What are Central heating systems?
Your central heating system plays an important role in your home - keeping you supplied with the heat and hot water that make life so much more comfortable. But what systems are available and how do they work?
Central heating is a way of providing warmth in your home from, as the name suggests, one central source. Central heating systems broadly fall into one of the following types:
With a 'wet system' hot water circulates through a system of pipes that connect to the radiators throughout a house. At the center of the system, a boiler burns a fuel - or sometimes there is a 'heat exchanger' and this heats the water that feeds the network of pipes. 'Wet systems' are the most popular form of heating system in the UK.
Radiators, despite their name, do not just give off radiant heat, in fact they deliver most of their heat through convection; air warmed by the radiator naturally rises, and cool air falls relative to it, as a result the warmed air circulates and the 'space' in a room is warmed.
The pipework may also be connected to a hot water cylinder (tank), which will provide a supply of hot water for bathing and washing.
Fuel is used in a boiler
The most common fuel used in boilers is natural gas, followed by heating oil, and occasionally liquid petroleum gas ( LPG). Although rare, some boilers burn coal (usually in the form of coal pellets) or biomass (usually in the form of wood chips). Electric central heating boilers are also available.
New gas (and oil) boilers have to be of around 90% efficiency or higher (an A or B energy efficiency rating) and generally use condensing technology to achieve this. If your boiler is more than fifteen years old, you may want to consider replacing it with a new energy-efficient one.
Combi boiler and a conventional boiler
As well as taking care of your heating needs, combi boilers provide instant hot water. They have the advantage of freeing up space in a home, because there's no need for a hot water cylinder (tank) like there is with a conventional boiler.
In most cases, heating water instantly is more energy-efficient than 'stored' hot water systems. However, the flow of hot water is slower than if it was coming from a cylinder, so a bath will take longer to run. Some combi boilers can in any case also heat water in a cylinder.
Modern boilers generally no longer have tanks in the loft to 'pressurize' the system through gravity. Instead they are sealed systems, and typically only require manual topping up from the mains water supply when the internal pressure has dropped (usually because of tiny leaks).