Option 3 - Air-cooled chillers

Good question Alicia, Anyone knows if the prescriptive compliance path requires to use water-cooled chillers? We have air-cooled chillers and the owner does not want to change the system because water is very expensive and this is a drought prone area.

The prescriptive compliance path requires that minimum efficiencies for equipment be met per ASHRAE 90.1-2007 section 6.4 (mandatory previsions). This section has the table and is specific to the equipment you are using. If you are utilizing an air cooled chiller, you must meet or beat the efficiency in the table for that specific piece of equipment. The LEED for HealthCare Reference Guide does stipulate the following: "Chillers shall operate at a maximum of 0.52 kW/ton at full load and an Integrated Part Load Value (IPLV) of 0.399 kW/ton." As rules usually go, you have to follow the strictest of both.