TA-23-C043 – A Building Performance Simulation-Based Investigation on Fault Tolerance of Sequences of Operation for VAV AHU Systems PDF

Optimal high-performance sequences of operation for multiple zone variable air volume (VAV) air handling unit (AHU) systems are often programmed by looking at the number of zones' requests, making these sequences vulnerable to zone-level sensors and actuator faults. Although some previous studies demonstrated that implementing ASHRAE Guideline 36 (G36) high-performance sequences of operation can significantly reduce heating, ventilation and air conditioning (HVAC) energy use, we couldn't find papers specifically investigating the robustness of these sequences to zone-level faults. Upgrades are likely needed to ensure that the next-generation high-performance sequences of operation are tolerant to common faults at the zone level. This paper investigates the fault tolerance of sequences of operation, including supply air temperature (SAT) and duct static pressure (DSP) setpoint reset for multiple zones single duct VAV AHU systems. First, customized subsequences of operation are defined for different scenarios in the energy management system (EMS) application of the building performance simulation (BPS) tool EnergyPlus. Then, common actuators and sensor faults, such as a broken valve/damper and an offset thermostat, are integrated into one of the modelled zones. The results demonstrated that the most efficient and fault-tolerant scenario for both SAT and DSP setpoint is G36 trim and respond reset logic, which can successfully eliminate the rogue zone from the control loop. In the end, the authors concluded that although the implementation of G36 sequences of operation for all control loops in the AHU leads to the identification and elimination of the majority of rogue zones, there are still some faults in the single duct multiple zone VAV systems that may cause a zone not to be identified as a rogue zone by the employed reset logic but cause occupant discomfort.