Low Energy House

About Boilers - What Are Condensing Boilers?

If you are planning to install or replace a heating boiler you should choose a condensing boiler. This is a requirement of Part L1 of the Building Regulations that relate to the conservation of heat and power

Condenser Boiler - Image Provided by VaillantAbout Boilers - Central Heating Boilers

There are two main types of central heating boiler:

  • Central heating boilers that provide hot water via a separate storage cylinder and are generally used in larger houses.
  • Combination boilers that provide instant hot water at mains pressure are generally used in small houses and flats because they do not take up as much space. Combination boilers heat water that is supplied directly from the water main, as and when it is required. Consequently, a cold water storage tank and hot water cylinder are not required.

Installing a Condensing Boiler

All gas and oil fired boilers installed must be condensing boilers, whether they are replacements or new installations.

Condensing boilers are more efficient than ordinary boilers as they:

  • Produce less carbon dioxide, while still meeting heating needs
  • Reduce the amount of heat that is lost through the flue, compared with ordinary boilers
  • Convert more of the fuel they use into useful heat
The new standards apply only if you decide to change your existing hot water central heating boiler or if you decide to change to a condensing boiler from another form of heating system.

About Boilers - Condensing Boilers

The term condensing is derived from the creation of condensation within the heat exchanger or flue. A condensing boiler releases a characteristic ‘plume’ of water vapour from the flue which indicates that it is operating efficiently. The condensate produced is taken to a drain or soakaway through a pipe fitted by the installer.

About Boilers - High Efficiency Condensing Boilers

High efficiency condensing boilers can easily be fitted to most new and existing central heating systems. They convert more than 90 per cent of their fuel into heat, compared with 60 per cent for some conventional boilers. The efficiency of condensing boilers is high even when working at a low level of output, such as for hot water only, in summer.

Condenser Boiler - Image Provided by VaillantSEDBUK Rating for Condensing Boilers

The SEDBUK rating is an average annual efficiency achieved in typical domestic situations. The rating is calculated from laboratory tests together with other important factors such as boiler type, fuel use, ignition type, UK climate, boiler water content and typical domestic usage patterns.

SEDBUK - Condensing Boilers

SEDBUK is an acronym for ‘seasonal efficiency of a domestic boiler in the UK’. The system was developed under the UK government’s energy efficient best practice programme with the co-operation of boiler manufacturers and provides a basis for fair comparison of different models of boiler.

Condensing Boilers Energy Rating

When choosing a new boiler the first thing to look for is the energy rating. Like most new appliances, boilers all carry a label rating them in bands from A to G according to their energy efficiency. 'A' rating is the most efficient as it can convert over 90 per cent of the energy into heat.

About Boilers - Gas Safe Register for Installers of Gas Condensing Boilers

For gas fired boilers, the installer you employ must be on the Gas Safe Register as a safety and legal requirement and they should also be capable of installing condensing boilers.

About Boilers - Oil Condensing Boilers

For oil fired boilers, you can employ an Oil Firing Technical Association (OFTEC) registered installer or some other reputable installer who is capable of installing condensing boilers. OFTEC members are approved to certify that their work meets building regulations. If you employ an installer who is not registered with OFTEC, you will need to tell your local authority building control department before installation work starts.

In all cases, check that your installer has recent qualifications in energy efficiency. Gas Safe Register or OFTEC can confirm this. If the installation is for an oil fired boiler, an alternative would be to ask your installer if they hold a Certificate in Energy Efficiency for Domestic Heating or an equivalent qualification

About Boilers - Eco-Boilers - Condensing Boilers