In a parallel system, “each unit needs to be fused individually”?

DIY
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1

Having recently redesigned and installed a complete Victron AC/DC (12v) system including Lithium Smart batteries and using one MultiPlus II (12/3000/120-50) inverter charger, I have realized that I not only need more AC power, but I also need more charging power as well, so paralleling 2 MultiPlus II’s seems to solve that issue.

According to wiring unlimited:
"Each unit needs to be fused individually. Make sure to use the same type of fuse on each unit due to the same resistance.**
Consider using mechanically connected fuses”

On my boat, Shore Power comes in at 240 volts/50 amps to an Isolation Transformer. Power from the Isolation Transformer goes to a Balance Transformer where it is converted to 120 volts. A single 120v hot line and neutral line come from the Balance Transformer, then through a 50-amp breaker and to the inverter (the explanation is somewhat simplified). I never want more than 50 amps through this line.

So, here’s my question:
Why do I need a circuit breaker for the line “IN” on both MultiPlus II’s? Why can’t I split the line after the 50-amp breaker and go directly to each unit?

2

The ability to have easy isolation, and protection for the device, would be my suggestion as to why having separate circuit breakers per AC IN is a good idea.

The part in wiring unlimited I read as referring to DC fuses and wiring. I would add that the DC wiring will need to be balanced.

Hope that helps.