Evaporator Control

Evaporator Control


  • Setpoint scheduling (zone independent):
    • Four programmable setpoint groups (cooling setpoint, deadband, high alarm, low alarm, and heating setpoint option).
    • Three daily schedules each with eight time slots.
    • Manual override provided for schedule number and setpoint group.
  • Air unit fans may be individually set to cycle with temperature or remain running. A programmable fan cycle off-time delay and/or on-time delay is also provided.
  • When the fans for a zone are cycled off due to temperature, the fans may be cycled on for a short period of time to sample the room air before resuming normal operation.
  • Support for various zone defrost types (hot gas, water, air, etc.)
  • Zone high temperature alarms are inhibited during defrost cycle and for a user programmable delay after defrost completion.
  • Manual override control of zone state (cooling, stop, manual, defrost, pump-out).
  • Adaptable to match each zones specific valve station configuration.
  • Defrost scheduling:
    • Defrost based on liquid feed runtime or fixed time schedules.
    • Programmable defrost times using three daily schedules with eight time slots.
  • Power fail staging to slowly bring zones on-line after power failures based on user defined staging time and zone priorities.
  • User-programmable setpoints to enable and disable defrosting based on head pressure
  • Ability to inhibit defrosting of zones when no compressors are available.
  • Ability to terminate defrost manually to force zone back to cooling state.
  • Ability to separate zones into different defrost queues to select number of zones which can defrost at a time


  • Zone shutdown due to NH3 detection or other user defined conditions.
  • Demand defrost based on discrete input, temperature differential across the coil or fan motor current.
  • Priority defrost of pre-defined zones or based on user issued command.
  • Heating option allows zone to maintain a heating setpoint. Optional ability to disable heating based on user-defined conditions.
  • Variable speed fan control using PID control loop based on user defined weighted average between room air and return air temperature sensors
  • Two speed fans, variable speed fans, or variable suction regulator control.

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