24 VAC & grounding

[timjimbob]

Is the control circuit required to have one leg grounded on a system fed by a 480 volt primary system?

I am trying to correct a repeated failure on a Liebert unit/ control side in a hi energy enviroment and was suprised I could not find a ground.

I am positive on this but cannot find the source of this fact? Is it in NEC?

[Williamsma]

Is the control circuit required to have one leg grounded on a system fed by a 480 volt primary system?

I am trying to correct a repeated failure on a Liebert unit/ control side in a hi energy enviroment and was suprised I could not find a ground.

I am positive on this but cannot find the source of this fact? Is it in NEC?

Check section 250-20 in the NEC. I believe it refers to any voltage higher than 150v to ground. But over the last 15 years I have not run across any control transformer from 24v to 230v that did not have the common side of the circuit grounded.

[timjimbob]

Read it. Grounding is required if primary is above 150 volt to ground. I am at 277 volt to ground.

[timebuilder]

250.20 (A) (1) refers to systems. The Leibert is both an "appliance" and "utilization equipment." The manufacturer can ground or not. The common began being "grounded" in gas appliances. Check with your rep to see if grounding one side of the secondary will cause any issues.