HEAT PUMPS | CIBSE AM17 GUIDANCE Selecting a suitable and future-proofed refrigerant is key to the long-term success of new heat pump systems and the integrated capacity, which includes an allowance for defrost cycles. The test regime for determining the integrated capacity of a heat pump is set out in EN 14511-3:2018. Selecting a unit based on an integrated capacity means that the system has extra capacity for the unit to supply additional heating to recharge the system after a defrost cycle. Simultaneous and independent heat pumps (SIHPs) represent some of the most sophisticated units available on the market. These can generate chilled water and lowtemperature hot water separately or at the same time. SIHPs are suited to applications with balanced and simultaneous heating and cooling loads. These units are, however, more costly than alternatives such as reversible heat pumps or heat recovery chillers. Many projects undertake an annual demand simulation to determine the true simultaneous heating and cooling load, and use this information to balance the quantity of SIHPs with other sources of heating and cooling. The integration or retrofit of heat pumps into our new and existing buildings has the potential to impact most aspects of the design, from MEP systems, space allowances, faade design and plantreplacement strategy. AM17 also offers guidance on some of the less obvious impacts of installing heat pumps in large buildings (see panel, Impacts of heat pumps). Engineers eagerly awaiting guidance on this important topic will not have long to wait. AM17 will be freely available this summer from CIBSE at www.cibse.org/ knowledge. CJ Figure 2: Considerations when installing heat pumps 1 Noise from equipment close to sensitive receptors 2 Visibility of plant 3 Different construction costs of plant areas 4 Impacts of vibration particularly important in hotels/mixed-use developments with residential use 5 Enclosure and acoustic considerations will differ for ground-level plant compared with roof installations LEARNING FROM PAST INSTALLATIONS AM17 contains several case studies of existing air and ground source heat pump installations, which offer real-world insights into specific elements of designing and operating large heat pump systems. These include: Using annual building-load analysis to optimise your heat pump sizing System monitoring Sizing a cascade heat pump system Temperature stability using thermal stores Minimum turndown of heat pumps JOSHUA BIRD is a lead building services engineer at Arup References: 1 Heat and Buildings Strategy, BEIS, Oct 2011, bit.ly/CJMay22AM17A 1 Phasing out the installation of fossil fuel heating systems in businesses and public buildings off the gas grid, BEIS, Oct 2011, bit.ly/CJMay22AM17B Heat pumps were retrofitted at Arups 80 Charlotte Street office 44 May 2022 www.cibsejournal.com CIBSE May 22 pp42-44 AM17 Supp.indd 44 22/04/2022 15:29