Why did my ductless mini split system freeze on the inside air handler?Updated 8 hours ago

Ductless mini split systems usually freeze up at the indoor air handler due to issues with airflow or temperature settings. The indoor air handler can freeze even if the filters are clean and the refrigerant charge is correct.

Listed below are potential reasons and solutions:  

• Low Airflow:
  • Fan Speed: If the fan speed is set too low, the coil can freeze from low airflow. Try increasing the fan speed to see if it resolves the issue.
  • Obstructed Air Intake: Ensure the air intake is not obstructed by furniture, curtains, or other objects.
• Temperature Setting:
  • Low-Temperature Setting: Setting the temperature too low can cause the unit to freeze up. Try setting the thermostat to a higher temperature.
• Humidity:
  • High Humidity: High-humidity levels can cause excess moisture to accumulate on the coils, potentially leading the unit to freeze. Running a dehumidifier in the space might help.
• Mechanical Issues:
  • Blower Motor: If the blower motor is not working correctly, it may not be providing sufficient airflow over the coils.
  • Dirty Coils: Even though the filters are clean, the evaporator coils themselves might be dirty. Clean the coils to ensure proper heat exchange.
• Defrost Cycle:
  • Faulty Defrost Control: Sometimes the defrost control can be faulty, causing the unit to not enter the defrost cycle when needed. Check if the defrost control is functioning properly.
• Sensor Problems:
  • Faulty Thermostat: A faulty thermostat can misread the room temperature, which causes the unit to run continuously and freeze up.
  • Temperature Sensor: The indoor unit has a temperature sensor that monitors the coil's temperature. If this sensor is malfunctioning, it can cause the unit to freeze up.
• Drainage Issues:
  • Blocked Drain Line: Ensure the drain line is not blocked and water can flow freely. A blockage can cause water to back up and freeze.
• Operating the Unit in Cold Weather:
  • Cold-Ambient Temperature: Operating the unit in cold-ambient temperatures can sometimes lead to freezing. It's advisable not to operate the AC when the outdoor temperature is too low.
• Continuous Operation:
  • Non-stop Operation: Running the system continuously without giving it time to defrost can cause freezing.

To diagnose the exact cause, you may need to consult with a HVAC professional. The professional can access the system and identify any underlying issues. In order to find the source of the problem, the professional might check the refrigerant pressure, coils, or the electronic components.