We have frequent power outages here, so maybe there are some things we understand better than others because we have more experiences with blackouts and have instances with certain permutations or scenarios, as I type the national grid is down. In my home I have a 25kva diesel generator, I have an external transfer switch to switch between grid and generator, I had an ATS but switched it to manual some years ago. I have had this set up for over 2 decades since the house was built. The utility meter, transfer switch and generator are co-located outside by the fence of the compound about 20 meters from the main house.
Inside the house, the inverter is connected to and hence takes its power from the main distribution board. The “AC IN” of the inverter does not know whether the power it sees is coming from the generator or the grid. It takes power from the DB and whatever power it sees at the DB depends on the position of the transfer switch I.e generator or GRID. Therefore if you connected the AC out of another inverter (which is effectively another generator) directly to the AC-in of a Deye (which is what a sunsynk is) it is the same thing. Deyes are very popular here and I know most if not everyone with a Deye here has a fuel powered generator here of some sort as a backup with a transfer switch like I described. If you can connect a generator directly to the main AC-In of the Deye which is effectively what you are doing when the transfer switch is set to generator, then you can connect the AC out of any inverter to the AC-IN of the Deye. The output and hence the input to the Deye of a generator or another inverter is the same….AC power!!!
Microinverters and string inverters are uncommon here because we do not have a stable grid, therefore it is natural that information on microinverters is difficult here, many do not even know what they are. Similarly those who live in countries with stable grid and are newer to the whole backup power thing are equally probaly not as knowledgeable in certain aspects as those of us who live in countries with unreliable grids and have been using power inverters for decades and have had to experience and try such scenarios. I lived in the Uk for 20 yrs, only had a blackout once, in all my life here I have only experienced 1 yr without a single blackout. Similarly, in every property I lived in the UK, the meter was inside the house or the property if a block of flats, you cannot find any house here where the meter is inside the house with implications for things like Ct coil. Or sometimes we don’t have mains power on all three phases and again because this is not abnormal, we have our own unique solutions. We all have our percularities and there are things you won’t know are possible because you have not had the situation to experience them and the solutions..but hey go ahead shutting people down because their experiences do not match yours!
I Came here initially in search of info on micro inverters, this is a forum where people come to learn but there are clearly a few arrogant people who feel they know it all.…but clearly don’t.
I don’t see any reason why he cannot get a transfer switch inside his home to switch between the grid and the output of his other inverter to feed the main AC-in of his Sunsynk, like I said it is the same thing as feeding the AC-in via a generator.