High-rise Electrical closet ground bars - When required?

[cipher31]

The following applies to a 30 story highrise building with medium voltage to low voltage substations (12kV - 480/277V or 12kV - 208/120V) at both the basement and penthouse levels.

I've been told that every electrical closet in a highrise building like the one described above should have a ground bar. The question that I have is what exactly connects to the ground bar?

Let's say that the electrical closet has a 208Y/120V busduct riser and no transformers. Is there a need for a ground bar? The busway, bus tap, distribution panel and panelboards within the closet are all grounded via the equipment grounding conductor run as part of the distribution feeders. In this case, what exactly would connect to the ground bar?

Let's say that the electrical closet has a 480Y/277V busduct riser and transformers every five floors. Since the transformers are not located on every floor, I would assume that the ground bar might only be necessary on the transformer floors for a convenient place to connect the GEC (grounding electrode conductor). Otherwise, the GEC could just connect to building steel if available (assuming it is in proper contact with earth and electrically continuous). In the case where building steel is not available, besides the GEC, what else would connect to the ground bar?

Besides for GEC connection purposes, are electrical closet ground bars needed? If GEC connections are not required within a particular closet, are ground bars a good design practice or a waste or client money?

Thanks in advance.

 

[ron]

I generally run a grounding electrode conductor through the closets to terminate transformer GEC's. Regular equip ground gets terminated to the busway.
You might want ground bus bars in each communications closet depending on the type of occupancy.

 

[cipher31]

Thanks Ron. I do the same even if there is structural steel since I'll use the steel as the lightning protection system down conductors and like to keep the GEC amd LPS systems separate until they terminate on the MEGB (but that is a whole new thread). And I do put ground bars in the telecom closets but only beacuse the telecom industry likes to do their multi-point grounding.

The design of ground bars in the electrical closets when a GEC connection is not required though really bugs me. I hate just providing something within knowing why I'm doing it just because it is what is "always" done.

 

[cipher31]

Anyone else?

 

[infinity]

Anyone else?

Didn't you post the same thread in another forum? I responded there.