9.1 Scope of guidance
This section provides guidance on the specification of heat pump systems in dwellings for the provision of space heating and domestic hot water to meet relevant energy efficiency requirements in the Building Regulations. A heat pump is a device which takes heat energy from a low temperature source and upgrades it to a higher temperature at which it can be usefully employed for heating or hot water. Heat pumps may supply all or part of the heating load. The guidance in this section applies to the types of electrically-driven heat pump in Table 35 used as the heat generator in underfloor, warm air and medium temperature radiator heating systems, etc. ****Table 35 Heat pump technologies****
9.2 Key terms
Coefficient of performance (COP) is a measure of the efficiency of a heat pump at specified source and sink temperatures, but may not accurately represent installed performance: Heating COPheat output / power input % COP (COP100) is the heat generator efficiency. COP is measured in accordance with the procedures in BS EN 14511:2013, Air conditioners, liquid chilling packages and heat pumps with electrically driven compressors for space heating and cooling. Seasonal coefficient of performance (SCOP) is the overall coefficient of performance of the heat pump over the designated heating season. It makes general assumptions about the amount of auxiliary heating needed to top up the space and water heating available from the heat pump. SCOP is measured in accordance with the procedures in BS EN 14825:2013, Air conditioners, liquid chilling packages and heat pumps with electrically driven compressors for space heating and cooling. Testing and rating at part load conditions and calculation of seasonal performance. The National Calculation Methodology for calculating carbon dioxide emission rates from buildings uses SCOP. Seasonal performance factor (SPF) is another measure of the operating performance of an electric heat pump over the season. It is the ratio of the heat delivered to the total electrical energy supplied over the season, but there are up to seven different ways to draw the system boundaries. For example, SPFH2 (which is SCOP) excludes auxiliary resistance heating whereas SPFH4 includes it – making a large difference. SAP 2012 calculations use SPF – either measured values for products listed in the Product Characteristics Database, or the default values in Table 4a for products not listed there. The Microgeneration Certification Scheme installation standard, MIS 3005, uses SPF to calculate system performance (although the heat pump product standard, MCS 007, currently specifies a minimum COP). Seasonal primary energy efficiency ratio (SPEER) is an emerging rating figure reflecting the use of primary energy for all types of heat pump, fossil fuel boiler and gas-driven cogeneration technologies, as well as hybrid systems where solar heating or a heat pump is backed up with electric heating or a fossil fuel boiler. Energy labelling with the SPEER will be mandatory from 2015 under the Energy Labelling Directive. Testing and rating will be in accordance with BS EN 14825, as for SCOP.
9.3 Warm water and hot water heat pumps
At the time of preparation of this guide, European Commission Regulation No 206/2012 sets standards for the SCOP of electrically-driven air-to-air heat pumps with an output 12 kW. There are currently no European test standards for part-load testing of air-to-air heat pumps with an output 12 kW or for other types of heat pump, and the performance of these must be specified using COP obtained at the heating system rating conditions. The current recommendations in this guide are that electrically-driven heat pumps should: a. if air-to-air with an output 12 kW, have at least a SCOP ‘D’ rating for the median temperature range in BS EN 14825 b. or else have a COP which is not less than: i. 2.5 for space heating in new dwellings ii. 2.2 for space heating in existing dwellings iii. 2.0 for heating domestic hot water c. meet the minimum standards for supply temperature, wet system radiator efficiency, installation and commissioning, hot water and controls in Table 36 for warm water and hot water heat pumps d. meet the minimum standards for installation and controls in Table 37 for warm air heat pumps. ****Table 36 Recommended minimum standards for warm water and hot water heat pumps (ground-to-water, water-to-water and air-to-water **** ****Table 37 Recommended minimum standards for warm air heat pumps (ground-to-air, water-to-air and air-to-air systems)**** ****Supplementary information****