Earth Leakage problem

[J.Spark]

This is important and needed to be stated explicity. VOELCBs can trip as a result of a fault in a nearby property even when the ELCB's own installation is switched off, because they monitor the CPC not the L & N. If there is a difference in potential between the earth electrode and any part of the installation CPC, perhaps at a fitting in casual or deliberate contact with an extraneous pipe, then a current will flow through the tripping coil. Possible causes include a non-protected circuit next door dumping current into a service pipe or the rods being too close together and in each others resistance area.

Conversely, this type of problem cannot affect an RCD as it neither knows nor cares what is going on with CPCs and main earthing conductors.

Ok....never came across a problem like this....came across many trippings but not one of this nature. [emoji16]

 

[Octopus]

Yes I have and it's all good.

with all the bulbs out and the lights switched "on", including checking the strappers on 2 way lighting?

 

[J.Spark]

No....didn't do that....will double check on that. Thanks for the advice

 

[Octopus]

Have you got a clamp meter?

 

[J.Spark]

Yes I do

 

[Octopus]

Yes I do

what is the "back ground" leakage like across the installation?

 

[J.Spark]

How does one test for back ground leakage?

 

[Lucien Nunes]

Murdoch dunno if you spotted the bit about the ELCB still tripping with the installation off at the main switch? I think that is what was meant (J.Spark, can you confirm?) in which case I don't think it's leakage from this installation but from elsewhere circulating via the MET. This is one of the rare cases where it's actually helpful to clamp either of the earth leads going through the ELCB, normally clamping a CPC can give misleading results but here it's relevant because that's the current in the trip coil. If it's more than the current measured with the two tails clamped together (this system's leakage) then the problem is external.

 

[Marvo]

In the OP he states he replaced the 'earth leakage unit' with a new one, after I read that I wrote off any possibility it was a VOELCB. Photos would be handy if JSpark can attach a couple..

 

[J.Spark]

Murdoch dunno if you spotted the bit about the ELCB still tripping with the installation off at the main switch? I think that is what was meant (J.Spark, can you confirm?) in which case I don't think it's leakage from this installation but from elsewhere circulating via the MET. This is one of the rare cases where it's actually helpful to clamp either of the earth leads going through the ELCB, normally clamping a CPC can give misleading results but here it's relevant because that's the current in the trip coil. If it's more than the current measured with the two tails clamped together (this system's leakage) then the problem is external.

Yes....still trips with the 3 phase main switch shut off. Tested no voltage to the top of the ELCB....which I find very odd. Cannot wrap my head around that.

 

[J.Spark]

In the OP he states he replaced the 'earth leakage unit' with a new one, after I read that I wrote off any possibility it was a VOELCB. Photos would be handy if JSpark can attach a couple..

Will do so when I am on site again

 

[Lucien Nunes]

An N-E fault can trip a TP+N RCD with the three lines isolated (not all 3-phase main switches isolate the neutral, unlike single phase DP). Current e.g. from a TN-S neutral above earth potential can pass to earth at the fault via the RCD N which the RCD will sense as a residual. Hence, the importance of the IR tests even though the fault doesn't require the system energised to trip.

But, what is this thing we're discussing? RCD? VOELCB? I was taking it to be a VOELCB because you said it was, but now I see Marvo has a point.

 

[J.Spark]

OK....let me rather attach some pics of the ELCB and take it from there. Thanks for the help guys. Appreciate this. Will be in contact during the course of the day tomorrow.

 

[J.Spark]

I am from South Africa so the wording may be a little different lol!

 

[Marvo]

I am from South Africa so the wording may be a little different lol!

Ahh, I've got a feeling your terminology is causing kak boet.