15 September 2011
This paper describes a laboratory evaluation of the relative performance of a residential integral electric heat pump water heater operating with two working fluids: (1) Refrigerant 134a (R-134a), the standard design working fluid, and (2) Refrigerant 1234yf (R-
1234yf), a potential replacement option with similar thermodynamic and transport properties, but with a substantially lower estimated global warming potential. The US 24-Hour
Simulated Use and First-Hour Rating Tests were performed on the unit employing the nameplate charge of R-134a. After replacement of the R-134a by R-1234yf (with no changes to the hardware or software), heat-up tests were conducted to determine the
appropriate R-1234yf charge. Finally, the 24-hour Simulated Use and First-Hour Rating Tests were repeated with R-1234yf. The first-hour rating calculated from the data for the R-1234yf case was found to be the same as that for the R-134a case, but the energy factor for the R-1234yf case was about 6% lower than that for the R-134a on this ”drop-in” basis. It is suggested that modification of the thermostatic expansion valve would allow a closer
approach to the R-134a system energy factor.