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  1. M

    Worrying earth problem

    You've not understood what I said above. Current in the earthing conductor is normal if you are on a PME supply. It flows from the supplier's neutral through the earthing conductor and through the main bonds back to earth. It is not causing the RCDs to trip. The only current which does this is...
  2. M

    RCD Problem

    If it's affecting all 3 conductors it sounds like a JB which is wet or a choc block buried in plaster. Like Handyspark says use the low res ohmmeter. Could even be mice chewing through the PVC under the boards.
  3. M

    Worrying earth problem

    If this house is on a PME supply then there will be neutral currents going to earth through the earthing and bonding conductors which as Tony says won't affect the RCD as these currents do not come from the final circuits. They flow from the incoming neutral, through the main earth to the MET...
  4. M

    Mains Tester screwdriver

    The continental view is that fuses can blow and give you a false indication of a safe conductor. The Steinel design has a high internal impedance so a fault in the instrument can't cause a short. If you use a fused instrument then you absolutley have to prove the instrument afterwards on a known...
  5. M

    63a tp&n

    No. A lot of questions (and the answers) on this site scare me. I've been in this business 40 years and I've seen a lot of the bad bits. They're not nice and it's turned me into a grumpy old man.
  6. M

    Mains Tester screwdriver

    I agree with the above comments that neon screwdrivers are not reliable indicators. They can also be dangerous. If the resistor in series with the neon inside is damaged or shorted or gets wet then you'll get 240v on your pinky. I'm guessing PJK that it lit up on the incoming cpc. That would...
  7. M

    63a tp&n

    WMB - Your lack of understanding of 3 phase is frightening me. Have you been asked to select and install a suitable cable for a 63A lift supply? There are several factors to consider including earth loop impedance, discrimination, volt drop as well as current carrying capacity/ grouping etc...
  8. M

    cable separation

    Check out Appendix I in IEE Guidance Note 1 It says screened IT cable and screened power cable (ie armoured) do not need separating for EMC reasons Also unscreened power eg T&E and screened IT, the separation is 50mm - again for EMC reasons. Segregation of voltage bands overrides this as per regs
  9. M

    The Mighty 3 Phase Flash

    Well apart from working on a live board, drilling and connecting loose cables which is illegal as it was possible to isolate.. the circuit breaker you mentioned could not handle the fault level - old C50s are only rated at 4.5kA - so would not have operated safely anyway. The design was wrong...
  10. M

    Question about sharing Neutral..

    I have to disagree with shakey Only single core PVC single phase has a rating of 27A clipped direct. You have 2nr 3 core cables which abroad will typically be wired through conduit This at 3 phase only has a rating of 20A (table 4D2A col 5) which then has to be derated by 0.8 for a group of 2...
  11. M

    Quicky - 2382 question

    The new table 4B1 is more limited than the old one. I think the first questioin may have been a typing error - not unusual for C&G). Your second question doesn't have the right answer - should be 0.91 - again another C&G error, but I think you copied it incorrectly as only one of the 4...

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