# Grounding problem



## joe.sommar (Aug 6, 2017)

I purchased a 10 KW PTO generator some time ago. It works just fine stand alone in my shed, but when I finally connected it to my house panel, it does not work. The display panel on the generator panel gets very dim and the display goes blank. No voltage is produced. The generator has a ground lug terminal with instructions that the generator must be grounded. I drove a separate ground rod at the shed and have the generator well grounded.

It is connected to my panel through a properly interlocked 40 amp breaker.

I ran 6 gauge (2 hots, a neutral and a #8 ground) wire from my house panel through a buried conduit to a male receptacle box in my shed and then on to the 14-50P plug at the generator via a generator cable. All wiring has been checked out and is correct.

I can get the generator to work by disconnecting the ground connections at the panel and at the generator (so just 2 hots and the neutral). But if I restore either ground connection, the generator produces no voltage.

The ground and neutral are not bonded at the generator. I tried connecting them but immediately the display dims and produces no voltage.

I am out of ideas and any help would be appreciated. Thanks


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## thehandyman1957 (Feb 11, 2017)

This might be of some help to you.

Generator Groundig

Can you supply a picture of the interlock with the cover off?


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## exmar (Jun 29, 2015)

IMHO, you don't need the ground at the generator to supply your load center in the house "ASSUMING" you have a driven ground connected there. e.g. When the rest of us plug in out gensets through the arrangement you describe, there is no additional ground provided. 


Again, IMHO, the note on your generator "Must be grounded" is when you use it in a stand alone mode. Actually, when you connect to your loadcenter as described the generator is grounded, through the #8 wire back at the service entrance. As I understand it, all grounds must go back to the generator when you're using it as a sole source of power, (contractor building a house and no power on site) the grounds then terminate on the frame. Then a very good idea to ground the frame for safety. I believe it's mandated in the NEC, but been a long time since I opened that. 


You mention that you can get it to work by disconnecting the ground at the panel and the one at the generator. Did you try it just disconnecting the ground rod at the generator and leaving the #8 tied in to the panel?


How long is the run between load center and generator? The #8 wire, is it bare or insulated, is it grounding anywhere along the way? 


What has me scratching my head is even with two grounds which is taboo, is it should work, unless there is a significant distance to provide a potential difference between the two points. Or, to use an extreme example one is on top of a high dry hill and the other in a swamp. Even then......


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## joe.sommar (Aug 6, 2017)

Yes, I tried only the ground wire at the panel. In fact I only grounded the generator because of this problem. I also thought two ground paths was a bad idea. It was an act of desperation.

So originally, I connected the generator with 2 hots, a neutral and the ground. The generator produced no voltage.
I de-termed the ground wire and it worked. The neutral and ground terminal strips are connected in the panel of course.

The ground wire is a green insulated and stranded THHN conductor. The wire run is only 120 ft or so.

There is no transfer switch only a simple mechanical arrangement which prevents the top left double pole breaker (generator breaker) from being turned on unless the main is off. I have read that this meets NEC requirements. This does not involve the house neutral.

My setup also includes load meters (non-contact CTs) and a sensor which alarms when utility power is restored.

Thanks for the responses.


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## joe.sommar (Aug 6, 2017)

So, been mulling this over. The ground and neutral are not bonded at the generator. I verified that If I connect them the display dims and goes blank and no voltage is output. This happens even in standby mode with no connection to the house at all. This in a nutshell is the problem.

I don't think it should do that, but what do do about it?


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## thehandyman1957 (Feb 11, 2017)

So at this point I would assume that you have a bonded neutral ground somewhere in the house. And apparently the gen set does not like this. The question is why is the generator having issues with this. I have seen many places that have ground neutral bonding and generators still work.


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## joe.sommar (Aug 6, 2017)

The generator does not work even in stand-alone mode if I connect the ground and neutral. I tested that this morning so the house can be eliminated as a source of the problem.

I am now thinking the gen has a problem but I don't know how to correct it.


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## exmar (Jun 29, 2015)

How old is it, and what kind of voltage and frequency regulation does it have? Maybe you've got a defective board in there that sees an issue which isn't. Manufacturer and model number would help. 


There are a few of those around here, folks with dairies have them in little sheds by the milking parlor for power outages. I don't know of anyone who has used them to backfeed their house though. Frequency can be tricky on those as it's simply a function of tractor RPM. Also, as load changes on them the tractor governor has to adjust. I believe the rule of thumb is 2HP per KW, so you don't need a huge tractor to power one, keeping up with the load though can be interesting. I was at a neighbors and he was running one, had just finished milking, 10KW hooked to a diesel 40 HP JD. All was smooth and then the tractor started laboring until the governor got it leveled out. No idea what the Frequency did. He said that happens when the motor on the milking machine and heater kicked in together. MIght be worth considering to pick up a 5KW genset just for the house, Applicances, computers, etc. can deal with dips and surges in voltage, frequency variation is another issue. JMHO


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## joe.sommar (Aug 6, 2017)

I went with a PTO unit because I don't want or have room for another motor in the shed. I have used smaller 6k portable gen sets in the past and they are not adequate. Plus I live in a fairly rural area, when my power goes out it is frequently out for days on end. I am not sure they would be up to that.

So this is what I have and I will make it work one way or another.

I purchased the unit from Value Leader Implements. Neither the unit nor the manual lists who makes it. I guess it was not the best decision to buy a no name unit but live and learn.


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## motormonkey (Jul 10, 2016)

What is the physical means of connecting the ground to the neutral?
The reason I ask is that it could be possible that you're grounding one of the legs of the output instead of the neutral.

The output windings should "float" with the ground unhooked... i.e. there should be no electrical continuity between the windings and ground. Could be something else is grounding the windings, possibly at one of the hot legs instead of the neutral.


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## joe.sommar (Aug 6, 2017)

I shorted the ground and neutral prongs at one of the 5-20R receptacles. I know which prongs are which but verified with my VOM anyway.


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