Comprehensive Maintenance Guide for Air - Conditioning Hosts, Ducts, Chilled Water, and Cooling Water

I.

Basic Knowledge of Air - Conditioning Systems

II. Causes of Air - Conditioning System Pollution

1. Various suspended substances in the air cannot be completely blocked by the central air - conditioning filtration device. The coarse - effect filters used in central air - conditioners can only block 40% of the suspended particulate matter, and some dust particles enter the pipeline and accumulate.
2. Fine particles are electrostatically adsorbed to the inner wall of the air duct, and the dust accumulates thicker and thicker.
3. The accumulated dust is extremely likely to breed various microorganisms, such as viruses, bacteria, Legionella, coronavirus, etc.
4. The temperature and humidity inside the air duct are suitable for the growth and parasitism of various germs and insects. There may even be rats and cockroaches.

II. Water System Pollution

1. Insoluble impurities, such as sand, clay, humus, dust, plant debris, etc.
2. Soluble impurities, that is, dissolved solids, also known as salt content, which exist in water in the form of ions or ion groups, such as Ca2+, Mg2+, Na+, HCO3-, CO32-, SO42-, Cl-.
3. Gaseous impurities: such as oxygen, carbon dioxide, ammonia, hydrogen sulfide, etc.
   The long - term accumulation of impurities in water will generate precipitation and form scale. The presence of dissolved oxygen in water also promotes the growth of a large number of algae and bacteria, forming biological slime. These scales, slimes, and corrosive substances will pose a serious threat to the safe operation of the central air - conditioning system.

III. Hazards of Not Cleaning the Air - Conditioning System

1. Breeding bacteria and spreading diseases: Since the air duct forms a relatively closed space with the room through the air outlet and return air outlet, the dust (usually invisible to the naked eye) and germs in the air duct will be blown to every corner of the room by the air - conditioning air, gradually becoming a source of indoor air pollution. At the same time, the germs in one room are also likely to be blown to other rooms by the air - conditioning circulating air, causing cross - infection.
2. The dust accumulated in the air duct will increase the wind resistance and energy consumption, and the cooling and heating effects of the air - conditioner will decline.
3. The thicker the dust on the inner surface of the air duct, the greater the air supply resistance. As a result, the load on the fan increases, the capacity of the unit decreases, the service life of the equipment is shortened, and energy consumption increases.
4. Various microorganisms such as molds, fungi, bacteria, and volatile organic compounds will pollute the indoor air and induce symptoms such as dizziness, allergic rhinitis, and migraines.

Hazards of Scaling and Corrosion in the Central Air - Conditioning Water System

1. Scaling will reduce the heat transfer efficiency of the heat - exchange tubes, resulting in a worse air - conditioning effect and increased energy consumption.
   The main components of scale are bicarbonates, sulfates, etc. The thermal conductivity of carbonate scale is only 0.15% of that of copper, with a huge difference. For every 1mm increase in scale on the heat - exchange tubes, the cooling capacity will be reduced by 20 - 40%, and the energy consumption of the air - conditioner will increase by 15 - 30%.
2. Impurities such as scale, rust residue, and algae will block the filters and heat - exchange tubes, leading to ineffective air - conditioning, and even pump tripping and shutdown.
   The water temperature in the cooling tower is between 32 - 37°C, which is relatively suitable for the reproduction of microorganisms. Algae, bacteria, and fungi multiply rapidly. These microorganisms secrete a large amount of mucus, which binds the insoluble impurities in the water together and adheres to the inner surfaces of equipment and pipelines, hindering water flow and heat exchange, consuming more electricity, and causing high - pressure operation.
3. The inner walls of system pipelines and heat - exchange tubes are corroded, and even perforated, shortening their service life and increasing operation and maintenance costs.
   Due to the presence of corrosive ions in the system circulating water, and the inner walls of pipelines are generally untreated, inner - wall corrosion is likely to occur. This will greatly shorten the service life of the equipment. Once corrosion causes perforation, water will enter the refrigeration unit, generating highly corrosive acidic substances and causing serious equipment damage accidents. Research by relevant institutions shows that the service life of untreated equipment is shortened by 30 - 50%.
4. The massive reproduction of bacteria (especially "Legionella") causes diseases and generates slime, causing under - scale corrosion and microbial corrosion.

