Single phase for three 30a panels

Running into something similar with a static off-grid cabin setup and wondered if anyone here has tackled this kind of distribution architecture.

The scenario: three separate consumer units, each fed independently, with the ability to switch between mains/generator and inverter supply. On a boat it's presumably a space and redundancy thing, but on land I've seen the same approach used where different "zones" have genuinely different power quality requirements — you might not want your sensitive electronics on the same feed as a pump motor, for instance.

My question for the thread is around the changeover switching when you've got multiple panels involved. A single transfer switch (or Victron's built-in transfer relay on something like a MultiPlus-II) handles one feed elegantly. But when you're talking three independent panels, each needing their own generator/inverter selection, it gets complicated fast.

Options I've been mulling:

• Three separate MultiPlus units in a non-parallel arrangement, each serving its own panel — expensive but clean
• One larger inverter with a proper 4-pole changeover contactor per panel, all interlocked
• A manual approach with Kraus & Naimer or similar rotary switches, with physical interlocks to prevent backfeed

The backfeed risk is the bit that keeps me up at night on this one. If someone's got a live generator feed and accidentally parallels it with an inverter output across two panels, you've got a very bad day incoming.

Has anyone done a multi-panel changeover install using Victron's GX ecosystem to manage the logic? Curious whether the DVCC controls and relay assistant can handle interlocking across multiple AC outputs cleanly, or whether you'd need external PLC logic.

@SueThompson what's the actual load profile across those three consumer units? Are they all running simultaneously or is it more staggered usage?

Reason I ask — I've been planning something similar for a garden office setup and the diversity factor makes a massive difference to how you size the upstream inverter. Three 30A panels could theoretically pull 21.6kW simultaneously but realistically nobody's maxing all three at once.

Are you considering a single large inverter feeding all three CUs from one distribution board, or separate inverters per circuit?

The Victron Quattro range would handle the aggregated load but the cost jumps significantly once you're looking at 8kVA+. Curious whether you've spoken to a DNO about this or if it's fully off-grid with no grid connection at all — that changes the earthing arrangements completely.

Looks like the OP got cut off there but I can probably guess where it's heading! @SueThompson are you looking at running all three CUs from a single phase inverter output and wondering about current sharing/busbar sizing?

If so, the key question before anything else is your total simultaneous peak draw across all three panels. Three 30A CUs sounds hefty but in practice most off-grid setups never see anything close to theoretical maximums across all circuits at once.

What inverter are you working with? Some of the Victron Quattro range handles this sort of distribution architecture quite cleanly with proper busbar arrangements. Also worth considering whether those CUs actually need to be separate or if that's inherited from a previous setup.

@Smithy98 makes a fair point about load profiling - that'll really drive the answer here more than anything else.

@SueThompson the OP did get cut off yes, classic forum software moment there 😄

Worth clarifying before anyone gives advice — are these three consumer units in the same structure or spread across separate outbuildings? Makes a significant difference to how you'd approach it.

I've got something vaguely similar at my static caravan setup, two separate distribution points fed from a single Victron Multiplus. The cable runs were the awkward bit more than anything else — voltage drop over distance adds up quickly if you're not careful, especially at 230V single phase.

What's your total expected draw across all three units? Even a rough figure helps. If it's modest you might be surprised what a single inverter can handle sensibly. If you're running anything with a big startup surge though that's a different conversation entirely.

@SueThompson yeah the post definitely got clipped before the key details came through! Hard to advise without knowing the full picture but a few things I'd want to know from a van conversion perspective that probably apply here too:

• What's the total anticipated draw across all three CUs simultaneously?
• Are you tied to 30A per CU or is that just what you've got fitted?
• Single phase throughout or is there any reason you've ruled out a small three-phase setup?

I've been wrestling with similar distribution headaches on a much smaller scale in my build. The Victron MultiPlus-II range handles single phase well but once you start stacking CUs the neutral arrangements get fiddly fast. Might be worth clarifying whether you're inverter-fed only or if there's any grid/generator backup in the mix too — completely changes the architecture options.

@SueThompson agree with the others that the post got cut off, but based on the thread title I'm guessing you've got three consumer units each rated at 30A and you're trying to feed them all from a single-phase inverter system? If that's the case, the total potential draw is quite significant and the inverter sizing conversation gets interesting pretty quickly.

If you can fill in the blanks it would really help — specifically what loads are on each CU, whether they're likely to run simultaneously, and what inverter(s) you're currently working with or considering. Also worth knowing your battery bank capacity and charging source (solar, gen, both?).

Static cabin setups often have more predictable load profiles than mobile applications which does help with the planning. Looking forward to seeing the full picture!