1061 Chillers

The most common type of water chiller for large buildings is the centrifugal chiller which employs a centrifugal compressor to compress the refrigerant, which extracts heat from a closed loop of water which is pumped through coils in air-handling or terminal units within the building. Heat is rejected from the condenser into a second water loop and ultimately rejected to the environment by a cooling tower.

The operating fluid used in these chillers may be either a CFC or HCFC type refrigerant. Many existing centrifugal chillers use CFC-11 refrigerants, the manufacture and use of which is being eliminated under the terms of the Montreal Protocol. New refrigerants HCFC-123 and HCFC-134a are being used to replace the CFC refrigerants but refrigerant modifications to existing equipment will reduce the overall capacity of this equipment by 15 to 25 percent.

Centrifugal chillers can be driven by open or hermetic electric motors or by internal combustion

Table 10.1 Summary of HVAC System Modifications for Energy Conservation

System type

Energy Conservation Opportunities

All-air systems (general):


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