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PRODUCTS & SERVICES Products of the month The importance of seasonal performance factors in heat pump design Rinnai commissions white paper to address heat pump efficiency R innai is issuing a white paper report that details the potential limitations of manufacturer-issued efficiency measures for heat pumps. Recognising the crucial role that heat pumps play in achieving energy efficiency and reducing carbon emissions, Rinnai is ramping up efforts to provide comprehensive information to its UK customers. The white paper will shed light on the limitations of traditional efficiency measures, such as coefficient of performance (COP) and seasonal coefficient of performance (SCOP), in evaluating the performance of heat pump systems. Authored by Sean Ehlen MEng, the white paper not only presents an alternative approach, but also includes a case study to emphasise the practical implications of this approach. Traditionally, manufacturers assess heat pump efficiency using COP, which measures the ratio of useful heat energy produced to the electricity consumed at specific external air temperatures and temperature-rise requirements. While COP is a valuable metric, it has limitations in assessing the overall efficiency of commercial hot water systems (CHWS), which encompass various energyconsuming components. There are a number of challenges presented by SCOP, which was introduced to try to provide a more comprehensive evaluation of heat pump performance over an entire season. The measure can fall short in accurately reflecting the systems efficiency as a whole, as it mainly focuses on the heat pumps performance in isolation. Rinnai has therefore adopted the seasonal performance factor (SPF) in its paper. In contrast to traditional efficiency measures, SPF is used to evaluate the efficiency of CHWS. It considers all energy-consuming components within the system, providing a more holistic and accurate representation of the systems overall performance. To illustrate the significance of SPF, the white paper includes a detailed case study that examines two distinct approaches to commercial hot water systems: System 1: This relies on a 100% heat pump solution to meet the DHW demand. The white paper will shed light on the limitations of traditional efficiency measures in evaluating the performance of heat pump systems System 2: This employs a combination of a 40% heat pump and an electric cylinder as a back-up heat source. The results of the case study reveal a crucial distinction in the performance of these systems when assessed from different perspectives: When examining the entire commercial hot water system, including the buildings piping, System 1 exhibits a higher SPF of 2.75 compared with System 2, which achieves an SPF of 1.49. The difference is primarily because Tel: 020 7880 6245 Email: cibsedirectory@redactive.co.uk of System 2 activating the back-up heater during peak demand periods and to recover secondary system heat losses. However, when evaluating only the heat pump units performance, System 2 surpasses System 1, which can potentially mislead customers. While customers might expect an SPF close to 3.33, the reality is that the system operates at an SPF of 1.49. The primary objective of this white paper is to emphasise the disparity in performance evaluation between different system boundaries. We believe it is essential to provide our UK customers with a transparent and accurate account of their commercial hot water systems performance, says Rinnai. By doing so, the manufacturer aims to help its customers make informed decisions that lead to cost savings and reduced carbon emissions, while also considering operational expenditure and environmental impact. In a time of escalating energy costs and growing environmental concerns, Rinnai remains committed to equipping its customers with the knowledge they need to make wise investments. Rinnai understands the significance of every decision made in this context, and its aim is to share information that, ultimately, benefits its customers, financially and environmentally. Visit: www.rinnaiuk.com www.cibsejournal.com November 2023 61