Hi everyone! I would like to add some experience to to this thread, and to invite everyone to keep on commenting on this issue.
This year, I have installed many Growatt SPF5000ES in different locations- and I had no trouble at all with all the earth/neutral bonding issue. Until now, every set up consisted in a single SPF5000ES connected to a 220V Grid (neutral distributed and grounded only on the energy provider transformer). Every set up was done with at least 2 RCD, one before the inverter in the main panel, and one after the inverter to feed the loads. Always the inverter ground terminals properly connected to the local earth rod. Never an issue with nuisance RCD tripping, and neither RCD blinding in battery mode. The bonding between Neutral and Ground while working in battery mode is done inside the inverter and seems to work just fine... I was pretty happy with these growatt until now.
Now, I am facing my first setup with paralell inverters (3 of them) and the RCD that is installed before the inverters keeps tripping inmidiatly after Grid is detected and energy is fed to the loads in bypass mode. I have tried with different RCD (types AC, A, B, inmunized, even a 300 mA RCD...) with no luck, until now I have not found what actually causes the main panel RCD tripping. For the moment, I have disconnected the main panel RCD, that is to say before the inverter, which is not totally bad, but leaves unprotected the installation between the mains and the inverter against earth faults.
I will keep on investigating, I have some theories to test:
1- The neutral/earth bonding internal relay does not work properly in paralell mode... would be odd, but you never know whith these guys
2- Leakeage of 3 inverters in paralell is too much for a single RCD (one may think that a 300 mA should do, but it actually does not....). I have found a Growatt note for SPH inverters (not the same as SPF, but should do...) suggesting that a separate 300mA RCD should be installed for each inverter while working in paralell, but I just don't buy it, and I can not do test it becaus I have no spare cables between the main panel and the inverters... One interesting test I did, was to shut down battery charging (by setting "only sun charges the battery in parameter 14 'OSO' "). In this way I supposed, that no high frequency currents would be generated, so leakeage should be minimum... even in this situation the RCD trips as soon the inverter tries to feed the loads with energy frome the grid. So, the leakeage problem doesn't seem to be asociated with high frequencies... strange
I think I could trick some way the RCD whith some external ground relay, but first I need to properly understand what is causing this. I am waiting for a leakeage current clamp meter recentrly bought to arrive, to further investigte this issue, and have many more tests to do...I will not surrender that easy
Please, if any one else has experience working with Growatt SPF paralell set-up and mains RCD tripping, I would be happy to know your experience
Regards,