Grounding question: Honda eu7000is generator connected through PG&E backup power transfer meter

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Dave Millman

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Earlier this year PG&E installed a free backup power transfer meter at our California property (info sheet here). Using the L14-30P cable they supplied, it connects our Honda eu7000is inverter generator (manual) to power the whole house. Overall it works well.

We have noticed some odd behavior on the gas furnace (2009 vintage) and TV (2021 vintage). In the past, using a smaller eu2000is generator, this furnace refused to fire up until I strapped ground to neutral. Here is a post about that problem. While the furnace seems to work with the new transfer switch and generator, it did shut off unexpectedly one time while on generator power. Similarly, the television shut off unexpectedly one time while on generator power.

The question is, should we connect the generator ground screw to the grounding rod at the power meter? This would be an easy task, and we do not plan to move the generator. According to the generator manual, "This generator has a system ground that connects generator frame components to ground terminals in the AC output receptacles. The system ground is not connected to the AC neutral wire."

Thanks!
 

wwhitney

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The question is, should we connect the generator ground screw to the grounding rod at the power meter?
While the generator is running and you are on backup power, you can check the resistance between the ground rod and generator ground screw (which I understand to be connected to the generator chassis, and its receptacle ground pins, but not directly connected at the generator to the neutral). I expect you will find that the resistance is already near 0, meaning that they are already connected.

If not, something odd is going on--either your ground rod is not actually connected to your electrical system as it should be, or the Backup Power Transfer Meter is not connecting the generator EGC to neutral within itself as I would expect (there is no house ground within the meter, so it can't connect the generator ground to house ground.)

In that case, there should be no downside to connecting the ground rod to the generator ground screw. But I don't see how it would help with your reported symptoms--they don't sound like a grounding problem. In contrast to your previous post, in this configuration the generator is definitely using the neutral-ground bond already present in your main service panel.

Cheers, Wayne
 

Dave Millman

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Wayne,

Thank you for the detailed reply @wwhitney !

While the generator is running and you are on backup power, you can check the resistance between the ground rod and generator ground screw (which I understand to be connected to the generator chassis, and its receptacle ground pins, but not directly connected at the generator to the neutral). I expect you will find that the resistance is already near 0, meaning that they are already connected.

I will absolutely test that...next time the power goes out. I can test my generator, but there's no way to simulate a power outage to test the switch. The PG&E installer (very sharp guy with a truckload of these meters he was installing) explained that the unit does continuous self tests and displays the results on the three status lights, which is only marginally useful.

Last winter we had 9 power outages, so I can likely report back results soon.
 
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