Two chillers from a single feeder

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Junior_EE

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As you can see from the image, I am attempting to power two new chillers from a single feeder. The service switchboard MCB is 3000Amps at 480Volts, 3-phase. I want to feed the chillers from one circuit breaker for two reasons: 1. The distance between the 1600A circuit breaker and the chillers is considerable, and I would only like to run 1200Amps of copper instead of 1200Amps two times, and 2. I do not think I can fit more than a single new 1600A circuit breaker into the existing 3000A service switchboard.

The chillers will not run at the same time. BMS programming will ensure this.

I have a couple of questions:

1.) This design looks strange, so I am wondering if anyone has done something like this before and has run into any issues, especially code-related issues?

2.) Each chiller's cutsheet says that the chiller requires a 1600A max OCPD and 1200A MCA. Would the local disconnect switches need to be 1600A or 1200A?
 

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If the two chillers are interlocked so they can not run simultaneously, a single feeder would be allowed. The disconnect would need to be rated per 440.12 at 115% so, IMO, the 1600 amp disconnect would be required.

I would caution to assure there is no "static load" such as condenser heaters, etc. present on the 2nd chiller when not operating
 
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augie47 said:
If the two chillers are interlocked so they can not run simultaneously, a single feeder would be allowed. The disconnect would need to be rated per 440.12 at 115% so, IMO, the 1600 amp disconnect would be required.
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The MCA is not the actual current though. The sizing of the switch is based on actual current.
 
I'm not sure that BMS programming would count as a sufficient interlock between machines (would it?). In something like this, where a breaker trip if both machines try to run at once would be a Bad Thing, some local hardware interlocking may be in order; could be as simple as cross-wiring whatever the VFDs call RUNNING and RUN-INHIBIT (so that when one machine starts, the other is blocked from operating).
 
I will gladly vow to your knowledge on the subject. My assumption was that chillers had hermetic compressors so I assumed 440 was applicable.
OP didn't give branch circuit selection circuit so I used MCA. My bad !
 
I agree with @zbang

In that situation I think you need something more than the BMS interlocking/locking out 1 chiller. Chillers usually need their control circuits and the 3 phase live to be able to run when needed.

They usually have pump interlock circuits that could be wired through a double throw switch or something
 
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