Comprehensive Maintenance and Troubleshooting Manual for Air Conditioning Units

April 02

Long-term operation of air conditioning equipment can easily lead to dust accumulation and component wear, affecting operating efficiency and even causing malfunctions. This article summarizes key points for the maintenance of air conditioning units for operation and maintenance personnel to refer to, standardize operations, and avoid risks.

I. Core Maintenance Outline for Air Conditioning Units

1. Maintenance and upkeep of chiller units:

Check if the three-phase voltage of the power supply is normal at 380V.
Check if the oil heater is working properly when powered on (the oil temperature should be maintained at 25~30℃ when in standby mode).
Check all parts of the machine for leaks or oil seepage.
Check if the temperature control probe is working properly.
Check whether each parameter of the unit is within the standard value during operation.
Check that the loading and unloading solenoid valves and slide valve mechanisms are flexible.
Check if the sound of the unit is normal during normal operation.
Check whether the temperature of the unit is normal during normal operation.
Including main motor, compressor, exhaust temperature, temperature, etc.
Measure the insulation resistance of the main motor and check whether it meets the value specified by the unit.
Check if the seal between the main motor and the compressor is normal.
Check whether the alignment of each safety protection device meets the specified requirements.
Check if the water flow protection switch is functioning properly; if it malfunctions, repair or replace it promptly.
Check the condition of the insulation layer of the evaporator; repair or replace any damaged parts promptly.
Clean scale from the pipes and covers of the evaporator and condenser (water treatment section).
Replace the oil filter element according to usage.
Replace the dryer filter as needed.
Replace the refrigeration oil with new oil depending on its quality.
Lubricate the main motor bearings with grease.
Rust removal and painting of the unit surface.
Calibrate the pressure sensor.
Add or replace the electronically controlled refrigerant.

2. Fan coil unit maintenance

Cleaning: Regularly clean the water tray, air filter, and coil fins to prevent clogging and dust accumulation;
Maintenance: Check the sensitivity of the temperature control switch and the motor's operating status; troubleshoot any abnormal noises or jamming.

3. Cooling tower maintenance

Water supply system: Check the water supply valve and float switch to ensure stable water level;
Water treatment: Regularly add chemicals, test water quality, and prevent scaling and corrosion;
Electric fan: Check operating parameters, add lubricating grease, and clean dust from the blades;
Overall cleaning: Regularly clean the internal packing and water collection tray to ensure heat dissipation.

4. Maintenance and upkeep of air supply and exhaust systems

Cleaning: Clean the filters, louvers, air vents and ducts to remove dust, and clean the fan room;
Maintenance: Check the fan's operating status, add lubricating grease, and ensure the motor insulation is normal.

5. Water pipe system maintenance

Pipeline maintenance: Inspect the pipeline for rust and remove rust and paint as needed;
Parts maintenance: Check valve flexibility and sealing, and calibrate pressure gauges and thermometers;
Pipeline unblocking: Regularly check for blockages and promptly remove debris.

6. Maintenance and upkeep of motors and water pumps

Component maintenance: Check the concentricity of the coupling and the packing seal, and regularly add grease to the bearings;
Safety inspection: The insulation resistance of the motor is tested every quarter to check for potential overheating and leakage.

7. Maintenance and upkeep of the electrical control system

Cleaning: Clean the dust inside the electrical control cabinet to prevent short circuits;
Functional checks: Inspect wiring and terminal connections, and check the accuracy of the automatic control system;
Safety precautions: Check electrical grounding and insulation performance to avoid potential safety hazards.

8. Daily maintenance and upkeep

Check and record the water temperature and water pressure when the main unit is running.
Check and record the operation of the main unit
Refrigerant temperature, evaporator and condenser temperature and pressure.
Check and record the operation of the main unit
And host voltage, current, etc.
Determine if the above data is normal and how to adjust it.
Check the rotating parts for any abnormal vibrations or noises.
Check the pipes and joints for oil or water leaks.
Keep all parts of the host unit clean.
Check if the motor bearing temperature and operating sound are normal.
Check and record the motor voltage and current.
Check the inlet and outlet water temperature and water pressure.
Check the gaskets for damage and leaks.
Check the water supply and pipeline valves to ensure they are functioning properly.
Check the stored water for any floating oil, impurities, or other contaminants.
Check the water level and the float control switch.
Check the operation of the fan motor and the voltage and current conditions.
Pay attention to cleaning the water outlet and filter screen.
Check that all valves and water pipes are in good working order.
Check if the water supply tank and float valve are functioning properly.
The daily inspection record is recorded in the daily inspection record sheet, and is recorded once every 4 hours.

9. Weekly maintenance and upkeep procedures

Check that all safety and operation controllers are functioning properly.
Check if the refrigerant piping system is functioning properly (especially the dryer, expansion valve, solenoid valve, etc.).
Check the refrigeration oil and replenish or replace it if necessary.
Check the safety vent valve.
Check the oil filter and clean or replace it if necessary.
Inspect the bearings and add lubricating oil if necessary.
Check the gasket for leaks.
Check for any looseness between the motor and valve body, and between the valve body and base.
Clean the water tray and the water filter and change the water.
Check the insulation of the motor and wiring.
Combined air conditioning units
Clean the filter screen and replace it if necessary.
Check and adjust the belt tension, and replace it if necessary.
Inspect and clean the windmill and copper pipes.
Check that the current of all motors is normal.
Check all wire ends and connections to ensure they are in good condition.
Remove dust from electrical components and the inside of the box.
Check that the valves, flexible joints, thermometers, pressure gauges and other accessories in the pipeline are in good condition.
Check the filter for blockage and clean it.
Check that all hangers and joints are in good condition and safe.

