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gettinfknrich avatar image
gettinfknrich asked

MultiPlus Grounding Requirement

I have two 110 lines feeding my breaker panel that I have isolated so that one line feeds all the breakers I want on the inverter and the other line feeds all the things I don't want such as water heater air conditioning electric fireplace .. one line bypasses the multiplus and goes straight to the breaker that I don't want running off the batteries the other line runs through the multiplus and into the panel to the breaker I do want running off batteries .. the neutral from the shore plug goes both to the panel and to the multiplus .. the neutral that comes back out of the multiplus goes to the same neutral that feeds the panel so that really all the neutrals are connected together any place they're convenient to be connected ... I was instructed to run from the chassis ground on the multiplus to a chassis ground on the RV using the same size wire as is coming out of my battery Bank because when the shore power is disconnected the multiplus switches the neutral to the chassis ground and it must be beefed up to accommodate the full load of the system ... this information came straight from tech support and it makes sense to me but I'm throwing it out here in case one of you guys thinks it's insane and Will blow me to the Moon

MultiPlus Quattro Inverter Charger
2 |3000
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2 Answers
Justin Cook avatar image
Justin Cook answered ·

@gettinfknrich while I won't address the safety of the system as a whole without being able to carefully inspect a comprehensive system diagram, I will say that the case ground screw of the MultiPlus should be connected to a good chassis ground using a cable gauge equal to the cable gauge between the batteries and the MultiPlus.

If absolutely necessary due to space or routing requirements, it is generally acceptable to use 1 gauge smaller than your primary gauge for your case ground - that is, if your main cables are 4/0, it is technically acceptable to use a 3/0 cable for your case ground strap, or (2) 2/0 cables, etc.

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hsteinhaus avatar image
hsteinhaus answered ·

I am about to connect a Multiplus 2 24/3000/70 and just test-fitted the cable lugs for the DC connections and the case ground (M6). The user manual recommends up to 95 mm^2 for the DC wiring and the example schematics suggests using the same wire gauge for the chassis ground.

However, there is not nearly enough space for even a 50 mm^2 M6 cable lug at and around the M6 ground bolt. When using an unmodified 50 or 70 mm^2 Klauke lug, there is a pretty good chance for a solid short between DC+ and the case ground lug due to contact to the PCB. I cannot imagine that a 95mm^2 lug does fit at all in the space available.

Any recommendations, except modifying the case ground lug?

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seb71 avatar image seb71 commented ·

I am using 16mm2 wire for inverter case ground.

Mine is a house system, not a RV/boat system.


Not saying that you should do the same.

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