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Inverter tripping please help.


spikegv

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Hi everyone. Hope someone can help me. My inverter (Pro line) was struck by lightning and it was replaced with a new inverter (Mecer) in December. The problem is we get random trips. Every second day or so usually towards sunset and one in the morning on Tuesday before sunrise. 

The earth leakage for the inverter is tripping and nothing on the main db? Electrician came out and strapped the earth and neutral yesterday hoping it would sort the problem out but it tripped again this afternoon. 

Anyone know what can be causing this?

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21 minutes ago, Jaws said:

But don't despair we have resident expert here with issue regarding inverters and tripping earth leakages. Im sure The Terrible Triplett will be here soon to assist you. :-)

:D:D:D:D - Amen brother Jaws, you are preaching to the choir!

I'm being taken step by step to check my DB and the search is getting more interesting by the moment. First time ever I am starting to understand how a DB works.

Tomorrow I can go all out, test the shiite out of it all, after all has left the building. I'll report back on the other thread of what we found.

I was earlier this afternoon on "random" trips. Now we have moved to the next level where I can consistently trip / not trip the DB..

Trick is to find the cause, as it is not apparent.

So what I can suggest, if their is tripping where there was none before, a lightning strike and new inverter, that maybe there is more to the problem than just looking at the inverter.

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1 hour ago, The Terrible Triplett said:

So what I can suggest, if their is tripping where there was none before, a lightning strike and new inverter, that maybe there is more to the problem than just looking at the inverter.

The reason I think it's the inverter is because the insurance company installed another inverter before the Mecer which was in place for 3 weeks and we had no trips. ( They swapped out the other inverter for the Mecer as the easy solar (axpert) was very noisy and the fans ran continuously. 

I was reading the manual and saw this option. It's currently on default is that correct?

38


Allow neutral and grounding 
of AC output is connected 
together:


When enabled, inverter can 
deliver signal to trigger
grounding box to short 
neutral and grounding
Disable: Neutral and grounding of AC output is disconnected. 
(Default)
Enable: Neutral and grounding of AC output is connected. 


This function is only available when the inverter is working 
with external grounding box. Only when the inverter is
working in battery mode, it will trigger grounding box to 
connect neutral and grounding of AC output

 

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1 hour ago, spikegv said:

The reason I think it's the inverter is because the insurance company installed another inverter before the Mecer which was in place for 3 weeks and we had no trips. ( They swapped out the other inverter for the Mecer as the easy solar (axpert) was very noisy and the fans ran continuously. 

I was reading the manual and saw this option. It's currently on default is that correct?

38


Allow neutral and grounding 
of AC output is connected 
together:

What that does is written there in clear Chinglish :)  If enabled, it drives a tiny relay on the Comms board (the one with the RS232 and/or USB connections, the RS232 is disguised as an RJ45 connector) so that you can drive an external relay to connect neutral output and earth, when and only when the inverter is running in battery mode. It will have absolutely no effect if you don't connect an external relay to the appropriate terminals on the comms board.

But some later model inverters come with a relay inside already doing that. Even ones where setting / parameter 38 is available.

Did your inverter come with main firmware version 73.00? You find this out by pressing the up button until you come to a screen with U1 on the left; there should be two groups of two digits that come with it, e.g. "73" in the middle and "00" at the right. But they could be all sorts of other numbers.

My understanding, not yet disproved by machines I've come across, is that machines that come with 73.00 are the ones with the internal relay to connect neutral and earth when in battery mode.

We need to know what your latest electrician did, since it's possible it has made things worse. We also need to know if you have the AC input connected to the utility or a generator or nothing at all.

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Current version is (U1)72 and (U2)04. 

The electrician told me he strapped or bonded the neutral and earth on the inverter. (In layman terms told me basically creating a transformer?) The earth leakage tripping is the one just after the inverter which supplies the load. 

The AC is connected to Utility. The inverter switches to solar in the morning and then to Utility in the evenings. 

IMG-20190111-WA0023.jpg

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4 hours ago, spikegv said:

The electrician told me he strapped or bonded the neutral and earth on the inverter

I believe that is a mistake. When the inverter is in bypass this will create an extra bond in addition to the one installed at the supply (either at the transformer for TN-S, or at the premises point of supply for TN-C-S). This allows operating current to flow on the earth wire, which is not allowed. The correct way to do this is to use the bonding relay, which @Coulomb referred to.

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2 hours ago, plonkster said:

This allows operating current to flow on the earth wire, which is not allowed.

And, pertinent to this thread, any current flowing in the earth conductor would have been flowing in a neutral conductor. So the active and neutral  currents won't balance, so the "earth leakage" breaker (really a residual current breaker these days?) will trip. 

