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Reversed live and neutral (Read 23800 times)
Beanzy
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Reversed live and neutral
Jan 10th, 2005, 9:09pm
 
I was posting this reply to a post about reversed L&N from Damocles, when the topic seemed to disappear......... in case it never comes back here's my reply. To whichever person removed it I'll just say that's not conducive to running a good forum if posts get deleted during times whan people are most likely to be using the reply. Please Post a warning that you may be doing this and give it a decent span of time before you do.


The answer;


I'll tell you what from now on I'll hang about all day just incase you happen by. I may give up work just in case Wink

No seriously different folks will be on at different times. And it's a propper answer you need rather than the quickest.

The reversed L-N can be fatal, it's one of those no if's and buts situations. The reason why is because when you switch off the appliance at the switch it will remain live even though the circuit will of corse not be completed. If there is a fault, or a casing got damaged etc then there could be a full 230v waiting to whack someone. Also if you switch off the TV or appliance at the socket at night, it could sit there with the power back-feeding into the TV all the while.

As for what you should do. Call the installer/builder and ask to see the test results. If there are none ask why. If your contract with them said they'd do the electrical installation as part of the build, and it's faulty/potentially lethal, then you have the same come-back as you would with any other purchase of a service or product which is unsuitable for the purpose. Find out how much of the build cost was for the electrical installation, then pursue it with the Consumers Association or your Local Trading Standards people.

The solution is cheap enough in that extentions can be crimped to the existing short wires (done properly not with those dodgy squishers you see sold. Although this is a simple fix, they could have killed you and that's the bit that should worry you most.
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« Last Edit: Jan 10th, 2005, 9:37pm by LSpark »  
 
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LSpark
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Reversed live and neutral
Reply #1 - Jan 10th, 2005, 9:19pm
 
Quote:
To whichever person removed it I'll just say that's not conducive to running a good forum


Sorry but if he wants to have a moan then he can go elsewhere and do it, if he wants to ask for serious advice then he can do so without the digs, we had all this before and we don't need it again.
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« Last Edit: Jan 10th, 2005, 9:37pm by LSpark »  
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Damocles
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Reversed live and neutral
Reply #2 - Jan 10th, 2005, 9:26pm
 
I posted a serious question about a serious matter of safety here. The work was knowingly done wrongly by another electrician, not me, and he will likely be back. I have the awkward problem of telling his employer (also mine) what he has been doing. I do not regard this in any way as a frivolous matter, and I posted here because you claim to be a useful resource used by PROFESSIONALS.

I posted some follow ups because I could see the post had been read, but with as yet no answers. I have to resolve this tonight.

I have had seriously better comments from you know where forums.
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« Last Edit: Jan 10th, 2005, 9:37pm by LSpark »  

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Reversed live and neutral
Reply #3 - Jan 10th, 2005, 9:29pm
 
Quote:
you claim to be a useful resource used by PROFESSIONALS


Don't know who said that

Quote:
I have had seriously better comments from you know where forums


Then go there instead

Quote:
I posted a serious question about a serious matter of safety here


Well you have your answer, see first post
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« Last Edit: Jan 10th, 2005, 9:37pm by LSpark »  
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Damocles
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Reply #4 - Jan 10th, 2005, 9:30pm
 
Oh, and thanks beanzy.

The point is, he did it on purpose. So i really do want a whys and wherefores of how this might be justified. Or not.

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« Last Edit: Jan 10th, 2005, 9:38pm by LSpark »  

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Beanzy
Re: Disappearing post from Damocles?
Reply #5 - Jan 10th, 2005, 9:37pm
 
Listen LS I don't want to be here replying to posts which are deleted 1/2 way through my attempts to answer them just because someone gets the pip with another. Damocles may annoy you but it's not necessary to delete posts just because they irk. That's mixing up personal preferences with your role as a Forum Admin, and insults those who want to use the Forum freely. 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.
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LSpark
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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.

Quote:
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 LSpark »  
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Beanzy
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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Damocles
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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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chtechie
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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Beanzy
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 #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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Beanzy
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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John   Davies
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 LSpark »  
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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 #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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zambezi
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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