IV. Cleaning of the Air - Conditioning Host

Purposes of Cleaning the Air - Conditioning Host

Principles of Cleaning the Air - Conditioning Host

1. Physical cleaning:
   A type of cleaning method that cleans the circulating water system or its equipment through physical or mechanical means.

1. The inner wall of the copper tube is free of scale and impurities.
2. The paint on the corresponding parts is evenly applied and completely dry.
3. The bolts of the end cover are tightened with appropriate force.
4. Anti - rust measures are taken for the bolts.
5. No leakage occurs during the pressure test.
6. The insulation layer is restored.
7. The construction site is cleaned up.
8. The paint on the end cover and the inner side of the host is evenly applied and completely dry.
9. There is no paint - running phenomenon, and there is no paint on the ground or other parts.
   Cleaning and Maintenance of Air - Cooled Hosts
   Adjust the water gun of the cleaning machine to a water - column shape. After flushing each component of the air - cooled host once, evenly spray a professional fin cleaning agent on the condenser fins. Wait for it to react. After foaming, flush it with a water gun until there is no residue, and then dry it.
   V. Cleaning and Maintenance of Terminal Equipment
   Terminal equipment mainly includes fan - coil units, air handling units, modular air - handling units, etc. Terminal equipment circulates the indoor air for a long time, causing dust, bacteria, etc. in the air to accumulate on internal components such as the aluminum fins and impellers of the equipment. The accumulation and blockage of dirt such as fibrous materials lead to a decrease in the air volume of the terminal equipment, seriously affecting the heat exchange and refrigeration efficiency of the central air - conditioning system. Moreover, the inside of the equipment is dark and humid, and various pathogenic bacteria, including Legionella, multiply in large numbers, seriously polluting the air and endangering human health.
   Service Standards for Cleaning Fan - Coil Units/Air Handling Units
10. Use dust - proof cloths for on - site protection.
11. Turn on the power supply, check whether the fan - coil unit operates normally, measure the temperature and wind speed at the air outlet with a temperature - and - wind - measuring instrument, and record them with numbers. If there is a fault, record the symptoms and make a maintenance plan for the customer's approval.
12. Use tools to remove the return air box (if any) and the filter screen of the fan - coil unit.
13. Remove the motor and the turbine.
14. Clean the dirt on the surface of the filter screen and the return air box.
15. Clean the dirt on the surface of the motor and the turbine blades.
16. Spray the fin cleaning agent on the surface - cooler for reaction.
17. After the cleaning agent fully reacts and foams with the fins and decomposes all the dirt inside the fins, use a portable professional cleaning machine to flush the fins of the surface - cooler group clean.
18. Clean the condensate water pan.
19. Unclog the condensate water pipe. If the water pipe is blocked, remove the water gun of the portable professional cleaning machine and use the water supply pipe of the cleaning machine to unclog it.
20. Install the motor, turbine, return air box and filter.
21. Remove the return air grille and scrub it clean.
22. Clean the filter of the return air grille.
23. Install the return air grille and the filter of the return air grille.
24. Clean the supply air grille.
25. Start the unit for a trial run. After it operates well, clean up the site and withdraw.
26. Acceptance criteria: The filter screen, supply air grille and return air grille are free of dust; the water filter is not blocked; the fins of the surface - cooler are not blocked, and the air supply is unobstructed.
    VI. Water Treatment and Water Quality Management
    Principle of water treatment:
    Various central air - conditioning water treatment agents, such as corrosion and scale inhibitors, dispersants, and bactericides, are often added to the cooling water system and chilled water system of central air - conditioning. These agents keep the scaling - forming ions stable in the water. The principle is that through chelation, complexation and adsorption - dispersion effects, calcium and magnesium ions are stably dissolved in water through chelates, and they have a good dispersion effect on colloids such as iron oxide and silicon dioxide. Since the corrosion inhibitor forms a water - insoluble or poorly - soluble protective film on the metal surface, it hinders the hydration reaction of metal ions or the reaction with dissolved oxygen, thereby inhibiting the corrosion reaction. This method is currently the most common method used in industrial circulating water treatment and central air - conditioning water treatment, and it has been proven to be an effective and economical method.
    Water treatment agents:
    Water treatment cleaning agents are added to the water circulation system of the equipment. The agents include corrosion inhibitors, scale inhibitors, pre - filming agents, scale removers, and bactericidal and algaecidal agents.
    Corrosion inhibitor: It can control corrosion and protect the unit. It forms a water - insoluble or poorly - soluble protective film on the metal surface, hindering the hydration reaction of metal ions or the reaction with dissolved oxygen, thus inhibiting the corrosion reaction.
    Scale inhibitor: It can prevent scaling.
    Pre - filming agent: It forms a very thin anti - corrosive protective film on the metal inner surfaces of all heat - exchange equipment and pipelines in the water system.
    Scale remover: It keeps the scaling - forming ions stable in the water. The principle is that through chelation, complexation and adsorption - dispersion effects, calcium and magnesium ions are stably dissolved in water through chelates, and it has a good dispersion effect on colloids such as iron oxide and silicon dioxide.
    Bactericidal and stripping agent: It can kill and prevent the growth of microorganisms and algae.

