The VFD-4 Variable Speed Fan Drive is designed to provide variable fan speed capability for HVAC applications. The VFD-4 can be used in either new or retrofit installations where a fixed fan speed motor is currently installed.

Where multiple fixed fan speeds are available, any one of the fixed speeds can be used for variable control. Variable speed fan control provides many advantages over fixed fan speeds including:

  • Acoustic Noise Reduction. The VDF-4 offers infinite fan speeds including slower than normal fan speeds. Slower fan speeds significantly reduce noise levels.

  • Smooth Speed Transitions. The VDF-4 eliminates stepped changes between fan speeds.

  • Steady-state Temperature Control Without Fan Speed Changes. Active fan speed cycling is not required to compensate for heat gain or loss. Instead, gradual changes are made based on heating and cooling requirements.

  • Extended Motor Life. Significantly fewer start-stops and speed change cycles reduces wear on mechanical components.

  • Increased Energy Savings. Running the fan at optimal fan speed increases energy savings.

  • Sub-low Fan Speed for Dehumidification. When in the dehumidification mode, the lowest achievable sub-low) fan speed can be selected to enhance the dehumidification process.

  • Fewer Control Wires Required. Only two fan motor control wires and three thermostat control wires are required for the VFD-4 to operate. Heating and cooling valve wiring remains the same.

Additional features include continuous fan operation, VIP over-ride capability with automatic restoration.


The VFD-4 assembly is wired between the e4 digital thermostat and the fan motor. Once installed, the VFD-4 controls fan speeds depending on the demand condition in the different air conditioning modes.

The VFD-4 provides two operational functionalities:

Noise reduction
The INNCOM VFD-4 incorporates four different built-in noise reduction configurations Whisper, Quiet, Standard, and Performance for both the variable fan speed mode and the discrete (fixed fan speed) mode. These four modes of operation are parameters that can be set by the hotel engineering department. When a centrally controlled system is installed, a parameter change can be made from the server, a terminal, or remotely from off property. In a standalone system, parameter changes can only be made at the thermostat.

Humidity control
The VFD-4 provides better dehumidification as a result of its ability to achieve lower fan speeds than can be achieved when using the pre-determined fixed fan speeds provided in the HVAC unit. When the fan is running at its lowest allowable speed, the air passes over the coils very slowly. While in the cooling mode, the air gets colder than it would when it passes over the coil at higher speeds. When the air gets colder, more water is condensed onto the coils which then dries the air more than it would at higher speeds. Additional humidity control strategies can be employed using the humidity control algorithms built into the e4 digital thermostat.


The VFD-4 is typically installed using a single UL approved electrical J-box ready or in two shallow electrical J-boxes (one low voltage and one high voltage). Final configuration will be determined by space requirements. No field wiring connections are required inside the VFD-4 assembly J-box.

The assembly is pre-wired ready for installation connection to thermostat and fan motor.


  • Easily installed

  • Continuous fan operation

  • Variable fan speeds for FCU applications

  • Ideal for retrofit and new construction projects

  • Infinite fan speeds, including slower than normal

  • Four built-in noise reduction configurations: Whisper, Quiet, Standard, and Performance

  • Smooth speed transitions

  • Extended motor life

  • Increased energy savings

  • Enhanced humidity control without impacting guest comfort

  • Sub-low fan speed for dehumidification

  • Fewer control wires required

  • VIP over-ride capability with automatic restoration

  • Customer programmable parameters


  • High Voltage Input 120vac 20 amp

  • High Voltage Output 120vac 3 amp

  • Low Voltage input Power 12VDC regulated, 200mA

  • Dimensions

  • Single J-box configuration 4"W x 4"H x 2-1/8"D

  • Two J-box configuration 4"W x 4"H x 1-3/4"D each box

  • Operating Temp Range 40o-120o Fahrenheit

  • UL / FCC Approved All line voltage components are UL and FCC approved