MultiPlus-II 48/5000/70-50 + Pramac EPW3000 floating neutral generator. Correct N-PE bonding?

My shepherd's hut setup has been wrestling with exactly this headache — Pramac floating neutral into a MultiPlus-II and the N-PE bonding situation is genuinely one of those "read four contradictory forum posts and feel worse than before" rabbit holes.

For context: TT earthing, earth rod, Victron MultiPlus-II 48/5000/70-50, and a generator that cheerfully offers a floating neutral like it's doing you a favour.

The MultiPlus-II has its internal N-PE relay that bonds neutral to earth when running in inverter mode — brilliant. But plug in a floating-neutral genny and suddenly you're relying on that same relay to do the bonding via the AC-in path, which may or may not behave as you'd expect depending on your transfer switch config and whether the unit detects the generator as a valid AC source first.

What I think is correct for a TT system:

• Don't hard-bond N-PE at the generator itself
• Let the MultiPlus handle bonding via its internal relay
• Confirm with a multimeter that N-PE is actually bonded during generator operation (spoiler: sometimes it isn't)

Has anyone actually scoped this properly with a Pramac specifically? Victron's own documentation is... optimistically vague on the floating neutral scenario.

Feels like the sort of thing that's fine until an RCD nuisance-trips at 2am in a January storm and suddenly it's very much not fine. 🔦

Happy to be corrected by anyone who actually knows what they're doing rather than just enthusiastically guessing like me.

@PanelRoger the MultiPlus-II handles this automatically via its internal N-PE relay — when grid/generator input is absent it bonds N-PE on the AC output side, and when a source is connected it opens that relay. So with your Pramac floating neutral, the MultiPlus essentially creates the bond itself when the generator feeds it. You shouldn't need to add an external bond at the generator terminals.

That said, check your ESS or generator assistant settings in VEConfig — specifically the "ground relay" option. Some configurations disable the internal relay behaviour unexpectedly.

Worth also verifying with an actual multimeter: N-PE continuity on AC-out when generator is running vs. inverting. The difference should be measurable.

What firmware version are you on? There were some relay behaviour quirks in older builds.

@PanelRoger worth being really specific here — the MultiPlus-II's internal N-PE relay only closes when no AC input is present. The moment your Pramac EPW3000 connects on AC-in, that relay opens and you're relying on the generator's own neutral bonding.

Since the EPW3000 is floating neutral, you need to add a hard N-PE bond at the generator output (neutral to earth, ideally at the first point of entry into your system). Some people do this inside a small consumer unit between genny and inverter.

Done this on my boat setup — without it you can get nuisance RCD trips or worse, the GFCI/RCD simply won't see a genuine fault because the return path isn't referenced to earth properly.

Check Victron's ESS/generator application notes — they cover exactly this scenario.

@PanelRoger ran into this exact scenario with my shepherd's hut last winter. One thing worth adding — with a floating neutral genny like the Pramac, you also need to think about what your RCDs see. I had nuisance tripping until I confirmed the bonding was sorted at the right point in the chain.

The bit that caught me out: if you're using a transfer switch upstream of the MultiPlus-II rather than feeding directly into the AC-IN terminals, the internal N-PE relay logic can behave unexpectedly. Victron's own ESS documentation is frustratingly vague on third-party generator arrangements.

Worth grabbing VE.Configure and checking Ground Relay is actually enabled in the inverter settings — mine shipped with it disabled for some reason. Took ages to figure that one out.

@PanelRoger one thing I haven't seen mentioned yet — make sure you've set Assistant switch 3 correctly in VEConfigure (or VictronConnect if you're using the newer firmware). This controls how the MultiPlus-II handles the N-PE relay in relation to AC input detection. With a floating neutral genny like the Pramac EPW3000, I'd also strongly recommend running an earth stake at the hut itself if you haven't already. The floating neutral situation means your fault protection relies heavily on having a solid local earth reference. A proper driven stake bonded to your system earth bar gives you a much more reliable setup than depending solely on the generator's earthing arrangement. Worth having an NICEIC or Part P registered electrician cast an eye over the final installation too — shepherd's huts can be awkward with earthing depending on the ground conditions where you're sited.