Field Assessment of Residential Three Function Heat Pump Performance

This project evaluates the performance of a production prototype residential three-function heat pump (TFHP) system. TFHPs are called “three function” systems as they utilize a single compressor to serve indoor heating, indoor cooling, and domestic hot water loads. The system evaluated in this project, called the AquaThermAire, was developed by Villara Building Systems. In addition to an innovative defrost strategy, the system also can provide simultaneous space cooling and water heating operation in the summer. 

Although the product can be applied in both new construction and retrofit applications, a primary goal in the product development was to provide an all-electric HVAC and DHW solution without making changes to an existing home’s electrical panel. By serving both space conditioning and water heating loads with the same outdoor unit, no electrical panel upgrades are needed. Another advantage of the system is that it uses heat from the DHW storage tank for defrost operation, eliminating the need for the commonly installed backup strip heat at the indoor air handling unit.

Frontier Energy carried out an evaluation of the first production prototype AquaThermAire unit installed at an occupied home in Davis, California. As a production prototype, the installed unit served as a valuable field-testing site for Villara to identify and resolve any remaining installation and operational issues. Any project results presented here should be viewed from a “pre-production” perspective, rather than depicting a commercial product.