Frequent defrosting in a mini-split system can be caused by several factors, including:
- Outdoor temperature: When the outdoor temperature drops below a certain point, the system’s outdoor unit can accumulate ice on the coils, interfering with the system’s ability to function correctly.
- Dirty filters: If the filters in the indoor unit become clogged with dust and debris, it can restrict the flow of air through the system and cause the system to overheat, which can trigger the defrost mode.
- Low refrigerant levels: If the system is low on refrigerant, it can cause the system to operate inefficiently, leading to ice buildup on the coils and triggering the defrost mode.
- Malfunctioning components: There could be a malfunctioning component, such as a faulty thermistor, outdoor fan motor, or control board, causing the system to operate improperly and triggering the defrost cycle mode more frequently than usual.
- Incorrect installation: An improperly installed mini-split system can cause refrigerant or airflow problems, leading to frequent defrosting.
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Procedure to troubleshoot an issue with defrosting:
- Understand the Defrost Function: The defrost function is a feature on every air conditioner designed to remove ice buildup on the outdoor unit heat exchanger. Ice buildup occurs during the heating process of the air conditioner because the temperature of the outdoor coils drops below zero degrees, causing the moisture on the coil to freeze.
- Check if the unit is defrosting: Most units will indicate defrost by flashing LEDs on the front cover, or the wall controller will display a defrost icon.
- Determine how often the unit should defrost: This depends on several factors, including the cold/dampness of the air around the outdoor unit, the unit’s workload, room insulation, thermostat setting, mechanical defects with the unit, and whether the unit is sized correctly. Assuming there are no mechanical defects, most units will only check for a defrost cycle about 45 minutes after the initial start-up.
- Determine how long it takes for the unit to complete defrosting: Defrosting function on most units is ended after a specific time has elapsed, OR the outdoor unit heat exchanger temperature has risen sufficiently, indicating that defrosting can be completed. Defrost termination can occur within 15 minutes.
- Determine the cause of frequent defrosting: Regular and unsuccessful attempts to defrost an outdoor unit can be a sign that the system is undersized for the area to be heated, the thermostat setting is too high, the unit has a mechanical defect, or there is a lack of maintenance. Refrigerant loss, blocked heat exchangers, restricted airflow due to obstructions such as foliage, blocked or clogged filters, or uncalibrated sensors are all possible problems.
- Clean air intake filters: First, try cleaning the air intake filters for the indoor unit, as this may help to reduce the frequency of defrosting and will help improve product performance.
- Adjust fan speed: Check that the unit is not set to a fixed low fan speed, as this will prevent the unit from delivering full heat capacity. Adjust the fan speed to ‘auto fan’ as this allows the unit to automatically adjust the fan speed so the output capacity will match the requirement.
- Contact Tech Support for assistance: If none of the above helps, it is advisable to seek the assistance of Tech Support to help diagnose the problem.