Electric Geysers (Water Heater)
To get the hot water, either continuously or intermittently, an electric water heater is more useful device. It can be easily installed anywhere with the electric power. Its water temperature can easily be regulated automatically by a thermostat. It works on the principle of thermal storage i.e. the water is preheated by immersion water in a storage vessel and is kept for future use. To get the water in a storage vessel and is kept for future use. To get the hot water from time to time, the storing vessel is provided with thick insulation or it is properly legged to dissipate the heat. The heating element is fixed at the bottom horizontally or vertically. As the water heater is switched ‘on’ the cold water is heated up, becomes lighter and starts moving up while the cold water being heavier comes down. Thus due to this circulation of water, we can get hot water from the outlet valve. If the element is fixed horizontally, the water above it, is heated very slowly but when the element is fixed vertically, the water surrounding this is heated up very soon. So the vertical fitting of the element in the water heater is more referred.
Water heater may be classified in the following ways:
(a) Immersion Heater or Rod. It can be put in any vessel full of water and by switching on, the water is heated up. It is a portable and cheap and has been described before.
(b) Self-contained Heaters. These are of two types:
(i) Non-Pressure type
(II) Pressure type These consist of a storage vessel, heavily legged, electrically heated and provided with a thermostat system.
(c) Non-pressure Type Water Heater. This type of water heater is used at that place where the hot water is required only at one service point e.g. for wash-basins and sinks etc. Such water heaters have an open outlet i.e. not having any stop-cock. Its water is controlled from the inlet side. These contain two cylindrical vessels, one fitted inside the outer. The inner vessel consists of heating chamber made of tinned copper. Inside it, the heating element and thermostat are fixed vertically at the bottom. The outer vessel is made of lead-coated-steel and painter outside with enamel paint. The space between the two vessels is filled with heat resisting insulating material to reduce heat loss. The temperature of the water is controlled automatically with thermostat. The inlet and outlet pipes are chromium plated to avoid corrosion. The cold water flows from the cold water supply pipe (inlet pipe) and enters in the heating chamber and is controlled by a valve. The hot water flows out from the top of the heating chamber through the hot water pipe (outlet pipe). An anti drip device is provided with the hot water pipe to cut off the quick hot water supply and to prevent the water to be drained off through the cold water pipe valve when the supply of cold water fails. As the hot water pipe is an open outlet, when the cold water inlet valve is opened, the cold water rushes into the heating chamber, displaces and forces out an equal quantity of hot water through the hot water outlet pipe.
To save the water heater from the developed pressure inside the heating chamber, a vent plug is fitted at the top which allows extra pressure in atmosphere. The wattage of this water heater is about 750 to 2000 W etc.
(i) Pressure Type Water Heater. In other words it is called cistern type water heater as it works on atmospheric pressure. This type of water heater is used at that place where the hot water is required at more than one service points with one heater only. This heater gets its supply of cold water from the cistern (over head tank) connected with the water mains and the water controlled with the help of a float valve. The copper pipes connected with the heating chamber are used to supply the hot water under pressure to different service points which are controlled with a tap. The element and thermostat are fixed at the removable plate fitted on the base of the water heater for their easy service and to remove them easily.
The water is of 750 to 3000 W. These are of two types:
(i) Constant volume pressure type water heater. In this water heater, the hot water drained off is replaced equally with cold water having equal volume. So it is called a constant pressure type water heater
(ii) Non-constant volume pressure type water heater. In this water heater, the rate at which the hot water flows out is not the same at which the cold water enters into the heating chamber. So it is known as non-constant or varying volume pressure type water heater.