10. Monthly maintenance and upkeep procedures

Check and pay attention to whether the refrigerant level is insufficient; if it is, it needs to be recharged.
Inspect all safety controllers.
Inspect the piping and exhaust system.
Check the circulating water for contamination and replace it if necessary.
Inspect and replace the oil seals, and add or replace the lubricating oil.
Check the bearings and couplings for damage.
Inspect the water tray, outer casing, and mesh panel; clean or paint if necessary.
Check the water quality, clean and change the water.
Check if the water outlet is working properly; if it is clogged, remove and clean it.
Inspect the piping and purge air.
Clean the windmill and copper pipes.
Check the belt.
Piping and others
Open and close all valves once or twice to prevent blockage.
Check that each electric valve is operating normally.

Table 1. Analysis and Solutions to Common Problems and Faults in Cabinet Fan Coil Units and Combined Air Conditioning Units
part	Problems and faults	Cause Analysis	Solution
air filter	Increased resistance	Too much dust	Regular cleaning
	Uneven surface temperature	Surface heat exchangers contain air	Open the heat exchanger vent valve to release the vent.
	Reduced heat exchange capacity	Scale inside the heat exchanger tubes Scale buildup on the surface of the heat exchanger	Remove scale from pipes Cleaning the surface of the heat exchanger
	water leakage	Interface or Hankou corrosion cracking	repair
	water leakage	Air valve not closed or not closed tightly	Close or tighten
Water tray	Overflow	Drain (pipe) blockage	Use methods such as suction, dredging, blowing, and flushing to clear blockages.
		Poor drainage	See the entry below
		The drain tray is tilted in the wrong direction.	Adjust the water tray so that the municipal drainage outlet is at its lowest setting.
	Poor condensate drainage	The horizontal slope of the external pipeline is too small.	Adjust the slope of the drain pipe to >= 0.8% or shorten the length of the drain pipe to drain water from the nearest available location.
		The drain outlet (pipe) is partially blocked.	Use methods such as suction, dredging, blowing, and flushing to clear blockages.
		The drain outlet of the water receiving pan inside the unit is under negative pressure, and the external drain pipe of the unit does not have a water seal or the water seal height is insufficient.	Install a water seal or increase the water seal height to correspond to the pressure head of the blower.
humidifier	Poor humidification	Humidifier power failure	Overhaul
		Damaged heating element	Repair or replacement
		Water supply float valve malfunction	Overhaul
		Improper temperature control	Overhaul
Spray chamber	Nozzle blockage	(1) Water filter failure (2) Rust and corrosion inside the metal drain pipes produce slag.	(1) Replacement (2) Enhance water treatment and remove nozzles for cleaning.
	Nozzle cracking	(1) The nozzle has quality problems (such as insufficient material strength, cracks left during manufacturing, etc.). (2) Uneven stress during installation (3) The water pressure of the sprayer is too high	(1) Replacement (2) Replacement (3) Adjust the water pressure to a suitable value.
	Water-blocking deformation	Insufficient material strength Uneven airflow distribution	(1) Replace (2) Investigate the cause and improve
	Scale buildup on nozzles or baffles	Poor water quality	Strengthen descaling treatment Remove the nozzle or baffle and clean it with a descaling agent.
unit	Condensation on the outer shell	Damage to insulation material	repair
unit	Condensation on the outer shell	Damaged casing causing air leakage	repair

