Omschakelen van net naar generator met node red

Been reading a Dutch thread about switching between grid and generator on a multi-phase ESS setup and it got me thinking about my own situation on the narrowboat.

Currently I'm running a single Victron Multiplus-II and switching between shore power and my Honda generator is a bit of a manual faff. I drop the input current limit down before switching to avoid the inverter throwing a wobble, but I'm wondering if anyone has automated this properly with Node-RED?

The Dutch chap was adjusting his AC input settings through the console each time — which seems error-prone if you're doing it regularly. On a boat you're constantly moving between marinas, mid-river anchoring, and relying solely on solar, so I'd love a flow that detects which source is connected and adjusts the input current limit automatically.

A few questions for those who've tackled this:

• Are you using a digital input on the Cerbo GX to detect generator state, or polling MQTT?
• What's the safest input current limit to set for a typical 2kVA portable genny — I've been using 8A but not sure if that's conservative enough
• Any risk of the ESS getting confused about grid codes when flipping between sources?

I've had a poke around VEConfigure but Node-RED feels like the cleaner solution if it can write to the relevant DBUS paths reliably. Fogstar have got me a decent battery bank so the last thing I want is a dodgy switchover causing a BMS trip in the middle of nowhere.

Anyone running something similar, particularly on a liveaboard setup?

@RustyNomad interesting one. The Dutch thread is probably referencing the ESS assistant's grid code behaviour, which behaves differently when you swap AC-in source from grid to generator.

Key thing with Victron multi-phase ESS and generators — you need to tell the system it's seeing a generator, not grid. In VEConfigure there's an AC input type setting. Get that wrong and the ESS assistant will try to export back into your genny which isn't ideal.

On my static caravan backup setup (single phase, much simpler than yours) I use a changeover contactor rather than relying on Node-RED for the switching logic itself. Node-RED then just monitors and logs.

For a narrowboat I'd also look at the Quattro if you haven't already — the dual AC input handles grid/generator switching natively without needing external automation.

What Victron unit are you running currently?

On a narrowboat single-phase setup you'll want the VEConfigure ESS assistant to handle the handoff automatically — Node-RED is great for orchestration but don't let it fight the built-in transfer logic or you'll get relay chatter that'll wake the ducks.

Key things I learnt the hard way on my boat:

• Set your AC input current limit correctly per source (shore vs. genny)
• Use DVCC if you're mixing battery types — saved my Fogstar Drift cells from an enthusiastic Victron charger
• Generator start/stop via the GX relay is far cleaner than trying to script it externally

@RustyNomad the Dutch thread is almost certainly about the GridCode and WeakAC settings — enable Weak AC for your generator input and the Multi will stop being precious about frequency wobbles.

Genuine question before going further down this rabbit hole — what's the typical handoff delay people are seeing in practice on single-phase setups when the generator kicks in?

I'm planning a garden office build and the Victron Multi I'm speccing would need to manage a similar grid/generator switch. My concern is whether sensitive equipment (NAS drive, monitors) would brown out during the transition even with the ESS assistant handling it.

Is the inverter's internal UPS function fast enough to bridge that gap, or do people typically add a separate UPS on top? I've seen mention of the transfer switch time being <20ms in Victron's docs but I'm not sure how that holds up in real-world conditions rather than ideal lab specs.

Also — does the behaviour differ between AC-in-1 and AC-in-2 inputs when switching sources?

@MuddySkipper on my narrowboat I'm typically seeing around 20ms handoff with the Victron Multi — basically imperceptible unless you're running something truly fussy, though my kettle doesn't seem to care either way.

The Node-RED angle is interesting if you want visibility into the switch events rather than actually controlling them — let the ESS assistant do the heavy lifting and just have Node-RED log it or trigger a notification when the genny kicks in.

what's the typical handoff delay people are seeing in practice

Honestly the bigger real-world delay is me remembering to actually start the generator. 🙃

@MuddySkipper 20ms is what @CornishNomad quoted, which is basically the time it takes you to think about whether the generator started properly — long before your brain has even registered the panic 😄

On my narrowboat I actually ran a test with a cheap desk lamp and a camera — couldn't catch a single flicker.