I'm modeling a building that wants to use modular air-cooled chillers. So in addition to several modular chillers, they want to install a few 'Free Cooling' units. These units will be tied in with the regular chillers and will be able to provide free cooling during the winter whenever the outdoor temperature drops below the mid 30s. To my understanding, this works when the ambient temperature is low enough, the return glycol is sent through economizer coils before it enters the evaporator. With colder temps, the refrigeration compressors unload until they are no longer required, and the full cooling capacity is provided by the condenser-fan alone.

I was wondering if anyone has had any experience with these types of chillers and what are some of the ways to model this 'free cooling.'

Thanks in advanced for all the help,

Neil Patel, EIT, LEED AP BD+C