Test Meter - Forum Sponsors since 2007!
This official sponsor may provide discounts for members

Discuss odd N-CPC results in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

A

andekoch

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:  American Electrical Advice Forum

Just looking for general pointers here as to what can cause low (approx 0.3M - 0.4M) readings when doing insulation resistance tests between N and CPC.
Obviously the main earth needs to be removed as well as the main bonding or there are likely to be low (probably zero) results esp on TNCS systems.

Lets assume that there is not a real dead short for now, to state the obvious.

To clarify I am lookin for things like say when doing P - N and you get a 0.3M it is probably a pilot light or RCD fused spur. extractor fan is another low P - N reading cause etc
 
S

Spudnik

  • Thread Starter Thread Starter
  • #3
Interesting as n-cpc should be fairly clear.

I would start by whipping off all the accessories and see if there is a trapped neutral in the back box. Thats normally the favorite.

I have had low readings right across the conductors, which is purely down to age.
 
A

andekoch

  • Thread Starter Thread Starter
  • #4
just a general question so assume a typical domestic installation. the last time this happened i isolated the circut completely (ie removed the N and CPC concerned from the consumer unit) and the error went away so there must have been somethign else in the house that was the error but it was not on the outside light spur I was extending.
Was a pain to have to do this since the CU was so jamed up and it took ages to find the relevant N and CPC (not a nice new board with well laid out terminals).
 
A

andekoch

  • Thread Starter Thread Starter
  • #6
Interesting as n-cpc should be fairly clear.

I would start by whipping off all the accessories and see if there is a trapped neutral in the back box. Thats normally the favorite.

I have had low readings right across the conductors, which is purely down to age.

Agreed N - CPC should be clear which made it frustrating when this occured. I would have been interested to trace the fault but (when isolating the circuit in question) it was not on the circuit I was working on and I did not feel like spending the day (or more) on my own time. The owner said there was a plug socket burried behind a cupboard that had never worked so I suspect this could have been the cause. but I will never know unless called back for more work.
 
SuperlecDirect - ElectriciansForums.net Electrical Suppliers
This official sponsor may provide discounts for members

Reply to odd N-CPC results in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

Top Bottom