In this regard, though I am a bit more permissive perhaps in my thinking, I too think the big issue with the Voltronic (why I an never recommend it to someone who is severely budget-strapped, which is the main selling point of these units), is that they have no paperwork at all. They only have a CE mark (the self-certified compliance mark, which has been jokingly called the “china export” mark since they all have it).
I’m going pretty much by the letter of NRS097 here, which if I recall, specifically delegates the compliance of a UPS used as an standby SSEG to SANS-10142.
The sticking point with these inverters have always been whether the internal transfer switch is “suitably interlocking”. For such standby units, the code requires that it be impossible to have both the grid and the generator connected. The generator (aka inverter) should only power up if the grid has been suitably locked out (this is if my memory on the topic serves).
One way to do that is to make the interlock physical. For example, two contactors with a physical interlock between them, which is something you can buy as a kit for many brands: For making star/delta starters (if the interlock fails you will create a massive short across all three phases).
The Voltronic, to my knowledge, doesn’t do a physical interlock. The relays are individual relays, which can in theory get stuck in a manner that leaves both sides connected.
Now make no mistake, I was explaining yesterday to @JacoDeJongh that the Multi also has individual relays, in fact it need it to be that way in order to do the tests it does (TN bonding, etc). But the Multi is tested and certified for that reason.
So for literally a decade now, that’s what some of us have been saying. Someone will have to send a model to a testing house, such as Bureau Veritas, or TÜV Rheinland, to have it certified. Somehow it never happens.