Fault Inspection Methods for Constant Temperature and Humidity Precision Air Conditioners (Systematic Troubleshooting Guide)

I. Basic Inspection Procedures

1. Check Alarm Information

• Read fault codes on the control panel (e.g., Emerson Liebert displays E1/E2 codes)

• Review historical alarm records (at least 72 hours back)

2. Sensory Diagnosis

   Inspection Item	Normal State	Abnormal Signs & Possible Faults
   Operating Sound	Smooth compressor hum (≤65dB)	Metal clanking → bearing damage; high-pitched squeal → refrigerant leak
   Air Outlet Temp	Supply/return air ΔT: 6-10°C	ΔT < 4°C → clogged filter/low refrigerant
   Pipe Frosting	Slight frost at expansion valve only	Full evaporator frost → filter blockage

II. Subsystem-Specific Deep Checks

1. Refrigeration System

• Pressure Test

  Standard values: High pressure 1.5-2.0MPa, Low pressure 0.4-0.6MPa (R407C refrigerant)

• Abnormally high pressure: Condenser clogging/cooling water failure

• Abnormally low pressure: Expansion valve stuck/dry filter clog

• Refrigerant Inspection

• Use electronic leak detector (sensitivity ≥5g/year)

• Refrigerant purity analysis (reclaim if moisture >100ppm)

2. Electrical System

• Key Test Points

  Test Location	Normal Value	Abnormal Response
  Compressor winding	Resistance balanced ±10%	>15% deviation → replace compressor
  Contactor contacts	Contact resistance <0.1Ω	Pitting → replace & check starting current
  VFD output	THD <5%	Excessive harmonics → check IGBT module

3. Humidity Control System

• Humidifier Check

• Electrode type: Measure electrode resistance (new ≈50Ω)

• Infrared type: Check quartz tube transmittance (clean if contamination >30%)

• Humidity Sensor Calibration

• Use standard salt solution (e.g., LiCl saturated solution)

• Replace if deviation >±3%RH

III. Typical Fault Resolution Cases

Case 1: Frequent Low Pressure Alarm

• Procedure:

1. Measure low pressure (<0.3MPa)

2. Check expansion valve opening (normal: 4-6 turns)

3. Apply hot towel to valve → pressure recovery indicates ice blockage

4. Replace dryer filter + vacuum >2 hours

Case 2: Compressor Overload Protection

• Diagnostic Tree:

  Check starting current → Abnormal → Test winding insulation (replace if <2MΩ)
  ↓Normal    Check condenser fan → Stopped → Measure capacitor capacitance (replace if >10% deviation)
  ↓Normal    Check refrigerant charge → Overcharged >10% → Reclaim and recharge  

IV. Smart Diagnostic Technologies

1. Predictive Maintenance Tools

• Vibration analyzer: Detect compressor bearing wear (FFT spectrum analysis)

• Thermal imager: Identify overheating electrical joints (ΔT >15°C = abnormal)

2. Cloud Monitoring Systems

• Huawei NetEco predicts compressor remaining life (based on 5000+ parameter modeling)

• Schneider EcoStruxure provides automated fault tree analysis

V. Recommended Maintenance Intervals

VI. Safety Precautions

1. Reclaim refrigerant before high-side maintenance (EPA-certified equipment required)

2. Discharge VFD for >15 minutes before servicing (voltage <50V)

3. Calibrate humidity sensors in stable environment (temperature fluctuation <1°C/h)

Appendix: Quick Troubleshooting Flowchart

A[Alarm code] --> B{Temperature abnormal?}    B -->|Yes| C[Check refrigerant/expansion valve]    B -->|No| D{Humidity abnormal?}    D -->|Yes| E[Calibrate sensor + inspect humidifier]    D -->|No| F[Check electrical system]    C & E & F --> G[Verify repair]    G --> H[72-hour stability test]

This systematic approach resolves 90% of common faults. Quarterly preventive maintenance with complete logs is recommended. For complex faults (e.g., VFD explosion), contact OEM engineers.