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Discuss IR connundrum in the Periodic Inspection Reporting & Certification area at ElectrciansForums.co.uk.

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  1. Mark.W
    Offline

    Mark.W Electrician's Arms

    Location:
    Swindon, Wilts
    Hey Guys

    I've got a bit of a head scratcher that I was hoping someone could help with.

    I have a ring main feeding 7 points. When testing IR btw L&N I get 967Mohm but when testing N-E & L-E I get 455Mohm. I split the ring and tested as 2 radials and the results suddenly come back all clear at >1000Mohm L-N L-E and N-E??? When I reconnect the ring it's back down to 455Mohm??

    I've checked all connections at the sockets and all good.

    Any ideas??

    Cheers
    Mark
     
  2. Mark.W
    Offline

    Mark.W Electrician's Arms

    Location:
    Swindon, Wilts
    Just a thought but it could be the damp! I'm on a site in Poole and it's very moist where I am.
     
  3. Pete999
    Online

    Pete999 Trusted Advisor

    Location:
    Northampton
    Business Name:
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    Are you disconnecting ALL the circuit conductors from the CO Ls, Ns and cpcs??
     
  4. Pete999
    Online

    Pete999 Trusted Advisor

    Location:
    Northampton
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    Well it would be damp in a poll wouldn't it? sorry my attempt at humour
     
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  5. HandySparks
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    HandySparks Trusted Advisor

    Location:
    Hampshire
    Business Name:
    Neish Electrical Services
    Is ring continuity OK?
     
  6. Mark.W
    Offline

    Mark.W Electrician's Arms

    Location:
    Swindon, Wilts
    Yeah end to ends are good, as is r1+r2

    R1 - 0.35
    Rn - 0.39
    R2 - 0.64
    R1+R2 - 0.27
     
  7. HandySparks
    Offline

    HandySparks Trusted Advisor

    Location:
    Hampshire
    Business Name:
    Neish Electrical Services
    OK. Obviously, missing ring continuity could affect IR results when the ring is split.

    BTW, I guess you mean r1, rn and r2.
     
  8. Mark.W
    Offline

    Mark.W Electrician's Arms

    Location:
    Swindon, Wilts
    Yeah it's auto correct lol

    Start of
    A new line
    Auto capitalises
    The first letter
     
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  9. HandySparks
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    HandySparks Trusted Advisor

    Location:
    Hampshire
    Business Name:
    Neish Electrical Services
    Actually, looking at the figures again.
    If you have about 500M IR for a complete ring, then splitting into two halves would give about 1000M for each half if the 'fault' is evenly distributed.

    I don't really see a problem, especially as the figures are so high.
     
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  10. tony mc
    Offline

    tony mc Electrician's Arms

    Keep the test on for at least a minute and see how the reading change i would say that the reading would slowly go up slowly if it is a damp problem but I wouldnt lose any sleep over the readings posted!
     
  11. Pat H
    Offline

    Pat H Don't ask, get an Electrician in.

    Location:
    Ware Herts
    Business Name:
    Sparks of Intelligence
    I'd agree the values look ok. The L-N us passing through two conductor insulations. L-E and N-E are only passing through the line conductor insulators as the CPC is bare.
    A little moisture in the cable and you will see lower values.
    Your tested proved the values where consistent even when split.
     
    • Like Like x 1
  12. westward10
    Online

    westward10 In echoed steps I walk across an empty dream. Staff Member Trusted Advisor

    Location:
    Northamptonshire
    I don't see a problem here.
     
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  13. telectrix
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    telectrix Scouser and Proud of It Trusted Advisor

    Top Poster Of Month

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    the only problem as i see it is OP considering that 455Mohms is worthy of a second look. many MFTs only read up to 299Meg.
     
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  14. Pete999
    Online

    Pete999 Trusted Advisor

    Location:
    Northampton
    Business Name:
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    probably a strange thought, but any chance the OP could be misreading the MFT and stating OHMS instead.
     
  15. westward10
    Online

    westward10 In echoed steps I walk across an empty dream. Staff Member Trusted Advisor

    Location:
    Northamptonshire
    Mmm, second look then look somewhere else.
     
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