I agree completely with Phillip.
Your standby generator will be sized to handle the starting current of the compressor and the rest of the load of the brewery if you choose to go that route. If running the chiller is your only concern, and I think Phillip explained quite well why it shouldn't be; the capacity of the generator set would only have to satisfy the starting current and load of the chiller system and controls.
It will mean that the electrical wiring for the chiller, valves and control system will be dedicated to the generator transfer switch, may require some re-wiring and another distribution box, the generator set should have an automatic start and transfer feature, and if you are not a 24 hour facility be sure to tie in an auto dialer to call you when your system or brewery is on standby power.
Head Brewer and everything else
North Jetty Brewing Co. (In My Barn)