Table 2 Key Points for Inspection and Maintenance of Unitary Air Conditioners
Systems and components		Inspection and maintenance points
Systems and components		daily	Monthly	year
overall		(1) Are the current and voltage normal? (2) Is there any air leakage or condensation in the machine body? (3) Is the indoor unit clean?	Are all fasteners loose? Are there any loose insulation or sound-absorbing materials?	(1) Whether the outer casing of the machine is corroded (2) Whether the exterior of the machine is thoroughly cleaned
Refrigeration system	compressor	Are the intake and exhaust pressures normal? Is the noise too loud?	Is the casing temperature too high?
	Evaporator	Whether condensation occurs	Is there dust accumulation?
	Water-cooled condenser	Are the inlet and outlet temperatures of the cooling water normal? Is the cooling water temperature normal?		Have you removed the scale from the pipes?
	Expansion valve, dryer filter		Are there condensations or frosts at the inlet and outlet? Is the connection status of the temperature sensor normal? Is the filter clogged?
	Refrigeration pipes			Is there a leak? Are the connection parts loose? Are there cracks in the welded area? Is the insulation layer damaged?
air system	Air outlet of direct-blowing model	Are the louvers damaged? Can the louvers swing as controlled? Does the louver produce noise when it oscillates?
	Air valves for duct-type units	Does the set position change ? Is there any noise emitted?
	Flexible joints for pipeline-type machines	Is it damaged and leaking air?
	Filter		Is the filter clean?
	Fan	See subsequent tables
	Transmission device	See subsequent tables
Drainage system	Water tray		Are there any dirt or water accumulation? Is there any water overflowing?
Drainage system	Drainage tray	Is the drainage unobstructed?		Are the drain pipes old or damaged?
PLC (Power Control System)	Operation switch	Is the contact intact? Is the operation smooth?
	indicator lights	Does it indicate normal?
	Relay protector			(1) Whether the contact is intact (2) Whether the movements are agile
	controller	Are the settings of the high and low voltage controllers appropriate? Are the set values and actions of the temperature controller consistent?		Are the high and low voltage controllers operating normally?
Cooling water system	Valves, flexible joints	Are the valves and flexible joints on the water pipes functioning properly?
	Cooling tower	See subsequent tables
	water pump	See subsequent tables
	water quality	See subsequent tables
Air-cooled outdoor unit	Condenser		(1) Is the surface clean? (2) Is the heat dissipation airflow good?
Air-cooled outdoor unit	Fan	See subsequent tables
Heating system	Four-way directional valve			Can it perform a reversing function?
	electric heater	Is the heating wire damaged?		Is the insulation good?
	hot water or steam heater		Is the outside of the pipe clean?	Is there scale buildup inside the pipe?
Indoor and outdoor unit connection pipes for air-cooled models				Are the insulation sleeves damaged? Are the straps loose?

Table 3. Analysis and Solutions to Common Problems and Faults in Unitary Air Conditioners
Problem or malfunction	Cause Analysis					Solution
The fan is not running or is not blowing air.	power failure Fuse blows Phase loss Poor contact of contactor contacts or burnt-out coil Motor-related faults Fan reverse					(1) Investigate the cause and wait for a reply. (2) Investigate the cause and replace the fuse. (3) Investigate the cause and make up for it. (4) Repair or replacement (5) Refer to the motor fault table. (6) Change the position of any two wires of the motor.
The fan can run, but the compressor cannot start.	Temperature setting too high Poor contact or intermediate relay connection or burnt-out coil Thermostat malfunction Motor burnout or inter-turn short circuit Overcurrent protector tripped High and low voltage protectors activated					Lower it to an appropriate value Repair or replacement Repair or replacement Repair or replacement Investigate the cause and eliminate the overcurrent fault. Investigate the cause and eliminate the overpressure fault.
Insufficient cooling capacity	(1) Temperature setting is too high					(1) Lower
	(2) Insufficient air supply	The fan speed setting is too low. Too much dust accumulated in the fresh air filter Evaporator fin oxidation or inter-fin blockage Fan failure Inappropriate fan capacity				improve clean Clean or replace the evaporator See the fan fault table Replace with a suitable fan
	(3) Evaporator surface freezing					Close the expansion valve
	(4) Insufficient refrigerant					Leak detection and sealing, and adding sufficient refrigerant.
	(5) Insufficient opening of the expansion valve					Open to the appropriate position
	(6) Expansion valve blockage					Disassembly and cleaning
	(7) Clogged dryer filter					replace
	(8) Compressor malfunction					Repair or replacement
	(9) The unit capacity is too small					Replace with a larger one or add a new one
	(10) There is air in the refrigeration system.					After removing or re-vacuuming, refill with refrigerant.
	(11) The condensation temperature is too high		Water cooling system		The cooling water volume is too small.	Investigate whether the water pump is faulty or the valve is not fully open.
					The inlet water temperature is too high	Investigate whether the cooling tower is malfunctioning or has insufficient cooling capacity.
					Poor heat exchange in condenser	Remove scale from the condenser
					Outdoor wet bulb temperature too high	There is no solution yet.
			air-cooled system		Too much dust on the condenser surface	clean
					Fan failure	See the fan fault table
					Poor ventilation or airflow short circuit	Improve or modify
					There is a heat source nearby.	Remove the heat source or relocate the air-cooling unit.
					outdoor temperature too high	There is no solution yet.
Excessive operating noise or vibration	A fastener has become loose or fallen off. Fan bearings lacking oil or damaged Loose or deformed fan impeller rubbing against casing Compressor liquid slugging Compressor parts damaged					Tighten or repair Refueling or replacing repair Close the expansion valve slightly or release some refrigerant. Repair or replacement
The compressor suddenly stopped during the refrigeration process	(1) Low-voltage protector activated	1) Refrigerant is low 2) Expansion valve is blocked 3) Clogged dryer filter 4) Refrigerant piping throttling 5) Clogged air filter				1) Detect and seal leaks, and add sufficient refrigerant. 2) Disassembly and cleaning 3) Replacement 4) Identify and repair the cause of the throttling. 5) Clean.
	(2) High voltage protector activated	1) Water-cooled condenser		Insufficient cooling water volume causes the temperature difference between the inlet and outlet water to exceed 8~10°C. Scale buildup or blockage in the condenser The inlet water temperature is too high, exceeding 33°C.		Investigate whether the water pump is faulty or the cooling tower is not returning enough water. Remove scale from the condenser Determine if the problem is caused by a cooling tower malfunction (excluding cases where the outdoor wet-bulb temperature is too high).
		2) Air-cooled condenser		Too much dust on the condenser surface The fan does not turn or reverses. Poor ventilation or airflow short circuit The intake air temperature is too high, exceeding 43°C.		clean Investigate the cause and repair or replace the wiring. Improve or change the installation location Investigate the cause and improve
		3) There is air in the refrigeration system. 4) Too much refrigerant charged 5) Inhalation pressure is too high				3) After removing or re-vacuuming, replenish the refrigerant. 4) Release a portion 5) Analyze the reasons and reduce [the impact].
	(3) The hydraulic protector is activated.	1) Excessive refrigerant dissolved in the oil 2) Clogged oil suction filter 3) Insufficient oil level 4) Oil pump failure				1) Turn on the oil heater 2) Disassemble and clean 3) Investigate the cause of low oil levels, resolve the issue, and add oil at the appropriate flow rate. 4) Perform maintenance.
	(4) Compressor mechanical failure					(4) Repair or replacement
Indoor unit leaking water	(1) The drain outlet of the water receiving tray and the drain pipe interface are not tight.					(1) The connection is tight and secure.
	(2) Leaking water in the drip tray	1) Clogged drain outlet (pipe) of water collection tray 2) Poor drainage from the drip tray 3) The machine is under negative pressure during operation and cannot discharge water.				1) Use methods such as suction, blowing, and flushing to unclog the blockage. 2) Increase the slope and diameter of the drainage pipes. 3) Install a water seal on the external drain pipe or increase the height difference of the gravity drainage.
Heat pump air conditioners can cool normally, but cannot heat.	Thermostat malfunction The hot/cold switch is malfunctioning. Electromagnetic directional valve malfunction Incorrect connection of electrical control circuit					Repair or replacement Repair or replacement Repair or replacement correct

