transformer sizing

[patc]

I need to size a 3 ph transformer to supply power to a 480 HVAC system. The primary of the xfmr is 208v and will be stepped up to 480. The name plate on the HVAC unit reads: FLA 36 amps, MIN CKT AMP 56 amps, both at 480volts. Which do I size the xfmr to? A 45kva xfmr would cover the FLA but not the minimum cicuits amps. Would the secondary overheat? Or is a 75kva the size which should be installed?
Thanks

 

[Smart $]

Size to MCA value.

 

[patc]

Thank you. Thats what I thought I should do but is there a code article that would lead me to that answer or just good practice.

 

[Smart $]

Thank you. Thats what I thought I should do but is there a code article that would lead me to that answer or just good practice.

HVAC falls under Article 440. From there you have to drill down according to the details of the installation. However, a good indicator is 440.35. It is the only section in the entire NEC which uses the term "minimum circuit ampacity".