Help understanding ocpd for buck boost transformer and supplied load

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Trawets

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I'm running electrical for split a/c unit for a server room. The condensing unit will be above the drop ceiling in an adjacent room. It requires 277 vac which is available. The cooling unit will be in a server room requiring 208/230 vac, 13 fla on a separate circuit which the voltage is not available. The manufacture supplies a buck boost transformer (277 vac, 37.5 amp) which will be above a drop ceiling also. The part that I don't understand is the ocpd for the transformer and the cooling unit. My plan is from breaker to unit....40 amp breaker, #8 awg thhn wire to non-fused disconnect for transformer above ceiling, #8 awg thhn wire from transformer to fused disconnect on wall by cooling unit, 25 amp fuses with #10 awg thhn to the unit. I've read 450.4 for the last 3 days and I still think I have it wrong. So where and why am I wrong?:?
 
I think that what you have described will work and meets code as long as the 25A OCPD does not exceed the MOCP per the manufacturer.

Your input conductor OCPD cannot exceed 125% of the rated full-load input of the transformer. This would be 50A for the 37.5A transformer you have described. Seeing as though the FLA of the cooling unit is 13A I do not think 40A OCPD and 8awg wire is required.
 
Thanks MD84. Yes the MOCP is per manufacture specs for the cooling unit and while looking up a similar transformer, that manufacture required a 40 amp max OCPD. I haven't seen the manufacture of the transformer to be used require a specific max OCPD. Per your last sentence, could I use a smaller OCPD for the transformer? Say 30 amp and #10 since the transformer is only to serve the cooling unit?
 
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