Central Heating Systems

A variety of different heating systems have been used over the years to heat homes in the UK, but by far the most common type in use today is central heating.

Over half the money spent on energy bills in a typical household is on heating and hot water; and in the face of rising gas and electricity prices, it is important to have the most efficient and cost-effective system as possible.

Domestic Central Heating Radiator!!

What is central heating?

A central heating system consists of a single boiler to heat water, and a network of pipes that carry it around the house to radiators which heat each room.

A coil of pipe may also pass through a hot water cylinder to ‘indirectly’ heat the water for domestic use.

The water travels around the circuit of pipes in a sealed loop, and is returned to the boiler to be re-heated.

A combination boiler runs the central heating in the same way, but supplies hot water by heating it on demand, rather than by heating a storage cylinder.

Central heating is usually controlled by a single thermostat, which will call for heat as and when necessary to maintain a preset temperature. The controls are linked to a timer, allowing you to programme the times of the day when the heating is on or off; and you can also use thermostatic radiator valves, which allow you to set different temperatures in different rooms.

Gas

Gas boilers are most popular for central heating systems, as gas is usually the cheapest fuel, and apart from wood, emits the least carbon dioxide. From 2005 onwards, the vast majority of boilers installed in the UK have been energy efficient condensing boilers.

These have larger heat exchangers and are able to draw more heat from the burning of the gas, which makes them more efficient.

If you are unsure which type of boiler you have, you can check the flue. If you have a plastic flue then you have a condensing boiler; a metal flue would be a sign that your boiler isn’t a condenser.

Equally, if there is a plastic pipe from the bottom of the boiler which goes through the wall and out to drain, you most likely have a condensing boiler. Again, if it was installed after 2005 then the chances are that it is a condensing boiler.

Oil

Oil central heating systems have an external storage tank for the oil, which is pumped to a boiler where it is burned to heat the water. Oil heating is generally more costly than gas and produces more carbon emissions, but can provide a good alternative for homes not connected to a mains gas supply.

Building regulations have dictated that condensing boilers must be installed with oil-fired systems since 2007, while combination boilers are also available for use with oil.

Most oil central heating systems in the UK use 28sec oil (kerosene), which can also be used in kitchen ranges. There is some development in bio-oils produced from vegetable oils in a similar way to bio-diesel, which may provide a greener alternative, but the fuel is not yet readily available in the UK.

The installation, servicing and repair of oil central heating systems does not require any specific training or qualifications, but it is sensible to use installers or contractors who are registered to Oftec (the oil fired technical association).

Wood-fuelled central heating systems burn logs, chips, or wood pellets.

Wood-Fuelled heating systems

Also known as biomass systems, wood-fuelled systems burn logs, chips, or wood pellets to provide central heating and hot water heating.

Wood prices can vary greatly, but in general wood is cheaper than most other types of fuel.

Also if you are installing a system, you might also benefit from financial aid through government funded schemes, the Renewable Heat Incentive and the Renewable Heat Premium Payment.
This is the most environmentally friendly form of central heating, as the carbon emitted from the burning of the wood is equal to the amount absorbed during its lifetime. If new trees are planted in place of those used for fuel, then the whole cycle is sustainable.

Electric

When electricity is used for heating it is usually in the form of storage heaters, which are typically very expensive to run. However, it is also possible to use an electric boiler to power a central heating system.

These boilers use up to 11KW of power to heat the water, and can be linked to conventional radiators and thermostatic valves. With no flue these types of boilers are very efficient, but are more suited to smaller properties; larger houses may require multiple boilers.

Using underfloor heating as part of the central heating system
Wet underfloor heating is often linked to the central heating system, to utilise the hot water from the condensing boiler. Underfloor heating is a much more energy efficient form of heating, and will lower energy bills when used as part of a central heating system.

Heating with renewable energy

Central heating systems can also be used in conjunction with renewable energy systems to further reduce heating bills. Hot water cylinders are now available with twin coils, one for the circulation of water heated by the boiler, and one for water heated by solar panels.

When there is enough heat from the solar panels, your domestic hot water is heated by solar power; if there is not enough heat from the sun, the boiler is used to heat the cylinder.

It is also possible to link low-temperature central heating systems with a ground source heat pump. A network of pipes carrying water and anti-freeze is circulated in the ground outside the property to draw heat from the earth, which is then passed through a heat exchanger to the central heating circuit.

However, due to the relatively low temperatures provided by ground source heat pumps, they are more often linked to underfloor heating than central heating.

Summary

Understanding which system you have will help you to establish what you can do to improve it and make your home more efficient. With over half of your energy bill paying for central and hot water heating, it is essential to have a cost-effective system.