086 HPM 1115

HPM November 2015

Got a story? Ring us on 01732 748041 or e-mail twood@unity-media.com WATERHEATING,TANKS&CYLINDERS ERP a game-changer for cylinders Stuart Elsy, managing director of OSO Hotwater, comments on the major issues affecting the water heating market and explores the rise in popularity of district or communal heating systems... The water heating and hot water storage market is undergoing its biggest shake-up for several years with the introduction in September of Energy labelling for boilers and hot water cylinders under the European Energy related Products (ErP) Directive. From now, cylinders, boilers and other heating devices up to 400kW sold to the trade and public must carry an energy label. ErP consists of new regulations to help the EU achieve its 20-20-20 target to reduce energy use by 20% and increase the share of renewable energies by 20% by 2020. ErP sets minimum performance and environment criteria for energy related products and heralds the introduction of the familiar A to G energy labels found elsewhere. CYLINDER EFFICIENCY Cylinder efficiency has improved over time to meet building regulations and gain an advantage in SAP, the Standard Assessment Procedure by which new build properties are energy rated. However, for the typical heating installer, energy efficiency has not always been the first criteria for selection of a product. ErP is a game-changer for the cylinder industry. For the first time, the cylinder efficiency will be obviously visible to the installer and, equally important, to the end user. Experience in the boiler and white goods industries has shown that customers are looking, and prepared to pay for superior energy ratings. ErP cylinder ratings are measured on parameters heavily affected by insulation efficiency. Achieving an A rating across a range of sizes is not easy for a cylinder manufacturer and simply adding more foam insulation is not enough. As cylinder capacity increases it is more challenging to achieve the highest rating and a different level of technology is required to achieve an A rating in the popular mid-range sizes and beyond. Installers should look at ratings across an entire range as heavily promoted A ratings may only be valid for 120 and 150 litres. Indeed, it is possible that a range could drop two full bands between smallest and largest. An A rated unit can save over 1.5kWh per day compared to a C rated product and will lead to significant long-term energy savings. Energy efficiency for indirect cylinders is calculated by measuring the standing heat loss. The domestic hot water is heated to 65°C in a controlled ambient temperature of 20°C and the energy required to maintain the domestic hot WWW.HPMMAG.COM water temperature is measured over time. The standing heat loss is that measurement, calculated either in Watts or Kilowatt hours per day. ERP gives performance bands within which the heat loss of every cylinder will fit, thus determining the energy rating. For direct electrically heated units, ratings are determined by measuring the amount of energy used to deliver set hot water draw off profiles over time. These profiles are designed to mimic typical use on a daily basis, and combine small draw offs for a hand basin with larger ones to simulate a bath or shower. Profiles vary for different sizes of properties and manufacturers will test against the profile which is closest to the intended usage situation of the particular cylinder. The reality is that a well-insulated cylinder will perform a lot better than a poorly insulated one, and the draw off profiles are likely to favour these units. Electric direct cylinders will normally have lower grades than indirect units. The ratings for electric heating reflect the inefficiencies in fossil fuelled power generation across Europe. A 2.5 times multiplier applies to electricity usage in efficiency calculation. This means that a perfect cylinder, which never lost any heat, ever, could only get a 40% efficiency. Smart control of thermostats, so that the water heater learns the usage habits of the household, are encouraged and will assist manufacturers to achieve C and in some cases B ratings, but again, only on a well-insulated cylinder. CENTRAL PLANT HEATING SYSTEMS Communal and district heating schemes are not new, but have been gaining traction on multi-occupancy buildings in urban areas for some time. London has lead the way, but other major centres of population are also seeing central plant heating systems, supplemented by Heat Interface Units (HIU) in individual apartments. Central plant offers a developer the option of a variety of heat sources, from traditional gas or oil to renewable sources, such as biomass. With the heat centrally generated, it is distributed around the building for connection to HIUs in individual apartments. Heat is transferred into apartments either on a direct system using the central pipes, or more typically in the UK using a plate heat exchanger to provide a thermal bridge, but keep the domestic and communal heating systems 86 NOVEMBER 2015 HEATING & PLUMBING MONTHLY mechanically separate. This ensures that any plumbing problem in an apartment is restricted to one property. Most HIUs contain sophisticated metering equipment that by measurement of flow and return temperature and of flow rates, will calculate the amount of energy used in the apartment for billing purposes. HIUs take a variety of forms, but most typically they operate a twin plate system to provide space heating and instantaneous hot water in a method not unlike a combi boiler. A very popular alternative is the use of a single plate HIU with an indirect hot water cylinder. This system can have two advantages. Storage of hot water allows for a higher flow rate and is suitable for properties with more than one shower or bath. This reflects the advantage of a hot water cylinder in a multi-bathroomed house, compared to a combi boiler. Also an apartment with hot water storage provides a greater level of security of supply of domestic hot water. A problem with the central plant can shut down the entire heating system, but whereas space heating can be temporarily supplied by electric fan heaters, a twin plate HIU system has no back-up of hot water provision. A cylinder will typically have a back-up immersion heater, which is always available for emergency use. HIUs and communal heating systems are highly prevalent in continental Europe, and all predictions are that this system will become increasingly popular in urban redevelopment in the UK. A modern A rated cylinder enquiry number 143


HPM November 2015
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