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McWidowmaker

Earth leakage and Inverter

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I have been having some interesting problems with my earth leakage since I have installed my solar system. Large inrush currents (2.5kw+) sometimes trip the earth leakage. What I have managed to find so far is that pure sine wave inverters have a capacitor between the neutral and earth, which causes a floating neutral. This may interfere with the earth leakage.

 

Anyone else had similar problems? How did you solve it? Bonding the neutral and earth on the DB should help I think. Other ideas?

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An earth leakage is pretty much useless unless neutral is bonded to earth, right? I mean, it might still work because some current is bypassing the EL, but you have no idea if and when it will work, if it will be within the designed 20mA, and so on.

 

Of course not all inverters allows for neutral/earth bonding, although the good ones do.

 

My victron is set up to close the bonding relay when running on battery, and to open it when running on grid, so I have both an EL on the input (DB board side) and on the output of the inverter. Not exactly per regulations, but certainly safe.

Also, that capacitor you speak of: Indeed, that would be it. A capacitor passes AC and blocks DC, so any AC component (such as changes in voltage/current) will pass a small amount between the two lines.

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So here is a fun factiod. The other day I stuck a volt meter across the neutral and earth on my inverter. It measured zero, as expected, because it was running off-grid. I then hit the button to make it fall back to the grid. Now what the smaller/older victrons do is first open the bonding relay, and then a few seconds later the transfer switch takes you back to the grid. So you have about 5-10 seconds to observe what a floating ground looks like. Now my ground floats at around 120 volts relative to Neutral. That's got to screw with a down-stream earth leakage...

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So far I know you do not feed an inverter from an E/L, but only on the output side, if the load requires it.

Indeed :-) But Victron makes these things to work on boats, and on a boat you often have an EL shore side and another one boat side, so it is obviously designed to work in such a setup. You're right that in a house you would normally feed the inverter from a non-EL protected feed, and then permanently tie the ground and neutral on the output of the inverter before it goes into the EL.

 

Also, I seem to recall it mentioned here that there's some caveats with the Axpert.

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Indeed :-) But Victron makes these things to work on boats, and on a boat you often have an EL shore side and another one boat side, so it is obviously designed to work in such a setup. You're right that in a house you would normally feed the inverter from a non-EL protected feed, and then permanently tie the ground and neutral on the output of the inverter before it goes into the EL.

 

Also, I seem to recall it mentioned here that there's some caveats with the Axpert.

I connected the Axpert neutral output to earth after Voltronics confirmed there wouldn't be a problem, have had no ill effects.

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