resistance testing ring main! help!!!!! Ask questions and find answers to many subjects relating to electrics and electrical work

[po5hscott]

i have just tested r1, r2, and rn, the results as follows:-

r1 = 0.46
r2 = 1.24
rn = 0.47

r1 and rn results are similar which they should, but r2 is much higher than it should, i belive should only be 1.67 times that of the phase conductors due to the reduced size of the cpc.....any suggestions why im getting such a high reading....the property is approx 40 years old. i hace niceic inspection shortly and would like to have all the answers or be able to fix the problem..

cheers scott

[kbrownie]

Is the CPC, connected to any parallel paths, is metal conduit also forming part of earth path have you disconnected that and pig tails to back boxes.
KB

[po5hscott]

[quote="kbrownie"]Is the CPC, connected to any parallel paths, is metal conduit also forming part of earth path have you disconnected that and pig tails to back boxes.
KB[/quote]

thanks for the reply, no other parrellel paths to the best of my knowledge, no earth condiut is used, but the cpc'c are connected to metal back boxes.

[kbrownie]

Try checking all CPC are tight in terminals this could also effect reading and you have good contact with your probes/croc-clips on the in and out CPCs
KB

[sparx]

Hi,
as the installation is 40yrs old the chances are the cpc is in fact 1.0mm not 1.5mm as now, this was normal in the 1960's, try a recalc based on that.
Any parallel earths would reduce your reading rather than increase it so don't think thats an issue,

regards & good luck,
SPARX