Table 4. Analysis and Solutions to Common Problems and Faults in Duct Systems

Problem or malfunction	Cause Analysis	Solution
Air duct leakage	The flange connection is not tight. Other joints are not tight.	Tighten the bolts or replace the rubber gaskets. Seal with silicone sealant or all-purpose adhesive.
Insulation layer detaches from duct wall	Adhesive failure Insulation nails detached from the pipe wall	Re-attach firmly Remove the insulation layer, re-attach the insulation nails, and then re-insulate.
Condensation and dripping water on the surface of the insulation layer	The insulation layer or moisture-proof layer is damaged due to air leakage in the insulated air duct. The insulation layer failed to provide insulation. The adhesive tape at the seam of the insulation layer has come loose.	(1) Referring to the above method, first solve the air leakage problem, and then replace the water-containing insulation layer. (2) Replace damp and water-containing parts (3) Increase the thickness of the insulation layer or replace the insulation material. (4) After replacing the damp or water-containing insulation layer, seal the joints with new adhesive tape.
The damper is not turning or is not flexible enough.	Foreign object stuck Rust on transmission connecting rod joint	Remove foreign objects Loosen with kerosene and add lubricating oil.
The air valve cannot be closed tightly	Deformation after installation or use Poor manufacturing quality	Correction Repair or replacement
The moving blades of the damper cannot be positioned or are easily moved after being positioned.	The control handle cannot be positioned. The active blades are too loose	Improve positioning conditions Tighten properly
Air vent exposed, dripping water	Supply air temperature is lower than indoor air dew point temperature	Increase the supply air temperature to 2-3°C above the indoor air dew point temperature. Replace the air outlet with one made of a material with lower thermal conductivity (such as wood).
The airflow from the vent is too strong.	Excessive airflow speed The position of the air outlet guide vanes is not suitable. Inappropriate air outlet design	Open the air vent regulating valve or increase the air vent area. Adjust to the appropriate position replace
Some air vents have insufficient airflow.	Insufficient opening of branch duct or air outlet valve Excessive pipe resistance Issues related to wind turbines	Increase the pipe cross-section or increase the total pressure of the fan by opening it to a full ten-degree angle. See the fan fault table
The airflow noise in the duct is too loud	Excessive wind speed	Reduce fan speed or close the air valve.
The duct walls vibrate and generate noise.	The pipe wall material is too thin	Take measures to strengthen the pipe wall or replace the duct with one of appropriate wall thickness.
stent exposure, dripping water	The crossbeams of the support frame are in direct contact with the air duct, forming a cold bridge.	Place the support beam outside the duct insulation layer or lay wooden blocks between the support beam and the duct.
Valve or vent blades vibrate and generate noise.	Excessive wind speed Insufficient stiffness of blade material Loose blades	Reduce wind speed by replacing blades with those that have better rigidity or are made of thicker material. Tighten

Table 5. Analysis of the causes and solutions to problems related to fresh air usage.

