Modern Building Services

MODERN BUILDING SERVICES FEBRUARY 2023 11 FEATURE VERTICAL FOCUS Electrification and heat pumps The drive towards decarbonisation and electrification of heat (including hot water) means that the favoured approach today will likely be to install heat pumps. There are two types of heat pumps. Some are able to deliver the high flow temperature required to meet the design hot water temperature. The benefit of using high temperature heat pumps is that it avoids the need for an alternative form of technology to store the domestic hot water (DHW) above legionella temperatures (60ºC or higher). However, while this option offers greater design flexibility, it should be noted that the coefficiency of performance of heat pumps falls off at higher temperatures. Another solutionmight be to use lower temperature air source heat pumps with direct-fired electric water heaters. This solution would involvemuch higher volumes of stored domestic hot water certainly compared with high energy, low storage direct gas fired water heaters which the buildingmay previously have relied on. Therefore, it’s important to consider potential issues relating to available space and weight for the larger cylinders particularly when dealing with roof top or non-basement plant rooms. Controlling legionella within the larger volumes of stored water will also need to bemanaged. Multivalent approach While the low carbon credentials of heat pumps are well established, capital expenditure and operating costs may influence the design strategy decision. Given the year-round requirement for hot water in healthcare, a balancing act between carbon reduction and operating costs could be required. On projects where an all-electric solution is not considered suitable, a multivalent approach to hot water generation should not be overlooked. With refurbishment, for example, where the natural gas supply might be maintained, there is the opportunity to use air source heat pumps to preheat direct gas- fired water heaters (DGFWH). There aremany advantages of using high efficiency DGFWH especially those like the Andrews MAXXflo EVOwhich come with anti-legionella functions as standard over indirect DHWsystems (boiler calorifiers) and also often compared to direct electric systems. DGFWHs have considerably reduced storage compared with other systems, meaning less weight and fewer issues with roof top plant rooms. Control of legionella is more straightforward and recovery times reduced. It is also generally accepted that where a design includes renewable technology, such as heat pumps, solar PV or CHP for example, project costs are higher. Water treatment Implementing a robust water treatment strategy should also be a key part of the maintenance programme to ensure the efficient operation of equipment and extend the lifetime of products. Water quality can differ across the UK. Selecting products with polycarbonate tanks, for example, will limit the amount of scale that builds up in a unit, while a conditioner will raise the quality of water supplied in a hospital. This is especially important for themajority of south, east and central England where water is hard to very hard. Water treatment is also identified as another effective method of bacteria control. For an entire overview of legionella control, refer to HTM 04-01, part B,4. This is a specialism in its own right, and we would advise consulting with specialist water treatment companies. Industry support Transitioning huge hospital premises from gas-powered steam or high temperature water heating systems to a low-carbon solution can be a hugely complex and daunting task for estates managers for the reasons outlined above. As each project and building type will have its own particular challenges, estates and facilities managers will look to the building services industry for advice and support to enable them to plan their own roadmap to the energy transition. The route they choose will depend on many factors, including costs, space requirements, available electrical power and reliability. Your manufacturer of choice should be able to offer the variety of equipment and solutions required tomeet all individual project requirements. They should also be able to provide guidance as to the most suitable technologies to use and how they will integrate with the building design as a whole. Accurate sizing is one example, to ensure sufficient DHWwithout oversizing the systemand wasting precious energy. Look for manufacturers who offer electronic sizing tools, like Andrews’s Size-it, that make it easier tomanage, match andmeasure up the different parts of the building type and hot water requirements. At Baxi we have decades of experience through our technical sales teams of workingwith consultants and contractors to identify the various options and the most appropriate solutions.Where expert help is required, we canwork together as an industry to help hospitals plan and achieve their net- zero pathway while avoiding the risks associatedwith hot water provision. Source 1 www.england.nhs.uk/greenern- hs/2022/10/blog-drive-for-energy- efficient-healthcare-is-delivering- for-patients-and-planet/ 2 www.hse.gov.uk/legionnaires/hot- and-cold.htm Infection preventionwith POUwater heaters and boilingwater units A further consideration in hospitals and healthcare premises is the inclusion of point-of-use water heaters, which could be fed by solar PV, for the immediate production of safe hot water. Installing a point-of-use water heater that incorporates anti- legionella functionality will ensure that water is adequately stored, cycled and distributed. An added concern in hygiene-critical environments is the need to prevent bacterial build up and cross-contamination. One solution might be to use electrically powered boiling water units like Heatrae Sadia’s Supreme that incorporate Polygiene Biomaster®, an antibacterial silver ion agent, to prevent the growth of bacteria. This helps keep the surfaces clean and hygienic and reduces the risk of cross-contamination, aiding HTM 04-01 compliance. Choosing robust products that are designed for easy upkeep and built to last will also help avoid unnecessary time and expense related to maintenance. More information can be found at www.baxi.co.uk