SAV Library

Explore our library to understand more about 4G heat networks, indoor environment and lookup useful topics and definitions.

Absorption chillers

Absorption chillers use heat energy to generate chilled water that can be used for air conditioning or process cooling applications. They are often used in conjunction with combined heat and power (CHP) making use of the surplus heat from CHP engines in summer to provide cooling.

An absorption chiller consists of a generator, a condenser, an evaporator and an absorber. The basic absorption cycle employs two fluids, a refrigerant (typically water) and an absorbent (typically lithium bromide). As the absorption cycle proceeds, these two fluids are separated and combined, as follows:

In the generator a dilute lithium bromide solution is heated, causing water to evaporate off – resulting in water vapour and a concentrated lithium bromide solution. The water vapour is transported to the condenser and the lithium bromide is transported to the absorber. In the condenser, the water vapour from the generator condenses under high pressure.

This condensed water is then transferred to a lower pressure evaporator, where it evaporates and absorbs heat from water in adjacent cooling coils. This generates chilled water that is then distributed to the cooling system. From the evaporator, the low pressure water vapour passes to the absorber where it re-combines and dilutes the concentrated lithium bromide solution, so that the cycle can be repeated.

Absorption chillers typically require a hot water temperature of 70-95 degC to produce chilled water at around 7 degC.

Air Handling Units (AHUs)


Air handling units (AHUs) are used to supply and circulate air around a building, or to extract stale air as part of a building’s heating, ventilating and air conditioning (HVAC) system.

Essentially, an Air Handling Unit system comprises a large insulated metal box that contains a fan, heating and/or cooling elements, filters, sound attenuators and dampers. In most cases, AHUs are connected to air distribution ductwork. Alternatively, an AHU can be open to the space it serves.

Supply air passing through the AHU is filtered and is either heated or cooled, depending on the specified duty and the ambient weather conditions. Air Handling Units can also be used to supply fresh air for ventilation and to extract stale air.

For heating or cooling, AHU coils may be connected to central plant such as boilers or chillers, receiving hot or chilled water for heat exchange with the incoming air. Alternatively, heating or cooling may be provided by electric heating elements or direct expansion refrigeration units built into the air handler.

When AHU systems are used to extract stale air from the building, a controlled proportion of this air may be recirculated to avoid having to condition all supplied air. AHUs can also incorporate heat recovery exchangers to extract heat from the air being expelled and use it to heat incoming supply air.

Air Handling Units vary considerably in size, capacity and complexity, depending on the job they are designed to perform.

Alupex flexible pipe (Alupex)

Alupex flexible piping systems enable faster and more reliable installation with no requirement for elbows or bends. Connections are made with Pressfit fittings, saving even more time.

Alupex is a composite of plastic (cross-linked polyethylene) and aluminium piping, that is ideal for a wide range of hot and cold water applications. SAV Alupex systems are supplied complete with all Pressfit end fittings, and piping can be supplied pre-insulated, if required.

A key benefit of Alupex is its flexibility. Large radius bends can be formed by hand and smaller radius bends (down to two pipe diameters) are easily made using a bending spring. This means that installation is considerably easier and quicker than would be the case for traditional copper systems, as bends and elbow pieces are not required.

End connections are easily made using FAR brass adaptors. Each adaptor comes with two pairs of O-rings, split olive and compression nut.

Alupex piping offers the following advantages:

  • Connection is only required at the ends.
  • Faster installation, fewer connections, no elbows or bends.
  • Helps to meet BSRIA guidelines for reducing installation time.
  • Fewer connections reduce the risk of leaks.
  • Easy to fit, with no requirement for specialist skills.
  • Robust design, resistant to rough handling on site.
  • Rated for temperatures up to 95 degC and a working pressure of 12 bar.
  • Life expectancy of 50 years, full guarantee for 10 years.
  • 100% barrier to oxygen diffusion, thus reducing corrosion risk.

Alupex pipe is made up of five layers that combine flexibility with high durability.

Boosted Cold Water Manifolds (BCW)

Boosted cold water (BCW) is required when the cold water tank is located lower than user level in a building, so that water needs to be pumped upwards for distribution. A BCW system typically comprises a cold water storage tank that supplies a number of pumps. These deliver water to a large bore riser pipe(s) for distribution to the building circuits. A non-return valve ensures that water is not able to drain back to the storage tank.

