PV inverter layout

Noticed something that might be worth a wider discussion — had a similar head-scratcher with my Victron setup recently.

When I first commissioned my Multiplus-II, the local display on the unit itself was showing my PV inverter (a Fronius Primo) sitting on the AC-in side of the diagram. Looked completely wrong to me since it's wired to AC-out. Spent a good hour double-checking my cabling before realising the display was the issue, not the wiring.

Logged into VRM and everything showed correctly — PV inverter on AC-out exactly where it should be. The local CCGX display eventually corrected itself after a firmware update, but for a while the two were showing contradictory information.

A few things worth checking if you're seeing similar:

• Firmware — keep the GX device, Multiplus, and any connected inverters in sync. Victron's VRM update tool makes this straightforward
• AC-coupled vs DC-coupled — easy to get muddled in the diagrams if you're running both
• Assistant configuration — if you haven't set up the PowerAssist or ESS assistant correctly, the GX can misidentify which AC bus your PV inverter is on

My van conversion uses DC-coupled solar (Victron MPPT straight to the battery) so I don't have this complexity there, but the tiny house setup with AC coupling is definitely where things get fiddly.

Anyone else run into display/VRM discrepancies like this? Curious whether it's a known gremlin with certain GX firmware versions or something more setup-specific.

@T6Solar the local display on the Multiplus-II shows AC input/output from the inverter's own perspective, which trips people up constantly. It's not the same view you get in VRM or even the GX device dashboard.

Worth checking whether you've got your AC-in and AC-out wiring confirmed correctly first — I've seen installs where someone's inadvertently fed AC-out back toward the shore power inlet, which creates some very confusing readings on that local display.

On my motorhome build I run a Multiplus-II 24/3000 and the local LED indicators are practically useless for diagnostics. Everything meaningful comes through the Cerbo GX → VRM chain. If you're not already on VRM, get it connected — the live power flow diagram immediately makes the layout logic click visually.

What firmware version are you running? Some earlier builds had display quirks that were patched.

Ran into exactly this rabbit hole when I first wired up my tiny house system.

The penny dropped for me when I stopped thinking about what the display shows and started thinking about where the sensor actually sits in the circuit. The Multiplus-II is measuring at its own terminals — it has no idea what's happening upstream at your distribution board.

So if you've got a grid-tied PV inverter feeding into the AC-in side, the Multiplus just sees net current flowing past it. Can look completely backwards to what you'd expect.

@DefenderDream is spot on about perspective. Once I added a Victron Energy Meter (the ET340 in my case) on the grid side, suddenly everything made sense in VRM. That real-world reference point is what ties the whole picture together.

@T6Solar this caught me out too when I set up my garden office system. The key thing that helped me was sketching an actual physical diagram — pen and paper, old school — showing each measurement point separately rather than trying to hold it all in my head.

What I'd add to what @ZI_Sparks said: the VRM portal gives you a much clearer picture than the local display once everything's talking to the GX device. The individual tile layout in VRM finally made it click for me which readings were pre- and post-inverter.

Worth also checking your CT clamp orientation if you're seeing values that look plausible but slightly wrong — had an embarrassing moment where mine was on backwards for about a week before I noticed the emergency backup numbers weren't adding up properly.

@T6Solar worth adding one more layer here that catches people out specifically with EV charging loads — because the draw is so sustained and high (even on a 7kW Type 2), the discrepancy between what VRM shows versus the local display becomes really apparent under load.

What I've found useful is cross-referencing the Multiplus-II's reported figures against a clamp meter on the AC input cable. If those two agree but VRM looks odd, you're almost certainly looking at a sign convention issue in how the portal is interpreting the data rather than any actual measurement error.

The Victron integration docs do clarify the positive/negative current direction assumptions, but frankly they're buried. Once you've mentally locked in which reference point each display is using, it stops being confusing — but that initial commissioning phase is genuinely a gotcha.