What is the princinple of electric water heater?

Answer 1

On a 240 volt hot water tank there is only one of the two elements on at any one time. The incoming cold water is taken to the bottom of the tank through a pipe inside the tank. When the lower thermostat senses the cold water, the lower element turns on. As you draw hot water from the top of the tank the cooler water from the bottom will rise. When the top thermostat senses the cool water it shuts off the bottom element and turns on the top element. When this water is heated to the tank set point it shuts off and the lower element turns on to heat the rest of the water. When the total tank temperature is at the set point all elements turn off. By using this type of procedure there is always hot water at the top of the tank for use.