"Relay test fault" error when selecting a country and connecting to grid

Been running my Multiplus II on the narrowboat for a good while now with absolutely zero country code set in VE.Configure — just happily ticking away in UPS mode, pulling from the marina shoreline hook-up and keeping the 48V Fogstar lithiums topped off, no complaints whatsoever.

Then I decided to be a responsible adult and actually configure it properly for UK Grid — cue the "Relay Test Fault" error appearing like an uninvited guest at a housewarming.

From what I can gather, once you select a country code (UK/G98 in our case), the Multiplus suddenly starts caring very deeply about the grid connection quality before it'll allow the relay to close — things like frequency, voltage tolerance, and the anti-islanding checks all kick in properly. Run it with no country set and it's basically operating on the honour system.

The fix that worked for me was:

• Double-checking the AC input wiring (had a dodgy neutral somewhere — classic)
• Making sure grid voltage was actually stable at the time of the test
• Doing a full power cycle after saving the country settings, not just a soft reset

Worth noting that on a boat or van, your shoreline/hookup supply can be genuinely wobbly compared to a fixed installation, which probably explains why the relay test is more temperamental than expected.

Anyone else found that certain marinas or campsites cause this more than others? I'm convinced some of these hookup pedestals are held together with optimism and gaffer tape.

@FETFan this rings a bell from when I was setting up my shepherd's hut emergency backup last winter.

The relay test is essentially the Multiplus II doing a self-check to verify grid compliance before it'll play nicely with the network — completely bypassed in UPS mode, which is why you never saw it before.

When I first applied a country code (GB, naturally), mine threw the same fault until I realised the AC input wire lengths were slightly out of spec, causing just enough impedance to flunk the test.

Worth checking:

• Cable sizing on AC-in
• That your shoreline supply is actually stable — marinas can be notoriously wobbly
• Whether your MK3 interface firmware matches your Multiplus firmware version

Victron's VE.Configure relay test threshold is genuinely quite strict once a country code activates the grid-code compliance checks.

Ooh this is interesting timing — I'm literally mid-way through setting up my Ducato conversion and about to connect to hookup points at campsites for the first time.

Does the relay test fault only appear when you change the country code, or can it also pop up on a fresh configuration? Wondering whether I should just set GB from the very beginning rather than starting in UPS mode like @FETFan did.

Also — is this something you can clear through VictronConnect on the phone or do you actually need a laptop with VE.Configure running? I don't always have the laptop with me on the road and that could be a right pain if it happens mid-trip somewhere.

The relay test checks the grid relay can actually open and close properly before it'll trust the mains — without a country code set it never bothered doing that check, so now you've told it "I'm in the UK, mate, follow the rules" it's actually doing its job for once and finding something it doesn't like.

Check your AC wiring first — a dodgy neutral connection will fail this every time, ask me how I know (static caravan, 2am, January, not my finest hour).

If the wiring's solid, reflash the firmware via VictronConnect and redo the country code selection fresh — sometimes the config just gets itself in a muddle.

Also double-check your grid frequency is stable at the marina; some shoreline supplies are absolutely minging and the Multiplus II is far less forgiving once it knows which country standards it's supposed to be enforcing.

@FETFan classic Victron "now I'm going to be awkward" moment 😄

Worth knowing: the relay test fault usually clears itself after a couple of attempts once the country code is properly saved and the unit does a full restart — not just a soft reset. Pull the AC input fuse, wait 30 seconds, reconnect.

Also double-check your grid settings in VE.Configure match what's actually coming off the marina pedestal. UK shore power can be surprisingly wobbly and if your voltage/frequency tolerance is set too tight it'll fail the relay test repeatedly because the grid itself keeps drifting outside acceptable limits.

@DucatoLife — for a camper conversion I'd honestly leave country code blank until you actually need grid compliance. Simpler life.