Effect of thermostat position and its set-point temperature on the performance of a domestic electric water heater

In domestic buildings, water is generally heated by an immersion type electric water heater, equipped with a thermostat as one unit, which is fitted at the bottom of the tank. Despite these systems are driven by electric energy, which is not favorable compared to direct solar water heaters, they are still widely used due to the practicality and low installation costs. In current use of electric water heaters, thermostat position and water set-point temperature are crucial and these parameters should be optimized for efficient and economic use of such systems. In this study, the impact of placing the thermostat at three different elevations; namely near the bottom, in the middle and near the top of an EWH is experimentally investigated. In addition, the effect of temperature setting of the thermostat near the bottom of the tank, on the performance of the EWH is experimentally investigated. Data were obtained for 5 L/min discharging rate of the heated water. The discharge efficiencies are found to be higher for the thermostat position at the bottom, while the discharge efficiencies for thermostat positions in the middle and near the top are very close but lower than that of the one near the bottom.

Electric Water Heater Energy Consumption Determination Using Outlet Temperature and Volumetric Estimation

This paper presents the use of outlet temperature and water meter data as inputs to a physical model of a domestic electric water heater (EWH) for estimating the energy consumption for various control settings. Four sets of actual household data, consisting of at least 7 consecutive days each, is used to determine the accuracy of the energy consumption estimates in comparison to measured energy consumption. Both the outlet temperature and water meter data inputs used were able to estimate the total energy input with an error of less than 10 percent for 3 of the 4 datasets considered. Additionally, both methods are also implemented as a smartphone application that can be used to obtain input from users, as well as provide instantaneous feedback on the impact of control changes.