Problems and faults	Cause Analysis	Solution
Fresh air cannot be supplied.	(1) The area of the fresh air intake is too small. (2) There is no valve in the return air main duct or return air window (door) that can be closed.	(1) Expand or increase the number of fresh air intakes. (2) Add air valves or use other materials for sealing.
Inaccurate control of fresh air usage	(1) Lack of understanding of the opening characteristics of the fresh air valve (2) The fresh air opening is not fixed. (3) The opening characteristics of the fresh air valve do not meet the adjustment requirements.	(1) Understand the relationship between opening degree and air volume (2) Take fastening measures (3) Replace with a suitable fresh air valve
The indoor air is not fresh (insufficient fresh air supply).	The fresh air valve opening is too small. The number of people indoors exceeded the designed capacity.	Open to the appropriate degree Control the number of people in the room within the design range

Table 6. Analysis of the causes and solutions for low room temperature in summer.

Cause Analysis				Solution
Providing too much cooling		(1) Excessive air supply	1) The opening of the air vent valve is too large. 2) The duct size or air velocity is too large. 3) Improper selection of fan	1) Close it to a suitable opening degree 2) Adjust the speed of the pipeline valves or the fan. 3) Replace with a fan that has the appropriate airflow.
Providing too much cooling		(2) The supply air temperature is too low	1) The room temperature setting is too low. 2) Chilled water temperature is too low 3) The chilled water flow rate is too high. 4) The new return air ratio is not suitable. 5) Issues related to the refrigeration system of unitary air conditioning units	1) Adjust to an appropriate value 2) Check for problems with the chiller unit. 3) Close the regulating water valve slightly. 4) When to adjust the ratio 5) See Table 3
Indoor load less than design value	The design calculations were too conservative, resulting in the selection of oversized air conditioning equipment or an excessive supply of cooling air. Room function change			(1) Close the water valve to reduce the chilled water flow. (2) Adjust the pipe or air outlet valve or fan speed to reduce the air supply volume. (3) Increase the temperature of chilled water supply

Table 7. Analysis of the reasons why room temperature fails to decrease in summer and solutions.

Cause Analysis				Solution
Insufficient cooling capacity	(1) Insufficient air supply	1) Too much dust accumulated on the surface of the filter or heat exchanger 2) The fan drive belt is loose or slipping. 3) Air leakage in the duct system 4) The opening degree of the air outlet valve is too small. 5) The duct size is too small. 6) Improper fan selection or fan malfunction		1) Cleaning 2) Tighten or replace the belt 3) Leak sealing 4) How wide should the opening be? 5) Increase wind speed or increase size 6) Replace with a fan of appropriate airflow or troubleshoot the problem.
	(2) Supply air temperature is too high	1) Room temperature setting is too high; 2) Chilled water temperature is too high; 3) Chilled water flow rate is too low. 4) Excessive duct temperature rise; 5) Inappropriate fresh air/return air ratio; 6) Problems with the refrigeration system of the unitary air conditioning unit.		1) Lower it to an appropriate value 2) Check for problems with the water supply to the chiller unit. 3) Open the water valve to the maximum or increase the diameter of the water pipe. 4) Thicken or replace the insulation material 5) When to adjust the ratio 6) See Table 3 for relevant information.
The room was a bit cold.		Room doors and windows not closed or not properly closed Frequent opening of doors		(1) Reduce the number of times the door is opened (2) Close the doors and windows and make them as airtight as possible.
Sunlight streamed into the room		The window has no shade.		Add sunshade devices or replace window glass with sunshade-equipped ones.
Short circuit of supply and return airflow		The distance between the air supply vent and the return air vent is too close (ideally more than 1.5m). Inappropriate air supply direction or air outlet type		Increase the distance between the supply and return air vents Change the air supply direction or change the type of air outlet
Indoor load exceeds design value		Occasionally (e.g., due to excessive number of people)		(1) Lower the freezing temperature, lower the air supply temperature, or increase the air supply volume.
		Frequently occurs	(1) Too many devices or personnel have been added indoors. (2) Change of room function	1) Add air conditioning equipment 2) Modify the original piping to increase cooling capacity.

Table 8. Analysis of the causes and solutions for noise and vibration problems.

Problems and faults

Cause Analysis

Solution

The operating noise of equipment such as cabinet fan coil units, combined air conditioning units, or unitary air conditioning units affects the air-conditioned room.

Transmitted through the building envelope

Entered through the vent

Entering through the centralized return air inlet

The computer room was treated for sound absorption, and the computer room doors were treated for sound insulation.

Add a silencer to the air supply and return vents, and wrap the ducts with sound insulation material.

Replace ordinary louvered centralized return air vents with silencers.

Vibration from the operation of equipment such as cabinet fan coil units, combined air conditioning units, or unitary air conditioning units can affect the air-conditioned room.

Transmission into the interior through the building envelope

Strengthen the existing vibration damping or isolation devices, or replace them with new and suitable vibration damping or isolation devices.