Because of the pressure used in BCW systems, it is essential to make use of high quality connections to avoid the risk of leakage. Effective control of distribution is also important, which is where multi-port manifolds come into their own. Manifolds have great potential to reduce site installation time. They are highly compact, making it possible to tuck them into corners usually considered inaccessible.

BCW manifolds can be supplied with 2, 3 or 4 ports, or end-connected to provide additional port connections. SAV’s BCW modules are assembled in a quality-controlled factory environment and hydraulically tested prior to despatch.

As potable water becomes an ever more valuable commodity, the need for reliable water meters can only be expected to increase. BCW meter manifolds can be supplied complete with meters, or with space allowed for those supplied free-issue (for utilities such as Thames Water for example, who supply their own). Manifold branches can be provided complete with isolation valves and approved non-return provision.


BREEAM (Building Research Establishment Environmental Assessment Method) is a rating system to evaluate the environmental impact of a building. It sets the standard for best practice in sustainable building design, construction and operation. Since its introduction in 1990, the BREEAM assessment method has been applied to over 200,000 buildings throughout the UK.

A BREEAM assessment uses recognised measures of performance, set against established benchmarks. It encompasses a wide range of criteria, from the way that a building is designed through to its predicted impact on the local environment. The key criteria are:

  • Energy consumption and carbon emissions
  • Water consumption
  • Health and wellbeing of the internal environment
  • Pollution
  • Impact on local transport networks
  • Materials used (environmental impact and embedded carbon)
  • Waste management
  • Ecology
  • Building management

In assessing the energy performance of a building, BREEAM awards points for the use of low or zero carbon technologies such as heat pumps, solar thermal heating, Combined Heat & Power (CHP) and biomass heating. To achieve a high environmental performance it is also important to ensure that a building’s services are commissioned correctly and controlled effectively once it enters service.

BREEAM is divided into the following ratings, which are awarded by certified assessors under the UKAS (UK Accreditation Service) competent person scheme:

  • Unclassified
  • Pass
  • Good
  • Very Good
  • Excellent
  • Outstanding (introduced in 2008)

The BREEAM standard covers the following main building types:

  • Retail
  • Offices
  • Education
  • Prisons
  • Courts
  • Healthcare
  • Industrial
  • Specialised buildings assessed under the BREEAM Bespoke method
  • Multi-Residential *

* Individual dwellings are subject to a similar assessment through the Code for Sustainable Homes


BSRIA (Building Services Research & Information Association) is a not-for-profit test, instrumentation, research and consultancy organisation, providing specialist assistance to the construction and building services sectors.

BSRIA has ongoing research programmes and produces industry-recognised best practice guidance. It also offers a wide range of services to help companies improve the design, building and operation of buildings. These include design validation of computer modelling, physical modelling and detail drawing reviews.

In parallel, the Association is well known for its market intelligence services in support of building services products. These are a mix of off-the-shelf and privately commissioned studies, which are backed by management consultancy to help companies improve their processes, manage staff and improve customer satisfaction.

BSRIA’s building compliance services include air-tightness testing, thermal imaging, smoke testing, roof inspections, SBEM calculations and Energy Performance Certificates.

BSRIA provides independent laboratory testing, certification and performance verification of a large variety of building services products. The Association can also carry out testing on products designed for specific project use, as well as help to develop new products.

Since 1990 BSRIA has offered a test and measurement service, through which it can  calibrate, offer for hire or sell specialist instruments for use within building services.

Beyond the construction process, BSRIA offers Facilities Management services which are designed to help building operators operate and maintain their buildings more efficiently, saving money and energy while minimising disruption to systems.

BSRIA was founded in 1955 and employs a total of 200 people at its head office in Bracknell (Berkshire) and at offices in France, Spain, Germany, China, Malaysia and North America.

Chilled Beams

Chilled beams are now widely used for cooling offices and other commercial spaces and are generally seen as consuming less energy than systems such as fan coil units.

The principle of a chilled beam is that pipes carrying chilled water pass through a ‘beam’ at ceiling level. These then cool the surrounding air, which increases in density and falls. In doing so, it displaces warm air upwards.

