What Causes Evaporator Icing in Air Conditioner Indoor Units?
As the core heat exchange component of air conditioner indoor units, the evaporator is responsible for absorbing indoor heat and achieving cooling and temperature reduction. Under normal operating conditions, the surface of the evaporator should maintain stable heat exchange efficiency. However, in practical use, affected by various factors such as installation and maintenance, component performance, and usage habits, evaporator icing has become a common fault. This problem not only reduces the cooling effect of the air conditioner and increases energy consumption but also may damage core components such as the compressor if ignored for a long time, affecting the service life of the equipment. Therefore, accurately identifying the causes of evaporator icing and handling them in a timely manner is crucial to ensuring the stable operation of the air conditioner. The following is a detailed breakdown of 7 common causes of evaporator icing and their corresponding solutions:
1. Insufficient Refrigerant
Refrigerant leakage or seepage may occur in split-type air conditioners due to improper installation or prolonged use. When the amount of refrigerant in the refrigeration system decreases, the evaporation pressure becomes excessively low, leading to evaporator icing—usually on the front part of the evaporator.
Solution: First repair the leakage point, then replenish sufficient refrigerant, and the fault will be resolved.
2. Low Compressor Efficiency
With long-term use, the compression efficiency of the compressor may decrease, or the valve train of the compressor may be damaged, resulting in excessively low pressure and subsequent icing. The icing position is also on the front part of the evaporator.
Solution: For the former case, adding some refrigerant can resolve the fault. If the fault persists, the compressor must be replaced.
3. Excessive Refrigerant
Some air conditioners require refrigerant refilling after relocation or leakage. If maintenance personnel add an excessive amount of refrigerant due to improper operation, the surplus refrigerant will flow to the rear part of the evaporator for evaporation, causing icing. Such ice mostly forms on the rear part of the evaporator and around the compressor's suction line.
Solution: Release the excess refrigerant to eliminate the fault.
4. Dirty Heat Exchanger (Evaporator)
After the air conditioner has been used for a period of time, dust in the air or microorganisms generated by the evaporator will accumulate on the evaporator, obstructing air circulation, reducing heat exchange, and causing the evaporator temperature to drop excessively, leading to icing. The icing position is on the rear part of the evaporator.
Solution: Allow the ice to melt completely, then rinse the evaporator with water and gently brush the fins with a soft brush (being careful not to wet the electrical components). After thorough cleaning, the fault will be resolved.
5. Overly Low Temperature Setting
Some users set the air conditioner temperature too low. If the cooling capacity of the air conditioner cannot keep up, the room temperature fails to reach the set value, causing the unit to run for a long time or have very short downtime, which can also lead to evaporator icing. In some cases, extremely low room temperatures can directly result in excessively low evaporator temperatures and icing. Such ice mostly starts to form from the lower part of the evaporator.
Solution: Simply set the temperature higher, and the fault will be resolved.
6. Faulty Temperature Sensor or Improper Installation
a. Faulty Temperature Sensor
For mechanical thermostats, the gas pressure in the temperature-sensing bulb changes with temperature, driving the action of the thermostat contacts. If the contacts remain closed due to adhesion, insufficient spring force, or other reasons, the air conditioner will run continuously, leading to icing.
Solution: Replace the thermostat to eliminate the fault.
b. Improper Sensor Installation
In special cases, the thermostat may be intact, but the air conditioner still has short downtime or runs continuously. The temperature-sensing bulb is usually suspended in the middle of the evaporator by a U-shaped plastic bracket, approximately 2mm away from the fins. This design is presumably intended to make the temperature-sensing bulb of the thermostat exert a temperature delay effect, preventing the air conditioner from starting frequently within a short period (3 minutes). In midsummer, due to high indoor temperatures and the inherent limitations of the air conditioner's cooling capacity, the thermostat is difficult to reach the temperature control cutoff point, resulting in short downtime or even continuous operation of the air conditioner, leading to icing. Such ice mostly forms on the lower part of the evaporator.
Solution: Reposition the temperature-sensing bulb to the lower end of the evaporator and fix it tightly against the evaporator fins, and the fault will be resolved.
7. Low Airflow from the Indoor Unit
a. Dirty Fan Blades
After the air conditioner has been used for a period of time, a lot of dirt and grime may adhere to the fan blades, affecting air supply and causing evaporator icing.
Solution: Clean the dirt and grime, and the fault will be resolved.
b. Fan Malfunction
Some fans may run at reduced speed due to mechanical or electrical faults, resulting in low airflow and evaporator icing. Mechanical causes are mostly wear of bearings or bushings, which increases resistance and reduces rotational speed. Electrical faults are mostly failure of capacitor charging and discharging or inter-turn short circuit of the fan, leading to reduced speed, or even burnout of the fan windings and motor stalling.
Solution: Repair or replace the fan according to the specific fault condition.
Although the problem of evaporator icing seems complex, it is mostly closely related to component quality, daily maintenance, and usage habits. Among these, high-quality core evaporator components are the foundation, standardized installation operations and regular maintenance are the guarantee, and all of these are inseparable from enterprises' in-depth cultivation of heat exchange technology and strict control over material processes. To fundamentally prevent faults such as evaporator icing, choosing the right core component supplier is crucial.
JUYON is deeply engaged in the heat exchange field. With solid R&D accumulation and refined manufacturing capabilities, it produces durable and efficient core products such as radiators, evaporators, and condensers, safeguarding the stable operation of equipment from the source. Contact us now to obtain customized targeted solutions and cost optimization suggestions, making cooperation hassle-free and cost-effective!
