In HEAT mode, the unit operates to heat the room.  The temperature control range in heating mode is 60°F - 86°F.


Indoor Unit


To enter the heat mode, point the infrared remote control at the indoor unit and press the power button, then press the HEAT mode button if not already set to heat mode.

  1. The signals received by the infrared receiver are relayed to the main board of the indoor unit to turn the system on and set it to heat mode. The temperature set by the remote control and the indoor unit's ambient temperature sensor will determine if a call for heating is needed.
  2. The indoor unit main board will activate the display of the indoor unit, illuminating the display, indicating the room temperature and current status of the unit.
  3. The indoor unit main board will signal the louver stepper motor to open the louver to a stationary position.
  4. As the louver opens, the indoor unit main board will power up the indoor fan motor, operating minimum speed until the indoor coil temperature reaches a minimum temperature. 

Temperature Sensors


  • The indoor unit has two sensors that provide temperature information to the indoor unit main board. The sensors are used for controlling the system during heat mode.
  • The sensors are: an indoor ambient temperature sensor, and pipe temperature sensor.

Communication Between Indoor and Outdoor Units


  • The indoor and outdoor unit main boards communicate via a digital signal on the wire connected to terminal 3 of each unit. A splice or break in this wire will cause a communication error.
  • When a command is received from the remote control, the indoor unit main board communicates with the outdoor unit main board via the terminal 3 wire to perform the requested function.

Outdoor Unit

  1. Upon a request for heat,the outdoor unit main board applies power to the 4-way valve, outdoor fan motor and compressor.
  2. Depending on system cycling, there can be a delay of up to 3 minutes before the outdoor unit fan and compressor start.
  3. When heating has been satisfied, the outdoor unit compressor will turn off, followed by the outdoor fan. The indoor unit fan will continue to run.


End Heating


The system will stop heating when the indoor ambient temperature sensor is equal to or higher than 2°F above the room set temperature. To stop heat mode manually, press the power button to turn the system off, or change to another mode.


  • The indoor control board will communicate to the outdoor control board to de-energize the compressor.
  • The outdoor fan will run for 60 seconds before stopping.
  • The 4-way valve will de-energize 2 minutes after the compressor stops.


If the system detects a malfunction, it may shut down or show an error code on the indoor unit display board and/or outdoor unit main board LED.