H
HappyHippyDad
Todays fault finding
I had a bit of a head scratcher today, I think I've got to the bottom of it but thought I would run it past you guys.
0.15MΩ between N and CPC on a ring circuit.
I started breaking down the circuit and when I disconnected one of the sockets the fault cleared. I now got 15MΩ. Nothing obvious to see, but it cleared so I was happy.
I then started putting the sockets back on. One of the sockets was a spur and it was feeding another spur. Before I put this socket back on I IR tested both cables, to eliminate the possibility of the fault being on the cable leading to the (2nd) spur. It tested fine, however, the cable feeding the first spur came up with an IR reading of 0.0MΩ. I then did a continuity test and got 0.1Ω (N-E)
I then retested the whole ring, and still got 15MΩ, even with the spur testing at 0.1Ω (N-E).
My plug in tester had indicated that all was ok when I was initially determining which sockets were on the circuit (i.e 3 lights showing on the tester).
I then did a R1 + R2 which showed me the CPC was broken.
I then calmed down and realised that the CPC must be completely broken, but something was causing continuity between the N-E.
I'm now thinking a screw through the cable, but how likely is it that a screw would completely severe the CPC and then make contact with the neutral, but actually only be in contact with one part of the now broken CPC?
Another thought is that the screw has been removed, somehow leaving the neutral still touching one part of the broken CPC?
Another thought is that the CPC is actually connected to the neutral in the JB under the floorboards?
Just thought I'd check if I'm missing anything obvious before I start chopping in to the wall or taking up floorboards?
Todays fault finding to Continue reading...
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I had a bit of a head scratcher today, I think I've got to the bottom of it but thought I would run it past you guys.
0.15MΩ between N and CPC on a ring circuit.
I started breaking down the circuit and when I disconnected one of the sockets the fault cleared. I now got 15MΩ. Nothing obvious to see, but it cleared so I was happy.
I then started putting the sockets back on. One of the sockets was a spur and it was feeding another spur. Before I put this socket back on I IR tested both cables, to eliminate the possibility of the fault being on the cable leading to the (2nd) spur. It tested fine, however, the cable feeding the first spur came up with an IR reading of 0.0MΩ. I then did a continuity test and got 0.1Ω (N-E)
I then retested the whole ring, and still got 15MΩ, even with the spur testing at 0.1Ω (N-E).
My plug in tester had indicated that all was ok when I was initially determining which sockets were on the circuit (i.e 3 lights showing on the tester).
I then did a R1 + R2 which showed me the CPC was broken.
I then calmed down and realised that the CPC must be completely broken, but something was causing continuity between the N-E.
I'm now thinking a screw through the cable, but how likely is it that a screw would completely severe the CPC and then make contact with the neutral, but actually only be in contact with one part of the now broken CPC?
Another thought is that the screw has been removed, somehow leaving the neutral still touching one part of the broken CPC?
Another thought is that the CPC is actually connected to the neutral in the JB under the floorboards?
Just thought I'd check if I'm missing anything obvious before I start chopping in to the wall or taking up floorboards?
Todays fault finding to Continue reading...
ElectriciansForums.net for the latest in electricians' jobs, news, advice and more