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Monitoring of a Split System CO2 Heat Pump Water Heater in an All-Electric ZNE Home

This report documents the performance of a heat pump water heater (HPWH) utilizing carbon dioxide (CO2) as the working refrigerant. The unit was installed in a Redding, California all-electric Zero Net Energy home and monitored in detail over the course of a year. The unit offers advantages over conventional HPWHs in that the efficiency is higher, the water heating capacity is higher, the heating output is stable over a much wider range of outdoor temperatures, there is no supplemental electric backup heating, and the CO2 refrigerant has a global warming potential of 1.

Original Publication Date: April 8, 2019

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