Bonding Requirements

[NSmithIN]

I have a new facility that utilizes a 480∆ : 480Y/277 VAC transformer for lighting loads. The X0 terminal at the transformer is bonded to a grounding electrode. (building steel)
The secondary of the transformer feeds a Lighting Distribution Panel with a main and branch breakers.
Does the code require a bond connection between the neutral bar and the can of the Lighting Distribution Panel?

Same situation with the 208Y/120 VAC Low Voltage Power Distribution Panels.
Each 480∆ : 208Y/120 VAC transformer is fed from a 3 pole breaker in the adjacent Lighting Distribution Panel.
The X0 terminal at the transformer is bonded to a grounding electrode (building steel) by a grounding electrode conductor.
The secondary of the transformer feeds a Low Voltage Power Distribution Panel with a main and branch breakers
Does the code require a bond connection between the neutral bar and the can of the Low Voltage Power Distribution Panel?

The building steel is bonded by cadwelded pigtails to a below grade level ground grid consisting of driven ground rods bonded to an unbroken bare copper conductor ring around the perimeter of the building.

 

[ADub]

Short answer is you only bond neutral (xo) to ground once and it can be in the transformer or your secondary panel. Your facilities electrician most likely knows this.


Sent from my iPhone using Tapatalk

 

[tom baker]

The SDS bond can be at the source or first disconnecting means, and the GEC connection is done in the same location.

 

[infinity]

You need a system bonding jumper as others have stated either in the transformer or at the panel. Right now your connection between the X0 and the metallic parts of the system is inadvertently through the GEC connection to the GES of the building. Not having a SBJ is a code violation and could be problematic if you have large transformers because with larger transformers the SBJ is typically larger than the maximum GEC size of #3/0 and is sized to carry the ground fault current.

 

[augie47]