MultiPlus-II three-phase system intermittently imports power from the grid and vibrates

Bit of an odd one here — not three-phase myself (just a single MultiPlus-II 3000 in the motorhome) but I've been reading up on three-phase ESS setups lately and this topic keeps cropping up.

From what I've gathered in various Victron community threads, the intermittent grid import in a three-phase MultiPlus-II setup often comes down to phase imbalance — if one phase is pulling more load than the others, the ESS logic can get a bit confused and briefly dips into the grid to compensate. Worth checking your grid setpoint settings on the Cerbo/Ekrano.

The vibration side of things is interesting though — is that audible transformer hum? I've noticed my single unit hums noticeably more when it's doing rapid AC switching or the charge current is fluctuating. Could be similar on a larger scale across three units.

Few things I'd check:

• Are all three units on the same firmware? Mixed versions can cause weird sync issues
• What's your ESS assistant configured to? Optimise with or without batterylife makes a difference
• Any chance it's a CT clamp positioning issue throwing off the grid meter readings?

Anyone else here running a three-phase setup in a UK property? Curious whether this is more common than people think. Victron's own community forum is decent but feels good to get a UK-specific angle on it — grid regs here aren't quite the same as mainland Europe.

Hey @CornishCamper, sounds like you've stumbled onto a fairly well-documented quirk! The intermittent grid import on three-phase ESS setups is often down to phase imbalance — if one phase is carrying a heavier load than the others, the system can briefly pull from the grid to compensate before it rebalances itself. Worth checking the ESS assistant settings, particularly the minimum SOC and grid setpoint values in VEConfigure.

The "vibration" description is interesting though — are we talking audible transformer hum from the units themselves? That can sometimes indicate the inverters are hunting slightly, which ties back to the phase sync settings. Definitely one for the Victron Community forum too if nobody here cracks it, as their engineers sometimes chip in directly. What firmware version is the system running?

@CornishCamper the vibration is your MultiPlus-II doing its best impression of a tumble dryer full of spanners 😄

Seriously though — on three-phase ESS setups the culprit is usually phase imbalance causing the system to momentarily lean on the grid to compensate. Victron's ESS algorithm

@MoorLee spanners is generous — mine on the narrowboat sounded more like a badger in a biscuit tin before I sorted the phase rotation sequence.

Worth checking your AC coupling balance across all three phases; an uneven load split will have the ESS constantly chasing its tail and pulling from the grid to compensate. Victron's ESS assistant needs the phase compensation set correctly in VEConfigure or it defaults to per-phase rather than total — classic gotcha that'll have your meter spinning like it owes someone money.

@ExFarmer a badger in a biscuit tin 😂 I'm absolutely stealing that phrase.

So on the actual three-phase question — is the intermittent grid import typically down to the phase compensation setting in ESS? I've been reading that if it's set to individual phase rather than total system, the inverters on lightly-loaded phases can end up pulling from grid to "balance" things out rather than using surplus from busier phases.

My little single-phase setup doesn't have this headache obviously, but I'm curious whether sorting the phase compensation in VictronConnect actually resolves the vibration too, or whether those are two separate gremlins entirely?

Also — does the Victron ESS assistant firmware version matter here? I've seen mentions of older versions behaving oddly on three-phase configs. Anyone running the latest and found it calmer?

@EcoFlow_Nerd the vibration side is usually the inverters hunting — they're constantly negotiating phase sync across L1/L2/L3 and if the grid assist threshold isn't tuned right you get that hunting behaviour which causes the buzzing.

In VE.Configure there's a grid setpoint and AC input current limit that really need dialling in carefully for three-phase ESS. If those are off even slightly the system yo-yos between import and inverting, which is exactly what causes the intermittent grid draw.

Worth checking the ESS assistant version too — older versions had known issues with three-phase grid interaction. Victron pushed some fixes a while back.

Not got three-phase myself (motorhome so single phase only) but I spent a fair bit of time on the Victron community forum reading through others' setups when I was configuring my ESS assistant. Loads of good threads over there specifically on this.