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TESTING OF REFRIGERANT MIXTURES IN RESIDENTIAL HEAT PUMPS
Hwang, Y., J. Judge, AND R. Radermacher. TESTING OF REFRIGERANT MIXTURES IN RESIDENTIAL HEAT PUMPS. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/R-95/157 (NTIS 96-113733), 1995.
The report gives results of an investigation of four possibilities for replacing Hydrochlorofluorocarbon-22 (HCFC-22) with the non-ozone-depleting new refrigerants R-407D and R-407C in residential heat pumps. The first and simplest scenario was a retrofit with no hardware modifications (drop-in). When R-407C was used in this scenario, it resulted in a 0-3% higher cooling capacity, a 4-9% lower cooling Coefficient of Performance (COP), a 4-21% lower heating capacity, a 9-24% lower heating COP, an 8.3% lower Seasonal Energy Efficiency Ratio, and a 7.2% lower Heating Seasonal Performance Factor. Retrofit test results with R-407D show a 5% higher cooling capacity, a 4% higher cooling COP, a 3% lower heating capacity, and an 8% lower heating COP. The second possibility investigated required altering the refrigerant path to attain a near-counterflow configuration in the indoor coil for the heating mode. The third and most complex possibility was optimization consisting of adjusting the refrigerant charge and expansion devices. Each modification progressively improved refrigerant performance. Study results show that the system should be optimized, rather than simply dropping in the new refrigerant, because dropping in R-407D or R-407C to replace the HCFC degrades performance. The fourth possibility did not improve performance.