There are two types of chilled beams, passive and active. Passive chilled beams rely solely on convection currents to distribute cooled air, whereas active chilled beams use ducts to direct air across the beam. Active chilled beams have a higher cooling capacity than passive chilled beams and are generally specified when internal heat loads are too high for the passive variety. Both systems may use pipe fins to increase the surface area for heat exchange.

As well as consuming less energy than a conventional fan coil system, chilled beams generally have a lower operating cost. There are several reasons for this. One is that the temperature of the chilled water is not so cold as that supplied to a fan coil system, so that chillers consume less energy. In addition, fewer circulation fans are required, thus reducing electrical energy consumption further. However, additional ductwork may be required to meet indoor air quality requirements, which to some degree would offset the savings in energy consumption.

There are also limitations on ceiling height, as passive chilled beam systems will not circulate cooled air effectively above a height of 2.7m. As chilled beams require less ceiling space than forced-air systems, they may enable lower ceiling heights in new build projects, which can reduce overall construction costs.


CIBSE is the Chartered Institution of Building Services Engineers and its stated role is to ‘support the Science, Art and Practice of building services engineering, by providing our members and the public with first class information and education services and promoting the spirit of fellowship which guides our work.’

CIBSE promotes the careers of building services engineers by accrediting courses of study in further and higher education, by approving work-based training programmes and providing routes to full professional registration and membership, including Chartered Engineer, Incorporated Engineer and Engineering Technician. Qualified engineers can also access a range of services to help with their continuing professional development (CPD).

In addition to its services for members, CIBSE is an authority on building services engineering, setting standards and publishing guidance (eg Commissioning Code W) to encourage best practice in the profession. It also publishes a series of Technical Memoranda, such as CIBSE TM39, Building Energy Metering.

CIBSE is regularly consulted by government on matters relating to construction, engineering and sustainability. It has representatives on major bodies and organisations which govern construction and engineering occupations in the UK, Europe and worldwide. CIBSE also works in partnership with other professional bodies and construction / engineering firms worldwide.

The Institution is organised on a regional basis – there are 16 regions in the UK and three overseas (the Republic of Ireland, Australia & New Zealand, and Hong Kong) with members in 87 countries outside the UK.

CIBSE Commissioning Code W

CIBSE Commissioning Code W: Water Distribution Systems describes the requirements for commissioning water distribution systems in buildings. It complements BSRIA Application Guide BG2/2010, which describes how commissioning is to be carried out.

Correct commissioning is a requirement of Part L of the Building Regulations and is vital in ensuring that water distribution systems in a building perform as they were designed to. Approved Document L2A of the Building Regulations 2010 states that ‘notice of completion should be given to the relevant Building Control Body (BCB) confirming that:

  • A commissioning plan has been followed so that every system has been inspected and commissioned in an appropriate sequence and to a reasonable standard; and
  • The results of tests confirm that the performance is reasonably in accordance with the actual building design, including written commentaries where excursions are proposed to be accepted.

Furthermore, the Building Control Body may not be able to provide a completion certificate until it receives the commissioning notice.

Commissioning is critical to achieving the safe, effective and efficient operation of hydronic systems (defined as those which use water as the medium for heat exchange) and must include circuit balancing of the distribution system. A properly commissioned system optimises performance and ensures good quality living / working environments.

The latest version of CIBSE Code W includes recommendations for achieving accurate commissioning of variable volume hydronic systems with ultra-low flows. The problem of measurement of low flows has become increasingly common, as space heating loads have reduced in response to higher internal heat gains and improved building insulation. Recommended techniques include the subtraction method, which is well suited to SAV’s FloCon Ultra Low Flow commissioning modules.


CIBSE TM39 (Technical Memorandum 39) ‘Building Energy Metering’ is a document published by the Chartered Institution of Building Services Engineers (CIBSE) to promote best practice in the design of energy metering and sub-metering in non-domestic buildings.

One of the key roles of TM39 is to help building services designers meet the requirements of Part L 2010 of the Building Regulations, which puts considerable emphasis on the ability to measure energy consumption. Part L includes a new rule that ‘output of any renewable electrical energy generation system is to be separately monitored’.

TM39 is designed to help facilities managers and building operators introduce metering and sub-metering in existing buildings. It has been written for designers, owner-occupiers, landlords and letting agents who act on their behalf, managing agents, tenants, office managers, facilities managers, and anyone else who can benefit from the energy data that meters and sub-meters can provide.

