transformer

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eeagleman

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I have a transformer fed with 3 phase 480/277 v which steps down to 3 phase 120/208 v. In the 120/208 panel does the neutral conductor and gorunding conductor need to be isolated from one another? confused again... ;-). thanks for your help.
 
Take a look at 250.30 to cover all aspects, but it says in part:
(1) System Bonding Jumper. An unspliced system bonding jumper in compliance with 250.28(A) through (D) that is sized based on the derived phase conductors shall be used to connect the equipment grounding conductors of the separately derived system to the grounded conductor. This connection shall be made at any single point on the separately derived system from the source to the first system disconnecting means or overcurrent device, or it shall be made at the source of a separately derived system that has no disconnecting means or overcurrent devices.
 
Welcome to the forum! :)

eeagleman said:
In the 120/208 panel does the neutral conductor and gorunding conductor need to be isolated from one another?
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In a word no. Treat the new neutral (of what is a separately-derived system) as you would the incoming neutral of a service.

It must be bonded to the new system's EGC once within your equipment, either in the transformer or in the panel or disco it supplies, but not both.


If I had a magnifier handy, I'd be able to tell you if that's what Gus's quote says. ;)
 
so if it the neutral is bonded to the GEC in the transformer than i would isolate it from the grounding conductor in the 120/208 panel?
 
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