In the effort to create more energy efficient buildings, an effective fault detection process must be developed for monitoring and diagnosing malfunctions in the Heating Ventilation and Air Conditioning (HVAC) system. This study provides energy loss signatures that can be used to diagnose a specific faulty component at the unit level. An analysis has been performed on a single air handling unit (AHU) to determine how faulty HVAC components effect the overall energy consumption of the unit.
To begin the process, the Engineering Laboratory building on the campus of the University of Oklahoma was modeled for the simulation, using EnergyPlus 7.0, Google Sketchup 8, and OpenStudio 0.6.0. The building has an existing single duct system with a 3hp AHU with a forward curved fan that discharges 2500 cfm (1.175 m3/s) that covers approximately 2809 square feet (261 m2). Inputs into the simulation included building constructions, architecture, internal loads, and external loads from weather, sun, and shade objects. Simulations were run using the stated software, and a base case was established for energy consumption. Next, components and variables on the AHU, such as minimum outside air intake, economizer outside damper control, cooling coil valve, duct work pressurization, and various sensors were individually modified to reflect a malfunction or inefficiency. The energy loss caused from these changes in inputs was quantified and analyzed for the purpose of establishing a graphical range of energy loss signatures associated with each faulty component. Building Engineers and operators will be able to not only detect the exact malfunction faster, but also to ascertain the associated energy loss cost associated with the fault. The results of the study will be used to automate an online energy monitoring fault detection and diagnosis process.