Charge Reduction and Performance Analysis of a Heat Pump Water Heater Using R290 as a Refrigerant—A Field Study

Ahmed Elatar (), Joseph Rendall, Jian Sun, Jamieson Brechtl and Kashif Nawaz
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Ahmed Elatar: Oak Ridge National Laboratory, Energy and Transportation Science Division, Oak Ridge, TN 37831, USA
Joseph Rendall: Oak Ridge National Laboratory, Energy and Transportation Science Division, Oak Ridge, TN 37831, USA
Jian Sun: Oak Ridge National Laboratory, Energy and Transportation Science Division, Oak Ridge, TN 37831, USA
Jamieson Brechtl: Oak Ridge National Laboratory, Energy and Transportation Science Division, Oak Ridge, TN 37831, USA
Kashif Nawaz: Oak Ridge National Laboratory, Energy and Transportation Science Division, Oak Ridge, TN 37831, USA

Energies, 2025, vol. 18, issue 14, 1-14

Abstract: Heat pump water heaters (HPWHs) are a proven technology for water heating that has been commercialized. The adoption of HPWHs for domestic and commercial water heating is growing rapidly because of their superior performance compared with alternative water heating methods. Whereas most existing systems use R-134a as a working refrigerant, R290 has gained major attention owing to its superior thermodynamic properties. The goal of the current study is to assess the performance of residential HPWH with R290 as a direct refrigerant replacement for R134a. Two units of a 50 gal HPWH were used in this experimental study. A baseline unit contained R134a refrigerant, and a prototype unit contained R290 refrigerant. The prototype unit was developed through the modification of a commercially available HPWH unit to achieve a low charge of R290 refrigerant. Another major modification was the replacement of the baseline compressor with a compressor designed for R290. Tests were conducted in a field environment (a research and demonstration house) using programmed drawn profiles daily. The prototype that reduced the charge by 43–47% provided displayed performance comparable to the baseline unit regarding first-hour rating (FHR) and the uniform energy factor (UEF).

Keywords: HPWH; R290; drop-in-replacement (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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