Water Heaters

Water heating is a thermodynamic process using an energy source to heat water above its initial temperature. Typical domestic uses of hot water are for cooking, cleaning, bathing, and space heating. In industry both hot water and water heated to steam have many uses. more...

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Domestically, water is traditionally heated in vessels known as kettles, cauldrons, pots or coppers. These vessels heat a batch of water but do not produce a continual supply. Appliances for providing a more-or-less constant supply of hot water are variously known as water heaters, boilers, heat exchangers, calorifiers or geysers depending on whether they are heating Potable or non-potable water, in domestic or industrial use, their energy source, and in which part of the world they are found. In domestic installations, potable water heated for uses other than space heating is sometimes known as Domestic Hot Water (DHW).

The most common energy sources for heating water are fossil fuels: natural gas, liquefied petroleum gas, oil or sometimes solid fuels. These fuels may be consumed directly or by the use of electricity (which may derive from any of the above fuels or from nuclear or renewable sources). Alternative energy such as solar energy, heat pumps, hot water heat recycling, and sometimes geothermal power, may also be used as available, usually in combination with gas, oil or electricity.

Types of water heating appliance

Water for space heating is usually heated by fossil fuels in a boiler. Potable water may be heated in a separate appliance: this is common practice in the USA where warm-air space heating is usually employed.

Gravity system

Where a space-heating water boiler is employed the traditional arrangement in the UK is to use boiler-heated ("primary") water to heat ("secondary") water in a cylindrical vessel (usually made of copper) containing potable water supplied from a cold water storage tank, usually in the roof space of the building. This produces a fairly steady supply of DHW at low pressure but usually with a good flow. Water heating appliances in most other parts of the world do not use cold water storage tanks but heat water at pressures close to that of the incoming mains water supply.

Instantaneous water heaters

Stand-alone appliances for instantaneously heating water for DHW (Domestic Hot Water) are known in North America as tankless heaters, elsewhere as multipoint heaters, geysers or Ascots. In Australia and New Zealand there was a similar wood fired appliance known as the chip heater.

A common arrangement where hot-water space heating is employed is for the boiler to also heat potable water giving a continuous supply of DHW without any extra equipment required. Appliances capable of supplying both space-heating and DHW are known as combination (or "combi") boilers.

Read more at Wikipedia.org