question

abrahamsolar avatar image

45k 3ph off grid: can RCD be wired to merely turn off one Quattro?

Based in Colorado, I'm building a Euro style 3 phase off grid setup with three 15kVA Quattros--non-mobile with a hard wired heavy AC generator. To protect all downstream wiring against AC "residual current" (also called earth leakage or ground fault), I normally would make only one connection between the AC neutral & the grounded metallic housings--through a GFI ground fault interrupting gizmo.

If the GFI sees no voltage between neutral & protective earth, that's what we want & the gizmo does nothing. If a voltage potential should develop between N & PE, the GFI will trip at a small amperage while also opening the contacts on at least one more breaker pole. I've not found any RCCB "residual current circuit breaker" burly enough to actually break the three power phases on the output side of the inverter stack, so what if a simpler RCD merely interrupts a light gauge wire that is connected to terminal H on one Quattro?

When one Quattro shuts down the other two should follow...managed by logic control wires instead of brute force switching.

(1) Other posts mention that all Victron inverters have the Neutral bonded to the metal case--which would nullify the GFI plan described above. Can the N<>PE bond on the Quattros be disconnected when I build the system?

(2) If the engine generator is running when the Quattros are switched off by an RCD fault...does generator AC still flow through the transfer relays & to the AC OUT terminals? (I would prefer if generator AC cannot make it thru when the Quattro stack is in an RCD fault shutdown.)

Thanks in advance, Community Folks~

MultiPlus Quattro Inverter Charger3 phaseGrounding
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1 Answer
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi Abraham,

This is definitely the exclusive domain of qualified licensed electricians. So outside the intended scope of this community.

The part that touches on Victron though, no I wouldn’t recommend what you are suggesting as a way to manage faults.

RCD’s are calibrated equipment and intended to safely disconnect is milliseconds. They have to be quicker than the heart attack from an electric shock.

I would use numerous smaller RCBO’s on each circuit and not 1 large one for the whole installation.

But this is extremely specific to local installation requirements. So check in with your master electricians or equivalent industry support group in your area.

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