Laboratory Performance Evaluation of Residential Integrated Heat Pump Water Heaters

An assessment of efficient water heating options for an all-electric single family residence in a mixed-humid climate

“…The measured standby power of 6.92 W is included in the model. Additionally, a laboratory test of the same model of water heater was carried out to determine the coefficient of performance (COP) as a function of stored water temperature for the heat pump as done by Sparn et al [29]. These data were compared to the TRNSYS heat pump water heater performance map obtained with an average inlet water temperature of 32.2 °C (90 °F), ambient air temperature of 21.7 °C (71 °F), and ambient relative humidity of 40%, which are representative of the conditions seen in operation.…”

Heat Pump Water Heater Ducting Strategies with Encapsulated Attics in Climate Zones 2 and 4

“…None of the studies investigated the use of the manufacturer's optional duct kits; however, two studies investigated the effect on COP of reduced airflow over the heat pump's evaporation coil. Reducing airflow by blocking onethird of the intake grille caused an insignificant decrease (<1%); a two-thirds blockage caused a decrease on COP values of ~6% to ~2% during the heating cycle (Sparn et al 2011). The effect of ducting the HPWH was expected to be similar to the one-third blocked case due to the grille area blockage of the duct kits and the increased static pressure from the ducts.…”

“…The performance and side effects of HPWHs are dependent upon a number of variables, such as ambient air temperature, humidity, outgoing draw profile, and incoming water temperature. HPWHs have undergone extensive testing in laboratory settings to quantify their individual performance (Sparn et al 2011).…”

“…The heat pump turns on when the tank temperature drops 9°F lower than the set point. Tank temperature is calculated through a weighted average of the two thermistor readings at the upper and lower parts of the tank, in which the upper thermistor reading accounts for 75% of the weight (Sparn et al 2011).…”

“…Inlet and Outlet Duct Kits, which are identical, are available from the manufacturer and enable multiple ducting configurations. the resulting COPs in efficiency mode ranged from 2.0 to 3.5 (Sparn et al 2011) and in hybrid mode from 1.8 to 3.5 (Larson and Bedney 2011). None of the studies investigated the use of the manufacturer's optional duct kits; however, two studies investigated the effect on COP of reduced airflow over the heat pump's evaporation coil.…”