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encore866 asked

120VAC on Ground on Shore Power - Multiplus 12/3000/120

I had my Multiplus 12/3000/120 charging my batteries on shore power (120Vac) using an extension cord which had a broken ground pin (dumb idea I know).

I found 120Vac on the ground conductor throughout my system connected to AC Out 1 with the ungrounded extension cord. (only found out as I got shocked)

After finding this out I tested the system using just the inverter function not on shore power, and then I tested using shore power with a grounded extension cord. In both of these scenarios I did not find 120Vac on the ground conductor. (ground relay was enabled in settings)

I am unsure why there is 120Vac on AC Out 1 ground when plugged into a non grounded shore power source. In my understanding of the Multi, ground and neutral are bonded in the Multi via the ground relay when inverting, and the relay opens when on shore power allowing the ground to neutral bond to take place on the shore power connected sub panel.

If the ground relay was open I would see there being no way for a ground fault to trip a breaker and provide protection, however I would not expect to find any voltage on AC Out 1 ground as it is essentially not connected to anything if the relay is open and shore power connection has no ground.

Hopefully someone can shed some light on how this would occur.

Multiplus-IIGrounding
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4 Answers
rh5555 avatar image
rh5555 answered ·

When connected to shore power, my Multiplus II leaks 1.5mA to ground, rising to 2mA when ACOUT2 is active. I've measured this on 2 units. You need look no further than the Multiplus itself for your source of leakage current.

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pwfarnell answered ·

This can happen if you have any items on the ac circuit that have a small leakage current such as some power supplies which can leak a few mA into the ground cable, as the ground is now floating the voltage can increase. Another reason is you have a high resistance earth fault such as damp in a socket which is too high resistance to trip an RCD type device but is large enough to give a voltage on the ground wire when floating.

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encore866 answered ·

Hello, thanks for the explanation, while it does make sense I don’t think it applies in this case as I had my ac out 1 breaker turned off, the breaker acts only on the line conductor however. With nothing connected to the multi ac out 1, and with shore power plugged in with ground missing on the cord, I found 120v measuring between neutral and ground on ac out 1. I cannot figure how this would occur. When I plug in shore power using a grounded extension cord this does not occur. Any additional thoughts from the community would be appreciated, also can anyone else duplicate this scenario and see if you have the same result? Thank you.

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encore866 answered ·

Thank you for the comment, I believe this is what I observed on my multi as well. I do wonder how this occurs as the ground relay is open when connected to shore power. It may be the case that the current on the ground conductor is actually coming from the shore power source and not the multi but that’s just a guess.

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