Evaluation of a Decoupling-Based Fault Detection and Diagnostic Technique – Part II: Field Evaluation and Application

Existing methods addressing automated fault detection and diagnosis (FDD) for vapor compression air conditioning system have good performance for faults that occur individually, but they have difficulty in handling multiple-simultaneous faults. The decouplingbased (DB) FDD method explicitly addresses diagnostics for multiple-simultaneous faults for the first time. This paper is the second part of a two-part evaluation of the decoupling-based (DB) fault detection and diagnosis (FDD) technique whose intent is to validate the DB FDD performance and demonstrate its applications. The first part focuses on sensitivity and robustness evaluation through controlled field emulation testing. In this paper, the technique is applied to a number of field sites in California. Detailed results are given for a single site and summary results are given for the other sites. In sum, about 70% of the investigated systems are impacted by faults and about 40% have more than one fault. Service is justified for about 40% of the units. Most of the diagnosed faults are verified through field visits.