Refrigeration System Top 10 Failures Check List! Do You Know How to Solve Them All?

1. Liquid reflux

Cause

1. In the refrigeration system using expansion valves, liquid reflux is closely related to the wrong selection of expansion valves. Oversized expansion valve, too small heat protection setting, incorrect installation method of temperature-sensor or broken insulation package, may cause reflux phenomenon.
2. For small refrigeration systems using capillary tubes, too much liquid addition can cause liquid reflux. When the evaporator frost is serious or the fan fails, the heat transfer becomes poor and the unevaporated liquid will cause liquid return. Frequent temperature fluctuations can also cause the expansion valve to fail to respond and cause the phenomenon

Method

For refrigeration systems where liquid reflux is difficult to avoid, installing a gas-liquid separator can effectively stop or reduce the hazards of this phenomenon.

2. Condensing temperature abnormal (high pressure protection)

Cause

1. Low condensing temperature

The reason for the low condensing temperature is that the refrigerant in the evaporator is too less or the throttle valve throttling effect is not good, listed as follows.

• the expansion valve is oversized.
• expansion valve failure or expansion valve open too large, no throttling effect.
• refrigerant charge is not enough.
• the leakage of refrigerant in the refrigeration system.

2. High condensing temperature

• Low flow of cooling water (or air) and high temperature.
• There is air in the system, which raises the condensing pressure.
• Too much refrigerant filling, the liquid occupies the effective condensing area.
• The condenser is in disrepair and the heat transfer surface is heavily fouled, which can also lead to higher condensing pressure. The presence of scale also has a greater impact on the condensing pressure.

Method

• Release some of the refrigerant in the system.
• Clean other impurities that occupy the condenser heat transfer area.
• Replace a new condenser.

3. Oil return difficulties

Cause

1. When the compressor is positioned higher than the evaporator, an oil return bend on the vertical return line is necessary. Oil return bend should be as compact as possible to reduce oil storage. The spacing between oil return bends should be appropriate, and when the number of oil return bends is relatively large, some lubricant should be replenished.
2. Frequent starting of compressor is not good for oil return, because the compressor stops after a short time of continuous operation, there’s no time to form a stable high-speed airflow in the return pipe, and the lubricating oil will only stay in the pipeline. The return oil is less than the running oil, the compressor will be short of oil. The shorter the running time, the longer the pipeline and the more complicated the system, the more prominent the oil return problem will be.
3. Oil shortage will cause serious lubrication shortage, the root cause of oil shortage does not lie in how much and how fast the compressor runs oil, but in the bad system oil return.

Method

Installing an oil separator can quickly return oil and extend the compressor running time without oil return.

4. Evaporation temperature abnormal

Too low evaporation temperature – Cause

The reason for the low evaporation temperature is that the refrigerant in the evaporator is less or the evaporator heat transfer is not good, listed below:

1. The expansion valve opening is small
2. Refrigeration system lack of refrigerant
3. The capillary tube or expansion valve is blocked
4. Filter blockage
5. Insufficient air volume
6. Evaporator frost severely

Too high evaporation temperature – Cause

1. Expansion valve opening is too large
2. Refrigerant is too much
3. Air in the system
4. Evaporator discharge outlet is blocked
5. Condensation effect is not good
6. Compressor efficiency is low or low speed
7. The compressor valve piece is broken or there is leakage
8. Too much heat load

Method

Evaporation temperature has a great impact on the cooling efficiency, every 1 degree lower, the same amount of cooling needs to increase the power by 4%. If possible, properly raise the evaporation temperature, which is good to improve the cooling efficiency of your chiller.

5. High exhaust temperature

1. High return gas temperature
2. High compression ratio
3. High condensing pressure
4. Poor cooling effect of refrigerant oil, excessive motor heating
5. Unqualified refrigerant

6. Liquid slugging

1. Make the chiller’s suction temperature a little higher than the evaporation temperature to keep the compressor a little superheated.
2. Excessive high or low suction temperature should be avoided. The suction temperature is too high (superheat is too large), which will lead to the compressor discharge temperature rise. Suction temperature is too low, it means that the refrigerant is not completely evaporated in the evaporator, which reduces the heat transfer efficiency of the evaporator, and the inhalation of wet steam will form the compressor liquid slugging. The suction temperature should be 5~10℃ higher than the evaporation temperature.

7. Lack of refrigerant

1. When the amount of refrigerant is low or its regulating pressure is low (or partially blocked), the cover (bellows) of the expansion valve and even the inlet port will be frosted.
2. When the amount of refrigerant is very little or basically no refrigerant, there is no special abnormalities in the appearance of the expansion valve, and only a little silk sound of airflow can be heard.
3. Check where the icing starts, from the liquid distribution head or from the compressor air return pipe to start icing? If it’s from the liquid distribution head, the refrigerant is very low. If it’s from the compressor then the refrigerant is filled too much.

8. Low suction temperature

1. Refrigerant filling too much, occupying part of the volume of the condenser and make the condensing pressure higher, the liquid entering the evaporator increased. The liquid in the evaporator cannot be completely vaporized, so that the compressor absorbs the gas with liquid micro-droplets. Thus, the temperature of the return line drops, but the evaporation temperature does not change because the pressure does not drop, and the superheat decreases. Even if the expansion valve is closed, there is no significant improvement.
2. The expansion valve is opened too large. Because the temperature sensor element is tied too loose, the contact area with the air return tube is small, or the temperature sensor is not wrapped with adiabatic material and its wrapping position is wrong, etc., resulting in the temperature measured by it is not accurate( close to the ambient temperature), so that the opening of the expansion valve increases, resulting in too much liquid supply.

9. Excessive suction temperature

1. The refrigerant charge in the system is insufficient, or the expansion valve is opened too small, resulting in insufficient circulation of refrigerant, less refrigerant into the evaporator, large superheat, and thus high suction temperature.
2. The filter of the expansion valve port is blocked, the liquid supply in the evaporator is insufficient, the amount of refrigerant liquid is reduced, and a part of the evaporator is occupied by superheated steam, so the suction temperature rises.
3. Other causes of high suction temperature, such as poorly insulated return line or too long pipe, can cause high suction temperature. Under normal circumstances, the compressor cylinder head should be half cool and half hot.

10. Low exhaust temperature

The exhaust pressure is too low, although its phenomenon is shown in the high pressure end, but the reason mostly arises in the low pressure end.

1. The expansion valve is clogged with ice or dirty, and the filter is clogged, which will certainly make the suction and exhaust pressure decrease.
2. The expansion valve hole is blocked, the supply quantity is reduced or even stopped, and the suction and discharge pressure are reduced at the same time.