I'm still playing with 3*MultiPlus II 48/5000 230V & 1ph generator.
"Switch as group" is OFF, generator is connected without any visible problem, it works to charge battery and pass power directly to L1 and indirectly to L2/L3. All software settings are tried in many (all?) combinations - Weak AC Input, Dynamic Current Limiter, UPS Function, Wide Input Frequence, Power Assist. Also Ground relay with/without Neutral/Ground jumper on Generator side.
The main problem - input current is limited to 10A max, usually 7-8 A. It's definitely too small value, official "Input Current Limit" = 25A. It's not a problem of Generator, it's enough branded & new, 11kVA, easily works at 5kWt load.
Note that there are many topics in forum talking about unexplained low input current.
OK, let's forget about generator :). What happens if connect only L1 from grid to the system? My pleasure to try.
1st picture - L1 only is connected, AC Output - Off, AC Input - 7.8A/1.8kWt, charging - 1.6 kWt, but should be at least 50A/2.5kWt according to spec.
2nd picture - L1/L2/L3 is connected, AC Output - Off, AC Input - ~24A total, charging - 100A/5 kWt as expected.
3rd picture - L1/L2/L3 is connected, AC Output - On, AC Input - ~45A/10kWt, charging - 100A/5 kWt as expected. It's just illustration that no problem to get 20A from L1, but only with L2/L3 connected.
How to explain such "balance" (?) limit up to 10A, if "physical" real limit for L1 - 25A? Looks as MultiPlus waiting for his/her colleagues and don't want to exceed "virtual" input current dedicated for 3*MultiPlus (8A for L1 and 8A*3 for L1/L2/L3). If it works "as designed", it means that no big sense to connect 1ph Gen to 3Ph, it can't cover all power expenses connected to that system.