Retrofitting of energy metering is particularly important in an existing building when refurbishment work triggers a requirement for ‘consequential improvements’ under Part L. As in Part L 2006, the 2010 regulation includes energy metering as an acceptable improvement. Metering is also important for those organisations participating in the Carbon Reduction Commitment Energy Efficiency Scheme, where an understanding of energy consumption is essential in the management and improvement of carbon emissions.

The latest edition of TM39 (published in 2009), offers a cost-effective and practical approach to the procurement of energy metering systems. It should be used to optimise metering strategy against cost, practicality, the value of the information gained and predicted energy savings. A step-by-step method is provided to assist in the selection of appropriate ways of metering energy use. It also provides advice on setting up the prescribed information logbook for use by building owners and occupiers.

CIM ball valves

CIM A Series ball valves with extended spindles reduce energy wastage by precise control of flows, which includes quick shut-off. The engineering of these valves is robust, ensuring all benefits are maintained throughout their long service life.

CIM A Series valves are unusual in being made from a solid ball, which eliminates any issues of distortion. They are designed to include a high blind angle, which means that there is plenty of turn in reserve once the point of closure has been passed. Both these features are significant in maintaining 100% shut-off.

Nylon wrap handles act as an insulator as well as facilitating a firm grip. The valves can be supplied with easy-to-fit insulation boxes, tailored to wrap around the valve body. This guarantees a reliable level of insulation around each valve, saving time on site fitting insulation to non-straight contours.

CIM A Series ball valves are available in diameters from ½ ” (12mm) to 2 ” (50 mm).

Circulator Pump

A circulator pump is a specific type of pump used to circulate liquids, gases or slurries in a closed circuit. A common use is in hydronic HVAC systems (defined as those which use water as the heat exchange medium), circulating hot or chilled water for heating or cooling.

Circulator pumps used in hydronic systems are usually centrifugal, driven by an integral electric motor. Alternatively, the motor may be mounted externally to the pump body, with a mechanical coupling.

In HVAC systems, variable speed circulator pumps can help to reduce overall system energy consumption when compared to fixed speed circulators. As variable volume hydronic systems have become more common, there has been a tendency to use inverter-control for the circulator motors. This enables rapid response to system changes.

Coanda effect

When ventilation supply air is introduced at high level it ‘attaches’ to the ceiling because of the phenomenon known as the Coanda effect. The result is that this air travels across the ceiling and falls gently towards the back of the ventilated space. It does not fall immediately upon entering the room and thus avoids creating draught.

The Coanda effect can be used to advantage by positioning ventilation units at high level, thus giving time for the air to gain in temperature and to slow down as it makes its way across the ceiling. Both these factors are significant to eliminating draught.

As air distribution is effectively duct-free, systems based on the Coanda effect have remarkably low Specific Fan Power.

Combined Heat and Power (CHP)

Combined heat and power (CHP) is the site generation of electricity and simultaneous use of process heat. It is also known as Cogeneration. Appreciable cost savings can be made by substitution of grid supplies, with by-product heat being captured for site use. The efficiency of fuel usage in CHP is much higher (typically around 90%) than is usually achievable in conventional power stations (40%).

CHP units range in size from 1 kW units for domestic use, up to 3 MW giants for large installations in hospitals. Selection can be based on a single unit to meet maximum site load, or by multiple CHP units arranged to enter service progressively through the load range.

When it comes to planning applications for new-builds (which are subject to either SAP or SAP or SBEM guidelines), CHP units can contribute carbon reductions. Certain European countries, such as Germany, operate Feed-In Tariffs (FITs) with significant rewards to any CHP operator exporting site-generated electricity to the Grid. Currently, the UK has a limited version of this system, with FITs available only to micro-CHP with ratings up to 2 kWe. Benefits are payable for a period of 20 years. (Previously the UK FIT scheme included CHPs up to 5 MWe, but this was closed to new applicants as from 01.04.2019).

The fuel used most frequently on CHP projects is natural gas. For sites outside the reach of the gas mains network, LPG versions can be made available instead. Diesel powered CHP units currently have limited appeal on account of the fuel price differential.

