Generator Grounding

[implant]

We are installing a 3P 120/208 Gen Set with Over current Protection – We have Building A and B on the same premises – the Gen is located in Building B we have a set of feeders in PVC feeding a 200A 3 Pole ATS (Non Separately Derived System) in bulding A What is the recommended Grounding Between the 2 buildings for the Emergency Back Up without bonding the two grounding systems – Building A and B have separate services

equipment grounding condcutors run with the feeder circuit conductors to the separate structure and connected at the equipment there

 

[bphgravity]

WHat "grounding" are you refering to?

Do you mean connecting the generator frame to a grounding electrode, or do you mean the equipment grounding condcutors run with the feeder circuit conductors to the separate structure and connected at the equipment there?

I don't follow what you don't know how to do?

 

[LISHAJI]

What is the recommended Grounding Between the 2 buildings for the Emergency Back Up without bonding the two grounding systems ? Building A and B have separate services

Neutral at each service disconnect in building A & B are already bonded to ground. As per NEC 250.32(b)(2) no EGC need to be run between the two buildings. Just the neutrals of both the services shall be connected to each other as required by Utility.

 

[electrofelon]

Perhaps the OP is wondering if there needs to be any bonding between the generator and building B, since it is in building B but not connected to that electrical system? If this is the question, I say no bonding between genny and B, bond the feeder EGC to the genny frame, make sure the generator neutral is not bonded to the frame, and no ground rod required. It is an intersting situation, since I could imagine a situation were there would be flash over or difference of potential between the generator and building B. But bonding the two could result in neutral current flowing between the two services, depending on if they are supplied from the same transformer and how the transformers are connected.

 

[don_resqcapt19]

There is no way to make that installation without creating a bond between the grounding systems at the two buildings. Each feeder from the generator will require an EGC and both EGCs will be bonded to the generator and one to each of the buildings creating a bond between the two buildings.
Don

 

[electrofelon]

Don,

My interpretation was that only building A is being supplied by the generator during a utility outage. Perhaps the OP'ster can clarify if this is or is not the case.

 

[suemarkp]

But he said they are not a separately derived system, so the neutrals and grounds are connected to their appropriate busses in the TS and not switched. Since they are not switched, the paths are always interconnected.

 

[electrofelon]

But if the generator does not supply building B (is only located in it), then there would not be a bond between the two buildings earthing systems, except possibly/probably thru the utility system.

 

[suemarkp]

It seems like it would just be too easy to have something from building B get tied into the generator, especially the grounding system. How does it keep its battery charged (a utility charger, or does the thing start itself periodically to keep it charged)? If there's a charger, the EGC in the charger may end up bonded to the generator frame and now its tied to building A.

 

[brian john]

The neutral is bonded in each building the OP is installing a generator with a neutral to each building and will set up down stream ground connection in building 2. He either needs 4 pole ATS's and set the gen set up as a SDS or use 3 phase 3 wire and transform for a SDS.

 

[electrofelon]

It seems like it would just be too easy to have something from building B get tied into the generator, especially the grounding system. How does it keep its battery charged (a utility charger, or does the thing start itself periodically to keep it charged)? If there's a charger, the EGC in the charger may end up bonded to the generator frame and now its tied to building A.

I agree. And if there was a bond, current could flow over the EGCs. If there was not a bond, the close proximity of the two systems could result in a dangerous situation.

the OP is installing a generator with a neutral to each building

My argument is based on my intepretation of the OP that the generator is not supplying building B. I agree that making it a SDS may be safer, but I dont see that as being required by code.