Boiler Further Information

Background 

The Seasonal Efficiency of Domestic Boilers in the UK (SEDBUK) calculation procedure was developed under the UK Government's Energy Efficiency Best Practice Programme with the co-operation of boiler manufacturers, and provides a basis for fair comparison of the energy performance of different boilers. 

The SEDBUK procedure provides an estimate of the average annual efficiency achieved in typical domestic conditions, making reasonable assumptions about pattern of usage, climate, control, and other influences. It is calculated from the results of standard full-load efficiency and part-load efficiency test results and other data, whilst considering factors such as boiler type, ignition arrangement, internal store size, fuel used, and knowledge of the UK climate and typical domestic usage patterns. The procedure is specified in Appendix D of the SAP specification, see: www.bre.co.uk/sap2012. 

SEDBUK was introduced in 1999 and has undergone a number of changes since then, the latest being from SEDBUK(2005) to SEDBUK(2009). Where boiler efficiency is quoted simply as "SEDBUK" it should be assumed this refers to SEDBUK(2005). 

Boilers in the Product Characteristics Database remain marked as current models, even though they have become obsolete, if the manufacturer has not informed the database manager production has ceased. 

Data for obsolete boilers without SEDBUK figures has not been checked to the same high standard. 

For estimating annual fuel costs SEDBUK is a better guide than laboratory test results alone. It can be applied to most gas and oil domestic boilers for which data is available from tests conducted to the relevant European standards. The SEDBUK method is used in SAP. Data for boilers in current production has been provided by boiler manufacturers, who have had an opportunity to check the database entries before publication. Quoted SEDBUK efficiency figures are based on test results submitted by manufacturers and certified by an independent Notified Body (accredited for the testing of boilers to European standards). From October 2010 it is possible for SAP to take into account hot water performance test data for combination boilers. 

Boiler efficiency tests are subject to measurement uncertainty. Consequently small differences in the efficiency values calculated from them are not significant and should not be relied on when comparing boilers. Statistical analysis suggests that if two boilers have SEDBUK values 3 percentage points apart then there is 95% confidence that the boiler with the higher value is more efficient. 

 

Explanations of PCDB data fields held for boilers 

Brand 

Name of brand, as shown on the boiler. 

Original name of manufacturer 

Name of boiler manufacturer, or company responsible for the boiler in the UK, at the time the boiler was manufactured. 

Current name of manufacturer 

Current name of manufacturer, or company responsible for the boiler in the UK, which may not be the same as the original name. 

Model name 

Name of boiler model, as it appears on the boiler casing or leaflet of owners' instructions. For boilers that comply with EN483 this should be "the trade name of the appliance" shown on the data plate, as specified in EN483 8.1.2. If the same boiler is sold under more than one model name then separate entries for each may appear in the database. 

Model qualifier 

Qualifier to model name, if needed in addition to the model name to discriminate between different versions of same model. 

Boiler ID 

Boiler identifier, which, in conjunction with manufacturer's name, is unique for the model. It may be GC (formerly Gas Council) number for a gas boiler or OFTEC Registration number for an oil boiler, or some other unique reference chosen by the manufacturer and marked on the boiler. 

First year of manufacture 

First year of manufacture, if known. 

Final year of manufacture 

Final year of manufacture, or "current" if still in production. If no longer produced but date production ceased is unknown, then "obsolete". 

Fuel 

Fuel type, which will be one of "gas", "LPG", or "oil". If the same boiler may use more than one type of fuel then separate entries for each may appear in the database. 

Mounting position 

Boiler mounting position, which will be one of "unknown", "floor", "wall", "either floor or wall", or "back boiler". Exposure rating, which will be one of "unknown", "indoor only", or "outdoor". 

Main type 

Main boiler type, for the purpose of SAP efficiency calculation. It will be one of "regular" (see SAP 2009 Appendix D (clause D1.3), "combi" (clause D1.6), or "CPSU" (clause D1.13/14). 

Condensing 

Either "non-condensing" or "condensing" (see SAP 2009 Appendix D clause D1.2). 

Flue type 

Flue type, which will be one of "unknown", "open" or "room-sealed". 

Fan assistance 

Whether or not flue is fan assisted. It will be one of "unknown", "no fan", or "fan". 

Boiler power 

Output power (to water) of the boiler in kW. For boilers with SEDBUK efficiency figures this is the rated output as required for the purpose of the Boiler Efficiency Directive (Council of the European Communities Directive 92/42/EEC). If the power was declared only in BTU/hr then it will have been converted using the factor 1 BTU/hr = 0.000293 kW. If the boiler is range rated then both the lower and higher limits of the range will be given. If it is a modulating boiler then the modulating range will be given. 

SAP 2005 seasonal efficiency 

This is used as the annual average efficiency in SAP 2005. For boilers which have been tested for full-load efficiency and part-load efficiency and the results accepted for the database, the SAP 2005 seasonal efficiency will be SEDBUK(2005). For older boilers, where test data is not available, the SAP 2005 seasonal efficiency is a default value based on type, age, and fuel, as found in Table 4b of SAP 2005. 

