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.

 

[Henry Ford]

Are all the circuits connected to the transfer switch isolated to a single sub panel? The simplest way to think about the Lightning's GFCI is if neutral touches ground (earth) ANYWHERE it will trip. This is why a neutral switching sub panel is required to make it work without pulling the ground wire.

Edit: the bolded paragraph is wrong. All grounds need to land at the main panel.

If I understand this diagram (don't assume I do, I'm an idiot with a wifi connection), the switch is grounded to the main panel (shore/utility), the Lightning (gen), and whatever circuits are being powered (load). If your system is wired like this Pro Power will never work with the ground connected because everything is connected to the main panel which means it's connected to the grounding rod of your house. In this case it doesn't matter if neutrals are switching or not.

As I often mention, I'm not a professional. I learned what I needed to work on my own stuff. I'm trying to be safe and follow code but I definitely have a knowledge gap.

 

[Hammick]

Are all the circuits connected to the transfer switch isolated to a single sub panel? The simplest way to think about the Lightning's GFCI is if neutral touches ground (earth) ANYWHERE it will trip. This is why a neutral switching sub panel is required to make it work without pulling the ground wire.

If I understand this diagram (don't assume I do, I'm an idiot with a wifi connection), the switch is grounded to the main panel (shore/utility), the Lightning (gen), and whatever circuits are being powered (load). If your system is wired like this Pro Power will never work with the ground connected because everything is connected to the main panel which means it's connected to the grounding rod of your house. In this case it doesn't matter if neutrals are switching or not.

As I often mention, I'm not a professional. I learned what I needed to work on my own stuff. I'm trying to be safe and follow code but I definitely have a knowledge gap.

So I should take the ground from the Lightning Pro Power directly to the subpanel bypassing the transfer switch grounding lug? Then remove the bonding screw in my sub panel.

 

[Maquis]

So I should take the ground from the Lightning Pro Power directly to the subpanel bypassing the transfer switch grounding lug? Then remove the bonding screw in my sub panel.

It doesn’t matter where the ground wire lands - they’re all connected together, electrically.
Yes, a subpanel should never have the N-G bonded. If everything else is in good order, this may be the cure.
One other thing. Be sure that all circuits in the subpanel also have their neutrals landed there. I’ve seen guys move only the hot wires to their backup subpanel, leaving the neutrals in the main panel, which is a big no-no.

 

[Hammick]

It doesn’t matter where the ground wire lands - they’re all connected together, electrically.
Yes, a subpanel should never have the N-G bonded. If everything else is in good order, this may be the cure.
One other thing. Be sure that all circuits in the subpanel also have their neutrals landed there. I’ve seen guys move only the hot wires to their backup subpanel, leaving the neutrals in the main panel, which is a big no-no.

Thanks. I moved all the neutrals to the sub panel but didn't move the grounds. I need to double check that my transfer switch load output isn't neutral to ground bonded somehow that isn't obvious. I'm assuming the transfer switch should have continuity between the load neutral and ground on grid power but not on Pro Power.

What really confuses me is the grounding when the sub panel is connect to Pro Power. So a sub panel has to be grounded to the main panel per code, right? Neutrals and grounds separated in the sub panel and the grounding lug removed. When using Pro Power the sub panel has two paths to ground (through the main panel grounding rod and the truck's GFCI. Are two paths to ground appropriate? Not seeing any alternative.

 

[Maquis]

Thanks. I moved all the neutrals to the sub panel but didn't move the grounds. I need to double check that my transfer switch load output isn't neutral to ground bonded somehow that isn't obvious. I'm assuming the transfer switch should have continuity between the load neutral and ground on grid power but not on Pro Power.

What really confuses me is the grounding when the sub panel is connect to Pro Power. So a sub panel has to be grounded to the main panel per code, right? Neutrals and grounds separated in the sub panel and the grounding lug removed. When using Pro Power the sub panel has two paths to ground (through the main panel grounding rod and the truck's GFCI. Are two paths to ground appropriate? Not seeing any alternative.

Paths to ground (for grounding conductors) is irrelevant.
The key is that the neutral and ground are only bonded in one place. On grid power, that’s the N-G bond either in the main panel or meter. On truck power, it’s in the truck.
With all power off and the transfer switch in backup position without the truck plugged in, you should have no continuity between N & G in the subpanel.

 

[Henry Ford]

So I should take the ground from the Lightning Pro Power directly to the subpanel bypassing the transfer switch grounding lug? Then remove the bonding screw in my sub panel.

I edited my original post. My thoughts on grounding were wrong.

If there is a bonding screw on your sub panel you should remove it. When on truck power the only path to ground should be through the truck. If neutral and ground are touching in the sub panel the truck GFCI will trip.

Do you have photos of your setup? @Maquis and I have already given bad advice. I think pictures on a screen are better than pictures in our heads.

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