Electrical connections can be arranged for a CHP unit to start by itself (known as synchronous, or island-mode operation). These are ideal for remote locations, and need to have start-up battery provision. For the majority of the UK land area covered by the national grid, so-called ‘asynchronous’ units work in tandem with the grid and effectively use this supply to get going.

For cogeneration to be applied successfully, there needs to be a reasonable match between the CHP rated output and site thermal / electrical demand. This should be verified at the design / proposal stage. For certain types of project such as office and retail developments, combined heat and power can be hard to justify on account of thermal loads being sporadic. Much greater success with the matching process can be expected for applications such as schools, high density housing, care homes, leisure centres and hotels.

Thermal output from combined heat and power can be used to supply radiator or UFH wet systems, DHW calorifier coils, space heating based on fan coil units or air handling units. CHP has the highest efficiency of all plant room boilers, and is usually required to act as lead. Increasingly, combined heat and power units are being considered for boiler replacement programmes, which is not surprising: because CHP units replace relatively expensive electricity grid supplies, their normal payback period is between 4 – 8 years.

Computer Aided Design (CAD)

CAD is the process of drawing and modelling of diagrams and products in either two and three dimensions on a computer package, such as AutoCAD.

This serves many purposes:  in the first instance CAD is used to produce manufacturing drawings of components, which the manufacturer uses to produce components; secondly, these component drawings can be assembled together within the CAD package, in particular in a 3D view, enabling visualisation of assemblies before construction, and ensuring that one can assemble the components in the desired manner. Furthermore, this aids in fault finding in assemblies before manufacture and construction.

CAD is also used to design plant layout. Given the details of a plant room, for example, CAD makes it possible to optimise the layout of plant items within the allocated space. Where there is limited space for the installation of valve modules, then alternative arrangements of components can be tried out inexpensively using CAD, before settling on the final design.

Demand Controlled Ventilation

Demand controlled ventilation is the automatic linking of fan speed with one of the indicators of indoor air quality (IAQ), such as carbon dioxide (CO2) or humidity.  In this way, good IAQ can be maintained during occupied times with the least energy consumption by fans.

For classroom ventilation, demand control is often arranged using a CO2 sensor, either integral to the unit or wall-mounted. With fan drive-motor speed arranged to modulate automatically, no teacher intervention is required for the control of classroom conditions.

Differential Pressure Control Valve (DPCV)

In variable flow circuits, Differential Pressure Control Valves (DPCV) are used to maintain a constant pressure differential across a sub-branch. This protects downstream control valves from having to operate with excessive pressure differences and neutralises the effects of system pressure variations.

A DPCV contains a spring-loaded piston and a diaphragm that separates the upper / lower chambers of the valve. The piston is connected to the diaphragm, which closes the valve when differential pressure rises and opens it by the action of the spring, as the differential pressure falls. For those periods of equilibrium between diaphragm pressure and the piston spring, the valve position remains steady.

Once a sub-branch has been commissioned, a DPCV prevents upset from other parts of the system, making the commissioning process much easier. Test points adjacent to DPCVs are recommended for ease of commissioning and future fault-finding.

District Heating

District heating or community heating is the use of a centralised heat source, often housed in an ‘energy centre’, to provide heating to a number of buildings. Heat sources may include boilers, combined heat and power (CHP), heat pumps and solar thermal systems.

The types of development that are suitable for district heating systems include apartment blocks, housing estates, retail parks and office complexes. Mixed use developments (combining offices or shops that require hot water during the day with dwellings that require heating and hot water at other times) provide a more consistent heat load and can thus help to secure high efficiencies from the heating plant.

A typical district heating installation consists of a highly insulated ‘heat main’ of flow and return pipes, which circulates hot water (or steam) past all the buildings or apartment blocks which might be connected. Junction points on the mains at each building allow easy connection at any time, by which the heating medium reaches a heat exchanger (or heat substation) within each user centre. In this way, heating circuits within each building are kept hydraulically separate from the heat main. The principal uses for such heating within buildings are for space heating and domestic hot water.

Energy meters can be installed to measure the actual heat usage within each building and apartment, with the output used to bill the occupant accordingly. Energy meters (or heat meters) are based on the measurement of temperature difference between flow and return, taken together with flow measurement.

