question

dylan-hyslop avatar image
dylan-hyslop asked

Victron MP2 Tripping earth leakage on Mains fail & recovery

Good day,

I have recently installed an MP2 5000 into a home that had a 3 phase db board.

Have essentially just taken L1 and run it through the inverter and then back to the original DB Board. So everything on L1 is backed up and L2,L3 is not.

Please note that this db board has an RCD per phase. ( we have kept the original one in place, we just went to the inverter along the way.

SO just to clarify the setup:

{Mains 3 phase 63A Breaker} => 40A Input Breaker => Victron MP2 => 40A output Breaker => Back to original RCD => (Plugs and lights on L1)

(There is no Upstream RCD)

Now I have an issue that when I trip the mains breaker, L1 RCD trips immediatly.

But strangely If I then go and put it back up, it will continue to work fine. (so this is a major issue as it basically removes the point of having a UPS backup).

Then secondly, after I have put the RCD back up, and I turn the mains breaker back on. After a few seconds (when the MP2 enables ACIN) the RCD trips again?

What I don't get is why would it trip only when it switches? after it has switched it seems fine?

This does not quite make sense to me.


<Further Playing AROUND>

  • I have noticed that if I turn all the breakers OFF, on L1 and do the same test the RCD does not trip.
  • I have noticed that if I leave just 3 of the light breakers up, it does not trip.
Multiplus-IIinstallation
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UPDATE:


I managed to fix the issue, however, I am not sure why...

There was very clearly some sort of earthing issue on this site. The RCD was not nuisance tripping (ever) so I was 90% sure it wasn't that.

The first thing we did was convert all 3 phases to a single phase with a common neutral and live, this was to rule out the chances that one of the circuits maybe had a neutral on another phase's bus (we have a rcd per phase). After this, we still had tripping when losing mains and when the mains returned.

Next, I disabled ESS, and tried to turn the earth relay on and off (this made no difference).

So next I tested with a volt meter AC & DC voltage between earth and neutral. It showed 0 Volts. But now the strangest thing happened. If I put a wire between neutral and earth (above the rcd) I would see sparks, like a small arc welding between the cable and the neutral bar. Clearly indicating that there was some form of energy flowing between the two. I again measured the voltage and it showed 0V. this made absolutely no sense. So I left this join/bridge in place.

I thought I had solved it, clearly the neutral to earth in the street box was not working correctly. I then tested again and the same thing, when I killed the mains breaker, the output RCD on the MP2 would trip, same as before.

As a last resort, I put a second wire/bridge between neutral and earth (after the Victron) and this seemed to have solved the issue.

Now, this doesn't make any sense to me, from what I understand you should only ever have 1 neutral to earth point. I now have 2. And the victrons earth relay is meant to do what my 2 wire is doing. ( So when the really is on 3 neutral to earth connections)

So there can only be two logical options, my victrons earth relay is faulty, or it takes too long to engage the relay that the earth leakage is tripping.

Subsequently, we found that the earth to neutral in the street box was indeed loose,(it actually fell out and is now totally disconnected).

So how do I proceed? Can I leave the earth to the neutral bridge in the Victron DB box, or do I need to get the utility provider to come and reconnect the earth on the street?


but yea I still don't know why it was tripping and why it's stopped now, none of this is logical or makes sense

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2 Answers
JohnC avatar image
JohnC answered ·

Hi @Dylan Hyslop

You don't mention the Multi's onboard Ground Relay, so may not be aware of it. Some discussion of it here.. https://community.victronenergy.com/questions/35325/ground-relay-setting-on-or-off.html

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The ground relay is on, as per default. I tried turning it off this morning just to test, and it didn't make any difference.
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seb71 avatar image
seb71 answered ·

I have noticed that if I leave just 3 of the light breakers up, it does not trip.

That RCD did not trip before adding the Multiplus? It sounds like there is a problem on one circuit.

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This, it sounds like there is a circuit with a wiring issue
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No, it did not trip ever.

We tested them all before installing the Mp2. Which is odd. Cause my suspicion is that there is a funny plug, But then surely that would cause RCD to trip if I bypass the MP2?

It seems to only happen when MP2 loses or regains Mains Power (ACIN). I cannot get it to trip when the MP2 is bypassed.

What I cannot understand is how can that action cause it to trip. What could be wrong with one of those plugs that the MP2 earth relay would cause the RCD to trip?

I was worried that a neutral of a plug has not been paired with the correct neutral bank. But even if I disconnect the other neutrals (the mains line to that bus bar). It still trips. Could the current be flowing through the shared Earth Bus Bar?

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So with some further testing, it makes no sense. Earth leakage only fails when mains is lost or restored. It's in ess mode so ground relay option is greyed out. Basically forced on.


I have the whole house wired as single phase. So mains => MP2 => earth leakage => entire house


Earth and neutral are joined at the supply box on the street. From what I read when mains fails the MP2 breaks both live and neutral. So that earth to neutral is lost. Hence why the internal ground relay enables.

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seb71 avatar image seb71 dylan-hyslop ·

It's in ess mode so ground relay option is greyed out. Basically forced on.

But in a previous answer you said that you tested with ground relay off/disabled and there was no difference.

Also you said that only one circuit is causing this issue. Did you investigate that circuit and the consumers connected to it?

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