question

sebastian-storholm avatar image

DC Leakage via Protective Earth Conductor

I'm have this weird problem that during a no-load condition with an Smartsolar MPPT charging, I'm seeing a phantom load of around 22 W that doesn't seem to exist. The MPPT is mounted in a cabinet along with a Multiplus, and the whole cabinet and both devices are tied to a protective earth bus bar, which is bonded to battery negative, aka before the SmartShunt in the system. The Multiplus and the MPPT are then grounded on the load side of the SmartShunt. I also measured the current in the earth conductor, and it's around 1.4 A, which correspond quite well to the 22W phantom load on the system (12V system). There's also an equal discrepancy between the battery + and - conductors of the MPPT. So, is there an issue with my MPPT charger, or should I bond the protective earth bus bar on the load side of the SmartShunt?

MultiPlus Quattro Inverter Chargermppt smart solarsmart shuntGrounding
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Don't forget even in standby mode the mppt and various components will draw something from the system. Our little multiplus 12v/16kva with mppts and shunt, uses about 16W doing "nothing".
1 Answer
Mike Dorsett avatar image
Mike Dorsett answered ·

Yes, the PE earth should be bonded on the load side of the shunt. Connection between the shunt and battery negative should be regarded as an ACTIVE connection, and no other wires connected to it.

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