Pro Power ground fault: I'd like to hear from the experts please

[chl]

So I have been using Pro Power for over a month to power our home. I wired in a three-pole (neutral switching) automatic transfer switch to a critical load panel. All has been working great except I am periodically getting a ground fault in the truck when I turn on the Pro Power. Turning off my main AC beaker (located in the critical load panel) seemed to eliminate the ground fault issue. I found this very odd since the AC wiring does not have a neutral. I checked the AC disconnect box for loose connections, insects, etc. and all looked proper. I should mention this is an inverter driven AC unit that is connected to the furnace by 4 communication wires (essentially a canbus connection).

These ground faults have become such an annoyance that I disconnected the truck's ground connection at the transfer switch. I am still getting periodic ground faults. I resolve this by shutting off the truck, disconnecting the cord to my generator inlet box, reconnecting the cord then turning the truck back on.

Just yesterday I had the truck throw a ground fault after it had been powering the house for hours with no issues. It just decided to ground fault and of course the transfer switch went back to grid power.

So my question for the experts is how is it possible for the truck to ground fault if it's ground is not connected?

Is the Pro Power just overly sensitive? Anyone else experiencing ground faults when the truck's ground is not connected?

I can live with these periodic ground faults but I'd much prefer to have the truck's ground connected since I went through all the time and expense of wiring it correctly.

I can't think what else to test.

1) Because turning off your AC (Air Conditioner) breaker eliminates the ground fault tripping, the AC unit is obviously the issue. Is it a leak to ground or is it HFI (high frequency interference)?

First, be aware, a ground fault can occur with or with out a neutral - it just means there is a difference in the current in vs the current out on the current carrying conductors, that is being measured/detected, indicating an unexpected path to ground.

Yes if the neutrals were not switched in the transfer switch, the panel would be the source since neutrals are bonded (grounded) in the main panel and cause a ground fault detection.

With no neutral to the AC unit, just the two 240v lines and a ground, it means one of the current carrying lines in the AC unit or between the AC unit and the breaker, could have a ground leak.

2) AC units connected to GFCI breakers will trip them if they are not rated for the high-harmonic-frequencies they may produce, a common problem if you have a GFCI breaker which is why they are not generally used with AC units.

The ProPower system may have GFCI protection that is NOT rated for high-harmonic-frequencies which is causing the issue.

3) Possible Solutions: First, rule out true a ground fault in the AC unit circuits - you seems to have looked for the most common issues already. But there are ways to check for ground faults in electrical systems, many are described by searching "how to locate a ground fault in an electrical system" for example.

Second, condition the AC circuitry to filter out the high-harmonics.

There are a number of ways to do the filtering, see: https://circuitdigest.com/tutorial/...ics-using-active-and-passive-harmonic-filters

Third, the simplest solution would be to simply open the AC circuit whenever you are powering the house with the Pro Power system.
I

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[chl]

1) Because turning off your AC (Air Conditioner) breaker eliminates the ground fault tripping, the AC unit is obviously the issue. Is it a leak to ground or is it HFI (high frequency interference)?

First, be aware, a ground fault can occur with or with out a neutral - it just means there is a difference in the current in vs the current out on the current carrying conductors, that is being measured/detected, indicating an unexpected path to ground.

Yes if the neutrals were not switched in the transfer switch, the panel would be the source since neutrals are bonded (grounded) in the main panel and cause a ground fault detection.

With no neutral to the AC unit, just the two 240v lines and a ground, it means one of the current carrying lines in the AC unit or between the AC unit and the breaker, could have a ground leak.

2) AC units connected to GFCI breakers will trip them if they are not rated for the high-harmonic-frequencies they may produce, a common problem if you have a GFCI breaker which is why they are not generally used with AC units.

The ProPower system may have GFCI protection that is NOT rated for high-harmonic-frequencies which is causing the issue.

3) Possible Solutions: First, rule out true a ground fault in the AC unit circuits - you seems to have looked for the most common issues already. But there are ways to check for ground faults in electrical systems, many are described by searching "how to locate a ground fault in an electrical system" for example.

Second, condition the AC circuitry to filter out the high-harmonics.

There are a number of ways to do the filtering, see: https://circuitdigest.com/tutorial/...ics-using-active-and-passive-harmonic-filters

Third, the simplest solution would be to simply open the AC circuit whenever you are powering the house with the Pro Power system.
I

PS: the most common sources of ground faults are water infiltration in a ciircuit box, such as an AC disconnect box and damaged wires/insulation. Since much of the wiring to an AC unit is within a conduit, any flaw could be hidden from view within the conduit.