Energy meters can be read via a web interface, for ease of monitoring and administration.

Hot water in heat mains is typically supplied at around the same temperature as would be expected from a domestic boiler. This should allow existing buildings to be connected up to heat mains without the need to replace user heat emitters.

Centralised boiler plant can be expected to achieve higher efficiencies than is possible from dispersed smaller units. District heating makes it possible to use technology which is only applicable on a large scale, such as biomass and co-generation.

Domestic Hot Water (DHW)

Domestic hot water (DHW) refers to the hot water used in sinks, showers and baths in any type of building (not just domestic dwellings). It is supplied on circuits separate from the hot water used for heating, although water for both purposes is often generated by the same system. Unlike water in heating systems, DHW is potable, as residents may consume it deliberately or accidentally during bathing / showering.

Typically, hot water generated by a heat source such as a boiler or combined heat and power unit goes through one stage of heat exchange before the resultant DHW is stored in a vessel, such as a calorifier. It is then available when the need for DHW arises. However, systems equipped with SAV FlatStation HIUs can generate DHW instantaneously within a user dwelling using hot water from a central plant room. Each HIU uses a compact plate heat exchanger to maintain separation of the two systems.

DHW is normally supplied to taps and showers at temperatures of between 50 – 60 degrees Celcius, and at 65 degrees C to professional kitchens so as to satisfy hygiene standards. DHW should be stored at temperatures above 60 degrees C, to ensure there is sufficient heat to kill off Legionella bacteria. This storage temperature can then be reduced at tap outlets by using blender valves to mix with cold water.

Electronically commutated motor

An electronically commutated motor (ECM) uses a microprocessor controller to sequentially energize/de-energize each winding of the stator.  This processor-based pulse control sets up the magnetic field that makes the rotor turn. The microprocessor uses a closed loop feedback mechanism to more precisely control the magnetic fields and minimize eddy current losses. This allows a brushless design to be used, so reducing points of moving physical contact.

An ECM motor has a minimum efficiency of 70% throughout its operating range, and at low speeds is over 30% more efficient than a standard induction motor.

Expansion vessel

An expansion vessel is a small tank in heating or domestic hot water systems, which provides protection from excessive pressure caused by thermal expansion in a closed system.

The vessel contains a diaphragm that divides it in two. One section is connected to the hot water system, whereas the other section is dry and contains compressed air. When the water pressure rises, the diaphragm is compressed against the air on the dry side of the vessel, thus relaxing any water pressure build up resulting from thermal expansion. Conversely, as the water pressure falls, the diaphragm regains its shape and returns water back into the hot system.

In this way, pressure excesses and risk of rupture are avoided.

Filtra CIM valve

Each FiltraCIM valve consists of a shut-off valve and integral strainer. This design greatly simplifies flushing and commissioning operations.

The fine-mesh strainer removes system debris. Access is easily gained by first closing the associated shut-off valve and then unscrewing the end plug of the strainer casing.

FiltraCIM valves are well suited to provide protection for pumps and domestic circulators. They have also been deployed successfully on fan coil systems.

FlatStation HIU

FlatStation HIUs (Heat Interface Units) are located at the interfaces between a communal heating system and each individual user. Hot water is generated in a centralized plant room using high efficiency heat generators such as combined heat and power (CHP), and is then circulated through flow and return mains. At each dwelling interface, an HIU draws only as much heat as the user requires from the circulating hot water. The interface circuits are kept hydraulically separate by a compact plate heat exchanger.

FlatStation HIUs are highly efficient, easy to install and come in 2 main types: Direct and Indirect. In both of these, a Domestic Hot Water (DHW) plate heat exchanger is heated by primary water circulating from the central plant room. Space heating is often arranged by Direct FlatStations, where the primary circuit connects directly to apartment space heating circuits. This arrangement can be adapted to either underfloor heating (UFH) or to radiators.

Alternatively, Indirect FlatStations enable the primary circuit to be kept hydraulically separate from the apartment space heating by using a second heat exchanger. In this situation, provision needs to be made for a circulator, strainer and expansion vessel.

DHW provided by a plate heat exchanger is available just as rapidly as if it were supplied from an adjacent hot water storage cylinder. Accurate control of DHW temperature and pressure at the tap ensure that user comfort is never compromised. FlatStations have no DHW storage requirement. This enables considerable savings to be made in terms of cylinder cost, standing heat losses and installation space.

