We have a temporary service being installed at a very large industrial plant in California. Within this site there is a service building with a 480V-120/208V Delta Wye system providing power to the building equipment. The temporary service is a 12kV-120/208V Delta Wye system with a temporary Switchgear and off this switchgear the electricians are installing a 120/208V-480V Wye Delta booster transformer with the primary circuit from the temporary switchgear protected with a circuit at the switchgear and a fused disconnect switch on the secondary winding which will supply the previously mention service building, with the 480V-120/208V transformer. My question is when the 3-phase delta system is routed to the 480V Delta winding at the building are we required to ground one corner of the delta winding. The code book seems a little vague about using non-grounded systems.
Grounding Delta windings
- Thread starter Ohmy2
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charlie
Senior Member
- Location
- Indianapolis
You are not required to ground a delta configuration; however, there are rules that must be followed such as ground detector lights. 
chevyx92
Senior Member
- Location
- VA BCH, VA
No you are not "Required" by the NEC to corner ground the "B" phase. But like Charlie mentioned there are requirements to be followed.Ohmy2 said:
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