The minimum appliance efficiencies quoted are measured at normal rated output and except for pellet burning appliances are on a Gross CV basis. They are not seasonal efficiencies. The majority of appliances listed in the HETAS Guide have efficiencies well above these minimum, pass mark, values. There is, however, evidence to show that with solid fuel appliances efficiency does not fall off greatly as the output of the appliance reduces. Additional useful heat, which is not included in these minimum values, can be available from the chimney and fireplace particularly if the chimney is centrally placed and enclosed in the building structure.
Testing has, until recently, been carried out to British Standards (BSs) using an appropriate standard test fuel. It is against these earlier BSs that most of the appliances listed in this Guide have been tested. After 1st January 2003 Type Testing is now carried out to the relevant BS ENs.
These new European Standards now adopted as British Standards are as follows:-
Independent boilers BS EN 12809; Cookers BS EN 12815;
Roomheaters BS EN 13240; Open Fires BS EN 13229.
The standard test fuels used are representative of those DEFRA Authorised Fuels which can be used in Smoke Control Areas (SCAs).
Bituminous Housecoal, Wood Logs and Wood Pellets are not permitted to be used in SCAs unless they are burned in specially designed, smoke reducing, DEFRA Exempted Appliances.
The minimum efficiency pass values that are listed are under review with the intent of raising them further.
Click here for information on heating appliance minimum efficiency levels
Historic “Heating Appliance Gross Efficiency at Nominal Output”
Government, implementing the Energy Performance of Buildings Directive in its initiative to reduce carbon emissions, brought into force in April 2006 a revision to Buiding Regulations requiring all replacement solid fuel heating appliances to have a Gross Efficiency not less than 2 percentage points less than the appliance it replaces.
The following mostly historic appliances and their Gross Efficiencies as Approved by HETAS following testing to the then operative British Standards are listed via the link below. These figures are made available to assist householders, specifiers and installers to comply with this regulation.
Click here for information on historic heating appliance gross efficiency levels
