The following hierarchy should be followed to establish suitable values for the ‘Effective Heat GeneratingSeasonal Efficiency’ for all boilers.
1. Use Enhanced Capital Allowance (ECA) product list part load values at 30% and 100%* - theseshould be used to calculate the seasonal efficiency as per the Non Domestic Building ServicesCompliance Guide (NDBSCG).
2. Use ECA product list full load value* (when part load values are not given).
3. Use current PCDB values where available.
4. Use either manufacturer’s information* or ‘boiler plate*’ information or information frommanufacturer’s technical helpdesk*. Where a gross efficiency value is established for a noncondensing boiler then a deduction of 0.05 (i.e. 5%) should be made to it to convert it to anappropriate seasonal efficiency.
5. Use SAP 2005 tables (up to 70kW output).
6. Use suitable SBEM default; it is essential for the site notes to provide evidence as to why the abovemethods were not used to obtain a more accurate value, i.e. by providing evidence of failedattempts.
In addition to any boiler efficiency values established from the above the relevant heating credits should beadded by following the guidance in the NDBSCG.
*Net efficiencies/values must be converted to gross efficiencies as per the NDBSCG.
Mike Gordon
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