Operation Process for Switching On and Off the Chiller Unit

2024-09-10

I. Main Equipment and Working Principles of Water Chillers
(1) Water-cooled chilled water unit;
(2) Cooling water tower;
(3) Cooling water pump;
(4) Chilled water pump;
(5) Circulating water pump;
(6) Terminal devices [air handling units (modular air conditioning boxes), fan coil units, dry coil units, etc.]
The principle of centrifugal refrigeration compressor: The gaseous refrigerant is sucked in at the axial suction port of the compressor and then enters the high-speed rotating impeller. Under the centrifugal force, the vapor passes through the flow passages composed of blades in the impeller and flows from the center to the periphery. At this time, the pressure rises and the speed of the refrigerant increases. After passing through the impeller, the refrigerant enters the diffuser to decelerate the refrigerant and increase the pressure. The vapor passing through the diffuser is collected in the volute and then discharged from the exhaust port.

The refrigerant vapor vaporized in the evaporator is sucked into the compressor, compressed, and then discharged into the condenser;
Due to the cooling effect of the cooling water, the refrigerant in the vapor state releases heat and condenses into a high-pressure liquid state;
The refrigerant flows into the evaporator after being throttled and depressurized by the expansion valve;
In the evaporator, the low-pressure liquid refrigerant absorbs heat and vaporizes into a vapor state, and is re-sucked into the compressor for compression to form a cycle.
The chilled water pipeline of the evaporator continuously sends in chilled water with a relatively high temperature, which is cooled and then flows out for on-site use.

II. Inspection and Operation Procedures for Switching On and Off
Inspection before starting:
Check whether the water level in the chilled water tank is at the high water level, check whether the water level in the cooling tower is at the high water level, and check whether the valves of the cooling water and chilled water pipelines are in the open state.
Starting the water pumps:
Start the chilled water pump, the circulating water pump, the cooling water pump, the cooling tower fan, and the cooling tower water level. Observe whether the pressure on the pipeline pressure gauge is within the normal value. After the above equipment operates normally, start the chilled water unit.

Operation Process for Switching On and Off the Chiller Unit1725969165005

Check whether all pipeline valves are open;
Check whether the water pressure and power supply are normal;
Start the unit after starting the chilled and cooling water pumps and the cooling tower fan.
Confirm that the main power supply voltage is within the normal value;
Confirm that the control system of the main unit is powered on;
Confirm that the oil temperature has been preheated and is within the normal value;
Check whether there is an alarm in the main unit. If there is, deal with it before starting the unit.
Shutdown procedures:

Main unit shutdown procedure: Shut down the chilled water unit (do not cut off the power supply except in special cases to ensure that the oil temperature remains within the normal value). Turn off the cooling tower fan, the cooling water pump, the circulating water pump, and the chilled water pump in sequence (do not close the valves unless necessary to avoid misoperation).
Cooling water system shutdown procedure:

Confirm that the main unit has stopped.
Shut down the cooling water pump (do not close the valves unless necessary to avoid misoperation).
Shut down the cooling tower fan.

Chilled water system shutdown procedure:

Confirm that the main unit has stopped.
Shut down the chilled water pump (do not close the valves unless necessary to avoid misoperation).

III. Precautions:

Do not easily change the water volume of the cooling tower and the automatic regulating valve to ensure that the unit operates with the normal middle oil temperature.
If an alarm occurs during the operation of the unit, the unit should be shut down first and the compressor switch should be in the off state. Then, find out and record the cause of the fault, and start the unit again after eliminating the fault.
During the shutdown in winter, generally keep the unit preheated. If it is necessary to cut off the power supply, the inlet and outlet valves of the oil pump should be closed after cutting off the power supply to prevent the oil from running into the system and affecting the next startup.
Inspect the unit once every 24 hours during its operation, observe the pressure, water temperature and oil level, and make good records.
Frequently inspect the cooling tower to ensure the cooling effect.
Regularly inspect the strong and weak cables.
The cooling water system should be emptied during the shutdown in winter to prevent frozen pipes (depending on the situation of the chilled water).