Gas central heating is the most common type of heating system in use in the UK today. Gas is generally one of the cheaper fuels and emits less carbon dioxide than most other fuels; with the exception of wood.
Gas boilers have improved greatly in efficiency in recent years and since 2005 most boilers fitted in the UK have been energy efficient condensing boilers.
Gas can be used to provide heat for the central heating system and the domestic hot water system, and can be used in conjunction with renewable energy systems such as solar power, underfloor heating and ground source heat pumps.
How does gas central heating work?
A single boiler burns gas and the heat is passed through a heat exchanger to heat the water for the central heating. The hot water is pumped through a network of pipes around the house to heat the radiators. The water is often circulated through a coil in a hot water cylinder as well, to heat water for domestic use. The pipes then return the water to the boiler to be reheated and redistributed.
An open vented system uses an expansion tank, which will usually be located in the loft, to cope with any water expansion and to provide an overflow in case of a fault. A sealed system uses an expansion tank to take up the expansion of the water as it heats and will have a relief valve that discharges to drain in the event of a problem.
The heating system is controlled by a single room thermostat which is often located in the hallway, although more modern systems may have the thermostat installed in a living room.
The system is also linked to a seven day timer, to enable you to programme the heating to be on at different times throughout the week. Thermostatic radiator valves can be incorporated into the system to give you more control over individual rooms, allowing you to set differing temperatures in each room.
The different types of boiler
Since 2007 building regulations have demanded that any gas boiler fitted in England and Wales should be a condensing boiler. These are highly efficient boilers which have larger or extra heat exchangers to extract much more heat from the burning gas.
During the combustion process water vapour is condensed, which provides additional heat, but this also means that the water must be piped out to a drain. If you have a plastic flue or there is a plastic pipe from the bottom of your boiler going out to drain, then you probably already have a condensing boiler. If not, it is worth considering upgrading your boiler to make your home much more energy efficient.
Combination or ‘combi’ boilers provide heat for central heating and domestic hot water; but rather than heating a large water cylinder, they can heat water on demand. The radiators are heated in exactly the same way, and combination boilers tend to be more efficient.
A great advantage of the combi boiler is that it frees up the space taken up by the hot water cylinder. Although a condensing boiler uses less energy to heat the water initially, heat loss from the cylinder means that a combi boiler is likely to be more efficient overall.
Gas central heating installation cost
It is very difficult to estimate the cost of installing a gas central heating system, as it will depend on a number of variables; the size of the house, the type of boiler to be installed, and the amount of extra work, such as installing storage tanks, will all have an effect on the cost.
Combination boilers tend to be the cheapest to install as they don’t require hot water cylinders or tanks in the loft. Installation would cost approximately £1,500 – £3,000 for a one to three bedroom house. A condensing boiler typically involves a more complex installation and more labour, and would cost in the region of £2,500 – £5,000.
Selecting the right size boiler
In the past, heating engineers had a tendency to oversize boilers so that they could always comfortably meet the demand for heat. This means that the boiler runs at part load, and does not operate at maximum efficiency. In fact, if you have recently upgraded the insulation in your home it is quite possible that you boiler is now oversized. The output of older boilers was measure in Btu/h (British thermal units per hour), but more modern boilers are rated in terms of Kilowatt output. It is advisable to select a boiler which carries the Energy Saving Trust kitemark, as this is reserved for ‘A’ rated boilers which consume less than 10 watts of electricity when in standby mode.
It is a legal requirement that the installation, service, or repair of a gas boiler is undertaken by a Gas Safe registered technician. The Gas Safe Scheme replaced the CORGI registration scheme in 2009, and the Gas Safe register holds details of all listed companies, which can be viewed and checked online. Your installer should be perfectly happy to provide you with details of their registration, and show you their certification. Always check the register to ensure their details are valid and up to date.
Gas central heating is the most common type of central heating used in the UK; if you have a connection to a mains gas supply it is the most energy efficient and environmentally friendly type of fuel you can use apart from wood.
It is possible to link a gas central heating system to renewable energy sources such as solar panels, which will make your overall heating system more efficient and help to reduce energy bills.
Gas can power condensing boilers or combination boilers; both will provide energy efficient heating and hot water. Although both could cost several thousand pounds to install, an efficient central heating system will save money on heating bills, reduce your carbon emissions, and make your home warmer and more comfortable.