480V Delta, 3-phase, 3-wire (ungrounded) service

Ranger86

Member
Location
Las Vegas, NV
A building built in the 60's, has a 480V delta, 3phase, 3wire, ungrounded service and a 120/208V, 3ph, 4wire grounded service.

Can somebody tell me what year the ground detection sensing equipment became a requirement per NEC 250.21 (B) for the ungrounded delta?

I understand all the theory behind and why we need this sensing equipment, I just would like to know if it met code when it was constructed back in the 60's.

The ground electrode system is fine and both services are tied to the same ground electrode system, the 120/208V service is fine too.
Thanks for your help.
 
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