Can I Size to a Smaller Chiller If I Use Pre-cooled Water?

If you can spare that amount of water from the existing 9°C supply, this should work. There may also be a slight operational savings because 280TR of your cooling will be at a better thermodynamic ratio.

Thanks for the quick advice!

a few more concerns;

- can I get a chiller that is size at 320tons and flow at 1440 gpm? Is it not a constraint that I can only get as much as 2.4x (320 TR*2.4 gpm/TR = 770 gpm)?

- if flow is a constraint, does that mean I still need to get the 600 TR chiller to meet the flow required, but will operate at 50% turndown?

The 2.4 gpm/TR figure is a common rule of thumb, but it is not really a constraint. If you inform the chiller manufacturer of the larger gpm, they may design the chiller with fewer but larger water passes. But your case is still well within reasonable ranges. I have in my plant a brine chiller for freezing herring. It is about 250 TR and 7000 gpm, with a small ΔT (brine in 2°F, out 0°F). (Rough numbers; they don't match exactly.)

This is in addition to the good answers provided by Tornado. As a thumb rule 3 USGPM is considered when I worked as HVAC design engineer two decades ago. You have to consider the operation costs of the plant also. Water cooled units always preferable due to high heat transfer coefficient. Incorporate heat exchangers at appropriate locations in the system to recover heat wherever possible to save the energy cost.

Pls. consider the following on chiller application:

1, Trane centrigugal chiller (R123) has a design effeciency from 0.45kw/ton to 0.52 kw/ton @ 87degF condenser inlet temp.

2, York, Mcquay, Carrier R134 chiller has a design effeciency at 0.58 Kw/ton upward.

3. Please check with sales engineer for your application considering that the capacity you need is below 500TR.

4. If the capacity requirement is not feasible, then you have to consider the screw compressor (200 to 500Tr) with variable speed from any of the manufacturer mentioned above.

I could not link up one aspect from your post. You have depicted as it is an open cycle. Where the chilled water supplied to new building will go? Is it going to your old chillers which are capable to produce chilled water at 9 deg C only? What is the chilled water return temp.?