Transformer

[john37]

Could someone please advise me if I'm doing this correctly. I have to provide a 30kva step down transformer for a small Chiller(3 phase). The Chiller is located on the 4th floor exposed parking deck, but the Architect is asking if we can ceiling or wall mount it on the 3rd floor covered parking deck directly below to protect it from the weather. Anyways, if we do that we need to provide a 3P50A breaker in the 480/277 volts panel, run the feeder to the transformer that is located about 200 feet away and then provide a 3P100A disconnect switch on the secondary side of the transformer. Can I provide the 3P100A disc sw on the 4th floor next to the Chiller or does it have to be next to the transformer on the 3rd floor? Or what makes better sense? By the way the Chiller only came in 208V, 3 phase. Also, am I missing something else? Do we need to provide a disc sw on the primary side of the transformer since it's located about 200 feet away from the distribution board? Thanks...

 

[don_resqcapt19]

The code does not require a primary disconnect at the transformer. The location of the secondary disconnect is limited by the rules in 240.21(C). If you can get to the 4th floor location without exceeding the maximum permitted conductor length, you can put the secondary conductor OCPD there.

 

[john37]

Thanks Don...The transformer will be located directly below the Chiller unit up on the 4th floor. They will core drill the slab to get the conduit up. Appreciate your help.