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Consumer Unit Replacement

Discussion in 'Electrics UK' started by Gazzer23, 25 Feb 2018.

  1. Iggifer

    Iggifer

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    If you’re wiring in singles, chances are you’d use the containment as the CPC and then there’s only one CPC for the whole installation, so essentially the same as what Owain is suggesting
     
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  3. JohnW2

    JohnW2

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    Yes, I mentioned that in the second paragraph of my response to him - but, as I said/asked, does that not present difficulties (or impossibilities) with some aspects of testing?

    As I said, I have zero experience of wiring in singles, so anything I'm told will be essentially education for me!

    Kind Regards, John
     
  4. ban-all-sheds

    ban-all-sheds

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    I don't see how having a cpc which is shared hampers fault loop measurement.
     
  5. JohnW2

    JohnW2

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    I never said anything about loop impedance measurements. What I did say is that it would presumably 'hamper' (usually actually preclude, I would have thought) checking of 'CPC continuity' in a ring final circuit in the usual sense - which I would have thought meant that would have to check continuity back to the MET from every socket on the ring.
     
  6. ban-all-sheds

    ban-all-sheds

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    I didn't want to say "continuity", as you get unnecessarily bent out of shape by it.

    But assuming that the cpc is present at every socket, what would hamper checking continuity back to the MET from every socket?
     
  7. JohnW2

    JohnW2

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    Nothing would hamper checking continuity back to the MET from every socket - but, as I said, it would be necessary if there were a shared CPC. In contrast, with T+E wiring, I suspect that most people don't check 'CPC continuity' back to the MET from every socket on a ring final if they have confirmed 'CPC continuity' around the ring.
     
  8. ban-all-sheds

    ban-all-sheds

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    Can you draw a diagram showing, or otherwise explain, how a dedicated cpc running to every socket on a ring final can be any more assuredly assumed to be connected to every socket without testing at every socket than with a shared cpc? Or why with a shared one it is more important to verify that every socket has a cpc connected than it is with a dedicated one?

    Does not loop impedance testing also verify that the cpc is connected to the MET?

    And OOI, what is the topology of a cpc shared between two ring finals, or a ring final and a radial?
     
  9. flameport

    flameport

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    They are doing it wrong.
    Should be checked at every socket.
    A connection between the two ends of a ring means nothing on it's own.
     
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  11. JohnW2

    JohnW2

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    Sure, it means nothing on its own, but in combination with checks on two or three sockets on a ring, it seems to satisfy many people.

    I'm not advocating the practice, but, over the years, I've watched a lot of PIRs/EICRs being done on existing installations and have rarely, if ever, seen any sort of testing being done on each and every socket in an installation.

    [ I did once see an 'electrician' doing a PIR 'test' most/all of the sockets with a 'socket tester', but when it became clear that he was not going to do any other testing on the sockets circuits, he was rapidly relieved of the job of doing the PIR! ]

    Kind Regards, John
     
  12. scousespark

    scousespark

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    An EICR may be carried out on a sample of circuits, but the requirement is to fully test each of those the selected circuits.
     
  13. OwainDIYer

    OwainDIYer

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    I find it quick and easy to test continuity between each socket and the lightswitch in the room. I know that's going from the socket back to the CU and then from the CU out to the lightswitch because of the way I wired my lighting.

    Doesn't work testing between eg a socket and a cooker point, because the back boxes on those circuits may be linked by conduit for spacing purposes.

    The 'socket tester' is useful of course, but it only works on a live circuit, and we all test before energising don't we :)
     
  14. JohnW2

    JohnW2

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    Good to see you.

    Do you perhaps mean 'sockets' rather than 'circuits'? I would certainly expect an EICR to include at least some testing of every circuit in the installation, not just a 'sample' of circuits.

    If you do mean sockets then, yes, I understand that that is the usual situation. However, perhaps I am over-demanding or over-cautious, but if the EICR were being done for me and the situation was such that the end-to-end continuity of a ring final circuit's CPC could not be tested, I think I would be more comfortable if I knew that it had been confirmed that each socket on the circuit had an earth connection.

    Kind Regards, John
     
  15. JohnW2

    JohnW2

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    Fair enough, provided it is true 'continuty', rather than the R2 of the circuit in question (from each socket) that one is interested in. I suppose that, in theory, one should also confirm that the light switch CPC has continuity with the MET - just to rule out the (very unlikely) situation of the whole CPC system being 'floating' (particularly when the MET is external to the CU), but I doubt many would bother - not the least because such a problem would be picked up by other tests on the installation..

    However, as I said, I have rarely seen any sort of testing being undertaken from each and every socket during a PIR/EICR - and I do accept that, in general, testing only a sample of sockets seems to be considered 'acceptable'.

    Kind Regards, John
     
  16. flameport

    flameport

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    This depends on the circumstances.
    On an existing installation where previous records of at least one test previously exist, and it is evident that no alterations have been made, then testing only some sockets may be acceptable.
    For any new installation, or ones where things have been changed/added, testing all of the sockets is really the only option.
    If not, then many defects would not be found - such as wires connected to the wrong terminals.
     
  17. JohnW2

    JohnW2

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    Agreed. I was talking about EICRs - so not new installations, but obviously including many 'altered' ones ...
    Again agreed, and that's what worries me a little about what I have observed. Most of the EICRs I see done are on installations of unknown history, and often in quite iffy condition - and it concerns me that, unless I intervene, it is so common (in my experience) for all sockets not to be tested, even by electricians who otherwise seem to be very competent and conscientious. However, maybe I've just been 'unlucky' in whom I have observed!

    I recently saw a case where I already knew that one of the sockets "didn't work", and the initial EICR did not pick that up (although that got changed after I "spoke up"!).

    Kind Regards, John
     
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