In this study, a concept of using a vapor compression heat pump for recovering and upgrading waste heat of an
air-conditioner has been presented. R-290 has been selected due to its high efficiency and the environmental impact. R-290 heat
pump at heating capacity 3 kW has been constructed to recover waste heat from the discharge refrigerant leaving compressor of
R-134a air-conditioner at cooling capacity 1 TR. From the study results, it could be seen that the modified unit gives better
EERAC when the cooling water does not over 43 ºC. A set of simplified model has been developed to predict the system
performance and the simulated results agree quite well with the measured data. Moreover, profile of hot water consumption in the
department of children's hospital room, Maharaj Nakorn Chiang Mai Hospital is chosen to study. It was found that the hospital
requires hot water is 0.815 m3/d at 50 ºC temperature, one unit of R-290 heat pump is enough to generate hot water with the
economic results of saving cost and payback period around 765.46 USD/y and 1.97 y, respectively.