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JACCD

Earth/ CPC very high potential

23 posts in this topic

ID: 1   Posted

Hi all, looking for some advice for a rookie please.  This concerns a 2-way lighting circuit, that's to have some LED downlights to replace old halogens.  It was just to be a replacement of lights so a ran a quick Zs test beforehand and MFT sounded "voltage/ polarity" alarm.  From the supply side I'm getting L-N 240v but L-E and N-E at 12.3v.  So Earth/ cpc has a very high potential.  No voltage on it itself with the voltage tester.

 

There's some very poor wiring in the property so I'm looking for some advice please on where to look and test to find the issue.

 

Many thanks

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ID: 2   Posted

You are probably "seeing" induced voltage... turn off other MCB's and see if it disappears... or you have no earth continuity......

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ID: 3   Posted

Thanks I will do that's very helpful.  So nice to post a question asking for advice and to actually get some.  On other forums you just get abused!

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ID: 4   Posted

Matey... I've come across you on another forum.... so be careful as you like scoring "own" goals.

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ID: 5   Posted

did you actually get a Zs reading or did it refuse to do the test?

 

 

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ID: 6   Posted

17 minutes ago, Murdoch said:

You are probably "seeing" induced voltage... turn off other MCB's and see if it disappears... or you have no earth continuity......

 

you cant have induced voltage on an earth unless its not connected

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ID: 7   Posted

Refused

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ID: 8   Posted

Just now, JACCD said:

Refused

 

then its almost guaranteed that the earth is open circuit. dont they teach basics on short courses anymore?

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ID: 9   Posted

Thanks for your comment.  They teach what they teach and you have to keep learning afterwards.  Not going to apologise for that.  Everyone was new once.  Just came on and asked for some advice.

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ID: 10   Posted

1 minute ago, JACCD said:

Thanks for your comment.  They teach what they teach and you have to keep learning afterwards.  Not going to apologise for that.  Everyone was new once.  Just came on and asked for some advice.

 

Own goal scored....

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ID: 11   Posted

27 minutes ago, JACCD said:

Thanks for your comment.  They teach what they teach and you have to keep learning afterwards.  Not going to apologise for that.  Everyone was new once.  Just came on and asked for some advice.

 

youre part right... you do still keep learning afterwards, but this is basic stuff that you should be well aware of

 

so what did you tell your customer? 'my test kit said there was a fault, but since i dont know how to use it or understand what it says ill come back tomorrow after i go ask on a forum for their advice'?

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ID: 12   Posted

So you were doing a live test ... what were the dead tests you did first? and the readings?

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ID: 13   Posted (edited)

C'mon guys....... :shakehead

 

 

Surely it's better to learn from someone than just make it up as you go along? 

 

 

The current system,  as much as its disliked is here to stay until they run out of gravy. 

 

:|

Edited by Blue Duck
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ID: 14   Posted

I'd hazard a crazy guess that you are replacing ELV MR16s with GU10 LEDs , and some very astute person has simply cut the CPC off at each previous fitting.

:shakehead

 

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ID: 15   Posted

The same astute person who nails  the cables to the joists then puts the ceiling up ?

 

:facepalm:

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ID: 16   Posted

12 minutes ago, steptoe said:

I'd hazard a crazy guess that you are replacing ELV MR16s with GU10 LEDs , and some very astute person has simply cut the CPC off at each previous fitting.

:shakehead

 

I am doing EXACTLY same at sons new house today

place is a total nightmare...only got keys last week !

BUT the only thing that is right is that all the M16s have the Earth in the T&E connected through!

 

 

 

REEEEEESULT as it is a flat roof

 

extension and conservatory and new kitchen and two new bathrooms within last ten years

NOT an RCD in sight

gas bonded on lead on incoming side

not an IP fitting in any bathroom

no paperwork for loft ensuite conversion

no steel,calculated 

no building regs

nohing for anything really........I,see it being a busy summer

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ID: 17   Posted

You mean our best friend the ..............plasterer who thinks can do " a bit of electric"  too. 

 

Just agreeing with The Duck ...this Forum is a bit different ...can't we help the guy out .  

I don't remember college telling me about an unconnected earth wire collecting induced voltages ......I think there was a huge list of stuff I only learned "on the tools"  from other sparks .  

 

Top of the head ....college didn't tell me that those circular fluorescent tubes are unlikely to strike with an FSU  starter  ....starter needs to match the tube watts .

Same with some ..(but not all) ....6 ft fluorescent ...some makes you can try  FSUs all day long  although they're marked up 38-- 58--70 w they won't strike ......only work with a 70w starter.

College didn't tell me how to connect a 3Ph  motor starter as 1Ph . etc 

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ID: 18   Posted

^^ we don't know what the op was doing, what tests he had done... So unless he comes back with the whole story we are simply guessing....

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ID: 19   Posted

I know that Murdo ... :Salute    just that I found that many younger sparks just on the tools ....AND... a lot of guys working for bigger firms on larger installation jobs hardly ever found themselves fault finding ..and some ..very little practice working live , fault finding etc. 

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ID: 20   Posted

Surely they know to do dead tests first, or if it's a cursory Zs during an accessory change....

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ID: 21   Posted

Is it too basic to ask if you did an R1+R2 test (dead of course)?  That I am willing to bet would have measured open circuit or as near as dam it, confirming a floating cpc.

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ID: 22   Posted

I would start by checking for cpc continuity at one of the switches. If yes then it's quite possible that Steps is correct ! (not that Steps is ever incorrect - especially when earth rods are the topic :Salute  )

 

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ID: 23   Posted

Oh don't get him started on earth rods again Revo,    you know his family coat of arms is  a Scull & Crossed Earth Rods  don't you . ?  :innocent 

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