Victron off grid - breaker size

DIY
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1

Hi all,
I’m running a three-phase off-grid setup with three Multiplus-II 48/6k5/100 inverter/chargers (one per phase). I’d like to understand the correct breaker sizing for the household distribution groups on the output side of the inverters.
Specifically: when a short circuit occurs in one of the household groups, what is the minimum breaker rating (and type) required to actually trip before the Multiplus-II units are damaged or shut down in an uncontrolled way?
Some context:
• In off-grid mode there is no grid to contribute fault current — the three Multiplus-II 48/6k5/100 units are the sole source of energy
• The Multiplus-II 48/6k5/100 has a specified peak current and short-circuit current output, but I’m unsure whether this is sufficient to trip standard MCBs in the instantaneous range
• I want the breaker in the affected group to trip first, protecting both the wiring and the inverters
Questions I’m hoping the community can help with:

  1. What short-circuit current does a Multiplus-II 48/6k5/100 actually deliver into a fault in off-grid mode?
  2. Is this enough to trip a type-B, type-C, or type-D MCB instantaneously, or will the Multiplus-II go into overload/shutdown before the breaker trips?
  3. What breaker type and rating is recommended for output group protection in this setup?
  4. Are fuses a better choice than MCBs on the output side for off-grid systems like this?
  5. Are there any Victron settings that influence short-circuit or overload behaviour in a three-phase off-grid configuration?
    Any experience, calculations, or documentation references are very welcome. Thanks!
2

I Think you mean Maximum breaker rating.. To an extent, this also depends on the type of breaker, as b curve breakers will trip faster than the more common c curve breaker. given the 6k5’s 11kW 1 min capacity, this gives 27 -29A of mains current. So the inverter should be able to clear (trip) anything smaller than 25A. However on a distribution board, with other circuits also taking current, the figure may be lower.