WATER HEATERS | HEAT PUMPS As the heating and hot water sector moves towards electric systems as part of the drive for improved sustainability, specifiers are increasingly looking at heat pump water heaters as the domestic hot water technology of choice. Kamlesh Vadukul, product manager at Ariston, explains Pump up the heat G iven the current drive and investment in renewables as the UK sets on the path to net zero by 2050, electricity has been identified as a cleaner, greener energy source, and heat pumps emphasised as a key driving technology. Manufacturers of water heating products have risen to the challenge by developing ranges of electrically powered heat pump-based domestic hot water (DHW) heating products for use in large residential and lightcommercial applications. The benefits of using heat pump water heaters for DHW only Heat pump water heaters are designed specifically for the production and storage of hot water, and are typically capable of operating at air temperatures as low as -10C or lower when a built-in electrical immersion heater is used. DHW storage requires a minimum of 55C; however, future building space-heating systems will require temperatures less than 55C and underfloor heating, for example, may only require 35C. So, keeping the hot water separate from heating ensures that both systems operate effectively. Heat pump water heaters are An example of a 200-litre heat pump water heater (Source: Ariston) particularly suitable for retrofit applications where additional DHW is required, or where conversion to a full heat pump system is not possible (for example, if upgrading the space-heating system is not practical or financially viable). Applications Heat pump water heaters can be sited in areas such as utility rooms, garages, outbuildings and cupboards in a variety of light-commercial applications including leisure centres, gyms, cafes, coffee shops and retail outlets as well as in residential apartment blocks. Combining an air source heat pump unit with an unvented DHW cylinder, such as the 200-litre unit shown above, can deliver hot water at a coefficient of performance (COP) of 3.1 (tested to EN 16147 at an outdoor air temperature of 7C, relative humidity of 87%, inlet water temperature of 10C and hot water temperature set at 55C). The manufacturers modelling* predicts that this can reduce energy consumption by up to 80% when compared with traditional electric storage water heaters. This example unit can deliver DHW temperatures of up to 62C with a full recovery time of less than four hours from the heat pump alone, producing sound power levels as low as 51dBA. Higher temperatures and speedier recovery rates are available if boosted via the direct electric immersion heater. Operational costs will depend on the mode of use many early, general heat pump installations suffered from unexpectedly high use of costly direct electric heater top-up 52 May 2022 www.cibsejournal.com CIBSE May 22 pp52-53 Ariston v2 Supp.indd 52 22/04/2022 15:45