Earthing arrangement - 12V campervan system with MultiPlus

Been mulling over this one myself after finishing my Transit build last spring, so good timing to get a discussion going.

My setup is similar — Victron MultiPlus 12/1600/70, a pair of SmartSolar MPPTs, and an Orion-Tr Smart (non-isolated) for the alternator charge. Everything ties into a Lynx Distributor rather than a Lynx Power In, which I suspect changes things slightly for earthing purposes.

The bit I'm still not 100% sure I've got right: where exactly the single chassis bond point should live when you've got multiple Victron devices all wanting a negative reference. I've run a single fat negative from the Fogstar Drift 200Ah battery negative terminal to the chassis, and left all the device negatives to meet at the busbar — but I've seen people do it differently and I wonder if I've introduced a potential ground loop somewhere.

Specifically curious whether anyone's had issues with the Orion-Tr causing noise or offset voltages when it's non-isolated and sharing the chassis bond. Victron's own docs are a bit vague on the practical specifics for 12V vehicle installs.

Also — does the MultiPlus neutral-to-earth relay complicate things when you're on hookup vs. inverting? I've read conflicting stuff about whether that relay behaviour plays nicely with a TN-C-S shore supply at a UK campsite.

If anyone's got a tidy wiring diagram for a similar setup I'd love to see it. Particularly interested in how folk are handling the AC side earthing relative to the chassis bond.

@TIW_Power oh god earthing on the MultiPlus nearly broke me when I did my motorhome 🙃

One thing that caught me out — the AC and DC earth bars need to be properly bonded but the MultiPlus has that transfer switch internally so people get confused about neutral switching vs earth. Victron's own wiring unlimited doc covers it but it's dense reading.

My actual gotcha: I ran my DC negative bus bar to chassis earth but forgot the MultiPlus chassis bolt itself needed a separate dedicated earth back to the bus bar. Had all sorts of weird behaviour until I sorted that.

Also worth checking your shore power inlet earthing — if you're on a site hookup the earth path back through the MultiPlus matters more than people realise.

What MPPT controllers are you running? That changes things slightly.

@BayLisa know that feeling — spent an afternoon with the Victron wiring unlimited doc and a strong brew before it clicked.

The bit that tripped me up initially was understanding that the MultiPlus's transfer switch breaks the neutral on shore power too, not just the live. So your chassis earth and your neutral genuinely need to stay separate until the MultiPlus decides to join them via its internal relay.

In my Transit I ran a dedicated 16mm² earth bar bolted straight to the chassis — everything earthed back to that single point. No daisy-chaining through the battery negative. The MultiPlus DC negative goes there, MPPT negative goes there, everything goes there.

Sounds overkill until you're troubleshooting a mystery voltage somewhere at 11pm on a campsite in the dark. Single point earth saves a lot of grief.

@BayLisa the MultiPlus earthing nearly broke my will to live too — and I did mine on a narrowboat where "floating" takes on a whole extra meaning when you're literally floating.

Not a van but I did the MultiPlus earthing on my shepherd's hut build and it's a similar headache.

One thing that caught me out specifically — the chassis earth vs the AC earth neutral bond. The MultiPlus has that internal transfer switch so when shore power's connected the neutral bonding behaviour changes. Took me an embarrassingly long time to get my head round it.

@VoltageViking floating systems are a whole other level, respect 😅

Worth checking whether you need the ground relay assistant enabled in VE.Configure depending on your setup. Mine needed it. Made a little table of which scenario bonded what before I wired anything — probably overkill but helped me not do something daft.