Disconnected Neutal Still Showing Connection To Neutral (somewhere)

[David M]

If there's an earth/ neutral fault on any of they circuits ,surely it would trip the rcd

Sorry, with you not mentioning whether or not the existing installation was RCD protected I just assumed that was possibly the reason for the swap of the CCU. Though you may still have a neutral to earth path that doesn't trip the RCD, where any leakage current is less than 30mA.

 

[Wilko]

It's a puzzler, but I'm liking Midwest's thought of an IR problem, otherwise as JAJ says the RCD would have been telling us? Cheers, David.

 

[J.A.J.]

Thanks ,I was upgrading from an older (not ancient CU ) which was a split board,the rcd in the existing board didn't trip of either before I disconnected it

 

[telectrix]

sometimes a N-E fault will stop a RCD from tripping.

 

[J.A.J.]

Have you carried out an IR test on the final circuits?

Yeh I have done IR , low readings on some circuits 7.2meg ,5.3meg lowest was 2.5meg

 

[J.A.J.]

sometimes a N-E fault will stop a RCD from tripping.

What do you mean "stop from tripping"

 

[J.A.J.]

Sorry, with you not mentioning whether or not the existing installation was RCD protected I just assumed that was possibly the reason for the swap of the CCU. Though you may still have a neutral to earth path that doesn't trip the RCD, where any leakage current is less than 30mA.

If there is a current less than 30mA on more than 1 circuit wouldn't this trip the rcd

 

[Midwest]

What do you mean "stop from tripping"

I'm led to believe, if you think of how an RCD works, imbalance between live & neutral, with an earth neutral fault, the fault current in the earth can flow back through the neutral, negating any trip. That's how it was explained to me. But being not expert on the technical bit, however I've had that happen to me.

 

[westward10]

I'm led to believe, if you think of how an RCD works, imbalance between live & neutral, with an earth neutral fault, the fault current in the earth can flow back through the neutral, negating any trip. That's how it was explained to me. But being not expert on the technical bit, however I've had that happen to me.

I believe this can happen on TT systems, for example if you have a neutral/earth fault, the current flow will take the path of least resistance and this is likely to be the neutral path and not earth due to the electrode impedance, hence the rcd will not sense an inbalance to make it trip.

 

[DPG]

I still dont get it. A fault current would still cause an imbalance and trip the rcd. Daz