Control Transformer Secondary Grounding

[ThePunisher]

I recall that as per NEC Code, one leg (return leg) of a single phase control transformer (like the ones in MCCs for space heaters or auxiliary controls) should be bonded to ground.

Is this going to be applicable if the system grounding is High Resistance?

Will this be also true if the system grounding is low reistance?

Thanks and regards..

 

[rbulsara]

What is high/low resistance grounded? Primary source of the control transformer?

If so, it has no bearing over what you do to the secondary side grounding. NEC 250 and 450 still applies.

Rafiq Bulsara

http://www.srengineersct.com

 

[jghrist]

NEC 250.20(B) requires grounding in general if the voltage does not exceed 150 V. NEC 250.21, however, allows certain control transformers to have ungrounded secondaries, but you need ground detectors.

It doesn't matter whether the primary system is solidly, high resistance, or low resistance grounded.