¶ Gross seasonal efficiency for solid fuel boilers from test data
This appendix specifies how to obtain a gross seasonal efficiency from test data on a solid fuel boiler that is provided in the Home-Heating Appliance Register of Performance (HARP). A HARP database record for a solid fuel boiler includes:
- DEAP gross seasonal efficiency, %
- Fuel input, heat to water and heat to room from test at full load, kW (based on gross calorific values)
- Fuel input, heat to water and heat to room from test at part load, kW (based on gross calorific values)
In the case where HARP data is not available, accredited certified boiler data to IS EN 303-5 can be used. All efficiencies must be based on gross rather than net values. To convert from net to gross efficiency, multiply the net efficiency by the appropriate factor in Table E4. HARP data does not require this conversion as all efficiencies and values on HARP are based on gross calorific values. Do not use HETAS to source efficiencies for boilers or appliances with back boilers in DEAP.
Where test data or HARP data is not available for solid fuel appliances, then default data may be taken from Table 4a.
¶ DEAP gross seasonal efficiency is given
If the overall DEAP gross seasonal efficiency is given in HARP, that value is used for both space and water heating, and the other data is disregarded. If the overall efficiency is available from a test certificate, that may also be used, provided it is converted to gross efficiency as outlined above.
¶ DEAP gross seasonal efficiency is not given
If the DEAP gross seasonal efficiency is not available, the appropriate efficiency for use in the calculations is obtained as follows:
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Part load data is available
The efficiency at full load is obtained from:
(J1)
and the efficiency at part load from:
(J2)
If the boiler is outside the boundary of the dwelling as defined in Section 1, ’Dwelling dimensions‘, the heat to room is omitted from (J1) and (J2). All efficiencies must be gross rather than net values. Fuel inputs must be based on gross calorific values.
The gross seasonal efficiency is then:
Gross seasonal efficiency = 0.5 * (Efull + Epart) (J3)
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Part load data is not available
If the data for the part load test is blank, part load efficiency is taken as 95% of full load efficiency, so that:
Gross seasonal efficiency = 0.975 x Efull (J4)
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Rounding
The seasonal efficiency should be rounded to one decimal place before using it in calculations.
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Heating type and responsiveness
The heating type and responsiveness is that for the applicable type of appliance given in Table 4a.