Table 9 Common Problems and Fault Analysis and Solutions for Fan Coil Units

Problem or malfunction	Cause Analysis		Solution
The fan is running but the air volume is small.	Improper air supply setting Too much dust on the filter Excessive dust accumulation between the coil fins Low voltage Fan reverse		Adjust to the appropriate gear clean clean Investigate the cause Change the phase sequence of the wiring
The air blowing out isn't cold (hot) enough.	Improper temperature setting There is air in the coil. Water supply temperature too low or too high Insufficient water supply		Adjust to the appropriate gear Open the coil vent valve to release air. Check cold and heat sources Open the water valve or increase the diameter of the branch pipe
Excessive vibration and noise	Poor lubrication or damage to the fan bearings Too much dust or damage to the fan blades Friction between the fan impeller and the casing The air outlet and the external air duct or air supply outlet are not connected by a flexible connection. The coils and drip trays are not flexible connections to the supply, return, and drain pipes. The fan coil unit is telling the current operation Loose connection parts for fixing the fan Loose louvers on air vent		Add lubricant or replace Clean or replace Clean or replace the fan Use soft links Use soft links Adjust to medium or low speed. Tighten Tighten
Foreign objects were blown out.	Damaged filter Too much dust in the unit or air duct Rust on the surface of wind turbine blades Coil fin oxidation Damage to insulation material inside the unit or duct		replace clean Replace the fan Replace the coil Repair or replace
Unit leaking water	(1) Water overflowing from the drip tray	(1) Clogged drain outlet (pipe) (2) Poor drainage (3) The drainage tray is tilted in the wrong direction.	(1) Use methods such as suction, ventilation, blowing, and flushing to unclog the blockage. (2) Adjust the slope of the drainage pipe to be greater than or equal to 0.8 percent or shorten the length of the drainage pipe to drain the water nearby. (3) Adjust the water receiving tray so that the drain outlet is at its lowest point.
	(2) Leakage and condensation in the pipelines of the unit	(1) The pipe joint is not tight. (2) There are exposed parts of the pipe with condensation on the surface.	(1) Tighten to make the connection tight. (2) Wrap the exposed parts of the pipes with insulation material.
	(3) Condensation at the bottom of the drip tray	The insulation layer at the bottom of the drip tray is damaged or has detached from the bottom of the tray.	(4) Repair or glue it.
	(4) The coil vent valve is not closed or not closed tightly.		(4) Close or tighten
Condensation on the unit casing	Damaged or detached insulation material inside the unit Damaged casing causing air leakage		Repair or glue repair
Condensate drainage is poor	The horizontal slope of the external pipeline is too small. Drainage outlet (pipe) connection		(1) Adjust the slope of the drainage pipe to be greater than or equal to 0.8 percent or shorten the length of the drainage pipe to drain the water nearby. (2) Use methods such as suction, ventilation, blowing, and flushing to unclog the blockage.

Table 10 Analysis and Solutions to Common Problems and Faults in Fans, Motors, and Drive Belts

Problem or malfunction

Cause Analysis

Solution

bearing temperature rise is too high

Insufficient lubricating oil (grease)

Poor quality lubricating oil (grease)

The fan shaft and the motor shaft are not concentric

bearing damage

Two bearings are not concentric

Add enough

Clean the bearing and replace with qualified lubricating oil.

Two concentric axes

replace

Find the right

Excessive noise

Friction between impeller and air inlet or casing

Bearing components are worn, and the clearance is too large.

Too high speed

See the relevant entries below.

Replace or adjust

Reduce speed or replace fan

Excessive vibration

The nuts of the anchor bolts or other connecting bolts are loose.

Bearing wear or looseness

The fan shaft and the motor shaft are not concentric

The connection between the impeller and the shaft is loose.

Uneven blade mass or partial blade wear and corrosion

Uneven deposits were attached to the leaves.

The counterweights on the impeller are of incorrect mass or position.

The shafts of the two pulleys of the fan and the motor are not parallel.

Tighten

Replace or tighten

Adjust concentric

Tighten

Adjust the balance or replace the blades or impeller.

clean

Perform balance correction

Adjust parallel

Friction between impeller and air inlet or casing

The bearing is loose in the bearing housing.

The impeller center is not at the air inlet center.

The connection between the impeller and the shaft is loose.

Impeller deformation

Tighten

Investigate the cause and make adjustments.

Tighten

replace

The air volume is too small.

The impeller rotates in the wrong direction.

Insufficient valve opening

Belt too loose

Insufficient speed

Blockage of air inlet or outlet, or ductwork

The connection between the impeller and the shaft is loose.

Excessive gap between impeller and air inlet

The fan is poorly manufactured and does not meet the rated air volume specified by the brand name.

Swap any two wire positions of the motor

Open to the maximum and leave the degree

Tighten or replace

Check voltage and bearings

Clear blockages

Tighten

Adjust to a suitable gap

Replace with a suitable fan

Motor temperature rise is too high

Air volume exceeds rated value

There is a problem with the motor or power supply.

Close the air volume regulating valve

Find the cause in the motor or power supply.

problems with drive belts

Belt overfeed (jumping) or overtight

Uneven tension when multiple belts are used for transmission

The belt is prone to coming off by itself.

Belt rubbing against belt protector

Belt wear, grease or dirt

Belt wears out too quickly

Adjust the motor position to tighten or loosen tension.

Replace all

Align the corresponding grooves of the two pulleys into a straight line.

Tighten the belt or adjust the protective cover.

replace

Adjust the shafts of the two pulleys of the fan and motor to be parallel.

Table 11 Analysis and Solutions to Common Water Pump Problems and Faults

Problem or malfunction

Cause Analysis

Solution

No water comes out of the outlet pipe after startup.

(1) The water in the inlet pipe and pump is seriously insufficient.

