 3:51pm
 
Billy,
What about lighting circuits that are not protected by an R.C.D? Install D/P switches? The switches are single poled at the moment, so it would mean changing existing wiring, and how some sparks would have to change their methods of installation in the future.
Correct polarity is the answer.
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Re: Reversed live and neutral
Reply #19 - Jan 11th, 2005, 3:49pm
 
When did they ever do anything that made sence?? Maybe if the gov owned shares in MK, Select etc they would consider making it a new law.
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Re: Reversed live and neutral
Reply #18 - Jan 11th, 2005, 3:33pm
 
why dont the government specify only dp switches then, this would seem a safer thing than part P!
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Re: Reversed live and neutral
Reply #17 - Jan 11th, 2005, 3:29pm
 
Billy,
I'm sure Crabtree are single pole,so I just tested one, and yes it is. I know Select is double pole, and guaranteed for 15 years, Not as pretty, but safer and cheaper.
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Re: Reversed live and neutral
Reply #16 - Jan 11th, 2005, 3:16pm
 
This is a common problem when poeple mixed up live and neutral (mostly people fitting the plug incorrectly).

Toast gets stuck in toaster, you know it bites if you stick your knife in to dig it out, you turn off the switch, insert your knife and get the shock of your life!! Shocked
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Re: Reversed live and neutral
Reply #15 - Jan 11th, 2005, 2:40pm
 
If the switches had been double pole this couldnt have happened right? Do sockets come with DP switches?
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Re: Reversed live and neutral
Reply #14 - Jan 11th, 2005, 12:52pm
 
Hi Lads,
Recall an incident not so long ago, that a DIYer wired his neighbour's house. Reversed polarity on ring main supplying the lounge.
Electric fire plugged in to socket, but the switch was in the off position, young child put hand through grill, touched end of element, died. It made the papers.
So, definitely a no no.
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Re: Reversed live and neutral
Reply #13 - Jan 11th, 2005, 11:59am
 
Surely, there are two possible courses of action.  

Firstly, point the mis-wiring out to the installer concerned.  If they put it right, well and good.

If they laugh it off, then either the householder or the firm employing the installer should be told, for safety's sake.  However, I don't feel that this would necessarily be the first course of action - why get someone into trouble for a simple mistake, we all make them from time to time, and if they are pointed out to us we tend to get more careful rather than the reverse.    

Whatever, the matter can't simply be left alone.   The possible consequences of leaving alone are potentially lethal - years ago I had a nasty shock from a miswired circuit  and wouldn't wish it on anyone else.  The golden rule is to always assume any wire you may be working on is live.

John Davies
 
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« Last Edit: Jan 11th, 2005, 1:46pm by L.Spark »  
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Re: Reversed live and neutral
Reply #12 - Jan 11th, 2005, 5:01am
 
A fault to earth won't pass though the appliance fuse so your flexible cable can be loaded with the full circuit current (we'll it'll melt on the way there). Nasty

The equipment remaining live when switched off at the wall and the user assumes it's safe isn't good. When you switch something off at the outlet you would expect the power to the appliance to be cut off. People do this kind of thing all the time where they switch the TV off but don't go to the faff of unplugging it overnight.

There doesn't have to be an RCD on the circuits, but if there is and you switch the neutral, you may get nuisance tripping due to the imbalance across the load. It would be similkar to when you get a faulty 2 pole switch which disconnects the neutral a fraction early. They trip out RCDs.

As for the rest of Europe (except the old sod) they've been sitting on dodgy practices for years. I'm not going to enourage us to follow suit.
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« Last Edit: Jan 11th, 2005, 5:13am by Beanzy »  

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Re: Reversed live and neutral
Reply #11 - Jan 11th, 2005, 4:11am
 
ok lets consider this rationally what are the real dangers of reversed live-neutral.

switches inside appliances? maybe but remeber MOST OF EUROPE DO NOT HAVE POLARISED SOCKETS.

switches on sockets? may be more of an issue if they are single pole.

all switches: how is switching the wrong side of an appliace leaving it in any more danberous a state than if its simpl left on (which is done all the time by householders)

Fault to earth: this is the biggest danger as overcurrent devices will be in the wrong side. However if an rcd is present then it should cover this situation.

Sure its not ideal to have live and neutral reveresed but making it out as an imminent danger to the users of the install is a GROSS EXAGGERATION.




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Re: Reversed live and neutral
Reply #10 - Jan 10th, 2005, 10:18pm
 
Like I say it's potentially fatal. That's what the regs are there for. Polarity is one of the most basic tests for just that reason.
As for whetere it'll normally matter; The circuits have to be designed for fault conditions, not best case scenarios. It's normally only under a fault that electrical problems arise. As the fuse is in the Neutral any fault to earth will not pass the fuse, although as it's a local reversal it will be limited to the overload passing current of the 32A MCB. the circuit under fault conditions will be live to earth with up to a steady 32A cooking the flexible cable and components of anything connected, not to mention the person making contact with any metalwork or the faceplates.
Lethal.
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Re: Reversed live and neutral
Reply #9 - Jan 10th, 2005, 10:16pm
 
Know how you feel Damocles - Had a similar problem where a qualified spark had reversed the tails into the CU - He told me I didn't know what I was talking about (well something like that) when I pointed out the error of his ways fortunately I don't have to work with him !
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Re: Reversed live and neutral
Reply #8 - Jan 10th, 2005, 9:50pm
 
Trying to get an answer here is likle being on a roler coaster. One minute your post is up, the next its down...

Thanks, I have had some useful and I guess decision making replies elsewhere already.

I thought the forum founder said he wanted it to be a useful resource for the public. I would hunt out the post, but it was deleted.

I shall start again, but I doubt there will be time to recieve any replies.

I today came across some replacement sockets in someones kitchen which had been deliberately wired up with n and L reversed, because the cables were too short to reach  the new screw positions. The guy who did this is experienced as an electrician though currently working as a general builder.  Tomorrow I shall most probably have to point out what has been done, as tactfully as possible. But stressing the most important points.

I know perfectly well this is not a good idea. However, I suspect it is in reality not as bad an idea as it first appears. If you guys, as professionals, actually sit and think about how the consequences might pan out.

So I was hoping for some informed comments.

There is very unlikely to be any documantation. The most expedient thing for me to do would be to say absolutely nothing and pretend I never saw it.
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Re: Reversed live and neutral
Reply #7 - Jan 10th, 2005, 9:49pm
 
The problem is that no matter what background history you may know, a post is a post and should be treated on its' merit. The post in question was tetchy but made no insults except to say that other fora were better for quick replies; that's why I began my answer with the dig at Damocles being impatient. But that should be the cut and thrust of posting, this isn't kindergarten.
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« Last Edit: Jan 10th, 2005, 9:50pm by Beanzy »  

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Re: Disappearing post from Damocles?
Reply #6 - Jan 10th, 2005, 9:41pm
 
Quote:
If you feel This is not the case then please let me know on here so I can make up my mind about the appropriateness of bothering to reply to posts


No you can carry on replying as you wish, that's up to you Beanzy, I will enlighten you about the rest.

Quote:
Damocles may annoy you but it's not necessary to delete posts just because they irk.


He doesn't annoy me, he just causes problems.

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That's mixing up personal preferences with your role as a Forum Admi, and insults those who want to use the Forum freely.


Moderator & my job is to keep the forum clean from any rubbish that might get posted, Insult's to the people who use the forum are to let it remain.
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« Last Edit: Jan 10th, 2005, 9:43pm by L.Spark »  
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