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pete-r avatar image
pete-r asked

Multiplus-II Earthing in a Motorhome & thick cable

When installing a Multiplus II in a UK motorhome with a Lynx distributor and also EHU provision on the motorhome then what is the BS7671 compliant way of keeping mains Earth & DC negative circuits not not passing mains fault current through a same part of a DC negative circuit - they should share the same common ground of the vehicle chassis on separate grounding posts which does avoid creating a circuit merely a shared connection.
The wiring diagrams suggest the inverter earth requires a very thick cable when normally 4mm² would be adequate and it also shows the earth wire connecting to the DC negative busbar which would be correct for a marine craft, but against UK regs for a motorhome. So in essence the supplied diagrams are wrong for a motorhome. Is this fixable perhaps with an amendment or revision?
The incoming mains consumer unit will have the incoming 2.5mm² safety earth conductor connected to the CU earth busbar which in turn uses a short 4mm² flexi cable to connect to vehicle chassis. It would be normal to expect a 4mm² cable from inverter to CU earth busbar to be adequate.
Is there a way to get definitive advice on this query from the Victron technical support team?

Thanks

Multiplus-IIGrounding
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kevgermany avatar image kevgermany ♦♦ commented ·
Please clarify/confirm

EHU -Electrical Hook Up aka shore power?

Where are the diagrams you're referring to?


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Kevin Windrem avatar image
Kevin Windrem answered ·

Not a recommendation but note that internally, the AC PE is connected to the case so if you need to keep AC and DC fault paths separate then this needs to be considered.

There is no DC negative to case connection inside the Multi but the idea of the case providing a DC fault path is I believe the reason large conductors are shown between the case and DC negative busbar.

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