(2) The impeller rotates in the wrong direction. (3) The inlet and outlet valves are not open.

(4) There are foreign objects blocking the water inlet pipe or impeller.

(1) Fill with water

(2) Swap the positions of any two wires of the motor

(3) Open the valve

(4) Remove foreign objects

The pressure gauge on the outlet pipe shows a reading after startup, but there is no water at the end of the pipeline system.

The speed did not reach the rated value.

The resistance of the pipeline system is greater than the rated head of the water pump.

Check if the voltage is too low. Also check if the packing is too tight or if the bearings are not adequately lubricated.

Replace with a suitable water pump or increase the pipe diameter or cut off a section of the pipeline.

After startup, the pointers of the pressure gauge on the outlet pipe and the vacuum gauge on the inlet pipe swing violently.

Air enters the pump through the inlet pipe along with the water flow.

Investigate the source of the air pollution and take measures to prevent it.

Water initially flowed after startup, but immediately stopped.

A large amount of air is trapped in the water inlet pipe.

A large amount of air was inhaled.

Investigate the cause and eliminate air pollution.

Check the tightness of the water inlet and pipes, as well as the sealing performance of the shaft seal.

Water suddenly stopped flowing during operation

Water inlet (port) blocked

A large amount of air was inhaled.

The impeller was severely damaged.

Clear blockages

Check the tightness of the water inlet and pipes, as well as the sealing performance of the shaft seal.

Replace impeller

bearing overheating

Insufficient lubricating oil

Lubricating oil aging or poor quality grease

Incorrect bearing installation or improper clearance

The shafts of the water pump and the motor are not concentric.

Refuel in time

Replace with appropriate lubricating oil after cleaning.

Adjust or replace

Adjust and find

Excessive leakage from the stuffing box

The packing was not compacted enough

Packing wear

incorrect packing wrapping method

The shaft can bend and wobble.

Tighten the gland or add another layer of filler.

replace

Rewind correctly

Straighten or correct

Abnormal sound inside the pump

Air is drawn in, causing cavitation.

There are solid foreign objects inside the pump.

Investigate the cause and prevent air intake.

Disassemble pump and clean

Pump body vibration

Anchor bolts or all chain bolts and nuts are loose

Air is drawn in, causing cavitation.

bearing damage

Impeller damage

Impeller partially blocked

The shafts of the water pump and the motor are not concentric.

Water pump shaft bent

Tighten

Investigate the cause and prevent air intake.

replace

Repair or replace

Disassemble pump and clean

Adjust and find

Straighten or replace

The flow rate does not reach the set value

The speed did not reach the set value

Insufficient valve opening

Water pipes that are too long or too high

Piping system with smaller pipe diameter

Air intake

Foreign objects are blocking the water inlet pipe or impeller.

Excessive wear of the sealing ring

The impeller is severely worn.

Loose impeller fastening screws caused the impeller to slip.

Check voltage, packing, and bearings.

Open to the appropriate degree

Shorten the water delivery distance or replace with a suitable water pump

Increase pipe diameter or replace with a suitable water pump

Investigate the cause and prevent air intake.

Remove foreign objects

Replace the sealing ring

Replace impeller

Tighten the screw

The motor consumes too much power.

Too high speed

Operating at higher than rated flow and head conditions

Packing too tight

The water contains mud, sand, or other foreign objects.

The shafts of the water pump and the motor are not concentric.

Friction between impeller and volute

Check the motor and voltage.

Adjust the opening of the outlet pipe valve

Relax appropriately

Investigate the cause and take cleaning or filtration measures.

Adjustment and calibration

Investigate the cause and eliminate it.

Table 12 Analysis and Solutions to Common Cooling Tower Problems and Faults

Problem or malfunction

Cause Analysis

Solution

Water temperature too high

Excessive circulating water volume

The water outlets in the water distribution pipe (water distribution tank) are blocked, causing uneven water flow.

Poor airflow or short circuit

Insufficient ventilation

The inlet water temperature is too high

Air short circuit

Partial blockage of the packing material caused uneven water distribution (flow deviation).

Outdoor wet bulb temperature too high

Adjust the valve to the appropriate water volume or replace the cooling tower with one of matching capacity.

Clear blockages

Investigate the cause and improve

See solutions for "insufficient ventilation"

Checking for problems with the chiller unit

Change the air circulation flow to direct current

Clear blockages

Reduce cooling water volume

Insufficient ventilation

(1) The fan speed decreased

1) Loose drive belt 2) Poor bearing lubrication

(1) 1) Adjust the motor tension or replace the belt.

2) Add oil or replace the bearing

(2) The angle of the fan blades is not appropriate.

(3) Damaged fan blades

(4) The packing material is partially blocked.

(2) Adjust the appropriate angle

(3) Repair or replacement

(4) Clear the blockage

Overflow of water collection tray (trough)

(1) The outlet (filter) of the water collection tray (trough) is blocked.

(2) The float valve is malfunctioning and cannot close automatically. (3) The circulating water volume exceeds the rated capacity of the cooling tower.

(1) Clear the blockage

(2) Repair

(3) Reduce the amount of circulating water or replace the cooling tower with one of matching capacity.

