Electrical system bonding with different voltages

We are having problems with a grounding system. The building has four different voltage systems: 3ph 277Y/480V for new lathes and Mills; 3ph 277Y/480V for special equipment; 3ph 120/240V with high leg for old lathes and Mills and 3ph 120/240V for building's general services.
The thing is that some workers have reported little tickles when touching some of the machines (both 480V and 240V).

We found out a big grounding problem, only The special equipment 480V system seems to have a Solid grounding and bonding, not the case of the rest. The question is: can we Bond the different transformer banks into a unify grounding systems for detection and cleaning of ground faults?

Or What would be the best solucion in you opinion.

Kind Regards!


Staff member
State Electrical Inspector (Retired) DINOSAUR
All of the services and separately derived systems should be properly grounded. 250.30(A)(6) discusses grounding of multiple systems to a common electrode.