A system-level auto-commissioning framework for proactive detection of hard and soft faults in VAV AHU systems

• Proactive FDD targets VAV AHU faults at early stages. • Auto-commissioning overcomes manual limitations with data-driven performance tests. • Active testing utilizes BAS bi-directional interactions for ongoing commissioning. • Auto-commissioning reveals both hardware and control-related system issues. Maintaining reliable and efficient operation of HVAC systems remains a challenge in commercial buildings. Conventional commissioning and recommissioning practices are resource-intensive and infrequent, allowing faults to persist unnoticed for extended periods. This paper presents a system-level auto-commissioning (AC) framework to proactively detect hard and soft faults in variable air volume (VAV) air handling unit (AHU) systems. Hard fault tests target hardware-related problems including mixing box damper faults, and heating/cooling coil malfunctions. Complimentary soft fault tests diagnose control errors related to state of operation, mode of operation, and supply air temperature setpoint (T SA,SP ) and duct static pressure setpoint (P duct,SP ) reset logic. Implementation of the framework in an occupied building successfully revealed a leaky outdoor air damper, an inefficient economizer sequence, and deficiencies in T SA,SP /P duct,SP reset strategies. The results demonstrated the capability of the framework to provide actionable diagnostic insights, reduce reliance on manual inspection, and enhance operational efficiency through early fault detection.