COMMON FAULTS AND THEIR IMPACTS FOR ROOFTOP AIR-CONDITIONERS

This paper identifies important faults and their performance impacts f or rooftop air conditioners. The frequencies of occurrence and the rel ative costs of service for different faults were estimated through ana lysis of service records. Several of the important and difficult to di agnose refrigeration cycle faults were simulated in the laboratory. Al so, the impacts an several performance indices were quantified through transient testing for a range of conditions and fault levels. The tra nsient test results indicated that fault detection and diagnostics cou ld be performed using methods that incorporate steady-state assumption s and models. Furthermore, the fault testing led to a set of generic r ules for the impacts of faults on measurements that could be used for fault diagnoses. The average impacts of the faults on cooling capacity and coefficient of performance (COP) were also evaluated. Based upon the results, all of the faults are significant at the levels introduce d, and should be detected and diagnosed by an FDD system. The data set obtained during this work was very comprehensive, and was used to des ign and evaluate the performance of an FDD method (Breuker 1997a) that will be reported in a future paper.