The water level in the collection basin (trough) is low.

(1) The float valve opening is too small, resulting in a small water supply.

(2) Insufficient water pressure results in a small water supply.

(3) There are leaks in the piping system.

(4) Excessive water loss during the cooling process

(5) The diameter of the water supply pipe is too small.

(1) Open to a suitable opening degree

(2) Investigate the cause and increase the pressure or pipe diameter.

(3) Locate the leak and seal it.

(4) See the solution for "excessive water volume during cooling process".

(5) Replacement

There is obvious floating phenomenon.

(1) The circulating water volume is too large or too small

(2) Excessive ventilation

(3) There is a flow deviation phenomenon in the packing.

(4) The water distribution device rotates too fast.

(5) Improper installation position of the water-blocking sleeve (water baffle)

Adjust the valve to the appropriate water volume or replace the cooling tower with one of matching capacity.

Reduce the fan speed, adjust the fan blade angle, or replace the fan with one that provides the appropriate airflow.

Investigate the cause and ensure its even distribution.

Adjust to the appropriate speed

Uneven water distribution

The water outlet of the water distribution pipe (water distribution tank) is blocked.

Insufficient circulating water volume

The circular water distribution device rotates too slowly.

The rotation speed of the circular water distribution tower is unstable and uneven.

Clear blockages

Increase the circulating water volume or replace the cooling tower with one of matching capacity.

Clear blockages from the water outlet or increase the circulation volume.

Air in the duct

The packing material and water collection tray (trough) contain dirt or microorganisms.

The environment where the cooling tower is located is too poor.

Poor water treatment effect

Shorten the maintenance (cleaning) cycle

Research and adjust water treatment solutions to enhance descaling and biodegradation.

There are abnormal sounds or vibrations.

The fan speed is too high and the ventilation volume is too large.

Fan bearings lacking oil or damaged

Fan blades rubbing against other components

The nuts on some of the fastening bolts were loose.

Loose screws on fan blades

Friction between belt and protective cover

Gearbox lack of oil or gear set wear

Friction between the water-blocking material (water baffle) and the packing

Reduce the fan speed, adjust the fan blade angle, or replace the fan with one that provides the appropriate airflow.

Refueling or replacing

Investigate the cause and eliminate the possibility.

Tighten

Tension the belt and secure the protective cover.

Add enough oil or replace the gear set

Adjust the baffle and packing

The dripping sound is too loud

Packing material deflects water flow

Excessive circulating water volume

No sound absorber was installed in the water collection tray (trough)

Investigate the cause and ensure its even distribution.

Reduce the circulating water volume or replace the cooling tower with one of matching capacity.

Install a sound absorber in the water collection tray (trough)

Table 13 Analysis and Solutions to Common Water Valve Problems and Faults

Problem or malfunction

Cause Analysis

Solution

The valve cannot be closed tightly.

There is debris between the valve core and the valve seat.

Wear or damage to the sealing surfaces of the valve core and valve seat

Remove debris

Grind the sealing surface or replace the damaged part

There is leakage between the valve body and the valve cover.

Valve cover not screwed on tightly

The gasket between the valve body and the valve cover is too thin or damaged.

Uneven tightness of flange connection bolts

Valve stem or thread/nut wear

Tighten

Thicken or replace

Tighten evenly

replace

There is condensation on the valve body surface

Insulated wrapping or incomplete wrapping

Insulation layer damage

Insulate or keep the package intact

repair

The stuffing box is leaking.

The packing gland is not tightened or is not properly tightened.

Insufficient packing

Packing deterioration and failure

Tighten, straighten

Refill

Replace packing

Valve stem does not rotate smoothly

Packing too tight

Thread wear on valve stem or valve cover

Valve stem bent and deformed stuck

Scale buildup on valve stems or modified threads

Surface corrosion of the valve stem under the packing

Relax appropriately

Replace valve

Straighten or replace

Remove limescale

Remove corrosion products

The check valve spool cannot be opened.

Valve seat and valve core stuck together

The valve core shaft is rusted

Remove ditch or rust

Remove rust

The check valve is not closing tightly.

Valve core stuck by debris

Valve core damaged

Remove debris

Replace valve core

Table 14 Analysis and Solutions to Common Problems and Faults in Water Piping Systems

Problem or malfunction	Cause Analysis	Solution
water leakage	The threaded connection was not tightened enough. Insufficient filler for threaded connections The flange connection is not tight. Pipe corrosion perforation	Tighten Apply water-repellent sealant or re-fill and bond the leak. Tighten the bolts or replace the rubber gaskets. Repair welding or replace new pipes
Insulation layer is damp or dripping	Leaking insulation pipes Damage to insulation or moisture barrier	(1) Refer to the above method to solve the water leakage problem first, and then replace the insulation layer. (2) Replace all damp and water-containing parts.
There is air in the pipe	Automatic air vent valve not working Insufficient automatic exhaust valve settings Improper setting of automatic air vent valve	Repair or replacement Add at longer bends on the branch ring road It should be installed at the highest point of the water pipeline.

Comprehensive Maintenance and Troubleshooting Manual for Air Conditioning Units

Comprehensive Maintenance and Troubleshooting Manual for Air Conditioning Units

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