Performance factors as a basis of practical fault detection and diagnostics methods for air-handling units

The technical term "performance" is defined as how well a system fulfills its intended purpose in different operational circumstances. This paper describes the process of establishing the performance factors of air-handling units (AHUs), defining the performance requirements, and connecting them tofault detection and diagnosis methods. The most important performance requirements of AHUs are related to heating and cooling energy, the supply airflow rate and purity energy efficiency, and control quality. Many solutions made during different life-cycle phases affect the final system performance. These solutions are discussed in this paper. Diagnostic tools and methods can be developed for monitoring the defined performance criteria. Practical FDD methods have been developed for the system considered here. The methods are simple and easy to apply in practice. Methods for monitoring the heat recovery unit and the AHU energy use are presented. Examples of utilizing characteristic curves and fault-symptom trees are also described.