I had this exact problem using my Mecer 3kva inverter. 

Electrician came tested everything and then connected a wire from earth to neutral in my sub DB. Tested everything and left it like that.

My house run like that for about 3 years until I upgraded to a 5KW inverter I then removed the link because the new inverter does this automatically

On 2019/02/10 at 12:13 PM, Coulomb said:

I'd say you have one of the Axpert models that has the neutral-out to earth relay (or extra contact, really). This is a normally closed contact, so with the unit switched off, you'll read zero ohms, as you did. And when in battery mode, it's also going to be shorted. But in line (bypass) mode, the assumption is that the incoming neutral will already be earthed, and the earth to inverter-out-neutral is floating.

With that in mind, the whole situation may become a lot less mysterious.

The models with this neutral to earth "virtual relay" seem to be the ones that come with main firmware version 73.00.

From this post:

http://forums.aeva.asn.au/download/file.php?id=381

@Coulomb, hi, trust you are well, Glad I stumbled on this post , because the internal routing and earth bonding of Neutrals on Axperts must be clearly understood by me to help myself and others.

So from your schematic above , and from the following snippet on aus post : 

"However, in the models that come with 73.00, there is a new changeover relay that connects the inverter neutral either to earth when in battery mode, or to the AC input neutral otherwise" 

 From this I infer: 

1 when input grid is available , then we have merely a passthru mode. Input neutral connected to output neutral, no additional bonding of neutral to earth done. Rationale behind this is that when input grid is available, upstream earth bonding is available , and this allows the inv to be compatible with being in series with an upstream ELD.

2 when input grid is NOT available , internal changeover contacts of the earth relay will :

(A) isolate the output neutral from the input neutral ,and 

(B) Bonds the output neutral to earth. 

 

Which effectively elaborates to a private island  , isolated but safe , given that we have an ELD on the inv load side.

 

Are these assumptions correct?

 

 

 

 

 

Edited November 10, 20214 yr by dropkick

4 minutes ago, dropkick said:

@Coulomb, hi, trust you are well, Glad I stumbled on this post , because the internal routing and earth bonding of Neutrals on Axperts must be clearly understood by me to help myself and others.

So from your schematic above , and from the following snippet on aus post : 

"However, in the models that come with 73.00, there is a new changeover relay that connects the inverter neutral either to earth when in battery mode, or to the AC input neutral otherwise" 

 From this I infer: 

1 when input grid is available , then we have merely a passthru mode. Input neutral connected to output neutral, no additional bonding of neutral to earth done.

2 when input grid is NOT available , internal changeover contacts of the earth relay will :

(A) isolate the output neutral from the input neutral ,and 

(B) Bonds the output neutral to earth. 

 

Which effectively elaborates to a private island  , isolated but safe , given that we have an ELD on the inv load side.

 

Are these assumptions correct?

 

 

 

 

 

Hi @Nic Holmes, waiting for Coulombe confirmation on the questions above in order to assist your situation, should that still be needed.

6 hours ago, dropkick said:

So from your schematic above , and from the following snippet on aus post : 

"However, in the models that come with 73.00, there is a new changeover relay that connects the inverter neutral either to earth when in battery mode, or to the AC input neutral otherwise" 

BTW, I've since realised that ALL models after about 2016 come with the extra contact. I don't know where I got the idea that later models reverted to not having this extra contact. My apologies for any confusion that may have caused.

6 hours ago, dropkick said:

 From this I infer: 

1 when input grid is available , then we have merely a passthru mode. Input neutral connected to output neutral, no additional bonding of neutral to earth done. Rationale behind this is that when input grid is available, upstream earth bonding is available , and this allows the inv to be compatible with being in series with an upstream ELD.

It's not just that when the utility neutral to earth bond is available, you might as well go ahead and use it, it's that you must only have one neutral to earth bond in your premises. That's because if there are more than one, then some of the neutral current flows through earth conductors, which are not designed or dimensioned for this, and also such currents will play havoc with earth leakage detectors (ELDs).

It's still not a good idea to have a sensitive earth leakage detector UPSTREAM from the inverter, because it's a high powered switching device, which has to have significant capacitors connected to earth, and these cause current to flow through the earth connection. Such currents can also play havoc with ELDs.

6 hours ago, dropkick said:

2 when input grid is NOT available , internal changeover contacts of the earth relay will :

(A) isolate the output neutral from the input neutral ,and 

(B) Bonds the output neutral to earth. 

Yes. Now you need that connection to make the neutral conductors safe, and also to provide a path for earth leakage detectors to work. Since the utility neutral is disconnected, this connection is now the only connection from the inverter's neutral output terminal to earth, so there will be no nuisance tripping of ELDs.

5 hours ago, Coulomb said:

BTW, I've since realised that ALL models after about 2016 come with the extra contact. I don't know where I got the idea that later models reverted to not having this extra contact. My apologies for any confusion that may have caused.

It's not just that when the utility neutral to earth bond is available, you might as well go ahead and use it, it's that you must only have one neutral to earth bond in your premises. That's because if there are more than one, then some of the neutral current flows through earth conductors, which are not designed or dimensioned for this, and also such currents will play havoc with earth leakage detectors (ELDs).

It's still not a good idea to have a sensitive earth leakage detector UPSTREAM from the inverter, because it's a high powered switching device, which has to have significant capacitors connected to earth, and these cause current to flow through the earth connection. Such currents can also play havoc with ELDs.

Yes. Now you need that connection to make the neutral conductors safe, and also to provide a path for earth leakage detectors to work. Since the utility neutral is disconnected, this connection is now the only connection from the inverter's neutral output terminal to earth, so there will be no nuisance tripping of ELDs.

Once again , thank you so much for the rigorous response to my questions.