I. Excessive Humidity Deviation

Typical Symptoms: A significant difference between the set humidity and the actual humidity (usually exceeding ±5%); the unit continuously humidifies or dehumidifies but fails to reach the target level.

Common Causes:

• Humidity sensor drift: After prolonged use, the sensing element may age or become contaminated, leading to inaccurate readings

• Actuator Sticking: Humidification valves, dehumidification control plates, or air dampers do not operate smoothly, preventing output adjustment according to commands

• Improper Control Parameter Settings: Target values do not match the unit’s capacity, or a hysteresis setting that is too narrow causes system oscillation

Troubleshooting Procedure:

• Verification Comparison: Place a calibrated portable thermo-hygrometer near the unit’s return air inlet, let it sit for 10 minutes, then compare the reading with the unit’s display. If the deviation persists and the difference remains constant, suspect sensor drift as the primary cause.

• Manually test the actuators: Enter the unit’s test mode and sequentially command the humidification valve to fully open and fully close, observing whether the movements are crisp and complete; in dehumidification mode, check whether the control mechanism can smoothly adjust the opening. If movement is sluggish, sticky, or accompanied by abnormal noises, disassemble and inspect the valve body or transmission components.

• Check for short-circuiting in the airflow path: Ensure there are no obstructions between the return air grille and the supply air grille, and avoid direct airflow between them. This prevents air that has just been treated from being re-drawn in without circulating through the space, causing a “false balance” phenomenon.

• Calibrate or replace the sensor: After confirming the deviation, perform zero-point and slope calibration of the sensor according to the equipment manual. If calibration is ineffective, replace the component with one of the same specifications.

II. Frequent Compressor Start-Stops

Typical Symptoms: The compressor shuts down after running for less than 3 minutes, restarts after a very short interval, accompanied by the repeated clicking sound of the relay. This phenomenon significantly shortens the compressor’s service life.

Common Causes:

• Poor Condenser Heat Dissipation: Dust accumulation on fins, insufficient fan speed, or limited installation space prevents heat from being dissipated, triggering the high-pressure switch to activate protective measures.

• Refrigerant Leak: A leak on the low-pressure side of the system causes excessively low suction pressure, triggering the low-pressure switch to activate protective measures.

• Unstable Power Supply Voltage: Significant voltage drop in the power supply line or phase voltage imbalance causes the overload protector to trip and reset periodically.

• Temperature Sensor Failure: False alarm from the evaporator anti-freeze sensor prematurely terminates the cooling and dehumidification process.

Troubleshooting Procedure:

• Observe the startup pattern: Record the duration of each run and the interval between shutdowns. If the runtime shortens as the ambient temperature rises, a heat dissipation issue is likely; If the system does not reset for an extended period after shutdown, check whether the protection device is locked.

• Inspect the condenser: While the system is off, clean dust and lint from the fin surfaces and ensure the exhaust fan rotates freely without obstruction. Check the outlet temperature by hand—under normal conditions, hot air should be clearly felt. If the exhaust temperature is close to the ambient temperature, the compressor may not be compressing effectively or there may be a refrigerant leak.

• Measure operating current and pressure: Use a clamp meter to measure the compressor’s operating current and compare it to the rated value on the nameplate. If the current is low (below 70% of the rated value) and the suction line is not cool, a refrigerant leak is highly suspected; if the current is high and rises rapidly before causing a trip, this indicates a heat dissipation or overload issue.

• Leak Detection and Refrigerant Recharge: If a leak is confirmed, first locate and repair the leak using an electronic leak detector, then evacuate the system and recharge with the correct amount of refrigerant. Never simply “top off” the refrigerant without addressing the leak.

• Inspect Power Supply Circuit: Measure the voltage drop at the moment the compressor starts. If the voltage drop exceeds 10%, inspect the wire gauge, connections, and upstream power distribution.

III. Water Leaks

Typical Symptoms: Water seeping from the bottom of the unit, water accumulation inside the unit, or continuous dripping from the drain pipe. Water leaks not only compromise equipment safety but may also cause property damage.

