Seven Common Problems For Chiller Operation

1.What should we do if the temperature difference between the inlet and outlet of the chiller is small?

When chiller operation, we may encounter this situation: the chiller current inlet water temperature is 24℃, and the outlet water temperature is 23℃. The temperature difference is too small to meet user needs. The main reasons for the small temperature difference between the inlet and outlet water are as follows:

(1)The output cooling capacity of the chiller is small, for example, the chiller itself is faulty, or not fully loaded, etc. These can be preliminary judged by observing the operating current and other parameters of the chiller.

(2)It may also be that the heat transfer effect is not good. For example, the heat transfer tube has serious scale and affects the heat transfer of the chiller. This can be judged by observing the heat transfer temperature difference between the water temperature and the evaporating temperature.

(3)The water flow is too large. This can be judged by observing the pressure difference between the inlet and outlet water of the evaporator and the running current of the water pump.

(4)After eliminating the above problems, you can consider whether the sensor or the thermometer is inaccurate.

2.The chiller fan produces noise

Noise is an annoying sound. Continuous noise will also pollute the surrounding environment. The reasons for the noise produced by the general chiller fan can be described as follows:

(1)When the blades rotate, they will rub against the air or impact. The frequency of noise is composed of multiple frequencies, and these frequencies are all related to the fan speed. Suggestion: If the axial flow fan has the configuration of moving and static wings, the number of blades of the two should be different to avoid greater noise resonance.

(2)Noise can also be generated when the blade generates vortex. During the operation of the fan, a vortex will be generated on the back of the moving wing. This vortex will not only reduce the efficiency of the fan, but also generate noise. In order to reduce this phenomenon, the installation angle of the blades should not be too large, and the bending of the blades should be smooth, and do not suddenly change too much.

(3)It resonates with the duct shell and generates noise. The joint between the air duct and the inner surface of the fan casing should be smooth to avoid roughness and unevenness, which may cause tearing noise. In addition, when designing, sometimes the outside of the duct can be covered with soundproof materials to reduce noise.

(4)In addition to the fixed noise of the fan itself, there are many noise sources. For example, due to insufficient precision of bearings, improper assembly or poor maintenance will cause abnormal noise.

3.Communication failure

The control of each module by the computer controller is realized through the communication line and the main interface board. The main cause of communication failure is the poor contact or open circuit of the communication line, especially the interface is damp and oxidized to cause poor contact, and the unit electronic board or the main interface board failure, improper selection of the address dial switch, and power failure can cause communication failure.

4.Low voltage failure

The compressor suction pressure is too low, causing the low-pressure protection relay to operate. The compressor suction pressure reflects the evaporation pressure, the normal value should be 0.4~0.6MPa, and the protection value is set to 0.2MPa. If the suction pressure is low, the return air volume is small, and the refrigeration capacity is insufficient, resulting in a waste of electric energy. For the return air cooling compressor motor, the heat dissipation is poor and the motor is easily damaged.

The causes of low-pressure faults are: insufficient refrigerant or leakage; insufficient chilled water flow; blockage of the evaporator and poor heat exchange; false alarms caused by electrical faults; low outside temperature.

5.High voltage failure

The compressor discharge pressure is too high, causing the high-pressure protection relay to operate. The compressor discharge pressure reflects the condensing pressure, the normal value should be 1.4~1.6MPa, and the protection value is set to 2.0MPa. If the pressure is too high for a long time, it will cause the compressor operating current to be too large, it is easy to burn the motor, and it is easy to cause damage to the compressor exhaust valve.

The reasons for the high pressure failure are as follows: The cooling water temperature is too high, and the condensation effect is not good; the cooling water flow is insufficient, and the rated water flow is not reached; the condenser is scaled or blocked; the refrigerant is overcharged; the refrigerant is mixed with air and nitrogen etc. non-condensable gas; false alarms caused by electrical faults.

6.Compressor overheating failure

The thermistor is embedded in the compressor motor winding, and the resistance is generally 1kΩ. When the winding is overheated, the resistance value will increase rapidly. When it exceeds 141kΩ, the thermal protection module SSM will act to cut off the operation of the chiller unit, and the overheating fault indicator will light up.

The reasons for the compressor overheating fault are as follows: the compressor is overloaded and running with overcurrent, caused by electrical faults; the overheating protection module is damp or damaged, the intermediate relay is damaged, and the contacts are bad.

7.Low valve temperature failure

The outlet temperature of the expansion valve reflects the evaporation temperature, which is a factor that affects the heat exchange. Generally, the difference between it and the outlet temperature of the refrigerant water is 5-6°C. When a low valve temperature failure occurs, the compressor will stop, and when the valve temperature rises, it will automatically resume operation with a protection value of -2°C.

The reasons for the low valve temperature failure are as follows: a small amount of refrigerant leakage; expansion valve blockage or too small opening; insufficient refrigerant water flow or blockage of the evaporator; false alarms caused by electrical failures.