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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.

Contents

History

Water heating

Sealed water-circulating system

Electric and gas-fired heaters

Hydronic and steam systems

Environmental aspects

Popularity

See also

External links

References

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.
Angier March Perkins developed and installed some of the earliest steam-heating systems in the 1830s. The first was installed in the home of Governor of the Bank of England John Horley Palmer so that he could grow grapes in England's temperate climate.^[2]

Water heating

Main articles: 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.

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.

Electric and gas-fired heaters

Electric heating or resistance heating converts electricity directly to heat. Electric heat is often more expensive than heat produced by combustion appliances like natural gas, propane, and oil. Electric resistance heat can be provided by baseboard heaters, space heaters, radiant heaters, furnaces, wall heaters, or thermal storage systems.
Electric heaters are usually part of a fan coil which is part of a central air conditioner. They circulate heat by blowing air across the heating element which is supplied to the furnace through return air ducts. Blowers in electric furnaces move air over one to five resistance coils or elements which are usually rated at five kilowatts. The heating elements activate one at a time to avoid overloading the electrical system. Overheating is prevented by a safety switch called a limit controller or limit switch. This limit controller may shut the furnace off if the blower fails or if something is blocking the air flow. The heated air is then sent back through the home through supply ducts.
In larger commercial applications, central heating is provided through an air handler which incorporates similar components as a furnace but on a larger scale.

Hydronic and steam systems

Hydronic heating systems are systems that circulate a medium for heating. Hydronic radiant floor heating systems use a boiler to heat up hot water and a pump to circulate the hot water in plastic pipes installed in a concrete slab. The pipes, embedded in the floor, carry heated water that conducts warmth to the surface of the floor where it broadcasts energy to the room.
Hydronic systems circulate hot water for heating. Steam heating systems are similar to heating water systems, except steam is used as the heating medium instead of water.
Hydronic heating systems generally consist of a boiler, hot water circulating pumps, distribution piping, and a fan coil unit or a radiator located in the room or space. Steam heating systems are similar except no circulating pumps are required.
Hydronic systems are closed loop: the same fluid is heated and then reheated. Hydronic heating systems are also used with antifreeze solutions in ice and snow melt systems for walkways, parking lots and streets. They are more commonly used in commercial and whole house radiant floor heat projects, while electric radiant heat systems are more commonly used in smaller "spot warming" applications.

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.

Popularity

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

See also

★ Energy conservation

★ HVAC

★ Renewable energy

★ Underfloor heating

★ Wind energy

★ Geothermal Systems

★ Solar combisystem

External links

★ HVAC Directory.

★ Emmanuelle Gallo site dedicated to heating history

★ Electric and Gas fired Heaters

★ Gas and Oil Boilers
High Performance HVACHVAC site with central heating articles

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

2. McConnell, A. (2004) "Perkins, Angier March (1799–1881)", ''Oxford Dictionary of National Biography'', Oxford University Press, accessed 14 Aug 2007 (subscription required)