    

    
    Two aspects need to be done well in water quality treatment:
    First, the formulation of the agent. Corrosion inhibition, scale prevention, and sterilization are all indispensable.
    Second, the adjustment of water quality indicators. In addition to the agent, water quality also has indicators that affect corrosion and scaling, such as turbidity, pH, alkalinity, calcium ions, chloride ions, etc. The water quality standards must be adjusted to the range required by the agent formulation. That is, both the former and the latter should be emphasized.

1. Connect an external water pump to add bactericidal and algaecidal agents through the drain port. Start the pump and circulate for 16 - 24 hours to carry out bactericidal, algaecidal, and living sludge stripping treatment for the entire system.
2. Connect an external water pump to add cleaning agents through the drain port. Start the pump and circulate for 24 hours to penetrate and peel off the floating rust and oil stains in the system.
3. Drain the chilled water to discharge the rust residue and sludge cleaned out of the chilled water system. Remove the filter of the main pipeline in the chilled water system machine room, clean the debris on the filter screen, then seal the filter. Fill the system with water and exhaust air until the chilled water is full. Start the chilled water pump and circulate for half to 1 hour, stop the pump and drain the water from the entire system. After draining completely, refill the water. Repeat this flushing process until the water is clear and transparent.
4. Connect an external water pump to add pre - filming liquid through the drain port. After the system is cleaned, its metal surface is in a very active state and is easily re - oxidized. Therefore, the system should be pre - filmed to prevent the metal surface from being corroded. Add the pre - filming agent, control the pH value between 5.5 - 6.5, and drain the water after operating for 24 hours.
5. Drain 2/3 of the chilled water. Connect an external water pump to add a corrosion inhibitor through the drain port. Start the pump and circulate for 2 hours to make the drug evenly distributed in the system. Test the pH value. When the normal pH value is between 8 - 10, conduct an immersion test.
   Maintenance of the Chilled Water System
   Add drugs once a month throughout the year and take water samples for testing once a quarter. Adjust the added agents in a timely manner according to the test results of the water samples.
   During the non - operating period when the seasons change from autumn to winter, clean and paint the expansion tank.
   Maintenance of the Cooling Water System
   During the refrigeration operation stage:
   Add drugs once a week and drain once a week;
   Take water samples for testing once a month;
   Clean the cooling tower once a quarter.
   During the non - refrigeration stage:
   In southern regions, do not drain the cooling water. Add a humidity - maintaining agent to ensure that the pipelines are not corroded.
   In northern regions, drain the cooling water completely to prevent the pipes from freezing.

