CPD PROGRAMME
Professional development
The CIBSE Journal CPD Programme
Members of the Chartered Institution of Building Services Engineers (CIBSE) and other professional bodies are required to maintain their professional competence throughout their careers.
Continuing professional development (CPD) means the systematic maintenance, improvement and broadening of your knowledge and skills, and is therefore a long-term commitment to enhancing your competence. CPD is a requirement of both CIBSE and the Register of the Engineering Council (UK).
CIBSE Journal is pleased to offer this module in its CPD programme. The programme is free and can be used by any reader. This module will help you to meet CIBSE’s requirement for CPD. It will equally assist members of other institutions, who should record CPD activities in accordance with their institution’s guidance.
Simply study the module and complete the questionnaire on the final page, following the instructions for its submission. Modules will be available online at
www.cibsejournal.com/cpd while the information they contain remains current.
You can also complete the questionnaire online, and receive your results by return email.
Air source VRF systems for flexible room heating and cooling, heat recovery and hydronic heating
This module considers the development of VRF systems and newer implementations for producing higher temperature hot water for hydronic heating systems
Variable refrigerant flow (VRF) systems are a refined and more flexible development of the mature technology that has been applied in ‘split’ direct expansion (DX) and heat pump systems. As well as providing distributed, temperature-controlled room units, by applying reversible heat pump technology VRF can simultaneously shift heating and cooling around the building, so reducing overall energy use. This CPD will consider the development of the VRF system and explore the newer implementations capable of efficiently producing directly useable hot water.
Reduced area Compared with a ducted air system, heat being transferred around a building through refrigerant pipework requires a fraction of the area, in terms of ‘conduit’ size, to provide similar heating or cooling to a space. For example a load of 5kW would require a circular air duct of around 350mm compared
with a pair of refrigerant pipes of less than 15mm diameter (plus insulation for both the duct and the pipes). Normally, there would also be a need for ventilation air where the volume flow of ducted air would be related to the fresh air requirement. This is likely to be far less than the air flow that would be required to meet the whole heating or cooling load in the space and, if required, is
www.cibsejournal.com One-way ceiling-mounted 'cassette' unit Four-way ceiling-mounted 'cassette' units
Room unit (with decorative panel)
Two-way ceiling-suspended units Zone control valve Zone control valve
Zone control valve
Wall-mounted surface unit
Zone control valve Floor-mounted concealed unit
Low-pressure vapour line High-pressure vapour line High-pressure liquid line Connections from zone control valve to unit
External unit housing compressors and coil and control equipment
Figure 1: An example three-pipe VRF system
often supplied using a dedicated outdoor air system (DOAS) that may also enable closer humidification control. The use of ‘split’ DX systems is common
across the globe due to both the reduced space required for the installation of ductwork and the relative simplicity of installation. (Note: direct expansion, or DX, refers to the direct expansion of refrigerant for cooling.) Often,
DX systems comprise a single room unit attached to a single external ‘condensing’ unit (either simply ‘through-the-wall’ or with a short length of pipework connecting the two units). Recent ‘multi-split’ DX systems – where several internal units are individually connected to a single external ‘condensing’ unit – are almost all powered through a variable flow compressor that will
April 2013 CIBSE Journal 47 Concurrently, individual units can be heating and cooling
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