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1 minute ago, Coulomb said:

So the active and neutral  currents won't balance, so the "earth leakage" breaker (really a residual current breaker these days?) will trip.  

If he doesn't have an RCD upstream from the inverter, there might be no tripping (I assume his trouble is with a downstream RCD). But it is still wrong... even if you can get away with it.

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7 hours ago, spikegv said:

The electrician told me he strapped or bonded the neutral and earth on the inverter. (In layman terms told me basically creating a transformer?)

Well, the transformer thing is nonsense. I agree with @plonkster, bonding earth and neutral anywhere other than at the main neutral to earth link in the DB is a mistake.

I also have a machine that came with 72.XX (in fact, 72.40), and I've had no trouble with my system. I join AC in neutral to AC out neutral, and my RCBO (combined residual current and overload breaker) is after the changeover contactor, and therefore after the inverter. The changeover contactor connects my loads to the AC input if there isn't 230 V from the inverter to power the coil.

Joining AC in neutral and AC out neutral immediately is not desirable for machines that came with 73.00, since they will join AC out neutral to earth when the inverter is running. If you have an RCD/RCBO before the inverter, that will trip. But you don't have that type of inverter.

So it seems to me, @spikegv, the solution is get an electrician to remove the neutral to earth connection, and instead connect AC out neutral to AC in neutral. If your RCD/RCBO (safety switch) is before the inverter, get it moved to after the inverter, if possible.

I've just noticed that joining AC in and AC out as I do shorts out one of the "safety" relays (the AC in neutral relay; the two relays that are designated as "safety relays" appear to be absolutely identical to the other relays). I wonder if shorting that neutral relay is frowned upon. It's quite possibly the reason that the machines that come with 73.00 have the "neutral to earth when in battery mode" functionality built in. Kudos to the manufacturer for achieving this merely by using a double pole relay in place of an existing single pole relay. 

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I belatedly notice that spikegv's photo shows "Earth leakage for inverter supply". That sure sounds like the RCBO is before the inverter. I note that this post states that the RCBO has to be after the inverter, not before it. However, I don't understand the reason why. Anyone care to enlighten me?

I know that there are small capacitors, of the order of 1 nF, from active and neutral to earth inside the inverter, but these would contribute well under 1 mA each (of 50 Hz AC) to the earth current, and besides that they are all paired (and therefore balanced, ignoring the tolerance of the capacitance values). So I'm guessing that these are not the reason, but I suppose that there could be some issues with switch-on surges. Perhaps it's the switching noise that travels through the earth conductor (that seems to be a well-known exception to the rule that earth conductors should only ever carry fault currents). I recall that a motor controller installed on a facility where I used to work had to have a specially insensitive RCBO protecting it, since it had such a lot of "noise current" to earth. So I think I've answered my own question: the switching noise is many orders of magnitude higher in frequency than 50 Hz, and so much more than "well under 1 mA" flows through those capacitors, and this can trip an RCBO upstream from the inverter.

My understanding is that only General Purpose Outlets (power points) and more recently lighting need to be protected by a residual current device, so there is no need for the inverter to be protected by one. But I could be wrong, and things may be different in South Africa.

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24 minutes ago, Coulomb said:

I wonder if shorting that neutral relay is frowned upon

If my reading of SANS 10142-1 is correct, you are allowed to use a common neutral like this if 1) it is a three-phase supply, and 2) the standby power is connected at the main supply point. If it only supplies a part of the installation, or if it is single phase, neutral must be switched.

31 minutes ago, Coulomb said:

Kudos to the manufacturer for achieving this merely by using a double pole relay in place of an existing single pole relay.  

Sarcasm? 🙂

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3 minutes ago, plonkster said:

If my reading of SANS 10142-1 is correct, you are allowed to use a common neutral like this if 1) it is a three-phase supply, and 2) the standby power is connected at the main supply point. If it only supplies a part of the installation, or if it is single phase, neutral must be switched.

Huh, interesting. Any idea what the reasoning is? For the three-phase case, I can vaguely see that you might need neutral connected to take some unbalance current. But supplying only part of the load... ?

3 minutes ago, plonkster said:

Sarcasm? 🙂

Not at all, this time. Weber and I were wondering how they accomplished it at all without any additional relays, till we noticed that one was a changeover type.

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The house is running on 3 phase but the inverter is running only on one of the phases. I can take a picture of the whole setup to make it clearer but the electrician called me and said that I should start the process of elimination by dropping a breaker each day and seeing if the power trips. Doesn't sound like it's going to solve anything as it's intermittent

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5 hours ago, spikegv said:

The house is running on 3 phase but the inverter is running only on one of the phases. I can take a picture of the whole setup to make it clearer but the electrician called me and said that I should start the process of elimination by dropping a breaker each day and seeing if the power trips. Doesn't sound like it's going to solve anything as it's intermittent

The setup

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1547743295172478.jpg

1547743294641697.jpg

1547743294816390.jpg

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Some observations.

