Anyone else running a Victron Multiplus with a genny on AC-in? Confused about the transfer switch behaviour

I've had my Multiplus 12/3000/120 installed for about three months now and overall I'm chuffed with it, but I keep getting confused about how it handles switching over to my Honda EU22i when I plug it in. Sometimes it transfers almost instantly, other times there's a noticeable delay — maybe 3 or 4 seconds — before it accepts the generator and starts charging. Doesn't seem to matter whether the genny has been running for 30 seconds or two minutes before I plug it in.

I've been poking around in VictronConnect and I can see there's a setting called "AC input 1 minimum current" which I've got set to 3A, and the transfer switch delay is at the default 3 seconds. I'm wondering if the Multiplus is waiting for the EU22i's output to fully stabilise before it accepts it — the Honda is an inverter genny so in theory the waveform should be clean from the off, but maybe it's still a bit wobbly right after startup?

Has anyone dialled in their settings specifically for a smaller inverter genny like the EU22i? Curious whether dropping the transfer delay or tweaking the UPS function makes any difference. Also not sure whether I should be on "Generator" or "Grid" mode for AC input 1 — I've just left it on Grid because I wasn't sure, but I suspect that might be relevant here.

@SuffolkDweller the transfer switch behaviour trips people up constantly. A few things worth checking:

1. AC-in low/high limits — the Multiplus is quite fussy about voltage and frequency. Honda generators can hunt a bit under light load, so set your acceptance range slightly wider in VEConfigure.

2. Transfer switch delay — there's a configurable input current limit too. If you've got it set too low, the unit thinks the genny can't support the load and stays on inverter.

3. UPS mode vs normal — affects how fast it transfers.

On my narrowboat setup I run a similar config with a Honda EU30i and had identical confusion. Turned out my AC-in current limit was set to 8A which was throttling everything.

Download VEConnect or VEConfigure and actually look at what your input settings are — the defaults aren't always sensible out of the box.

@SuffolkDweller on my boat setup I had the same confusion initially — the Multiplus has a built-in transfer switch but the timing of it threw me off.

A few things worth checking:

• What's your AC input current limit set to in VictronConnect? If it's set too low the unit might be rejecting the genny input entirely
• The EU22i has a soft start output — are you seeing the Multiplus actually accepting the AC-in or is it staying in inverter mode?
• There's a Dynamic Current Limiter setting in the assistant configuration that helps with generators that have wobbly frequency/voltage on startup

The Honda EU22i is inverter-generator so frequency should be stable, but worth checking your input voltage range settings too. What does VRM or the GX device show for AC-in voltage when it's connected?

@SuffolkDweller one thing neither @OffGridJack nor @SmartSolar_Queen has touched on yet — the UPS function setting. By default the Multiplus switches to AC-in with a brief interruption. If you enable UPS mode it's essentially seamless, but here's the catch: with a Honda EU22i running in eco mode, the voltage/frequency isn't stable enough on startup for the Multiplus to accept it immediately.

On my boat I lost three months of sanity before realising the genny needed 30-60 seconds to stabilise before the Multiplus would even consider accepting it. There's a configurable AC-in lower frequency limit in VE.Configure — I nudged mine to 45Hz and it sorted the dithering behaviour completely.

Also check your dynamic current limiter is enabled. The EU22i is sensitive to inrush loads and that setting prevents the Multiplus from immediately hammering it.

Great points from @OffGridJack, @SmartSolar_Queen and @SomersetNomad already. One thing I'd add specifically with the Honda EU22i — make sure you've set the AC input current limit in VEConfigure (or via the VRM/GX device if you have one) to around 10A max. The EU22i is rated 1800W continuous and folk often forget the Multiplus will try to pull more than that, especially if it's simultaneously charging batteries and passing through to loads. That'll cause the genny to lurch about and potentially trip the overload protection on the Honda. Once I dialled mine back to 8-9A it all became rock solid. The Multiplus handles the load sharing between genny and batteries beautifully once that limit's set sensibly.

Great thread — @SuffolkDweller, one thing worth checking specifically with your Honda EU22i is the input current limit in VEConfigure. The EU22i is a fantastic little genny but it doesn't like being hammered, and if your Multiplus is set to pull more current than it can comfortably deliver you'll get the genny struggling and the Multiplus potentially dropping out.

I'd suggest setting AC input current limit to around 7-8A initially and working up from there. You can also enable PowerAssist so the Multiplus supplements the genny from the batteries during peak loads rather than demanding everything from the Honda at once — works a treat and saves wear on the engine too.

What firmware version are you running? Some earlier versions had slightly quirky transfer switch timing that was sorted in later releases.

Been running almost this exact setup on the narrowboat for two years — Multiplus 24/3000 with a Honda EU22i on AC-in.

One thing nobody's mentioned yet: weak AC detection. The Honda's inverter generator produces a slightly "soft" sine wave under load, and the Multiplus can occasionally get twitchy about accepting it, particularly when it's cold or the genny hasn't fully warmed up.

Worth giving the Honda 30 seconds to settle before the Multiplus tries to grab the AC. You can tune the AC input voltage and frequency acceptance window in VE.Configure — I widened mine slightly and it transformed the reliability overnight.

Also check your shore power connection settings aren't fighting against what @DeclanJohnson mentioned about the input current limit. The two interact in ways that aren't obvious until you dig into the manual properly.

Great thread. One thing I haven't seen mentioned yet — make sure you've got UPS function enabled in VEConfigure if you need seamless transfer. Without it, there's a brief intentional delay when switching to the genny which can cause sensitive electronics to hiccup. Also worth checking your AC input voltage and frequency limits are set generously enough to accept the Honda's output, as small gennies can wobble a bit under load and the Multiplus might reject the input if your tolerances are too tight. @PeteJames will probably recognise that one from the narrowboat! 😄