Discuss Insulation resistance difference both ends of ring final cct in the Electrical Testing & PAT Testing Forum area at ElectriciansForums.net

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timhoward

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Initial fault was RCD tripping, narrowed down to a ring final cct.
IR tests on that cct with all loads removed were showing almost zero between neutral and cpc.

So I broke the ring apart and eventually found the nail through a cable, and got that all sorted.
Now its testing ok in as much as r1+r2 and r1 + rn tests at sockets are all well within range, earth loop ok and RCD test ok.

Wish I'd walked at this point - but thought I'd better double check IR again for peace of mind.
Insulation tests between phase and neutral for that cct are around 600 Mohm. No problem there.
But insulation tests between phase and cpc are 75Mohm from one end of ring and 171 Mohm from other end of ring. This is a new one on me.

My only idea was a loose earth connection at a socket somewhere. I've now checked all connections are tight at each socket, and it's made no difference.
So slightly curious in whether others would take view that it's a pass from both ends and time to move on, or start pulling whole thing apart again!
 
move on. the lower reading could just be sweaty hands when you're having your panic attack over the difference. ?
 
move on. the lower reading could just be sweaty hands when you're having your panic attack over the difference. ?
Lol! Cheers.
I won't lie that I can't wait to leave this one and had reached point of frustration where I didn't 100% trust my judgement - it's been rather a mare...
  • nail through cable (that no one was willing to admit to happening or point me towards)
  • then finding and sorting out a spur off a spur off a spur, only to then find another identical arrangement in the next room.
  • Then finding neutral from ring serving a lighting point
  • Then finally thinking I was on home straight then finding a bridge in the ring during testing
  • Then replacing a few older sockets that were showing very high continuity resistance via test plug but not when using probes on connection screws, or wildly different readings on left and right socket
So very glad to finally walk away!
 
I won't lie that I can't wait to leave this one and had reached point of frustration where I didn't 100% trust my judgement - it's been rather a mare...
you must call judgement whether to carry on to sort the job out ,but doing saw .
then it is no safer now or when you walked . me tell the customer what you have found and leave has it his .
 
you must call judgement whether to carry on to sort the job out ,but doing saw .
then it is no safer now or when you walked . me tell the customer what you have found and leave has it his .
Yes I agree. I fixed the faults above and advised a rewire due to age of wiring, or at very least an EICR test. I also made sure he knew that I haven't fully tested other circuits ( other than quick loop test on lighting circuit I touched).
 

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