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Reversed live and neutral (Read 23811 times)
didds
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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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billythekid
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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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zambezi
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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didds
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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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Beanzy
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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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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LSpark
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Re: Reversed live and neutral
Reply #23 - Jan 11th, 2005, 4:50pm
 
[quote author=zambezi  link=1105391377/15#19 date=1105458553]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. [/quote]

MK logic Plus Sockets are all double pole.
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plugwash
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Re: Reversed live and neutral
Reply #24 - Jan 11th, 2005, 6:02pm
 
i think thats his point. If the compaines that already make all dp sockets had influence in goventment then the goverment might push it as a requirement.

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Damocles
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Re: Reversed live and neutral
Reply #25 - Jan 11th, 2005, 7:32pm
 
Well in this case there is an RCD (though I did not personally check the wiring). Which must help. As has been pointed out, there are guys on the continent merrily getting by with reversed voltage each time they pull out and replace the plug.  RCD should deal with shock in the event of someone discovering it was live when he thought it switched off.

I agree Beanzy, it is a pretty basic principle to get the wires the right way round. Thing is, once upon a time this might have been your only safety device-knowing which one was live- but now it is not. So bearing in mind that the question is not whether the regulations have been followed to the letter, but whether the installation is safe, it seems necessary to think carefully.

It is beginning to sound as though this might actually squeak through as being safe. The plug fuse is not isolating live, but it will anyway only cover cases of n-l short in the range 13-32A. Less or more than that either would not have been covered anyway, or should trip the mcb. I know this is not ideal. But it is not a million miles away from normal continental practice, which does not kill huge swathes of the population over there.

??
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chtechie
Re: Reversed live and neutral
Reply #26 - Jan 11th, 2005, 7:57pm
 
Safety aside there are a number of CH boilers on the market which don't work if L & N are reversed. (Baxi Solo, Glow worm Ultimate .........)
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Damocles
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Re: Reversed live and neutral
Reply #27 - Jan 11th, 2005, 8:17pm
 
Yeah, that is the kind of thing I was interested in. Whether there really is equipment out there wich is polarity sensitive. (as well as people)
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Beanzy
Re: Reversed live and neutral
Reply #28 - Jan 11th, 2005, 8:39pm
 
[quote author=Damocles  link=1105391377/15#25 date=1105471938] but it will anyway only cover cases of n-l short in the range 13-32A. Less or more than that either would not have been covered anyway, or should trip the mcb. I know this is not ideal. But it is not a million miles away from normal continental practice, which does not kill huge swathes of the population over there. [/quote]

I don't understand why you discount the fuse in protecting a L-E fault? That's why we measure Zs to make sure it will disconnect in time. As I said earlier, the fault will pass to earth, through the high resistance (the poor bugger toucing the shiny faceplate), or through the faulty equipment with that resistance. It may never even dead short, so could pass 30-36 amps for one heck of a time. By then the person is either dead or the flexible cable has started a fire. How would this be safe? I'm not taking into account whether this will happen or not, it can happen and probably would happen in the event of a fault, 32A is a heck of a load for a .75mm flexible.

The real concern I would have here is that there is a known fault with the sysyem, which is potentially fatal, so how can it be ok to leave it? or try to talk a way around it? Surely it would be a bit callous if they were to leave it for someone else to cop it, just for the sake of getting it sorted properly. I wouldn't sleep well knowing there was a bodge job there waiting to kill. Look at the infamous MPs daughter scenario and that was just a cable zones/ protection issue.
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Re: Reversed live and neutral
Reply #29 - Jan 11th, 2005, 10:02pm
 
[quote author=chtechie  link=1105391377/15#26 date=1105473434]Safety aside there are a number of CH boilers on the market which don't work if L & N are reversed. (Baxi Solo, Glow worm Ultimate .........)
[/quote]
got references for that?

and did they mean it doesn't work if L and N are reveresed at the boiler or if L and N are reveresed for the system as a whole (there is a BIG difference)

if it doesn't work with L and N reveresed for the system as a whole then it means that somewhere it is connecting something between live and earth which is rather dodgy to say the least.
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Lectrician
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Re: Reversed live and neutral
Reply #30 - Jan 11th, 2005, 10:08pm
 
I know of atleast  one make of boiler that will not fire on reverse polarity - long story Plug - I will tell it another day Wink
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Re: Reversed live and neutral
Reply #31 - Jan 11th, 2005, 10:43pm
 
lectrican was that with just the boiler on reverse polarity or the whole CH system?
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chtechie
Re: Reversed live and neutral
Reply #32 - Jan 11th, 2005, 11:14pm
 
Hi PW

Sorry been busy doing other things - If you reverse the L & N to certain boilers they do not fire up - I've worked on both standard boilers and combis which behave like this - I quote from one manual (Baxi Solo) "Polarity of the appliance must be correct otherwise the appliance will not work correctly"
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Re: Reversed live and neutral
Reply #33 - Jan 12th, 2005, 6:25pm
 
Just the boiler.  Everything else worked fine.

The story....

First fixed and second fixed a house.

Cent heat wired to the CU via an FCU.

Plumber wanted to commision, and without asking, disconnected the FCU and wired it directly to a plug top to power the whole cent heat circuit.

I didn't get along with the plumber to begin with, as we had 'stolen' his sons job (quote was cheaper Wink).

The system didn't fire up.  The valves worked, the pump fired etc etc, but the boiler didn't fire, and showed an error.

The plumber got his son to have a look with out ringing us.  His son found the live and neutral reversed at the boiler(as in the flex brown was neutral, and the flex blue was live  Shocked).  Without removing any other covers, he put the blue into the live terminal of the boiler and the brown to the neutral. (dick head).

The plumber couldn't wait to throw abuse.  I new I had done it properly.  Can't get a lot wrong with colours!!!!

The first thing I tried was the extension lead he had plugged the whole system into - It was reverse polarity (good old plug-in martindale socket tester Wink).  Checked the site temp supply socket that the extension was plugged into - all ok.

The extension was wired with reverse polarity in the trailing end.........The plumbers son had made it up from some old flex and a plug and  trailing socket  Grin

That was a great day, I made sure I kept abusing the plumber all day - As he had to me when I first arrived of site  Wink
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« Last Edit: Jan 12th, 2005, 6:28pm by Lectrician »  

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