Energy Efficiency Reference/Refrigeration/Recommendations/Install ASD on Evaporator Fans

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Recommendation: Install ASD on Evaporator Fans[edit | edit source]

Summary: Convert fan motors to adjustable speed drives (ASD's) on air-cooled evaporators to reduce part-load fan power.

When to apply: When single-speed or two-speed fan motors demand a lot of power.

Key Engineering Concepts:

  • Ideally, fan power is cubically related to fan capacity with a variable speed motor
  • Fan power is linearly related to capacity with on-off fan control
  • Fan capacity is proportional to the condensing approach temperature difference


Tools required

  • DMM or power analyzer
  • Clamp-on Ammeter
  • Stopwatch
  • Thermometer
  • Refrigeration Data Sheets

Data Sheet

  • Suction Temperature (ST)- from pressure gauge or compressor display
  • Total fan power (FP) - measured
  • Dry bulb temperature - measured
  • Evaporator approach temperature difference (DT, approximately 10 degree F) - measured
  • Fan cycling schedule, if any.

Analysis Process: ?????