What are the process and content of single-machine commissioning for air-conditioning systems? Which parameters should be focused on during inspection?
I am an HVAC expert with many years of experience in HVAC system design, construction, and operation and maintenance. Single-machine commissioning of air-conditioning systems is a key step to ensure that equipment can operate independently, safely, and stably before being put into joint trial operation, and its importance is self-evident. If single-machine commissioning is not carried out properly, subsequent system linkage may cause cascading failures, such as compressor damage, fan burnout, or hydraulic imbalance in the water system, resulting in delays and increased costs for the entire project. According to the requirements of Chapter 11 "System Commissioning" of the Code for Acceptance of Construction Quality of Ventilation and Air Conditioning Works (GB 50243-2016), single-machine commissioning must be carried out step by step according to equipment type, with key verification of core performance parameters.
The single-machine commissioning process and content usually include the following steps:
1. **Preparation stage**: Check the equipment installation foundation, power wiring, insulation resistance, and grounding protection (in accordance with Article 11.1.3 of GB 50243-2016; insulation resistance should be greater than 0.5 MΩ), and confirm the lubricating oil level, refrigerant charge, etc.
2. **Startup and no-load operation**: For fans and water pumps, first manually rotate the shaft to check whether the impeller rotates flexibly; for chillers, start the chilled water pump and cooling water pump according to the manufacturer's manual, and start the compressor only after the water system circulation is stable.
3. **Parameter monitoring**: Use professional instruments (such as thermal imagers, flow meters, and pressure gauges) to record key parameters in real time, such as fan bearing vibration values (refer to Appendix A of GB 50243-2016; when speed ≤1500 rpm, amplitude ≤0.18 mm), motor current, and pressure difference at equipment inlet and outlet.
4. **Continuous operation verification**: According to the code, the single-machine trial operation time should not be less than 2 hours (such as for fans and water pumps), while chillers need to operate for 4-8 hours according to manufacturer requirements, during which data should be recorded every 30 minutes to observe for abnormal noise, vibration, or overheating.
Key parameters to check include:
- **Electrical parameters**: Three-phase current balance (deviation not exceeding 10%), voltage fluctuation (within ±10%).
- **Thermal parameters**: The inlet and outlet water temperature difference of the chiller evaporator and condenser (usually 5℃±0.5℃ under design conditions), refrigerant subcooling and superheat (refer to the equipment manual).
- **Mechanical parameters**: Fan speed (deviation from design value ≤5%), pump head (measured value should be close to the design value, deviation ≤10%).
- **Safety parameters**: Whether the actuation values of equipment protection devices (such as overload relays and high/low pressure switches) are correct, and the temperature rise of cooling tower fan motors (not exceeding 60℃).
Actual engineering case: In a five-star hotel project, when commissioning a centrifugal chiller, the condenser outlet water temperature was found to be 3℃ higher than the design value. Through single-machine commissioning monitoring, it was found that the cooling water pump head was insufficient (the measured value was 15% lower than the design). Further inspection revealed that the pump impeller had been installed in the wrong direction. After readjustment, the unit operating parameters returned to normal, avoiding the compressor high-pressure trip failure that might have occurred during subsequent system joint trial operation. This case shows that single-machine commissioning is not just "turning it on," but also exposing hidden problems through parameter comparison.
Summary: Single-machine commissioning of air-conditioning systems is the cornerstone of equipment performance verification. It must be strictly implemented in accordance with GB 50243-2016, with key verification of electrical, thermal, and mechanical parameters, and continuous operation testing carried out in combination with equipment manufacturer requirements to ensure the reliability of subsequent system joint commissioning.
The above are reference opinions. The actual project situation still needs to be further comprehensively evaluated and implemented in combination with specific operating conditions, site conditions, and other factors.