Another Generator Grounding Question

[DanS26]

About six years ago I installed a 10kW fixed mounted non-SDS generator and a 10 position transfer switch. The system was installed to code at the time and all manufacturing installation instructions were followed to the letter.

One of the manufacturer's installation requirements was to sink a grounding electrode at the generator location and to bond it to the ground lug at the back of the generator. Since the generator location was near the main service entrance grounding electrode, I just dug a trench and bonded the generator lug directly to the main grounding electrode. So far so good or so I thought.

Now the manufacturer has stopped recommending bonding a non-SDS generator to a grounding electrode. Probably in no small part due to Mike Holt's mission to inform everyone of the dangers of this procedure due to voltage rise issues during high voltage events between unbonded ground rods.

So my question is since I do not have a separate unbonded rod is there any harm in having the generator bonded directly to the system grounding electrode? Have I created a ground loop? Should I just disconnect the bonding jumper?

 

[mopowr steve]

I'm familiar with mike Holts stance on the Grounding electrode at generator. As far as your install I don't see a problem as long as the neutral and grounding are not bonded together within the generator which by your description, I don't think that generator is bonded together internally. That ground lug may be there to satisfy ( grounding a structure ) which the generator could be debatable.

 

[DanS26]

I'm familiar with mike Holts stance on the Grounding electrode at generator. As far as your install I don't see a problem as long as the neutral and grounding are not bonded together within the generator which by your description, I don't think that generator is bonded together internally. That ground lug may be there to satisfy ( grounding a structure ) which the generator could be debatable.

Thanks Steve. Yes I'm with you...the generator bonded directly to the main grounding electrode is at the same electrical ground potential as everything electrical in the structure and always will be even in a direct or indirect strike event.

No neutral/ground bonding in the generator means no alternate/dual return paths for electrical energy. Should be good there.

It is my understanding that the grounding lug is there on the back of a non-SDS generator to satisfy UL listing requirements. If that is really true then the EE's at UL need a remedial course in electrical theory.

 

[DanS26]

I suppose I should not be so hard on the EE's at UL. It is possible that someone could bond the neutral and ground in the generator and make it an SDS, then of course the grounding lug would be handy.

Getting back to my original question......by bonding the generator directly to the main grounding electrode, have I created an objectionable "ground loop"? In other words the grounding electrode is bonded to the main distribution panel (first disconnect) thru the GEC, then the ground bus in the panel is bonded to the generator thru the EGC, the generator is bonded back to the grounding electrode with that underground bonding jumper.

 

[suemarkp]

Yes, but I don't believe that is a problem (ground loops aren't a problem when "ground" is a fault path). You could also think of it as a redundant path between ground electrodes.

 

[GoldDigger]

Yes, but I don't believe that is a problem (ground loops aren't a problem when "ground" is a fault path). You could also think of it as a redundant path between ground electrodes.

:thumbsup:
Multiple parallel paths are good, but not required, for fault current and bad for normal circuit current(s).