  1. It seems that your inverter's AC input is fed from the white phase, via breakers 26 and 27 (line and neutral as well?). But the outputs are labelled as "red phase". I assume that the "red phase" loads are fed either by Eskom red phase, or the inverter output, which will synchronise with, and when in bypass be supplied by, the white phase. This seems odd and confusing to me, but should be safe since the Hager changeover switch has a "0" (off) position in the middle.
  2. Your inverter's AC input seems to be fed from the RCD, which I suspect is the source of your problem. There is a Schneider 16 A breaker right next to the Onesto RCD in the small white box. Does that feed the inverter's AC input? 16 A is too low for something that could potentially supply 5 kVA to the loads (about 22 A), and AC charge at up to 3000 W (about 13 A), a total of some 35 A. Even breakers 26 and 27 at 30 A seem a little small, but nowhere near as under-rated as the 16 A. If you never charge from utility, then 30 A is fine, but 16 A is not.
  3. When your system has its nuisance trips, is it the RCD itself (the Onesto), or the Schneider right beside it, or possibly breakers 26 or 27, or possibly also the white phase RCD, position 21? If there is an unbalance into the inverter, the Onesto and RCD 21 should both see it, so either could potentially trip.
  4. There is only one Mecer inverter, yet it is showing "HS". This indicates that it is a "master", so setting 28 has either "PAR" (for parallel mode), or one of the three phase settings ("3P1", "3P2", or "3P3"). I feel is should be set to "SIG" (for single). This is not a serious problem, and I don't see how it could be contributing to the tripping. But I feel it may as well be eliminated, just to eliminate a remote possibility.
  5. Breaker 19 is labelled as a "SUB DB". What is connected to that? It seems it may have some relevance to a tripping issue. Perhaps if you do the breaker elimination exercise, start with that one.
  6. The long row of breakers is labelled "Red phase inverter supply and output", which seems confusing to me. But of course it will always be confusing as it is a sort of red and white phase composite. Breaker 20 is the main input breaker, so the "CB 1-20 fed from inverter power" should be 1-19. Just being pedantic with that last one.

So from the above, no solution as yet, but the answer to questions in point 3 might help pinpoint the problem.

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1) everything on the red phase runs on the inverter unless I push the changeover to Eskom.

2) The inverter is supplied by 27. If I drop that breaker it goes to batterries. (I will check 26 as well)

3) when we get these nuisance trips the ones to is the one that drops and no other breakers. 

4) will change that today.

5) sub db is a small board outside that has outside lights on it. (I think the original electrician removed earth on this one as the lights still stay on when this nuisance trip happens)

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2 hours ago, spikegv said:

5) sub db is a small board outside that has outside lights on it. (I think the original electrician removed earth on this one as the lights still stay on when this nuisance trip happens)

Did he remove the earth (which would be evil and wrong) or did he move it to the other side of the RCD (ie remove residual current protection, which is allowed)? I hope it is the latter. Merely removing the earth will not stop an RCD from seeing an imbalance and tripping, but moving the circuits off of the RCD will.

Personally I would much rather put my lights on their own RCD if I needed them to stay on when there is a fault elsewhere. Which is also what I did in my own home. But that is an aside... not relevant to your issue here 🙂

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2 hours ago, spikegv said:

3) when we get these nuisance trips the ones to is the one that drops and no other breakers. 

Sorry, I don't follow that. Exactly which breaker trips when the nuisance trip happens, please? And can you please verify that turning off the Schneider breaker (the only one not named) will remove AC in from the inverter (the "tennis ball" AC symbol goes away).

2 hours ago, spikegv said:

Setting 28 only has the option PAL.

You can't change setting 28 unless the inverter's "power switch" (bottom right corner) is off. That's why it appears that there is only one setting. Switch it off just before you attempt to change that parameter, then switch it back again when the parameter is changed. I can't recall how long after you switch the inverter off that it actually goes dark, and under what conditions it will stay on.

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2 hours ago, Coulomb said:

Sorry, I don't follow that. Exactly which breaker trips when the nuisance trip happens, please? And can you please verify that turning off the Schneider breaker (the only one not named) will remove AC in from the inverter (the "tennis ball" AC symbol goes away).

Sorry, the onesto trips only.

I will confirm what the Schneider breaker drops but to my knowledge only breaker 27 removes AC from the inverter. 

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