I believe the books say about not having two PE+N bonds of the same “earth rod” type…
Having the Multiplus PE+N relay option activated will just bring the inverter’s N to the grid PE potential.
In this case the screwdriver live detector will not light when put on N.
I have the same configuration as your (with different inverter, but the same topology) and my screwdriver doesn’t light when put on N…
Of course once again, ChatGPT is wrong.
You say you have an RCCB, which is a residual-current device that detects when the current in L is different from the current in N. That happens e.g. when someone touches L and the current flows thru that person to earth. The RCCB trips and the person stays alive.
For that fault current to flow, there must be a circuit, which is why in the grid, the N is grounded.
With your setup as in your drawing, the L and N of the Multi are floating – no connection to earth anywhere*. So the circuit never closes and the person above stays alive – as long as there is only a single fault. This is called an IT system (see Earthing system - Wikipedia) and it requires isolation fault detection of some kind and is generally only used in special circumstances.
So, long story short, you need to tie N to PE, which is exactely what the ground relay in the Multi does by default.
I think there will be no problem when you turn that relay on, multiple N-PE bonds are only a problem if that is not only the same PE, but also the same N, which it is not in your system (and the worst that can happen with multiple bonds would be nuisance tripping of GFCIs/RCDs/RCCBs).
What you need to think about, however, is where your PEN coming in from the grid is earthed (connected to an earth rod), because if that is outside of your premises, when the grid connection would be cut, there would again be no earth connection and you’re back to an IT system…
Disclaimer: I’m not a licensed electrician, and specifically not licensed by your grid operator or aware of any specific regulations that apply in your location.
*) Actually, there is capacitive coupling through filters, which is why a minimal current flows and lights up your screwdriver.
Thanks all. if everybody tells me to turn on that relay - i will try tommorow, day.
Christian - i do not have photo right now but im 99% sure that PE+N bond in grid service panel near house is done in a way that will work no matter if grid circuit is off or on, cause from grid circuit protection is only on phases, so N and PE is directly going into the house circuit breakers panel.
Would be pretty dumb to break PE in case of short. Im sure about this becasue i remember that my CB had only 3 inputs/outputs, cause house gets 3 phases, so 5 wires, 3 are phases, so N and PE must be comming with no breakers and so on, so PE and N always connected…grounded. Maybe in other countries are different, but in mine, Lithuania is like this. which i guess is good thing.
Will write my expiriance when turn on relay..i hope RCCB will not break. thats what im afraid the most, that electrons from other sources may flow in other source’s N wire. which is not very possible cause there is circuit, to flow..but who knows 
will see.
OK thanks everybody for your input, enabled ground relay, problem solved, nothing exploded, nothing has tripped. Nothing has burned - great success.
Now mark your above message as Solution for others to quickly see what has to be done.
LE: Sorry, didn’t see that you’ve already marked another message as the Solution…
Probably because N is NOT bonded to Ground, enable ground relay & ensure the MP is bonded to gnd..
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