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Recommended checks before CU change

Former Community Member
Former Community Member
As most of you know I’ve only been qualified for just over a year and I’ve got a quote to do for a cu upgrade.


I know I’m nowhere experienced enough to do EICR’s yet, but what would you guys recommend I check/test before doing the cu upgrade and should I do these checks/tests at the quote stage?
  • Former Community Member
    0 Former Community Member
    Forgot to mention that you bypass all neon indicators etc as these will give low readings, have a look in the onsite guide it will tell you the minimum allowable figure I thing it may be 1Mohm but cant be 100% sure.

    Ts
  • Former Community Member
    0 Former Community Member

    Timeserved:

    Hi Fitzy,

    Doing a L-L would be a dead short so you would expect 0.00Mohms..you sure you don't mean L-N?


    Ts




    Yes, sorry, I did mean, L-N which was 0.00 ohms.  I couldn’t possibly have unplugged everything, as some of the rooms were filled with boxes etc,  blocking some sockets with items plugged in, they had all kinds of electronic items plugged in all over the house, double oven had no separate isolation switch and there were at least 15 luminaries downstairs with about the same upstairs, none of the circuits were labelled either. 

  • 0
    no need to test L-N. maybe not even a good idea, if any of the things left plugged in contain electronics.


    I'd just do (L+N) to E - that is the one that picks up all likely RCD problems in one test, and then there is no need to disconnect loads. Also worth noting that if you are not to sure if you do have electronics connected, it is worth doing the test at a lower voltage than the full 500, at least  initially.

  • Former Community Member
    0 Former Community Member
    If there's stuff plugged in I usually test at 250V, I'd second Mike with the L+N to E, if you still have low readings you may have to test individual circuits to locate faulty circuit(s) or make a judgement call if you feel that the connected load is affecting the readings.
  • Former Community Member
    0 Former Community Member
    Yea, so I cocked up a bit then on the IR test as I only done L-E, N-E & L-N at 500v, forgot to do the L+N-E test, hopefully I didn’t cause any damage then.  ?   So all the connected loads including ALL the luminaries would’ve caused the low .42Mohms readings?


    I did how ever get my first electric shock ‘TWICE’, as I was holding the L cables in the mcb holder to tighten the little screws, my little finger brushed the incoming Live tail.  Does that make me a proper sparkie now then?  ? ? ?
  • Former Community Member
    0 Former Community Member
    Lol, not until you blow something UP!!!

    No need to do the L+N if you've done them individually pal, its just quicker to do the L+N.


    Ts
  • Former Community Member
    0 Former Community Member

    Timeserved:

    Lol, not until you blow something UP!!!

    No need to do the L+N if you've done them individually pal, its just quicker to do the L+N.


    Ts




    Ahh, i did the global IR test, instead of individual ones.  ?

  • 0

    Fitzy71:

    I carried out my initial inspection and testing tonight and I’m concerned about the IR results, firstly though I think I done the IR test wrong on this board.  I tested (global test) L-E, N-E then L-L, using the live busbar, results were .42Mohms on both L-E & N-E, but the L-L was 0.00???




     

    Difficult to see how anybody could do L-L in a SP installation!
  • 0

    Fitzy71:

    So all connected loads including ALL the luminaries would’ve caused the low .42Mohms readings?



    Unlikely. A single neon is tens of kohms. The more loads you have, the lower the resistance.

    I did how ever get my first electric shock ‘TWICE’, as I was holding the L cables in the mcb holder to tighten the little screws, my little finger brushed the incoming Live tail.  Does that make me a proper sparkie now then?  ? ? ?

    Have you put your foot through a ceiling yet? 


    More seriously, much more seriously, no live conductor should have exposed copper. Assuming that your pinky is a normal size, that implies that there is a significant amount of copper exposed.
  • 0
    There is a reason for not working with things open and the power on if you can avoid it - why was the exposed tail live? Or, why was the live tail exposed? Please take care, we'd like you to be able to write posts on here  at the end of the job as well as the beginning!


    I have been known to fashion some  temporary insulation in places where touchable live copper looked too risky. Even a bit of chopped up water bottle (clean and dry) cable tied or taped over  something  can reduce the risk of tools falling on a live bus, or a stray back of hand touching something until it can be re-instated properly.


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