A simulation-based investigation of the robustness of sequences of operation to zone-level faults in single-duct multi-zone variable air volume air handling unit systems

High-performance sequences of operation for variable air volume (VAV) air handling units (AHUs) respond to requests from zones, leaving these sequences vulnerable to faults that occur at the zone level. While prior research has shown that ASHRAE Guideline 36 reduces energy consumption, its ability to withstand zone-level faults is understudied. This paper investigates the fault tolerance of supply air temperature (SAT) setpoint, duct static pressure (DSP) setpoint and mode of operation (MOP) in single-duct multi-zone VAV AHUs. First, customized sequences were defined for different scenarios in EnergyPlus in this study. Then, common actuator/sensor faults were injected into one zone to identify the most efficient fault-tolerant scenario. The results indicate that trim and respond reset logic is the most fault-tolerant scenario for this paper’s case study, with a 12% energy use intensity (EUI) increase for the SAT setpoint and an 11% increase for the DSP setpoint. Moreover, implementing an average temperature–based control for MOP significantly reduces the setup/setback mode activation, resulting in a lower EUI.