Central heating

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For the Grand Central Records albums, see Central Heating (Grand Central album) and Central Heating 2.

A central-heating system provides warmth to the whole interior of a building (or portion of a building) from one point to multiple rooms.

When combined with other systems in order to control the building climate, the whole system may comprise a HVAC (Heating, Ventilation and Air-Conditioning).

Central heating differs from local heating in that the heat generation occurs in one place, such as a furnace room in a house or a mechanical room in a large building (though not necessarily at the "central" geometric point). The most common method of heat-generation involves the combustion of fossil fuel in a furnace or boiler. The resultant heat then gets distributed: typically by forced air through ductwork, by water circulating through pipes, or by steam fed through pipes. Increasingly, buildings utilize solar-powered heat sources, in which case the distribution-system normally uses water-circulation.

In the UK, in much of northern Europe and in urban portions of Russia, where people seldom require air-conditioning in homes due to the temperate climate, most new housing comes with central heating installed. Such areas normally use gas-fired heating, or — where no ready supply of gas exists — oil-fired systems. In the western and southern United States natural-gas-fired central forced-air systems occur most commonly; these systems and central-boiler systems both occur in the far northern regions of the USA. Steam-heating systems, fired by coal, oil or gas, feature in the USA, Russia and Europe: primarily for larger buildings. Electrical heating systems, far less energy-efficient, occur less commonly[citation needed].

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[edit] History

Cities in the northern Roman empire used central heating systems circa 100AD, conducting air heated by furnaces through empty spaces under the floors and out of pipes in the walls — the system known as a hypocaust. The Cistercian monks revived central heating using river-diversions combined with indoor wood-fired furnaces. The well-preserved Royal Monastery of Our Lady of the Wheel (founded 1202) on the Ebro River in the Aragon region of Spain provides an excellent example of such an application.

By about 1700 Russian engineers had started designing hydrologically-based systems for central heating. The Summer Palace (1710 - 1714) of Peter the Great in Saint Petersburg provides the best extant example. Slightly later, in the year 1716, came the first use of water in Sweden to distribute heat in buildings. Martin Triewald, a Swedish engineer, used this method for a greenhouse at Newcastle upon Tyne. Jean Simon Bonnemain (1743-1830), a French architect, [1] introduced the technique to industry on a cooperative, at Château du Pêcq, near Paris.

[edit] Water heating

Main article: Water heating

Common components of a central-heating system using water-circulation include:

  • Gas supply lines (sometimes including a propane tank) or oil tank and supply lines
  • Boiler — heats water in a closed-water system
  • Pump — circulates the water in the closed system
  • Radiators — wall-mounted panels through which the heated water passes in order to release heat into rooms

Engineers in the United Kingdom and in other parts of Europe commonly combine the needs of room heating with hot-water heating and storage. These systems occur less commonly in the USA. In this case, the heated water in a sealed system flows through a heat exchanger in a hot-water tank or hot-water cylinder where it heats water from the normal water supply before that water gets fed to hot-water outlets in the house. These outlets may service hot-water taps or appliances such as washing machines or dishwashers.

[edit] Sealed water-circulating system

A sealed system provides a form of central heating in which the water used for heating usually circulates independently of the building's normal water-supply. A pressure vessel contains compressed gas, separated from the sealed-system water by a diaphragm. This allows for normal variations of pressure in the system. A safety valve allows water to escape from the system when pressure becomes too high, and a valve can open to replenish water from the normal water supply if the pressure drops too low. Sealed systems offer an alternative to open-vent systems, in which steam can escape from the system, and gets replaced from the building's water supply via a feed and central storage system.

[edit] Environmental aspects

From an energy-efficiency standpoint considerable heat gets lost or goes to waste if only a single room needs heating, since central heating has distribution losses and (in the case of forced-air systems particularly) may heat some unoccupied rooms without need. In such buildings which require isolated heating, one may wish to consider non-central systems such as individual room heaters, fireplaces or other devices. Alternatively, architects can design new buildings to use low-energy building techniques which can virtually eliminate the need for heating, such as those built to the Passive House standard.

However, if a building does need fully heating, water-based combustion central heating offers a more environmentally friendly solution than electric-air central heating or than other direct electric heating devices. This stems from the fact that most electricity originates remotely using fossil fuels, with up to two-thirds of the energy in the fuel lost at the power station and in transmission losses. In Sweden proposals exist to phase out direct electric heating for this reason — see oil phase-out in Sweden.

In contrast, hot-water central-heating systems can use water heated in or close to the building using high-efficiency condensing boilers, biofuels, or district heating. Wet underfloor heating has proven ideal. This offers the option of relatively easy conversion in the future to use developing technologies such as heat pumps and solar combisystems, thereby also providing future-proofing.

[edit] Popularity

Not everyone fully appreciates central heating. Slighty tongue-in-cheek, Amy Clampitt wrote a poem called "On the Disadvantages of Central Heating."

[edit] See also

[edit] External links

[edit] References

  1. ^ Emmanuelle Gallo: "Jean Simon Bonnemain (1743-1830) and the Origins of Hot Water Central Heating" in Proceedings of the Second International Congress on Construction History (2006-06-17), pages 1043-1060; retrieved from http://halshs.archives-ouvertes.fr/halshs-00080479/en/ on 2007-02-05
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