Ground rods for Generator and Panel

[Working Xpat]

Hope that I can get some help. We have been having a huge discussion about Parallel paths to ground. The issue came about on an installation that I had not seen before, but have found nothing in the code book to say that it is incorrect. So, the issue is:

Generator is bonded neutral to ground

Electrical panel inside of the building is not bonded neutral to ground

There are 5 conductors running from generator to electrical panel (3 phases, 1 neutral, 1 ground)

A ground rod is driven into the ground at the generator

A ground rod is driven into the ground at the building

A conductor is run from the ground lug of the generator to the first ground rod to the second ground rod and then to the bus bar of the electrical panel inside of the building unbroken

By running the GEC from the generator to the ground rods and to the electrical panel inside of the building does this create a parallel path to ground? Our company policies require that a ground rod is driven at the generator and at the electrical panel. Would this setup be suitable for a 4 conductor system from the generator to the electrical panel?

 

[Smart $]

Is the generator the only source of electric for this system?

Parallel paths to earth ground is not the concern. Its parallel paths for normal grounded conductor (neutral) current. There should be only one system bonding jumper (neutral to ground connection) for the system.

 

[Working Xpat]

Is the generator the only source of electric for this system?

Parallel paths to earth ground is not the concern. Its parallel paths for normal grounded conductor (neutral) current. There should be only one system bonding jumper (neutral to ground connection) for the system.

Yes, the generator is the only source of electricity for this system. There is only one system bond and it is in the generator. There is not another generator or power source, MDP, or SDP. Just the generator and CDP.

 

[augie47]

I think the installation is as it should be. There are other scenarios where we have current paths thru grounding electrodes such as multiple service disconnects. The Code seems to accept this as inevitable.

 

[jxofaltrds]

 

[Working Xpat]

View attachment 7473

Right, and I agree with your drawing if you have an electrical service that is bonded and generator that is bonded. Utilizing a 4 conductor system using 2 phases. In the 4 conductor system that we would be using it would be 3 phases with a neutral. The EGC would not be run from the generator to the electrical panel (first means of disconnect). In this case the generator would be bonded neutral to ground and the panel would be bonded neutral to ground. Hmm, but then if you ran a GEC from the generator to the 2 ground rods and then back up to the electrical panel this would cause the same problem I would assume. Although I'm not sure if the ground rods would make a difference with the objectionable current or not. What would be your opinion on this?

 

[Smart $]

Right, and I agree with your drawing if you have an electrical service that is bonded and generator that is bonded. Utilizing a 4 conductor system using 2 phases. In the 4 conductor system that we would be using it would be 3 phases with a neutral. The EGC would not be run from the generator to the electrical panel (first means of disconnect). In this case the generator would be bonded neutral to ground and the panel would be bonded neutral to ground. Hmm, but then if you ran a GEC from the generator to the 2 ground rods and then back up to the electrical panel this would cause the same problem I would assume. Although I'm not sure if the ground rods would make a difference with the objectionable current or not. What would be your opinion on this?

Under recent Code editions, an EGC is required between generator and building main with the generator having an integral disconnecting means and OCPD, and a system bonding jumper at the generator disconnect. The building is required to have its own grounding electrode system (GES) bonded to the EGC, but no bonding of EGC/GES to grounded conductor (neutral). This method effectively takes earth return of objectionable current out of consideration, even though some may be present.

 

[Working Xpat]

Under recent Code editions, an EGC is required between generator and building main with the generator having an integral disconnecting means and OCPD, and a system bonding jumper at the generator disconnect. The building is required to have its own grounding electrode system (GES) bonded to the EGC, but no bonding of EGC/GES to grounded conductor (neutral). This method effectively takes earth return of objectionable current out of consideration, even though some may be present.

That seems to follow with our 5 conductor system. Is the buildings GES required to be seperate from the generator's GES? Understand that we have 1 power source which is the generator. The current code that we are working under is the 2008.

 

[Smart $]

That seems to follow with our 5 conductor system. Is the buildings GES required to be seperate from the generator's GES? Understand that we have 1 power source which is the generator. The current code that we are working under is the 2008.

No, the GES of the generator and building are not "required" to be separate... though there is a good chance that is the intent. IMO, the Code is not written from the perspective of a generator being the sole supply of electric.

In this regard there's quite a few wording changes between 2008 and 2011 editions, but the net effect is very little has changed (IMO).