Bus-Duct and Grounding

[rwilsond]

A large 1 MVA, Delta-Wye transformer supplies a 480V, 3-Wire MCC via a bus-duct. The 20-foot length of bus-duct contains NO ground-bus, and no neutral, and the enclosure is NOT Listed for grounding.

The transformer secondary, and the Ground-Bar inside the MCC, are both connected to the grounding electrode system (i.e., underground ground grid, etc.).

Where in the NEC is this prohibited?

 

[benaround]

rwilsond,

Good one! After reading the definitions of GC,EGC,GE,and GEC, in article 100

the (all) GEC must tie in at the service or the source before the MBJ before

an EGC can be considered.

IMO, the bus duct needs to be changed to a listed for grounding type and

the connection to the GES removed at the MCC.