Analysis of common faults and treatment methods for chillers

Analysis of common faults and treatment methods for chillers

A chiller is an energy-saving machine that achieves cooling effects through steam compression or absorption circulation. The full name of chiller is cooling water circulation machine, also known as refrigeration machine, etc. Currently, the main types of chillers on the market are air-cooled chillers, water-cooled chillers, and screw chillers.

1、 Classification of chillers:

Firstly, we need to distinguish the types of chillers: generally, chillers are divided into two types: water-cooled and air-cooled.

Air cooled chiller, containing water tank and water pump, does not require cooling tower for heat dissipation. Easy to install and move.

However, it has high environmental requirements. Firstly, because it is cooled by a hot air cycle, if the ventilation effect in the installation workshop is not good, it will directly affect the cooling effect of the chiller. In addition, if you want to place the chiller in a dust-free workshop with humidity requirements, a large amount of water vapor will be generated on the top of the chiller.

Water cooled chillers are divided into open type chillers, sealed type (sometimes referred to as box type chillers), and screw type chillers.

Water cooled chillers require additional cooling towers and water pumps to achieve better cooling effects. An open chiller requires an additional water tank, so a sealed one is not necessary because it has a built-in water tank. Open type chillers are usually installed outside the workshop for easy maintenance, but due to their lack of aesthetics, sealed water-cooled chillers have emerged. The sealed water-cooled chiller is a box structure that is easy to install and use.

2、 Equipment of chiller:
1. Compressor; 2. Water pump; 3. Computer PC board, touch control, safe and convenient; 4. Temperature controller: LCD temperature control electronic board; 5. Expansion valve and filter; 6. One 304 stainless steel water tank with built-in external insulation material; 7. Electrical appliances; 8. Security protection system:

Compressor delayed start protection;

Ice water pump overload and indicator light;

Compressor overload protection;

Motor reverse protection;

Compressor overload protection and indicator light;

Insufficient refrigerant protection and indicator light;

High pressure safety valve for refrigerant;

Poor heat dissipation protection and indicator light malfunction alarm;

Alarm buzzer;

3、 Common faults of chiller units:

1. High cooling water temperature and poor condensation effect:

The cooling water required by the chiller unit is rated at 30-35 ℃, with high water temperature and poor heat dissipation, which inevitably leads to high condensation pressure. This phenomenon often occurs during high temperature seasons. The reason for high water temperature may be: cooling tower failure, such as the fan not turning on or even reversing, and the water distributor not turning, manifested as high and rapid increase in cooling water temperature; The external temperature is high, the water supply is short, and the amount of circulating water is low. In this situation, the temperature of the cooling water is generally maintained at a high level, and the solution can be to increase the water

storage tank.

2. Insufficient cooling water flow rate, unable to reach the rated water flow rate:

The main manifestation is that the pressure difference between the inlet and outlet water of the unit decreases (compared to the pressure difference at the beginning of system operation), and the temperature difference increases. The reason for insufficient water flow is due to a lack of water or air in the system. The solution is to install an exhaust valve at a high position in the pipeline for exhaust; If the pipeline filter is blocked or selected too fine, and the permeability is limited, a suitable filter should be selected and the filter screen should be cleaned regularly; The selection of water pumps is relatively small and not compatible with the system.

3. Scaling or blockage of the condenser:

Condensed water generally uses tap water, which is prone to scaling above 30 ℃. Moreover, due to the open cooling tower, dust and foreign objects are easily exposed to the air, which can enter the cooling water system, causing fouling and blockage of the condenser, small heat exchange area, low efficiency, and also affecting water flow rate. Its manifestation is that the pressure difference and temperature difference between the inlet and outlet water of the unit increase, and the temperature of the upper and lower parts of the condenser is very high when touched by hand. The copper tube for the condenser outlet is hot to the touch. The unit should be regularly backwashed, and if necessary, chemical cleaning and descaling should be carried out.

4. Excessive refrigerant charge:

This situation usually occurs after maintenance, manifested as high suction and exhaust pressure, balance pressure, and high compressor operating current. The air should be released according to the suction and exhaust pressure, balance pressure, and operating current under rated operating conditions until it is normal.

5. The refrigerant is mixed with non condensable gases such as air and nitrogen:

This situation usually occurs after maintenance, with incomplete vacuum pumping. Can only be drained, vacuumed again, and refilled with refrigerant.

6. False alarms caused by electrical faults:

Due to moisture, poor contact, or damage to the high-voltage protection relay, the electronic board of the unit may become damp or damaged, resulting in false alarms due to communication failures. This type of false fault often results in the high voltage fault indicator light on the electronic board not being on or slightly lit, the manual reset of the high voltage protection relay being ineffective, and the compressor operating current and suction and exhaust pressure being measured to be normal.

7. Evaporation pressure too low:

Perhaps due to insufficient refrigerant, the evaporation pressure of the water-cooled chiller is too low. Common reasons: Insufficient cold water volume; Low cooling load; Throttling orifice plate malfunction (only causing low evaporation pressure); The heat transfer tube of the evaporator deteriorates due to pollution such as scale (only causing the evaporation pressure to be too low); Insufficient refrigerant volume (only causing low evaporation pressure).

8. Oil pressure difference too low:

The compressor oil pressure is too low, and the compressor stops running. Common reasons include: oil filter blockage; Too much refrigerant mixed in the lubricating oil.

9. Oil temperature too high:

Long term operation of refrigeration compressors with excessively high oil temperature can reduce the quality of refrigeration oil and even carbonize it. Common reasons: The cooling capacity of the oil cooler is reduced; The supply of refrigerant for cooling the oil cooler is insufficient due to the blockage of the refrigerant filter screen.

10. Main motor overload:

Power phase voltage imbalance; The voltage drop of the power supply line is large;