The presence of storage/losses MUST be entered for all storage systems and this should be done wherepossible by entering the losses (in MJ/month) in preference to the volume and insulation type and thickness.The source information (such as manufacturer’s data) and/or calculation must be included in site notes.
Where losses cannot be established then the volume and insulation details should be entered.
• Where the volume and/or insulation cannot be established via external visual inspection and/orpaperwork they should be estimated as follows:
o For a modern steel or plastic encased unvented pressurised hot-water cylinder larger than 50litres (e.g. Megaflo), enter insulation as 50 mm factory insulated and calculate the volume basedon external dimensions less 50mm of insulation.
o For a modern steel or plastic encased unvented pressurised hot-water cylinder up to 50 litres, orelectric multipoint, enter insulation as 25 mm factory insulated and calculate the volume basedon external dimensions less 25mm of insulation.
o For a modern steel or plastic encased point of use water heater (typically over/under sink up to10 litres) enter insulation as 10 mm factory insulated and calculate volumes based on externaldimensions less 10mm of insulation.
o For other types of HWS storage the external dimensions of the unit will be used as if the storagevessel completely fills the unit with no deduction for insulation thickness and where the insulationtype cannot be established via survey and/or paperwork it should be assumed to be uninsulated.
• Where details of the HWS are unavailable or there is no system then the HWS shall be entered as an‘instantaneous system’ with no storage with a seasonal efficiency of 0.5 (i.e. 50%). Where the fuel typecan be readily determined then the appropriate fuel type must be entered otherwise ‘grid electric’ shouldbe assumed.
• Where the DHW serves multiple buildings, the losses should be apportioned between those buildingsbased on floor area.
o If the losses are not known so volume and insulation details are being used the volume cannotbe apportioned between the buildings. The assessor should initially run the SBEM calculationallocating all of the storage to the building being assessed and look up the Calculated SBEMvalue for Storage losses. This figure should then be apportioned between the buildings based onfloor area and entered as the Storage losses MJ/month.
Mike Gordon
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