Phoenix inverters - PE-N bridge

Been running a pair of Phoenix inverters on my narrowboat for the better part of four years now — a 1600VA for auxiliary loads and a 3000VA for the main system — so this PE-N bridging question's been rattling around in my head for a while.

The thing that catches me out is that the smaller Phoenix units (1600/2000VA range) handle the PE-N connection differently than the larger models. On mine, the 1600 doesn't have an internal bridge, which means you need that external connection for proper RCD operation. Miss it and your RCBOs become unpredictable.

The 3000 and 5000VA units are more forgiving since they've got integrated solutions, but I've noticed installers treating them all the same way regardless — usually just assuming the factory knows best.

What I'm keen to understand better: are people actually measuring continuity between PE and N on the output side, or are we mostly going on Victron's documentation? I've got a fluke multimeter that suggests mine's not quite where it should be, though the system's running faultlessly.

Also curious whether anyone's using split-load boards with multiple inverters. That's the real headache on narrow spaces — trying to keep everything isolated whilst maintaining that PE-N integrity.

Would be useful if someone with a proper test rig could verify whether there's variance between production batches. Phoenix gear's solid, but this particular detail seems to get glossed over on a lot of installations.

What's everyone else's setup looking like?

Mate, if you've got two Phoenixes running independently you'll want to keep that PE-N bridge off on both units — mixing bridged and unbridged on the same system is how you end up chasing phantom earth faults at 2am in a field somewhere, trust me on that one.

The bridge is only really useful if you're running a single inverter and absolutely need that neutral reference point. With your setup it's cleaner to let the shore power or your charger handle the PE-N bond and keep the inverters themselves out of it.

What's your current earthing arrangement on the narrowboat? That'll probably dictate whether you need the bridge anywhere at all.

@PikeGazer's spot on there. I learned this the hard way when I first plumbed in my 3000VA on the narrowboat—had the bridge enabled on both units initially and spent a bewildering afternoon tracking down phantom earth faults that weren't actually there.

The thing is, once you've got two independent inverters sharing the same AC distribution, enabling PE-N bridging on either one creates ambiguity in your earth reference. You end up with multiple paths for fault current, which confuses RCD behaviour something chronic.

Keep both bridges off and let your shore power or main CU handle the PE-N connection at a single point. Your RCDs will actually work properly then, and you won't spend three hours debugging what your Victron assistant is screaming about.

@JohnBaker—four years without drama suggests you've already got this sorted, but worth spelling out for anyone reading this later.

Running dual Phoenixes? Clever setup. The bit everyone forgets is that bridging PE-N on both units creates a parallel path for neutral current — your RCD will have a field day and you'll trip randomly at 3am when the kettle's on. Keep the bridge off on your auxiliary unit, definitely, but here's the thing: if your 3000VA is handling the main loads, you can actually run the bridge on that one only, provided it's your primary inverter and the 1600VA is genuinely isolated for auxilliary stuff. Just make sure your main switchboard's wired so only one unit ever sees the bridge active at any given time. On narrowboats especially, where space is tight and cables get creative, I'd sketch out your AC distribution before committing — saved me a rewire when I realised my garden office setup would've been a nightmare otherwise.

Right, so the thing everyone seems to dance around is why this matters on a narrowboat specifically. You've got limited earthing options compared to a house — your PE and N are often bonded at the boat's main entry point already, yeah?

When both Phoenixes have PE-N bridging enabled, you're essentially creating multiple parallel earth paths back to your battery negative. Sounds fine in theory, but in practice you get circulating currents that'll make your RCDs twitch like they've had too much coffee. Plus, if one inverter's struggling with a transient, the other one "helps" in ways you really don't want.

Keep the bridge off on both units and you'll sleep better. Single point of bonding at your main cut-out. Tested this myself when I reconfigured my garden office setup last year — made a noticeable difference to nuisance trips on the sensitive loads.

The 1600VA/3000VA split you're running is the sensible approach, mind. Just don't let them PE-N chat to each other.

Right, good question and glad you're thinking about this properly. The key thing with dual Phoenixes is that you absolutely cannot bridge PE-N on both units simultaneously—you'll create a parallel earth path that plays havoc with RCD protection and can cause nuisance trips or worse, mask genuine faults.

Standard practice is to bridge PE-N on your smaller unit (the 1600VA for auxiliaries) only, keeping the 3000VA properly isolated. This way you've got a single, clean earth reference without doubling up.

On a narrowboat where space is tight and you're already running minimal margin on battery capacity, those nuisance RCD trips become a proper headache. Worth getting the installation checked if you haven't already—it's one of those details that gets overlooked too often.

What's your current setup like?

Only bridge PE-N on the master unit — having two neutral-earth bonds in the same system is basically asking your RCD to have an existential crisis at 3am in a damp marina.