2 Transformers Together

[james wuebker]

Question is: Have 1 480/240 3 phase delta/delta transformer. Right next to it have a 480/208/120 3 phase delta/wye transformer. Because they are going to be next to each other can I use 1 ground rod for both or do I need one for each. From there each one will be feed to there panel. Will also run a ground to the building beams above from each panel.
Thanks!
Jim

 

[jtester]

Re: 2 Transformers Together

Jim

Are the transformers installed as separately derived systems, or another system to be grounded? Probably the 120/208 is, but the 240 delta may or may not be.

If they are required to be grounded as separately derived systems for example, then 250.30(A)(7) tells you what type of electrode to use, and ground rods aren't listed. Building steel or metal water pipe grounding electrode, which ever is closer should be your choice. Only if they aren't available is a ground rod an option.

Jim T

 

[charlie b]

Re: 2 Transformers Together

Why does the delta/delta need a ground rod? Is this to be a "corner grounded delta"?

I don't know a rule that prohibits the sharing of grounding electrodes among two or more separately derived systems.

 

[james wuebker]

Re: 2 Transformers Together

charlie b,
The delta/delta is a 4 wire.480/240/120.Sorry about that. This is what the company ordered. Could have been OK with the 480/240 because all they will run from this is motors.
Thanks Charlie!
Jim