I. Main Types and Characteristics of Indoor Unit Noise

 

Liquid Flow Noise:

 

1.Description: A bubbling sound similar to boiling water heard during cooling, originating from the evaporator.

 

2.Cause: The sound is caused by refrigerant flow in the evaporator. Turbulence occurs when the refrigerant passes through narrow pipes or valves, generating the noise.

 

3.Influencing Factors: The refrigerant charge, system pressure, and temperature changes can all affect the intensity of the liquid flow noise.

 

Abnormal Motor Noise:

 

1.Description: A “rustling” friction sound, usually near the air outlet.

 

2.Cause: Poor fit between the fan bearing and blades, possibly due to bearing wear, insufficient lubrication, improper assembly, or intrusion of foreign particles. Factors such as usage duration, environmental dust, and installation precision also play a role.

 

Unusual Sounds:

 

1.Description: Collisions or friction between internal mechanical components.

 

2.Cause: Loose screws, aging or deformation of plastic parts, or unbalanced fan blades.

 

System Pulsation Noise:

 

1.Description: Intermittent noise caused by unstable refrigerant flow.

 

2.Cause: This could result from compressor operation status, improper expansion valve adjustment, or incorrect refrigerant charge levels.

 

Thermal Expansion and Contraction Noise:

 

1.Description: “Clicking” sounds caused by materials expanding or contracting due to temperature changes.

 

2.Cause: Differences in thermal expansion coefficients of various materials can lead to slight movements or contact between parts.
 

Deflector and Swing Louver Noise:

 

1.Description: Noise caused by air deflector structures, often due to design flaws or deteriorated part fit after prolonged use.

 

Uneven Airflow Noise:

 

1.Description: Noise from uneven airflow distribution, sometimes accompanied by uneven temperature distribution.

 

2.Cause: Possible causes include clogged filters, improperly set deflector positions, or poor internal duct design.

 

Compressor Noise Transmission:

 

1.Description: Noise from the outdoor compressor transmitted indoors via pipes.

 

2.Cause: Factors include compressor characteristics, inadequate vibration reduction measures, and pipe connection design.

 

II. Noise Troubleshooting Reference for Indoor Units

 

Liquid Flow Noise:

 

1.Switch the air conditioner to fan mode (no refrigerant flow) and observe if the noise disappears. If the sound diminishes or stops, it is likely liquid flow noise.

 

2.Use a screwdriver to touch different parts of the evaporator piping, listen closely through the screwdriver handle to locate the loudest noise source.

 

3.Inspect the evaporator piping for dents or twists, ensuring smooth flow.

 

4.Wrap high-quality soundproofing materials like damping blocks around the loudest sections of the piping. Ensure the wrapping is thick enough for noise reduction.

 

5.Replace damaged evaporator components if pipe blockages are detected to maintain refrigerant flow.

 

Bearing Friction Noise in Indoor Units:

 

1.Disassemble the indoor fan and check for impurities in the bearings. If found, thoroughly clean and re-lubricate.

 

2.Examine the steel shaft of the cross-flow fan or the surface of bearing balls for scratches or damage; replace faulty parts as necessary.

 

3.If no obvious issues are detected, reassemble the fan and bearings to ensure proper fit, reducing friction noise.

 

Indoor Unit “Buzzing” Noise:

 

1.Check if the motor wires are touching the casing to avoid safety hazards caused by short circuits.

 

2.If assembly is normal but the noise persists, consider replacing the motor with a higher-quality, low-noise model.

 

Thermal Expansion and Contraction Noise:

 

1.Apply fabric or fiber tape at potential friction points, such as panel card slots, the upper edge of the bottom shell, or surface clips, to act as a buffer during material expansion or contraction, reducing noise.

 

Abnormal Throttling Noise:

 

1.During installation, incorrect handling, such as over-bending pipes, may lead to local stress concentration in the main liquid inlet pipe, causing throttling effects and restricting refrigerant flow.

 

2.Readjust the pipe shape to ensure straight pipes and compliance with the manufacturer's installation guidelines, avoiding stress concentration and refrigerant flow obstruction.