Ring testing

[Jel]

Hi had some rather strange reading today, that i have never seen.
Was carrying out a ring test today on a EICR (r1,rn,r2) and i was getting r1=0.38 r2 = 0.39 and was getting a strange reading of r2=75v???
Any idea why im getting a voltage reading?

 

[i=p/u]

broken earth

 

[Jel]

Yes but normally i would get a reading of just 0.00, not a voltage reading?

 

[Top Cat]

Hi had some rather strange reading today, that i have never seen.
Was carrying out a ring test today on a EICR (r1,rn,r2) and i was getting r1=0.38 r2 = 0.39 and was getting a strange reading of r2=75v???
Any idea why im getting a voltage reading?

Not sure if you have done a typo on this? r2 = 0.39 - r2 = 75v

 

[Guitarist]

You mean Rn=0.39? Broken earth would give R2 of +999 rather than 0.00, surely?

 

[Jel]

sorry the cpc is the circuit which is showing 75v

 

[Guitarist]

End to end is showing 75v on a continuity test? If it's an MFT then as i=p/u says, broken cpc with some stray inductance messing with the tester's head.

 

[Jel]

Great, that sounds a bit more like it. Just couldn't get my head around why it was showing a voltage.

 

[TPES]

It's a dead test, should be no voltage, if you still have other circuits powered up, turn then off one at a time and see when the voltages on earth goes, its abit high though to be an induced voltage.

 

[Guitarist]

It's a dead test, should be no voltage, if you still have other circuits powered up, turn then off one at a time and see when the voltages on earth goes, its abit high though to be an induced voltage.

It does seem high, but on an isolated RFC, I can't see what else it could be. Testers can be sensitive beasts at times.
As always, hard to say anything with certainty without being there.

 

[Moses]

End to end is showing 75v on a continuity test? If it's an MFT then as i=p/u says, broken cpc with some stray inductance messing with the tester's head.

I concur, The CPC is open along the route.

 

[Moses]

You need to trace the open circuit by checking all socket and spur earth connections, possibly testing the continuity by the long lead test method.