Table of Contents
This paper describes the processes and mechanisms behind electrical water heating system
Water is stored in the tank because when it comes in through the dip tube it is normally at lower temperature than the one set by the user. Water is stored until it reaches the minimum set temperature using the dial back system it is then heated. The tank has a thermostat located underneath a protective cover which provides the heating. The outer cover is normally covered with insulating material like polyurethane foam to prevent heat loss from already heated water which is not yet at the required minimum temperature. There is also a decorative outer shell with extra insulating blanket. The water heater is normally set at a given temperature at which heated water will be released through the heat-out pipe. The heater is able to “know” water needs to be heated as long as the minimum dialed temperature is not yet reached at the top water in the tank (U.S. Department of Energy, 2011).
Reheating of water is effected through the principle of warmer water rising to occupy the top space as cold water goes below. The heating mechanism—the thermostat is located below the tank. When water in contact is heated, it becomes less dense than the water at the top. This forces the top water to come down as the bottom one rises. This process is repeated until the water reaches a certain temperature when it can now go through the heat-out tube. The temperature of water can become too low when the dial back knob on the tank is set off preventing the thermostat from using electricity to heat water. The thermostat will continue heating the water as long as the set temperature is not yet reached and the hottest water in the tank cannot go through the heat-out pipe. Water is only allowed to go through the heat-out pipe when it reaches the temperature indicated on the dial (Novate Media, 2011).
When water is heated in the tank, temperature rises in the tank and the temperature accumulates. The accumulated temperature forces hot water at the top to find a way out. The only opening at the top is the heat-out pipe and hot water naturally finds its way through this pipe. To keep the pressure inside the tank within the safe limits, there is a pressure relief valve that controls the amount of pressure that can accumulate inside the tank as water is heated. The hot out pipe is located at the top part of the tank because hot water will always rise over cold water depending on the temperature inside the tank. If it were located at the lower part of the tank, the cold water will go through it as warm water rises above the tank. The hot water at the top goes through the heat-out pipe which directs it to the faucet. Water stops going through the hot out pipe when heating stops below the tank (U.S. Department of Energy, 2011).
When water is heated at the bottom of the tank, the hot water rises with heat leaving a region with higher pressure compared to the other parts. The high pressure caused by the rising water does a number of things. First it allows cold water to come into the tank through the dip tube. It also allows cold water from the top of the tank to come down. However, because cold water is much dense than hot warm water coming from the top, the rate of cold water entering the tank through the dip tube located below the tank is higher than the warm water from the top. This fills the tank with cold water at the same rate as hot water leaves the tank at the top through the heat-out pipe. The new cold water goes to the bottom of the tank by virtue of the fact that it is denser than all the water in the tank. The cold water stops coming when heating stops and there is no hot water going through the heat-out pipe. The pressure in the tank stabilizes and thus prevents cold water from coming in because there is no water leaving it (Klenck, 2012).