Equipment bonding jumper

[DARUSA]

I had a transformer 45 kva 480 volts pri..120/208 sec.
The elevator guys use a FMC on the secondary side like me on the primary side of the transformer ,The transformer is protected for a 70amps fuse only on the primary side. I sized my EBJ (primary side of the transformer) based on table 250.122 , for the breaker size. On the secondary how i have to size the EBJ ? It will be the same size as the primary?

 

[DARUSA]

Transformer protected only with a primary side fuses .How do I size the EBJ fo the FMC on the secondary side? Can it be based on the primary fuse size ?table 250.122?

 

[erickench]

Look at NEC 240.4(F). Under certain conditions the secondary conductors are protected by the primary OCPD. However, there would be no ground fault current path flowing from the secondary back to the primary side. Now if you had an OCPD on the secondary then the EGC would be sized according to NEC 250.122 based on the rating of the secondary OCPD.

 

[Volta]

Transformer protected only with a primary side fuses .How do I size the EBJ fo the FMC on the secondary side? Can it be based on the primary fuse size ?table 250.122?

It needs protection on the secondary side. As Eric pointed out, 240.4(F) shows that a wye secondary is not protected by the primary OCP.

You would need to size the secondary GEC and the EBJ per the size of the secondary conductors 250.30(2) + (3).

Only after the secondary OCP can the EGC be sized to 250.122.

 

[Smart $]

Transformer protected only with a primary side fuses .How do I size the EBJ fo the FMC on the secondary side? Can it be based on the primary fuse size ?table 250.122?

EBJ on secondary side, between xfmr and system disconnecting means, is sized per 250.66.