Maintenance of commercial central air-conditioning

Large-scale central air conditioners are generally used in large shopping malls, factories, office buildings and other areas. They are large consumers of electricity and often cause electricity shortages. Maintained central air conditioners can save a lot of energy waste. This article introduces large-scale central air conditioners. Maintenance methods.

For users, the maintenance of large central air conditioners should be done in the following four items:

1. Air conditioner host plus protective cover
2. During thunderstorms, it is best not to turn on the air conditioner
3. Frequent use in humid weather
4. Find the situation and repair it in time

Professional maintenance methods are divided into the following parts:

Maintenance of central air-conditioning chiller

1. Maintenance and inspection during normal operation

• Check the oil pressure and quantity of the compressor refrigerating oil
• Leak detection in the system (refrigerant), and promptly deal with any leaks found
• Check for abnormal sound, vibration and high temperature
• Check the temperature and pressure of the condenser and cooler
• Check whether various valves are normal
• Check the temperature and pressure of the water entering and leaving the chiller
• Check whether the wiring terminals on the main circuit are loose and compacted
• Check whether the electrical control part is abnormal; check the working status of each instrument and controller
• Check whether the lubricating system oil of the unit is sufficient
• Check the setting value of the safety protection device of the refrigeration equipment
• Check the oil pressure and quantity of the compressor refrigerating oil, replace the refrigerating oil if necessary, and supplement the insulation of the compressor motor
• Check and tighten the wire contacts on the circuit
• Check if there is air in the refrigeration system

2. Condenser and evaporator maintenance (remove dirt)

• Prepare 10% hydrochloric acid solution (add 0.5g corrosion inhibitor to every 1kg acid solution);
• Disassemble the condenser and the evaporator at both ends of the inlet and outlet flanges, and then fill it with an acid solution. The pickling time is about 24 hours. It can also be cleaned by acid pump cycle, the cleaning time is about 12 hours;
• After pickling, wash with 1% NaOH solution or 5% Na2CO3 solution for 15 minutes, and finally, rinse with water for more than 3 times;
• After all the cleaning is completed, check whether there is water leakage; if there is no water leakage, reinstall it (replace the aging rubber pads).

3. Maintenance of the electrical control part

• Do simulation experiments on intermediate relays and signal relays. If there is a problem, replace the intermediate relays and signal relays of the same model;
• PC central processing unit, printed circuit board.

4. Compressor maintenance

• Insulation resistance of compressor motor (normally above 0.5MΩ);
• Compressor operating current (normally rated value, three-phase basically balanced);
• Compressor oil pressure (normally 10～15kgf/Cm2);
• Compressor shell temperature (normally below 85℃);
• Inspiratory pressure (normal value 4.9～5.4kgf/cm2);
• Exhaust pressure (normal value 12.5kgf/cm2);
• Check whether the compressor has abnormal noise or vibration;
• Check whether the compressor has an unusual smell.
• Check the compressor oil level and oil color.

Maintenance of the central air-conditioning water circulation pipe part

1. Water pump maintenance

• Rotate the shaft of the water pump to observe whether there is a blockage, collision, or jamming;
• Check if there is water leakage at the root of the packing

2. Maintenance of control valve and regulating valve

• Check for leakage, if so, pressurize the packing;
• Check whether the valve opens and closes flexibly;
• If the valve is broken or fails to open and close;
• Check for leaks at the flange joints.

3. Inspection and maintenance of the entire circulating water system

• Check the elastic coupling for damage.
• Clean the filter screen of the water pump.
• Tighten all the fastening bolts of the water pump unit.
• Clean the casing of the water pump unit. If the paint is stripped or rusted severely, it should be repainted.
• Check whether there is a large amount of condensed water or the insulation layer is damaged at the chilled water pipeline, cold air supply pipeline, and fan tray pipeline.

4. Motor maintenance

• Use a 500V shaker to check whether the insulation resistance of the motor coil is 0.5MΩ or more
• Check whether the motor bearing is blocked. If there is, add lubricating oil. If it still fails after adding lubricating oil, replace it with the same model and specifications.

Maintenance of central air conditioning cooling tower

1. Partial maintenance of the motor

• The insulation resistance of the motor should not be less than 0.5MΩ with a 500V shaker. Otherwise, the motor coil should be dried. If it still does not reach more than 0.5MΩ after drying, the motor coil should be disassembled and repaired.
• Check whether the motor and fan rotate flexibly. If there is a blockage, add lubricating oil; if there is abnormal friction, replace the bearing of the same model and specification.
• Check whether the belt is cracked or severely worn
• Check whether the belt is too loose, if so, adjust and check; check whether the belt pulley and shaft fit are loose

2. Overall inspection

• Check whether the water distributor is evenly distributed
• Clean the cooling tower (including packing, water collection tank), clean the fan blades
• Check whether the water replenishment float valve is reliable
• Tighten all fasteners
• Clean the exterior of the entire cooling tower

Maintenance of the wind cabinet at the end of the central air conditioner

The entire end air cabinet is maintained and maintained

• Clean the fan coil casing, condensate pan, and unblock the condensate pipe
• Clean the primary effect air filter of the inlet and return air to remove the air in the coil
• Check whether the fan rotates flexibly and the belt tightens.
• Lubricate oil and adjust the distance of the motor. If there is abnormal friction noise, the fan bearing should be replaced.
• Use a 500V shaker to test the fan motor coil. The insulation resistance should not be less than 0.5 MΩ, otherwise, it should be adjusted. (6) Check whether the capacitor is deformed, swollen or cracked; check whether the terminals are firm and whether there are signs of overheating
• Clean the dirt on the fan blades, coils, and water trays
• Use hydrochloric acid solution (with corrosion inhibitor) to remove the scale on the inner wall of the coil
• Tighten all fasteners

Maintenance of all control cabinets of central air-conditioning

1. Maintenance of AC contactor

• Remove carbides and metal particles in the arc extinguisher;
• Remove dirt on and around the contact surface
• If the contact is severely ablated, the AC contactor of the same specification should be replaced;
• Clean the dust and dirt on the iron core;
• Tighten all fastening bolts

2. Maintenance of thermal relay

• Check whether there are overheating or burn marks at the wire joints of the thermal relay;
• Check whether the insulation cover on the thermal relay is complete

3. Automatic air switch maintenance

• The insulation resistance measured with a 500V shaker should not be less than 0.5MΩ, otherwise, it should be dried;
• Remove the carbide or metal particles in the arc extinguisher, if the arc extinguisher is damaged, it should be replaced;
• Remove small metal particles on the surface of the contact (do not file)

4. Signal lights indicate instrument maintenance

• Check whether the signal lights are normal, if they do not light up, replace small bulbs of the same specification;
• Check whether the indication of each indicator is correct 5. Other items
• Clean the dust and dirt inside and outside the control cabinet
• Check and tighten all wiring heads, and replace the wiring heads with severe ablation