Cause analysis of common faults of water chillers

August 29, 2023

Chiller is an energy-saving machine that achieves refrigeration effect through vapor compression or absorption cycle. Chillers are called cooling water circulators, also called refrigerators, etc. At present, air-cooled chillers, water-cooled chillers and screw chillers are the main types in the market.

1. The classification of chillers

First of all, we should distinguish the types of chillers: generally, chillers are divided into water cooling and air cooling.


Air-cooled water chiller, which contains water tank and water pump, does not need cooling tower to dissipate heat. Easy to install and move. However, it has high requirements for the environment. First of all, because it is cooled by hot air circulation, if the ventilation effect of the installation workshop is not good, it will directly affect the refrigeration effect of the chiller. In addition, if you want to put the chiller in a dust-free workshop with humidity requirements, a lot of water vapor will be generated at the top of the chiller.


Water-cooled chillers are divided into open chillers, sealed chillers (some are called box chillers) and screw chillers. Water-cooled chillers need additional cooling towers and pumps to achieve better cooling effect. An open-type chiller needs to be equipped with another water tank, but a sealed one is not necessary because it has a built-in water tank. The open type is usually installed outside the workshop, which is convenient for maintenance, but because it is not beautiful enough, a sealed water-cooled chiller is produced. Sealed water-cooled chiller is a box structure, which is convenient to install and use.


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2.The common protection control of water chillers

1. Compressor; 2. Water pump; 3, computer PC board, touch control, safe and convenient; 4. Temperature controller: liquid crystal display temperature control electronic board; 5. Expansion valve and filter; 6. One 304 stainless steel water tank with built-in thermal insulation material; 7. Electrical appliances; 8, safety protection system:

Delayed start protection of compressor;

Ice water pump overload and indicator light;

Compressor overload protection;

Motor reverse protection;

Compressor overload protection and indicator light;

Refrigerant shortage protection and indicator light;

Refrigerant high pressure safety valve;

Bad heat dissipation protection and indicator lamp fault alarm;

Report buzzer;


3.Common faults of water chillers:

1, the cooling water temperature is high, the condensation effect is bad: The rated working condition of cooling water required by water chillers is 30~35℃. The high water temperature and poor heat dissipation will inevitably lead to high condensation pressure, which often occurs in high temperature seasons. The causes of high water temperature may be: cooling tower failure, such as the fan is not turned on or even reversed, and the water distributor does not turn, which shows that the cooling water temperature is very high and rises rapidly; The outside temperature is high, the waterway is short, and the amount of water that can be circulated is small. In this case, the cooling water temperature is generally maintained at a high level, which can be solved by increasing the water storage tank.


2, cooling water flow is insufficient, can not meet the rated water flow: The main performance is that the pressure difference between the inlet and outlet of the unit becomes smaller (compared with the pressure difference at the beginning of the system operation) and the temperature difference becomes larger. The reason of insufficient water flow is that the system lacks water or has air. The solution is to install an exhaust valve at the height of the pipeline for exhaust. The pipeline filter is blocked or too fine, and the water permeability is limited. Appropriate filters should be selected and the filter screen should be cleaned regularly; The selection of water pump is small, which is not compatible with the system.


3, condenser scaling or blockage: The condensate water is usually tap water, which is easy to scale when it is above 30℃. Moreover, because the cooling tower is open and directly exposed to the air, dust and foreign matter can easily enter the cooling water system, resulting in dirty blockage of the condenser, small heat exchange area and low efficiency, and also affecting the water flow. Its performance is that the pressure difference between the inlet and outlet water of the unit and the temperature difference become larger, the temperature of the condenser is very high when touched by hand, and the copper tube of the condenser is hot. The unit shall be backwashed regularly, and chemical cleaning and descaling shall be carried out when necessary.


4. Too much refrigerant charge: This situation generally occurs after maintenance, which is characterized by high suction and discharge pressure, high equilibrium pressure and high compressor operating current. Under rated working conditions, air shall be discharged according to the suction and discharge pressure, balance pressure and operating current until it is normal.


5, refrigerant mixed with air, nitrogen and other non-condensable gases: This kind of situation usually happens after maintenance, and the vacuum pumping is not complete. It can only be drained, re-vacuumed and refilled with refrigerant.


6. False alarm caused by electrical failure: Due to damp, poor contact or damage of the high-voltage protection relay, the electronic board of the unit is damp or damaged, and the communication fault causes false alarm. This kind of false fault, often the high-voltage fault indicator light on the electronic board is not bright or slightly bright, the manual reset of the high-voltage protection relay is invalid, the running current of the compressor is normal, and the suction and exhaust pressures are normal.


7, evaporation pressure is too low: It may be that the evaporation pressure of water-cooled chiller is too low because of insufficient refrigerant. Common reasons: insufficient cold water; Less cooling load; Throttle orifice plate failure (only make evaporation pressure low); The heat transfer tube of evaporator deteriorates heat transfer due to scale pollution (only the evaporation pressure is too low); Insufficient refrigerant quantity (only the evaporation pressure is too low).


8, oil pressure difference is too low: If the compressor oil pressure is too low, the compressor will stop running. Common reasons are: oil filter is blocked; Too much refrigerant is mixed in the lubricating oil.


9, the oil temperature is too high: The high oil temperature of refrigeration compressor and long-term operation will reduce the quality of refrigeration oil and even carbonize it. Common reasons: the cooling capacity of oil cooler is reduced; The supply of coolant for oil cooler cooling is insufficient due to the blockage of the filter screen of the coolant filter.


10, the main motor overload: Unbalanced phase voltage of power supply; The voltage drop of power supply line is large;



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