Fan Speed Control

Three Phase VFD66 Series

Condensor Fan Speed Control


The VFD66 Series Condenser Fan Speed Controls are designed for speed control of 3-phase condenser fan motors in refrigeration and HVAC systems. The VFD66 controls regulate condenser fan motor speed by varying the frequency and voltage of the power supplied to the motor. The VFD66 controls use input signals from various devices to adjust fan speed and optimize condenser head pressure, especially during low ambient conditions. Condenser fan speed may be controlled by pressure or temperature. The VFD66 controls accept input signals from the P35 Pressure Transducer, P499 Electronic Pressure Transducer, System 450™ controls or any other device that provides a 0-5 VDC or 0-10 VDC analog input signal.

The VFD66 controls have a simple interface, and are easy to understand and use. Minimal end-user setup is required because of the application-specific design.


  • Permits application with 0-5 VDC or 0-10 VDC controllers, sensors, and transducers including Johnson Controls System 350™.
  • Allows use on dual refrigeration circuits cooled by a single fan.
  • Provides installation ease and flexibility.
  • 3-phase motors ranging from fractional to 3 hp at 208/230 VAC or 400/460 VAC.
  • Provides fast, easy installation and setup.
  • NEMA 1 or NEMA 4 enclosures.


The VFD66 controls are intended for air-cooled condenser fan speed control in refrigeration and HVAC applications:

  • Commercial air-cooled condensers.
  • Cooling tower fans.
  • Fans in evaporative condensing units.

The VFD66 controls allow the system to:

  • Maintain optimum condenser head pressure in low ambient temperature conditions.
  • Eliminate short cycling in low ambient or changing load conditions.
  • Match the condenser fan speed to the load on the condenser, which increases the efficiency of the refrigeration system. This can reduce electricity cost and help maintain a constant evaporator temperature.

Other advantages of using the VFD66 controls are:

  • Stabilized condenser head pressures help optimize compressor operation, which may reduce wear and extend compressor life.
  • Eliminating condenser fan short cycling may result in reduced motor repair and replacement costs.
  • Stable evaporator temperatures extend refrigerated product life and provide more consistent comfort coolingCommercial air conditioning, head pressure control.


Refer to Product Literature (listed below) for selection criteria.