Central heating

Central heating is a method of providing warmth to multiple spaces within a building from a single, primary heat source. Unlike space heating, which relies on individual units like fireplaces, central heating generates heat in one specific location. This location is often a basement, a furnace room, or a mechanical room. The system provides much more uniform temperature control throughout a building than separate stoves or fireplaces. It also offers greater convenience through automatic fuel handling and temperature controls.

The mechanism of central heating depends on how the heat is distributed. In a forced-air system, a furnace burns fuel to heat air inside a heat exchanger. Blower fans then force this warmed air through a network of ducts to various rooms. In steam systems, a central boiler generates high-pressure steam. This steam travels through pipes to reach different parts of the building.

A third method uses pumps to circulate hot water through pipes to room radiators. While air systems are often cheaper because ducts are easier to install than pipes, water and steam systems are also very effective.

Different types of heating systems are defined by their energy sources and distribution methods. Primary energy sources include fossil fuels such as coal, oil, kerosene, and natural gas. Electricity is also used, though electric resistance heating is often less efficient than using fossil fuels directly. Some modern buildings utilize central solar heating, which typically uses water circulation for distribution. Other advanced setups use district heating. This system uses waste heat from an industrial process or an electrical generating plant to heat neighboring buildings through underground piping.

Humans have developed various ways to heat living spaces for millennia. In ancient Korea, the ondol system used a firebox called an agungi to heat stone floors. The smoke traveled through horizontal passages under a raised masonry floor to provide warmth for sitting and sleeping.

The ancient Greeks also used flues to circulate heat from fires in temples. The Roman Empire later refined this with the hypocaust. This system conducted heated air from furnaces through empty spaces under floors and through wall pipes called caliducts.

Modern heating technologies saw significant breakthroughs between the late 18th and mid-19th centuries. In 1793, William Strutt designed a mill using a central hot air furnace with large underground passages. Later, in 1807, Charles Sylvester helped apply similar systems to hospitals, allowing patients to breathe fresh, heated air. The steam method was advanced by the Scottish inventor James Watt, who built a working system in his own home.

In Russia, the Summer Palace of Peter the Great used an early hydrologic system from 1710 to 1714.

Significant technical improvements made modern hot water systems viable. In the 1830s, Angier March Perkins developed an apparatus that distributed water at 200 degrees Celsius. This required high pressure and the invention of the thread screwed joint. This joint allowed the connection between pipes to withstand the same pressure as the pipes themselves. These innovations allowed for smaller diameter pipes, making the technology much more practical for widespread use.

Central heating connects to many broader fields of engineering and environmental science. The development of the system has shifted from burning coal to using cleaner fuels like natural gas to avoid ash removal. It also connects to modern climate control, as systems with ducts can often include central air conditioning. Today, the field continues to evolve with technologies like ground source heat pumps. These systems use electricity to move heat, representing a different approach to managing building temperatures efficiently.