SAP 2009 annual efficiency 

This is the best available estimate of annual average efficiency when installed in typical domestic conditions in the UK, and it is used in SAP 2009. For boilers which have been tested for full-load efficiency and part-load efficiency and the results accepted for the database, the SAP 2009 annual efficiency will be SEDBUK(2009). For older boilers, where test data is not available, the SAP 2009 annual efficiency is a default value based on type, age, and fuel, as found in Table 4b of SAP 2009. 

Although the SAP 2009 annual efficiency is a reasonable estimate there will always be variations in individual buildings due to local climate, exposure, occupancy patterns, heating controls, insulation, and other factors. The SAP 2009 annual efficiency is used in SAP to determine the SAP winter seasonal efficiency and SAP summer seasonal efficiency. 

SEDBUK (2005) efficiency bands 
In SAP 2009 the efficiency scale, which consisted of 7 bands from A to G, was dropped in lieu of the European Union's Ecodesign regulation (811/2013) coming into force. This regulation introduces similar efficiency bands and will come into force on 26th September 2015. 

SAP 2009 winter seasonal efficiency and SAP 2009 summer seasonal efficiency  

In SAP 2009 the calculation of an annual efficiency value is used as an intermediate step to working out a separate winter seasonal efficiency and summer seasonal efficiency. In the winter season the boiler provides both space and water heating; in the summer it provides water heating only. For combination boilers, hot water performance test data can now be included in the calculation of winter and summer seasonal efficiency, and the database will show whether data has been supplied. 

The summer seasonal efficiency should not be used to compare boilers for their water heating efficiency, as it is worked out by different methods for SAP according to boiler type and whether or not hot water test data has been included in the database. This is because the energy associated with hot water storage and rejected hot water must be treated separately from efficiency so that SAP can calculate any advantageous heat gains from them. A better guide to annual average hot water efficiency is given by the comparative hot water efficiency. 

Full-load efficiency and Part-load efficiency  

This is the efficiency at full- or part-load measured under closely controlled conditions and undertaken in a laboratory in accordance with a European standard test method. Although this provides valuable data to allow other efficiencies to be calculated, the results are not themselves a satisfactory guide to efficiency achieved under installed conditions. Neither can the results be used to compare one boiler with another, as different test conditions are applied according to boiler type and fuel used. Full- and part-load efficiency test results are stored within the database and used in SEDBUK calculations but are not shown on the website. 

Comparative hot water efficiency 

The purpose of the comparative hot water efficiency parameter is to present a fair comparison between the water heating performance of boilers of different types (both regular and combination boilers). For an explanation of the calculation procedure see Appendix D of SAP 2012 at: www.bre.co.uk/sap2012. The comparative hot water efficiency is not needed for SAP calculations, and is not the same as the result from the European test standard (EN13203) for measuring the water heating performance of gas combination boilers. If hot water performance is of particular concern then the comparative hot water efficiency can be used as a guide to annual average hot water efficiency (the SAP summer seasonal efficiency should not be used for that purpose). 

Efficiency category 

Category of SAP efficiency, which will be one of "SEDBUK", "SAP default" (meaning taken from SAP Table 4b), or "estimated" (for obsolete boilers only). 

SAP equation used 

The number of the SEDBUK equation used to calculate SAP efficiency, as defined in SAP 2009 Appendix D Tables D2.4 and D2.5. Number 0 indicates that no SEDBUK calculation has been performed. The equation number must be consistent with boiler type and other properties (whether gas/oil, instantaneous/storage/CPSU, and on-off/modulating). 

Ignition 

Whether or not has a permanent pilot light. 

Burner control 

Whether on-off or variable (variable may be either stepped or modulating). 

Electrical power while boiler is firing 

Average electrical power consumed while the boiler is firing, in watts. This includes fans, motors, heaters, and other electrical equipment but excludes any pump used to circulate water outside the boiler. 

Electrical power while boiler is not firing 

Average electrical power consumed while the boiler is not firing, in watts. This includes fans, motors, heaters, and other electrical equipment but excludes any pump used to circulate water outside the boiler. 

Store type 

For a storage combination boiler this will be "primary" or "secondary" according to whether the internal hot water store contains mainly primary water (heated directly by the boiler) or secondary water (heated indirectly for domestic hot water supply). It applies only to storage combination boilers and CPSUs. 

Store loss in test 

This will be "excluded" or "included" according to whether heat loss from the internal hot water store has been excluded or included in the efficiency tests carried out. It applies only to storage combination boilers and CPSUs. 

Store volume 

The total water volume (primary and secondary) of the internal hot water store in litres. It applies only to storage combination boilers and CPSUs. 

Store insulation thickness 

The thickness of the insulation applied to the internal hot water store, in mm. It applies only to storage combination boilers and CPSUs. 

Store insulation type 

The material used to insulate the internal hot water store, which will be one of "mineral wool", "polyurethane foam", or "fibreglass". It applies only to storage combination boilers and CPSUs. 

Store temperature 

The average temperature of the hot water in contact with the exterior walls of the internal hot water store in degrees Celsius. It applies only to storage combination boilers and CPSUs. 

Store heat loss 

The measured heat loss from the internal hot water store in watts. It applies only to storage combination boilers and CPSUs.