Based on the debates we have had on the forum I would say there is *not* a consensus. I can only give you my understanding and recommendation.
First the basic rules.
- There should always be one N-G bond in the circuit.
- There should never be more than one N-G bond in the circuit.
How to meet these rules depends on what the inverter does.
Since this thread is about the 6000EX, you are obviously asking what should be done for bonding on the 6000EX. Unfortunately, I don't yet know. Do you know if there are even bonding screws on that unit? (If you do know please let us know. It would be very helpful)
From the responses I have seen on this thread, it looks like the output has an N-G bond in both the pass-through mode and in inverter mode in it's default configuration out of the box. What I don't know is if it is a dynamic bonding system or a common neutral system.
Always having a bond on the output is great for using a single inverter, but since you are asking about a dual inverter, it can be problematic. (There will be two N-G bonds in the system). If there are bonding screws in the inverters, the screw should be removed on ONE of the inverters.)
For incompleteness, here are descriptions of what I have found on other inverters:
* Switched Neutral, Dynamic bonding AIOs or inverter chargers
A lot of the low-cost Chinees All-in-ones (MPP, EG4, etc) are built with an internal transfer switch that switches neutral and has dynamic bonding that adds an N-G bond when in inverter mode and removes it when in pass-through mode. For these inverters, it is usually best to leave the bonding screw in and not do a bond in the critical load panel. However, if you are stacking these inverters to get split-phase or single-phase with more wattage, the bonding screws should be removed in all but one of the inverters. Unfortunately, I have yet to find one of these that document the bonding scheme.
BTW: The Victron inverter-chargers I have worked with have Switched Neutral with Dynamic bonding. They document it all very well.
Common Neutral, no bonding AIOs or inverter chargers.
* Some higher-end all-in-ones like Schnider and Solark don't switch the neutral. I call these common neutral because the input and output neutral are the same conductors. These inverters count on the N-G bond in the grid connection for both inverter mode and transfer mode. The only time you would add an n-g bond with these inverters is if the installation is completely off-grid and there is no existing N-G bond.
IMHO. Common Neutral inverters are the best solution for stationary systems that have a constant tie to the N-G bond from the grid. However, in a mobile system where the grid connection comes and goes, it is very difficult to make these work well for bonding.
Switched Neutral, No bonding
*Some of the low-cost Chinese all-in-ones switch neutral but do not have dynamic bonding. (Growatt seems to have a few of these). These are a PITA. The only way I know how to deal with these is to connect the input neutral to the output neutral and treat it like a common neutral inverter. This seems to work but it is not clear whether the manufacturers support it. What is worse, on most of these there is no documentation that explains any of this to you.
Battery-powered Inverters.
The regular battery inverters (Not AIOs or Inverter Chargers) are all over the map. Most of them do not add an N-G bond and you need to have one in the system you are driving. Some (like giandle) do not add an N-G bond and the inverter does not provide an N-G bond. The output circuit is left floating.
Grid Tie inverters that feed power back to the grid.
As far as I know, all of these do not create an N-G bond and count on the circuit they are tieing to having the bond.