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pokgunner · 05-30-2015, 11:00 AM

The only post I could find that comes close to my issue was done 2009. I hope this is not rehashing a resolved issue.

I installed an inverter using an automatic transfer switch to power a circuit. The circuit has a GFI on it. The transfer switch is located between the AC panel and the GFI. The inverter also has a GFI. If I have a brain fade and connect to shore power while the inverter is on, or try to turn the inverter on while connected to shore power; either the one or both of the two GFI’s trip, usually it is the inverter’s.

I have chased the circuits, multiple times and cannot find any place where the hot or neutral might come in touch with the ground, except of course at the ac panel and maybe inside of the inverter or the transfer switch. I suspect the later. I suspect that during the “transfer” there is just enough current flowing in both circuits to trip the GFI. The switch was made by Xantrex, but I think they quit making them.

Does anyone concur or have another idea? More importantly since the circuit is already protected by a house GFI, why would it be unsafe to just bypass the Inverter’s GFI.

Please note that the inverter’s GFI will no longer reset. I suspect that is because it has tripped so many times. Is that reasonable?

The inverter is out of warranty so I either have to replace it or open it up to replace the GFI, I am leaning strongly towards replace it with a standard receptacle.

Any thoughts or suggestion are appreciated.

BFlinn181 · 05-30-2015, 01:37 PM

A GFI is designed to notice a difference in the current flow in the hot and neutral wires in a circuit. A transfer switch is a mechanical device. I would think one set of contacts are connecting a fraction of a second before the other set, causing the GFI to trip.

I'm just curious, wonder if it would still trip if no loads were on the circuit when the switch changes over?

pokgunner · 05-30-2015, 02:03 PM

BFlinn181

Your comment that "one set of contacts are connecting a fraction of a second before the other set" is precisely what I think is going on.

And I think that the fix would be to bypass the Inverter's GFI since the circuit, when powered by the Inverter, would still have GFI protection. But I know just enough about this stuff to get in trouble.

I note that the OEM inverter had no GFI protection and uses a transfer switch it is still installed on a different circuit. However that circuit also has no GFI on it regardless of the power source.

Your comment about trying it with out a load is a good one. But now that the GFI on the inverter is not resetting. I could not test it unless I replace the inverter's GFI. it would be a ton easier if I could jut safely by pass the Inverter's GFI. Which I think will work if the problem is the timing of the contacts. I do worry that the house GFI will still trip.

However: I am pretty sure that the GFI tripping happened when there was no load on the circuit. Which is the only reason I am not convinced it is the timing of the contacts causing the problem. However again the relay coil use a small amount of power, but not sure it is enough juice to trip a GFI.

And the final however, the Inverter's out put is a GFI duplex and I have wired in two circuits (two transfer switches). I did test to see if the problem occurred on one circuit only and it does on either circuit.

Of course the best solution (if the problem has been identified correctly) is a transfer switch that disconnects completely before connecting, I've search the web for such an only found them for large power applications, not for a 15 amp 120 volt circuit.

May be my government is protecting me form my self an not allowing them to be used on a GFI protected circuit?

BFlinn181 · 05-30-2015, 02:23 PM

An auto transfer switch is required to disconnect one source before connecting to the other to prevent back feed into the first circuit. This is especially important for linemen working during power outages. I'd suggest you have a professional look at your system and diagnose what's going on. The fact that the GFI trips even without a load isn't a surprise, I was just wondering if it did. I wouldn't disable the GFI circuits, they are there for safety.

pokgunner · 05-30-2015, 02:50 PM

Thanks:
If I could find a professional that seemed to know more than I would ask them.

And having worked in the electric utility business for 33 years I am fully aware of how transfer switches are suppose to work. That is another reason why I am not sure that it is the relay at fault. Actually two relays. I just do not think mine are working that way. It may be why Xantrex no longer sells them. (Note that one of them did not work at first. I discovered a drop of solder shorting the pc control board. So perhaps they had even bigger design/manufacturing issues.)

If I were to bypass the inverter's GFI, it would still be powering up a GFI protected circuit, so I THINK that would still be safe. But I am not sure that such will prevent the house GFI from tripping.

R&Ring the inverter is a pain, AND I am sure that getting to the busted GFI after I remove the inverter will not be easy. I am hoping that someone can help me on this issue so I do not have to do it twice. First to bypass the Inverter's gfi, then after finding the house GFI still trips, and then have to go back and install the Inverter's GFI.