Grounding 240V Delta System

[Jbyars]

I am designing a new 240VAC 3 Phase system and was trying to determine the proper way to ground the system.
Our system will be composed of a Delta-Delta transformer and a single panelboard.
At the transformer will be the GEC and the grounding electrode(ground rod).

Could I install a separate ground bus bar in the panelboard and bond the neutral bus bar to the ground bus and run a single bond conductor from the ground bus to the transformer ground bus bar to ground this system and establish the neutral?

 

[jim dungar]

Is your system a straight 240V delta (3 wire), or a 240/120V delta (4 wire) with a ' high leg'?

 

[mbrooke]

If I can be the one- why are you designing a new delta system?

 

[Jbyars]

It will be 240/120V 4 wire. We are relocating old equipment which are all 3 phase 240V, but I wanted to ensure that 120V was available if needed in the future.

 

[mbrooke]

It will be 240/120V 4 wire. We are relocating old equipment which are all 3 phase 240V, but I wanted to ensure that 120V was available if needed in the future.

Ah, got it. I was going to say go 139/240Y if not 120/208Y, but 120 volts makes sense.

 

[ActionDave]

I am designing a new 240VAC 3 Phase system and was trying to determine the proper way to ground the system.
Our system will be composed of a Delta-Delta transformer and a single panelboard.
At the transformer will be the GEC and the grounding electrode(ground rod).

Could I install a separate ground bus bar in the panelboard and bond the neutral bus bar to the ground bus and run a single bond conductor from the ground bus to the transformer ground bus bar to ground this system and establish the neutral?


View attachment 2556423

Your illustration shows a delta service from a utility owned transformer. If your transformer is privately owned you would bond the neutral to the metal case in the transformer or in the first disconnect but not both. The grounding electrode conductor would land wherever the neutral bond is established. Code reference is 250.30

 

[Jbyars]

@ActionDave Thank you! After reading through 250.30 that makes sense now. We will install the GEC and grounding electrode at the transformer and run a neutral and bonding jumper from the panel to the transformer terminal bar.