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Topic Title: No lighting Cpc's
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Created On: 06 February 2013 07:07 PM
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 06 February 2013 07:07 PM
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alpelec

Posts: 89
Joined: 04 November 2008

Hi All,

I'm fitting a consumer unit on an old installation (must be pre 1966) because the lighting cables have no cpc's and conductors are all aluminium. Really a re-wire is needed but as usual customer doesn't want to spend. I've come across this scenario before in houses but not when fitting a new consumer unit.

My question is how do I test continuity and ELFI for the certificate, or would I just put it down as a limitation and add a note in the observations? No metal fittings are present and installation is TN-S.

Thanks for any advice.
 06 February 2013 07:17 PM
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Approvedspark

Posts: 107
Joined: 09 March 2008

http://www.esc.org.uk/fileadmi...actice/BPG1v2_web.pdf

Try this.

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If you think you're too small to have an impact, try going to bed with a mosquito in the room.
 06 February 2013 07:18 PM
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Ricicle

Posts: 834
Joined: 23 October 2006

Try the last guide here:-

ESC

DOH ! Too slow

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Empty barrels make the most noise.
 06 February 2013 07:21 PM
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GB

Posts: 357
Joined: 04 September 2002

Aluminium conductors are probablt tinned copper and ok if readings are ok (thats not ok having no cpc)
 06 February 2013 07:31 PM
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Zs

Posts: 2787
Joined: 20 July 2006

alpelec, is there any conduit? I see this quite often in some of the blocks of flats around this way. Sometimes you will find old conduit which might be suitable for use as CPC. Usually it has been used as CPC in the past and messed with over time. A look behind a ceiling rose will tell you.

Or, what meter do you use? A two lead tester will offer you a line to neutral option and hence show you a path to earth, of sorts, on your TNS. I'm really not a fan of this test though, IMO it's a fudge compared to a pure EFLI down a CPC. But it does exist. There are also ways of fudging a two lead test out of a three lead only tester but I didn't tell you that.

Ultimately, I would not get into the realms of calculation or anything, I think I would offer an r1 and an rn measured end to end with flying leads (dead) and outline the limitations carefully on the form or a covering letter.

But don't forget a special label on the board about this and to talk to the client about switching off if they change a lamp. I reckon the client knowing and understanding about it is more important than the paperwork.

Zs
 06 February 2013 07:50 PM
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primo

Posts: 430
Joined: 10 January 2008

Originally posted by: Zs





Or, what meter do you use? A two lead tester will offer you a line to neutral option and hence show you a path to earth, of sorts, on your TNS. I'm really not a fan of this test though, IMO it's a fudge compared to a pure EFLI down a CPC.



Zs



What would a L-N test tell you with regards to having no CPC at lighting positions? Or are you suggesting that the class 1 bit of a metal fitting be connected to neutral if no CPC present?!! (I know that's not really what you are suggesting).


Originally posted by: Zs





There are also ways of fudging a two lead test out of a three lead only tester but I didn't tell you that.




Zs


What are you referring to here? On my Fluke I often use the L-N setting (obviously with the probes on L & E) to take make Zs or Ze readings if there is no RCD present. As far as I know this is a high current test and is certainly a lot quicker than waiting for the low current Zs test.

I think the new Flukes may do this slightly differently now but probably exactly the same test, just don't have to swap leads over / toggle settings.
 06 February 2013 08:02 PM
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Zs

Posts: 2787
Joined: 20 July 2006

Originally posted by: primo

Originally posted by: Zs











Or, what meter do you use? A two lead tester will offer you a line to neutral option and hence show you a path to earth, of sorts, on your TNS. I'm really not a fan of this test though, IMO it's a fudge compared to a pure EFLI down a CPC.







Zs






What would a L-N test tell you with regards to having no CPC at lighting positions? Or are you suggesting that the class 1 bit of a metal fitting be connected to neutral if no CPC present?!! (I know that's not really what you are suggesting).

I agree primo, which is exactly why I am not a fan of this test. I think it is a chocolate teapot but I see it in use over and over again because it is quick. I think it says nothing. It trips RCDs as well. I'd rather wait for a low current l-e result to come back but believe me, high current l-n is the preferred method of many.



Originally posted by: Zs











There are also ways of fudging a two lead test out of a three lead only tester but I didn't tell you that.









Zs




What are you referring to here? On my Fluke I often use the L-N setting (obviously with the probes on L & E) to take make Zs or Ze readings if there is no RCD present. As far as I know this is a high current test and is certainly a lot quicker than waiting for the low current Zs test.

That's about it primo, or doing what the DNO does when they come round to see if a supply is suitable for pme, with the two crocs combined and a screw found on the floor stuck in the neutral terminal....bet you've seen it too. But as above, I think you and I are of like mind on this and whilst you will get a test result to write down on a bit of paper, the reality of the installation is quite different.


I think the new Flukes may do this slightly differently now but probably exactly the same test, just don't have to swap leads over / toggle settings.

Sadly, I don't know about the new Flukes. I bought a megger when the old fluke was stolen.
 06 February 2013 08:08 PM
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daveparry1

Posts: 6105
Joined: 04 July 2007

Not really much of a problem provided there are no class 1 fittings on the lighting circuit. Put the appropriate label on the new consumer unit which shows there is no cpc on lighting circuits. Also put a note on your EIC "comments on existing installation" saying that class 1 accessories are not to be used on circuit no. ____. If there are metal light switches I tell the client I will need to replace them with plastic ones when I change the c/unit. (what they do when i've gone is up to them of course!) In the Zs box just write "no cpc",

Dave
 06 February 2013 08:36 PM
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alpelec

Posts: 89
Joined: 04 November 2008

Hi Zs,

I've not fully checked but there is conduit to the cooker control unit and all walls seem to be some kind of concrete with chippings mix.

Thanks.
 06 February 2013 09:01 PM
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Zs

Posts: 2787
Joined: 20 July 2006

Oh, is it one of the metal framed houses with walls made of compressed straw and concrete type material?

Not really relevant that, just curious. Watch out before you offer to reinstate conduit as CPC...it can be very time consuming unless it is complete between close to the DB and the final circuits. I've had to do it a couple of times but only when the electrician before me chopped the conduit off two inches short of all the socket boxes and left the place completely unearthed. I learned how to thread and join conduit back at college, never thought I would really do it.

Zs
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