In this paper, the design of a heat recovery system is presented and analyzed. It allows recovering the heat waste from Heating, Ventilating, and Air Conditioning (HVAC) systems to obtain hot water. A code is developed for this purpose, which allows simulating the heat transfer in the system. The outlet temperature is studied in terms of the water flow rate and the amount of ton refrigerant in the system. It is shown that the water can be heated up to 347 K with a HVAC system of 9 tons of refrigerant (108 000 Btu/hr).