How to solve N/G bond problem with my cheap AIO ?

[timselectric]

A common neutral (all neutrals connected together) is the industry standard.
And is code compliant.

 

[Zsan]

A common neutral (all neutrals connected together) is the industry standard.
And is code compliant.

Then I don't understand the long discussions ( I am no exception ). This is how it runs now on my place all good.
The inverter Ground are connected ( same ) inside inverter.

I see when inverter is off-grid ( grid off by inverter internal relay ), on power-meter value of 1-3 watt from time to time , but hey when I disconnected the common neutrals i see same so...

My scenarios
Inverter is in "Grid" mode




and now when inverter goes in "Solar/Battery" mode



No need of all kind of relays and stuff.

 

[timselectric]

Right

 

[meetyg]

Then I don't understand the long discussions ( I am no exception ). This is how it runs now on my place all good.
The inverter Ground are connected ( same ) inside inverter.

I see when inverter is off-grid ( grid off by inverter internal relay ), on power-meter value of 1-3 watt from time to time , but hey when I disconnected the common neutrals i see same so...

My scenarios
Inverter is in "Grid" mode

View attachment 134468


and now when inverter goes in "Solar/Battery" mode
View attachment 134469


No need of all kind of relays and stuff.

The only issue with common Neutral is: What happens if you loose the grid's Neutral?
This highly depends on your local Earthing system (TN-S, TN-C-S etc...).
In my case, the house has a main RCD at grid input, and that main RCD disconnects Neutral too.
So for a backup situation, this is not good.
Say your away from home, you have a fridge on your inverter loads, and some other appliance causes a fault. The main RCD might open, disconnecting Neutral and now your fridge has a floating Neutral.

I know it sounds far fetched, but I suppose that the grid Neutral could be lost in other scenarios too, again, depending on your local Earthing system.

 

[Zsan]

The only issue with common Neutral is: What happens if you loose the grid's Neutral?
This highly depends on your local Earthing system (TN-S, TN-C-S etc...).
In my case, the house has a main RCD at grid input, and that main RCD disconnects Neutral too.
So for a backup situation, this is not good.
Say your away from home, you have a fridge on your inverter loads, and some other appliance causes a fault. The main RCD might open, disconnecting Neutral and now your fridge has a floating Neutral.

I know it sounds far fetched, but I suppose that the grid Neutral could be lost in other scenarios too, again, depending on your local Earthing system.

Thanks for sharing.

Earthing system I made the drawing 2 posts above. All setup is there. N from grid is down then I still have earth bonding N+E.

Well, I have now battery 48Vx ~90A, so can do trick. can run the 300 watt things for a while.
Yes everyone has its own use case. Clearly if N goes down from grid input you still have N+E bond there.... so no fluctuating neutral.

Why don't just remove that RCD from in front of inverter ? just MCB and SPD?. When the inverter relay switches may cause RCD to trip, also as I understood form some of electricians I consulted they do not recommend RCD where relay of switching motors are in pace in front of relays only after. I parameterized the inverter to start on fault but not on over temp etc..

Put RCD after inverter and if all goes down well... what can I say. I guess in 10 years once. I do not recall a power outage in last 15 years around here. Fluctuations yes..
In my case I have hard wired input in protective cable tray up to below inverter where all input / output fuses and bonding are done. No way I can just touch the incoming power cables .. in case of true short will trip main fuse outside house. In case incoming power touches the inverter case inverter will go down. But they are well fitted there..in cable tray so... I don't really see risk to have RCD in front, again my case.

All together is a risk and the probability of it to happen., When protecting life and your house there is zero tolerance for the rest...

I will let system run in this setup and get back with some experience and lessons learned.

I also have "smart home" I will add monitoring and alert in case battery is at level of "Switch back to grid" and if grid is not ON then to get alert on my mobile. At least I know I have an issue at home. .... so when getting home to have a cold beer form shop... to fix the thing..

EDITED:
Inverter was on battery mode and battery( is evening ) reached ( my 50 volt ) return to grid- we had heavy load of wash machine + other. Switched grid on. Seamlessly without any issue. ..etc.. N+E voltage all good ( 0.3 volt ).

 

[Zsan]

As promised with some feedback

EASUN SML III 5.5 KW
Neutrals are linked together - common neutral - N+E at the entry ( as in above post) - all is working fine, no fluctuating N. The MCB is tripping, I had a small short on one of my PSU (12V charger) - tripped the MCB.