Pro Power Ground Fault

[Hammick]

I agree, that TS is switching the neutral. You probably have something amiss in one of the circuits in the backup subpanel. Here is how I would troubleshoot:

Reconnect the ground wire between ProPower and the transfer switch.
Switch off all breakers in the subpanel.
Kill main power causing the ATS to switch over to PP. The PP should not trip on ground fault with all breakers off. If it does, something is wired wrong in the transfer switch.
Turn on one breaker at a time in the subpanel until the PP indicates a ground fault. That is the circuit with a problem.

Thanks. I'll likely get motivated in April and figure this out.

I'm sure I'll get flamed for mentioning this but initially my Panamax power conditioner was showing a ground fault and often a line fault when PP was running the house. Also L1 and L2 were showing different voltages. Can't remember the voltages exactly but they were off proportionally. So if L2 was reading 130v then L1 was reading 110. On grid power everything was fine.

Troubleshooting this I determined that if I bonded the neutral and ground in the sub panel (I know this is bad) the L1 and L2 voltages on PP both read 120v and the ground fault and line faults on my Powermax power conditioner went away. Way over my pay grade to understand why bonding the sub panel fixed the issue.

I've been rolling with my sub panel bonded for months now with no issues (again I know this is a code violation).

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[Maquis]

@Henry Ford and @Maquis ...

Can you guys get on the same page about breakers on or off and GFCI in truck tripping? . I mean I thought I learned something on the 3rd... But then unlearned it tonight. Did you just forget Maquis?

This is said in jest...not to be a dick.

Ya know….I was second guessing myself as I was typing this. I have to stop relying on my memory.

Instead of just switching the breakers off, you’d have to disconnect all the neutrals and reconnect one at a time in order to find the offending circuit.