Transformer secondary OCPD

embryo3

Member
To all,

I have a 45kva 480v to 120/208v 3ph transformer that the Primary is being feed by a 70amp fused disconnect. The Secondary is feeding a 100amp disconnect that in turn feeds a 100amp 120/208v panel board. All of this equipment is currently located on a single column.

I am being asked to relocate just the 100amp Disconnect and panel approx. 100' from the 45kva transformer, to another column. How far can the secondary disconnect be located from the transformer? I s their any code that specifies distance of OCPD from the transformers location?

Thank you for any help​
 

iwire

Moderator
Staff member
Check out 240.21(C) but likely you will be limited to 10' of conductor length before you hit some fuses or a breaker.
 

infinity

Moderator
Staff member
I would leave the disconnect next to the transformer and just move the panel the 100' or you will have issues with the conductor rules in Article 240 as Bob mentioned.
 
I have a similar situation, the 208 panel off the secondary is approximately 40' from the transformer. In reading through NEC would not 450.3(A) and 450.3(B) come into play?
 

electrofelon

Senior Member
I have a similar situation, the 208 panel off the secondary is approximately 40' from the transformer. In reading through NEC would not 450.3(A) and 450.3(B) come into play?
450 is only about the transformer protection. There is no distance requirement for this. The conductors are covered by 240.21(C) which does have distance limitations.

Generally we request you start a new thread rather than reviving a very old one.
 
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