As the "heart" of a refrigeration system, the compressor is responsible for driving refrigerant circulation and maintaining the entire cooling process. Once a compressor fails, the whole system shuts down—leading to costly downtime, product spoilage, and expensive repairs. Understanding the root causes of compressor failure is the first step toward effective prevention.
1. Liquid Slugging (Liquid Refrigerant Entering the Compressor)
This is one of the most common and destructive failures. Compressors are designed to compress gas, not liquid. When liquid refrigerant or oil enters the compression chamber, it cannot be compressed, resulting in a phenomenon known as "liquid slugging" (or "liquid hammer").
The impact force of liquid slugging is immense: it can break scrolls, crack valve plates, damage pistons and connecting rods, and even snap crankshafts. These broken metal fragments can then enter the motor windings, causing short circuits and ultimately burning out the motor completely.
Common Causes:
Overcharging of refrigerant
Evaporator fan failure or blocked air ducts
Improper selection or malfunction of the expansion valve
Incorrect defrost cycle settings
Refrigerant migration during compressor shutdown (i.e., "flooded start")
2. Oil Starvation and Poor Oil Return
Compressor lubricating oil not only provides lubrication but also seals gaps between moving parts and carries away heat. When oil is insufficient, metal parts rub directly against each other, generating excessive heat and wear, leading to bearing damage, journal scoring, shaft seizure, and eventual total compressor failure.
Oil leaves the compressor with the refrigerant discharge and must return via the suction line. If oil cannot flow back smoothly, the compressor runs "starved."
Common Causes:
Improper piping design (lack of oil traps, oversized suction lines)
Frequent starts and stops
Refrigerant leaks causing significant oil loss
Excessively long piping without additional oil charge
Clogged oil return holes in accumulators or filters
3. Overheating and High Discharge Temperature
High temperature is a "silent killer." When a compressor operates beyond its designed temperature range for extended periods, the oil degrades, loses its lubricating properties, and forms carbon deposits. Meanwhile, the motor windings overheat, insulation ages, and eventually the motor burns out.
Common Causes:
Insufficient refrigerant or system leaks (less refrigerant means less motor cooling)
Dirty or poorly ventilated condenser (reduced heat dissipation)
Non-condensable gases (air or moisture) in the system
Excessive compression ratio (high discharge pressure / low suction pressure)
Many compressor failures are fundamentally electrical in nature but are often overlooked. Voltage that is too high or too low, three-phase imbalance, or phase loss can burn out a compressor motor in a very short time.
Key Electrical Standards (Must Remember):
Voltage fluctuation must not exceed ±10% of rated voltage
Three-phase voltage imbalance must not exceed 5%
Single-phasing causes a sharp increase in motor current, leading to overheating and burnout
Additionally, worn, pitted, or welded contactor contacts can cause unstable power supply and lead to motor failure. Always use properly rated contactors and install phase sequence/phase loss protection devices.
5. System Cleanliness and Contamination
A clean system is a healthy system. Impurities—such as moisture, dust, metal debris, or welding flux—can cause severe damage.
Moisture reacts with refrigerant and oil to form acids, which corrode motor windings and destroy insulation. It can also freeze and block the expansion valve.
Metal debris can embed itself in bearings or directly short-circuit motor windings.
Copper plating (copper depositing on steel surfaces), often caused by inadequate evacuation, accelerates wear and damages seals.
6. Improper Installation and Maintenance
The root cause of many compressor failures can be traced back to the day of installation.
Incorrect wiring – Compressor windings have a specific correct connection (Common C, Main M, Start S). Wrong connections will immediately burn out the start winding.
Inadequate evacuation – Failure to achieve sufficient vacuum leaves moisture and air inside the system.
No additional oil for extended lines – When piping exceeds standard lengths, supplementary oil is required.
Compressor reversal (incorrect phase sequence) – Prevents the oil pump from supplying oil properly.
Using the compressor to evacuate the system – This causes extreme overheating and rapidly damages the compressor.
7. Frequent Starts and Stops
Each time a compressor starts, the inrush current is several times higher than the normal running current. If the compressor cycles on and off too frequently due to improper thermostat settings, oversized equipment, or poor system design, the motor does not have enough time to cool down between starts. This cumulative thermal stress significantly shortens compressor life.
Prevention Guide: What Buyers and Operators Should Do
Although compressor failures may seem unpredictable, the vast majority are preventable. Focus on these key areas:
Correct refrigerant charge – Neither overcharged nor undercharged
Proper system evacuation – Thoroughly remove moisture and non-condensable gases
Good oil return design – Piping should have proper slopes and oil traps
Stable power quality – Monitor voltage and three-phase balance; install protective devices
Standardized installation practices – Follow manufacturer guidelines strictly for wiring, piping, and commissioning
Conclusion
Whether you are purchasing refrigeration equipment for cold storage, refrigerated transport, or HVAC systems, compressor reliability should be a top priority. The failure of a single compressor means not just replacement costs, but business interruption, product loss, and decreased customer satisfaction.
For any questions regarding compressor selection, installation, or maintenance, your trusted supplier should be your first stop for technical support and guidance.
We are a professional supplier of air conditioning and refrigeration compressors, committed to providing customers with high-quality compressors from globally renowned brands, including Copeland, Daikin, Danfoss, GMCC, Sanyo, Panasonic, LG, Samsung, and Mitsubishi.
