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Energy – Case Study 2


Client Need


Three sets of redundant exhaust systems serving a high-tech production facility required fan replacements. One dedicated system for each type of exhaust; corrosive, solvent and heat. This presented our client with an opportunity to incorporate a fully integrated, retrofit liquid refrigerant overfeed energy recovery system. Energy recovery coils were designed into the existing exhaust systems and a local make-up air handling unit. Energy recovery is obtained year round by reversing the refrigerant cycle. This reduced overall operating cost while restoring some additional capacity to the make-up air handling unit. Our design also resolved a long standing problem with snow entrainment at the make-up air handling unit.

Design Features

  • Full sequence of operations for all new equipment including all interface points with existing equipment and systems.
  • Designed modifications to an existing 20,000 CFM make-up air handling unit to integrate new energy recovery coil, filter section and outdoor air inlet section to eliminate snow entrainment during winter conditions.
  • Designed and integrated new energy recovery coils for each set of new exhaust fans. New fans designed and arranged for N+1 redundancy with controls and dampers for automatic changeover. Detailing included discharge configuration, inlet and outlet conditions, support, and sound attenuation.
  • New refrigerant pumps and receivers designed with fully integrated controls including automatic changeover. Refrigerant cycle reverses based on adjustable outdoor air temperature setpoints with built in deadband. A typical design requires only a single pump and receiver with refrigerant flowing by gravity under one condition. However, the unique circumstances associated with geometry relative to equipment locations in the field required two [2] pumps and receivers. One pump and receiver set each for cooling and heating.
  • Designed power for refrigerant pumps including feeders, disconnect switches, and motor controllers.

Design Benefits

  • Fully integrated energy recovery system provided year round operational energy savings for make-up air handling unit with a total load reduction of 371 MBH (108 kw) wintertime and 198 MBH (16 tons) summertime.
  • Served clients original need of fan replacements for exhaust systems and also incorporated a custom liquid refrigerant overfeed energy recovery system for overall operational savings and efficiency.