The basic compact cooling system consists of 4 indispensable parts, including a small refrigeration compressor, a condenser, a capillary or expansion valve, and an evaporator.  The small refrigeration compressor is the key part used to pump and increase the pressure of the refrigerant gas and transport the gas to the condenser( heat exchanger). With the development of technology and science, the application of small refrigeration compressors is increasingly extensive.

While like many other intensively mechanical devices, some compressor failures and even accidents are inevitable in daily operations. It’s a must-have to identify the problems you are dealing with and know how to fix them, in order to preserve efficiency and reliability.

The following 7 points are the compressor common problems and their causes in the Refrigeration System.

1. Fails to Start or  Stop
2. Uncharacteristic Vibration and Noise
3. Abnormal Suction Temperature
4. Excessive Discharge Temperature
5. Abnormal Discharge Pressure
6. Insufficient Gas Displacement
7. Overheating

Let’s dive right in.

1. Fails to Start or  Stop

Compressor Fails to Start

When you don’t get any response while trying to start your mini compressor, this is usually caused by:

• 1)Power supply issue. The first thing you should do is check the switch, power button, and power cord.
• 2)Tripped breaker which prevents power from reaching your machinery.
• 3)Insufficient pressure or lubricating oil. First, check your cut-in pressure settings on the compressor. Next, check your fluid levels.

Compressor Fails to Stop

Once your tank reaches its cut-off point, the compressor should stop operating.  If this doesn’t happen, might be caused by:

• 1)  Power switch issue
• 2)  Pressure release valve issue.

If the pressure isn’t released properly, the compressor will be too pressurized and might become damaged. Cutting power and replacing the valve would be a good option.

2. Uncharacteristic Vibration and Noise

When your compressor makes an unusual noise or vibrates unexpectedly,  these are signs of potential trouble. Noise and vibrations from a miniature compressor can be caused by:

• Loose parts — Adjust or tighten misaligned or loose belts, bolts, or pulleys.
• Bad pistons — Pistons striking the valve plate can make a loud noise.
• Problem crankcase — Inspect the crankcase for sufficient oil levels and any defects.
• Faulty mounting — Insecurely mounting will be noisy when in operation
• Worn-out foundation chocks- Replace with new chocks

3. Abnormal Suction Temperature

To ensure the safe operation of the small refrigeration compressors and prevent liquid strikes, the suction temp is required to be higher than the evaporating temp which means a certain superheat is needed.

Higher or lower suction temp won’t be allowed. If it operates too high, will lead to a higher discharge temp of the mini dc compressor. If it operates too low, will cause the result that refrigerant cannot be completely evaporated, which not only reduces the heat transfer efficiency of the evaporator but also causes the suction of wet steam to form the compressor liquid strike. Generally, the suction temp should be 5 to 10 ° C higher than the evaporating temp.

Excessive Suction temperature

Normally, the compressor cylinder head should be half cool, and half hot. If the suction temp is too high, will make the cylinder fully hot. If the suction temp is higher than the normal value, the discharge temp will also rise.

Excessive suction temperature is mainly caused by:

• (1) Less refrigerant gas charged in the system.
• (2)  Insufficient circulation of refrigerant entering the evaporator
• (3) Insufficient liquid supply in the evaporator
• (4) Poor insulation or too long return pipe

Insufficient Suction Temperature

In theory,  the small refrigeration compressors operate with the best result when the suction steam is saturated. To ensure the compressor in safe operation and prevent wet stroke, a certain superheat is needed.

If the suction temp of the tiny compressor is too low, it is easy to cause a wet stroke and worsen the lubrication condition, so this phenomenon should be avoided.

The insufficient suction temperature may be caused by:

• (1) Over-amount refrigerant infill makes extra liquid refrigerant into the compressor which causes liquid-return issues.
• (2) Temperature sensor loosen, small contact with the return pipe
• (3) Temperature sensor not wrapped with insulation material or incorrect wrapped position results in improper temp measured

4. Excessive Discharge Temperature

The compressor discharge temp is related to the adiabatic index, compression ratio (condensing pressure/evaporation pressure), and suction temp. The higher the suction temp, the higher the compression ratio, and the higher the discharge temp, and vice versa. Too high discharge temp will dilute or even carbonize the lubricating oil, thus worsening the lubrication condition of the compressor.

The main causes of discharge temperature rise are:

• (1) Higher suction temp that results in refrigerant gas compressed in high temp.
• (2) Condensing temp increases, and condensing pressure does
• (3) Discharge valve is broken, the temp of the high-pressure vapor increases.
• (4) Liquid coolant shortage( water-cooled system)
• (5) Abnormal condensing pressure

5. High Discharge Pressure

Normally, the discharge pressure of the small refrigeration compressors is very close to the condensing pressure. When the condensing pressure increases, the compressor discharge temp increases which increase the compression ratio. The increasing compression ratio can decrease the gas transmission coefficient and lower the cooling capacity of refrigeration systems.

The main reasons for this failure are:

• (1) Small flow, high temperature of cooling water
• (2) Air enters the system making condensing pressure rise.
• (3) Too much refrigerant charged leads to liquid coolant taking the effective room of condenser
• (4) The existence of scale in the condenser increases the condensing pressure.

6. Insufficient Displacement

Insufficient displacement is mainly compared with the design volume of the small refrigeration compressors. Insufficient displacement volume is one of the most prone to failure of the miniature compressor.

The following reasons mainly cause this:

• (1) Too long suction pipe and too small pipe diameter increases the suction resistance
• (2) Compressor speed reduction.
• (3) The cylinder, piston, and piston ring damaged seriously
• (6) The valve spring force not well matched the gas force.

7. Overheating

In the crankshaft and bearing, crosshead, and slide plate friction area, when the temperature exceeds the specified value are called overheating.

The main reasons for bearing overheating are:

• (1) Uneven fitting of bearing and journal or too small contact area;
• (2) Bearing deflection, crankshaft bending, twisting deformation;
• (3) The viscosity of lubrication pumping is too small, and the oil circuit is blocked
• (4) No leveling installation, no good clearance, the main shaft, and the motor shaft are not aligned, and the two shafts are tilted.

Conclusion

Above are the common compressor problems that will cause the efficiency and capability of the compact refrigeration system. The article cannot completely cover some more faults caused by different conditions. Whether you are dealing with refrigerated compressor issues currently or would like to prevent mini compressor failure through appropriate maintenance, our experienced service team can work closely with you to solve it.

We are a professional and knowledge-comprehensive manufacturer of small refrigeration compressors, small cooling systems, and other micro refrigeration equipment. Besides the off-the-shelf service, we happily partner with our customers for a turn-key solution in the segment of compact or mobile thermal management.