Automatically detecting faulty regulation in HVAC controls

Abstract

A new method is introduced to automatically detect faulty regulation of temperatures, pressures, and flow rates within HVAC systems and equipment of commercial buildings by using digital data typically available from an existing building automation system. The building automation system passes data by network to a general-purpose microprocessor executing this method. The method computerizes control charts and combines them with expert system logic to identify transients and record excursions of regulated variables beyond allowance bands set by the user. Its three separate functions monitor (1) variables regulated to a single set-point value, (2) actuating variables that drive the regulation, and (3), temperatures regulated to duplex set-points (i.e., thermostats). Faults detected include unstable, excessively oscillatory regulation and failure of regulated variable to maintain the allowed band. A brief background on control charts and expert systems is in Appendix A.