Size 2.4KV transformer for chiller

[zemingduan]

I'm now working on sizing a 2.4kV to 480V transformer for a nominal 160 tons chiller. The unit power is 175.61 kW. It has 4 direct-drive hermetic,3600 rpm 60HZ compressor with 69A RLA, two per circuit. It also has its own factory-installed control panel. See the pictures below.



My question is that is 225 KVA 2.4 KV to 480V transformer enough for this chiller. The unit power is 175.61 KW but the MCA is 317A which is 317A x 460V x 1.732 = 252.56 KVA and it has 4 compressors with 69 RLA. My co-worker thinks we should use a 300 KVA transformer. But I think MCA indicates the minimum circuit ampacity. It seems that there is no code requirement for sizing the transformer with MCA. And it's highly possible that the 4 compressors won't work at the same time. What do you guys think? Is there any other consideration here? What is the price of a 225KVA and 300KVA 2.4KV to 480V transformer?

 

[jim dungar]

Your transformer needs to be sized to:
1) Provide continuous current to the compressor of the listed MCA.
2) Provide sufficient starting current to handle all concurrent LRA + continuous amps, that may occur at one time, while providing an acceptable voltage drop.

You need to know the starting characteristics for the motors.

 

[ron]

Since it is an across the line starter, the transformer at the incoming will match or be larger than the MCA, which is a smidgen over 250kVA and handle voltage drop.