The main goal of this project is development of detection and diagnostics software for operation of heat pumps. Despite the fact that most heat pump manufactures offer basic operation fault detection, main goal of the project is development of operational diagnostics, which should be able to detect different faults as well as monitor lowering performance of the system. By developing expert detection rules, it will be possible to detect simple problems, which can over time develop into more serious operation faults. Diagnostics is primarily focused on building owners/management or heat pump manufactures, who would like to identify increased energy use as well as degradation of system components.