Specifying, designing and installing heat pump systems presents building services engineers with several challenges, but how are they best met? Bob Towse
, Head of Technical and Safety at B&ES, has an answer
A WIDE-RANGING field study conducted by the Energy Saving Trust (EST) between 2008 and July last year concluded that heat pumps can play a significant part in helping the UK reach its targets for reducing carbon emissions, but only if they are correctly installed.
According to the EST, a number of interventions - including applying updated installation methods - improved the performance of heat pump systems during its study. The success of the heat pumps' performance was underpinned by the experience of the users surveyed. Eighty per cent were satisfied with their heat pumps, while more than three quarters said they would recommend a heat pump to a friend.
The EST's performance monitoring trials provided early indications that the introduction of improved installation standards, amongst other things, will lead to improved performance.
If heat pumps were installed today under the current installer guidelines, alongside further customer guidance on operating the system, they should achieve even better performances than indicated in the study.
B&ES is playing a part in helping building services engineers specify, design and install heat pump systems for optimum performance.
The Building & Engineering Services Association (B&ES) recently updated its good practice guide to heat pumps - TR30. This publication provides an overview of different heat pump applications with their benefits and limitations, as well as giving outline design information for each.
B&ES technical committee chairman Graham Manly points out in the introduction to TR30 that regulation and, in some cases, client requirements are leading to more innovative solutions in the provision of heating, hot water and cooling.
Invariably, such solutions lie in new applications of existing technologies, but the skill is in knowing when they are appropriate and how to make them efficient.
Heat pump technology can be used in a variety of ways but TR30 provides an overview of the different applications, with their benefits and limitations, as well as giving some outline design information for each of them.
Heat pump systems are typically based on packaged equipment, where all the components and controls for the refrigerant circuits are pre-assembled and tested.
For space heating and hot water systems, packaged heat pumps with electrically driven compressors are usually found in residential applications and small commercial premises.
Essentially, heat pumps work by extracting low temperature heat from a source (usually the ground, the air or water) and rejecting high temperature heat to a sink (the building heat distribution system and/or hot water calorifier). During this process, the source gets cooler and the sink gets hotter. The energy used to drive the process usually comes from an electric motor connected to the refrigerant compressor.
Heat pumps can be used as an alternative to a boiler for space heating and domestic hot water. The key characteristic of a heat pump compared with a boiler is that the amount of heat produced is greater than the energy used to drive the process, e.g. the electrical energy supplied to the compressor motor and fans or pumps.
For this reason, the cost of heat provided by a heat pump can be less than the cost of heat provided by a boiler, even though the cost of electricity is greater than alternative fuel sources.
However, as the EST study makes abundantly clear, the performance of the heat pump depends on the quality of the installation. This brings us back to the need for good, solid installation advice and that is where TR30 comes in.
TR30 covers a range of topics relating to heat pumps, including selection and sizing, siting, noise issues, regulations, specific requirements for different types, operation and maintenance, commissioning and handover.
The 50-page A4 guide is intended to be part of a suite of publications covering generic installation requirements for a range of renewable energy systems, including biomass fuels, solar hot water and combined heat and power. It provides an overview of the different applications with their benefits and limitations, as well as giving outline design information for each.
For more information or to purchase a copy of TR30, call B&ES Publications on 01768 860405 or visit www.b-espublications.co.uk
Two phases of EST heat pump study
The EnergySaving Trust (EST) field study into heat pumps was in two parts. Phase 1 - which involved the participation of 83 properties - was started in 2008 and reported in 2010. The study revealed that many heat pumps performed well, but a number delivered lower than expected efficiencies.
Heat pump performance was found to be particularly sensitive to specification, design, installation and commissioning practices. This led to a thorough review of installation and training guidance and the eventual revision of Microgeneration Certification Scheme (MCS) installer standards.
For phase 2 of the trial, 38 of the heat pumps from phase 1 were selected for a range of interventions from major (for example, resizing the heat pump) to minor (for example, altering control parameters). Six new heat pumps were also monitored. These were sized and designed according to the heat pump standard MCS MIS 3005 version 3.1.
Phase 2, which began in 2010, was designed to build on the lessons learned from phase 1 and to investigate the reasons that caused the varied measured performances of heat pumps. It reported in July last year (see http://bit.ly/14xJXiK