ABSTRACT
Fault detection and diagnosis (FDD) plays an increasingly important role in the operation and maintenance of heating, ventilation and air-conditioning (HVAC) equipment. California’s 2013 Title 24 building energy code, effective from January 1, 2014, requires an FDD system on all newly installed air-cooled unitary direct-expansion units with an economizer and mechanical cooling capacity larger than 4.5 tons. This entry provides an overview of FDD technique and practice as applied to unitary HVAC equipment such as rooftop units (RTUs) and split systems, including the introduction of unitary HVAC equipment, description of common faults in unitary HVAC equipment, elements of FDD process, fundamental FDD methods, and the factors in selecting a specific FDD method in unitary HVAC equipment.