Common Causes:

• Drain pump failure: Wear and tear on the pump body, a seized impeller, or a malfunctioning check valve can cause the water level in the sump to rise continuously until it overflows

• Clogged Drainage Pipes: Kinked hoses, blockages from foreign objects, or a “reverse slope” where the pipe opening is higher than the pump outlet, preventing smooth drainage

• Damaged or Tilted Drip Pan: Cracks caused by long-term corrosion, or water overflowing from the lower side due to uneven installation

• Humidification System Leaks: Loose connections in the wet-towel water supply lines or a stuck float valve that remains open, causing excessive overflow

Troubleshooting Procedure:

• Observe when leakage occurs: If leakage occurs in humidification mode, prioritize checking the water supply system; if leakage occurs in dehumidification mode, focus on the drainage system. If leakage persists even when the unit is shut down, it is likely due to an improperly closed inlet valve.

• Inspect the drain line: Remove the inlet end of the drain pipe and blow air into the pipe; airflow should be unobstructed. Clean any biofilm or sediment adhering to the inner walls of the pipe and ensure there are no sagging bends along the entire length. Ensure the drain pipe outlet is higher than the unit’s drain port but below the pump’s maximum head limit.

• Test the drain pump function: Fill the drain pan with clean water until it submerges the pump’s float switch (or level sensor), and observe whether the pump automatically starts and drains the water. If the pump does not start, check if the float is stuck in the low position or if the sensor is dirty or clogged; if the pump starts but does not drain completely, the impeller may be worn or the head may be insufficient.

• Inspect the sump and seals: After draining the water, inspect the sump for cracks or rust perforations, paying close attention to welds and pipe joints. Clean out sediment from the sump to prevent foreign objects from blocking the pump suction inlet.

• Adjust the equipment level: Use a spirit level to calibrate the equipment base, ensuring a slight slope toward the drain outlet (typically 1–2 degrees).

Key Points for Daily Maintenance

Preventive maintenance is far superior to emergency repairs after a failure. Operations and maintenance personnel should establish a periodic maintenance schedule:

Filter Cleaning (Once a month or more frequently)

The pre-filter at the air intake captures the vast majority of dust in the air. A dirty or clogged filter can lead to reduced airflow, decreased dehumidification efficiency, frost buildup on the evaporator, and even liquid carryover in the compressor. When cleaning, soak the filter in a neutral detergent solution, rinse thoroughly, air-dry, and reinstall. Never force the unit to start while the filter is still damp. In dusty environments, clean the filter every two weeks.

Humidifier Pad Maintenance (Inspect every three months; replace annually or as needed)

The humidifier pad is the core component of the humidification system. Over time, its surface may develop scale and a sticky biofilm, reducing humidification efficiency and causing unpleasant odors. During inspection, check whether the humidification pad is evenly moist and look for white hard scale or black mold spots. Minor scaling can be cleaned by soaking in a citric acid solution; severe blockages or deformation require replacement. Record the date of each replacement; the typical service life is 1–2 operating seasons.

Condenser Fin Cleaning (Every Six Months)

Use a soft-bristle brush or compressed air (reverse blow) to remove dust accumulated between the fins. If there is heavy oil contamination, use a specialized fin cleaner with a low-pressure water gun, taking care to protect electrical components. Cleaning can restore heat dissipation efficiency by more than 15%.

Drainage System Inspection (Quarterly)

Fill the drain pan with water to test the drain pump’s start-stop response, and simultaneously check the piping for signs of aging, hardening, or loose connections. Remove sludge and stringy debris from the bottom of the pan to prevent clogging of the pump inlet strainer.

Tightening Electrical Connections (Annually)

After powering down, inspect the main power terminals, compressor relay contacts, and control board cables for looseness, oxidation, or burn marks. Use a torque screwdriver to tighten all connection points to the specified torque values.

Conclusion

The vast majority of humidifier failures are not sudden disasters, but rather the inevitable result of operating parameters gradually deviating from normal ranges. By adopting a closed-loop mindset of “anticipation—troubleshooting—verification,” combined with periodic filter cleaning and humidification pad replacement, maintenance personnel can effectively minimize unplanned downtime. Briefly recording key parameters (operating current, filter pressure drop, humidity deviation) after each maintenance session will provide the most accurate basis for fault prediction through long-term data accumulation.