   

   
   Perform tube - rodding treatment on the copper tubes of the host.
   VII. Duct Cleaning
   Purposes of Duct Cleaning
6. Improve the efficiency of the air - conditioning system and save a large amount of energy.
7. Improve indoor air quality and prevent diseases.
8. Extend the service life of the equipment and reduce potential safety hazards.
   Methods of Duct Cleaning
   There are three methods for duct cleaning: mechanical cleaning, manual cleaning, and wet disinfection:
9. Mechanical cleaning is a physical removal method that uses a complete set of duct cleaning equipment such as robots to detect, clean, collect, and treat pollutants inside the central air - conditioning ducts.
10. Manual cleaning is used when certain parts of the central air - conditioning air system cannot be cleaned by mechanical methods and can only be cleaned manually.
11. Disinfection of the air system.
    Supporting Equipment for Duct Cleaning
    Operation Sequence of Duct Cleaning
    The operation sequence of duct cleaning: First, clean the branch ducts, and then clean the main ducts, advancing from the end far away from the dust collection box port to the dust - suction port of the dust collection box.
    Construction Preparation for Duct Cleaning
12. Determine the construction space sequence and effectively protect the site.
13. Move the equipment onto the site, place it in a fixed position, connect the machines, install them, connect the power supply, and conduct a trial run.
14. Determine the length of the cleaning section (determined by the capacity of the dust - suction equipment to ensure a negative pressure in the working area) and the position of the holes.
15. Drill dust - suction holes and inlets and outlets for cleaning and detection equipment on the ducts.
16. Install the access doors of the equipment and the connection parts of the dust - suction pipe of the dust collection box.
    Cleaning of Branch Ducts
17. Use a detection robot to detect and record the inside of the duct.
18. Connect the dust - suction pipe of the dust collection box to the dust - suction opening on the main duct.
19. Remove the diffusers and return air grilles on the branch ducts, clean them, and then dry them.
20. Use tools such as soft brushes, nozzles, and electric universal brushes to clean the fan - coil units and branch ducts. The fire - dampers at the connections between the uncleaned branch ducts and the main duct are in the closed state, and the dust collection box is in the open working state during cleaning.
21. Detect the cleaning effect until it reaches visual cleanliness.
    Cleaning of Main Ducts
22. Close the fire - dampers of the fresh air inlet and the fire - dampers at the connections between the main and branch ducts. If necessary, block both ends of the cleaning section with airbags and open the dust collection box.
23. Differentiate ducts of different specifications and use tools such as cleaning robots, electric universal brushes, and air nozzles to clean and blow away pollutants. The negative pressure generated by the dust collection box collects the pollutants.
24. For ducts with a specification of 800×800 or above that can withstand pressure, it is more efficient for workers to enter directly for cleaning. Workers should pay attention to taking necessary labor protection and safety protection measures, especially to ensure good ventilation inside the pipes.
25. After cleaning, remove the tools, detect the effect, install the diffusers and return air grilles, install the access doors and close them, open the fire - dampers, and fill in the records.
    Cleaning of the Filter Screen
    When removing the air - conditioning filter screen, be careful not to touch the metal parts of the indoor unit to prevent scratches. After removing the air filter screen, gently tap or use an electric vacuum cleaner to remove dust.
    If the filter screen is too dusty, it can be cleaned with water or a neutral detergent, but do not use hot water above 50 degrees Celsius to clean it to avoid deformation. Do not use a sponge to clean it either, otherwise, the surface of the filter screen will be damaged.
    After rinsing it thoroughly with clean water, dry it in a cool place. Never expose it to the sun or dry it near a stove, as that may cause the filter screen to deform.
    Install the dried filter screen back to its original position on the air conditioner, and the entire maintenance process of the filter screen is completed.
    After the construction is completed, organize the relevant records and drawings during the construction process. The acceptance report must be approved and signed by the customer and filed in the corresponding project construction files for future reference.