Plate heat exchangers are excellent in maintaining a high Δt across the primary connections, thereby helping to secure low return temperatures. This is a valuable benefit when it comes to reducing heat losses from all return pipe work. It leads to lower requirements for pumped volume round the primary system and provides good operating conditions for high-efficiency condensing boilers.

Most FlatStation installations are specified with in-built metering. Energy meters can easily be incorporated at works, with output made available by either MBus wiring or radio signal. Individual usage data can be made available for easy download or for individual billing. Where specified, water meters can be installed at works within each FlatStation.

Applications for FlatStation HIUs vary from 1-bedroom flats to large houses. Unit specification can be adapted to take account of the exact user needs: Direct or Indirect, with / without energy metering, rating between 35 and 90kW, connecting piping to be either from above or below. To assist with site construction, bespoke first-fix rails with isolators can provide the hydraulic boundary where pipework fill is required before HIUs are required on site.

FloCon Commissioning Modules

Flocon HVAC Commissioning Modules act as distribution hubs to clusters of terminal units. Each module can accommodate up to 7 terminal units for either heating or cooling circuits. They have been used successfully with groups of fan coil units, air handling units, chilled beams and trench heaters. Commissioning module projects have included office fit-outs, hospital operating theatres and retail premises.

Commissioning modules enable large numbers of connections to be made and tested hydraulically at works. This offers major time and labour savings to site contractors. When used with Alupex flexible piping, installation times are reduced further, as all line joints which lie between terminal points can be dispensed with.

For terminal units installed in ceiling voids, the commissioning of FloCon units is  much easier than the traditional method. FloCon modules enable the hydraulic balancing of several units at a time from a single point of ladder access. Balancing is readily achieved by double regulating valves (or commissioning sets), with differential pressure between flow & return held steady by an integral DPCV. Where system fluctuations in flow and return pressures are of no concern, balancing can be effected by pressure-independent regulating valves.

Pre-commissioning flush requirements are greatly assisted by the design of internal pathways. A full-bore bypass between flow and return sections gives the best chance of moving internal debris out of the system. Isolation is provided to enable flushing in contraflow, as well as via normal path. Once commissioned, a large-bodied, fine-mesh strainer at the entry to the flow header keeps the downstream system clean.

Most commissioning modules are supplied mounted within a galvanised steel enclosure, insulated internally to prevent condensation. Insulation of the box means that the module components can be left uncovered, which makes access for maintenance tasks considerably easier.

A recent development has been the introduction of fine-bore bypasses between flow and return manifolds. These remain permanently open, and are designed to pass approximately 10% of full load flow. When demand ceases from the terminal units, bypass flow prevents the build up of ‘dead legs’ in the flow pipework, helping to ensure prompt response when demand from the terminal units is restored. A further advantage is the avoidance of settlement of any impurities that may be in circulation.

During the life of any commissioning module installation, there is a high chance that modifications to terminal unit layout will be required by the client. SAV provide comprehensive support for just this eventuality. Fresh runs of the equipment sizing programmes would be undertaken, with the remit to re-deploy as much of the original complement of equipment as possible. Any additional components would then be identified and instructions drawn up for use by the client’s site team.

Full Bore Bypass

In SAV FloCon commissioning modules, fast and effective flushing is facilitated by provision of a bypass between the flow and return manifolds, with a bore not less than the internal diameter of the manifolds themselves. This promotes the effective flushing of internal debris introduced to the system during construction, and reduces time spent subsequently in cleaning line filters.

The full-bore bypass is combined with a full-bore drain valve, making it easy to arrange both standard / back flush of the commissioning module circuits. During flushing operations, line filter internals should be temporarily removed.

After flushing has been completed, the bypass should be closed off and the filter basket replaced. In operation, SAV’s large capacity strainers capture system debris down to 0.7mm diameter particle size.

Heat Networks - Definition

Heat Networks distribute hot water from a centralised source through a looped system of insulated pipes.  Users access their energy via individual heat exchangers, serving space heating and / or hot water needs. Heat can be provided by dedicated plant (such as boilers, heat pumps or CHP) or by processes having surplus heat. Networks can be arranged either in single buildings (block heating) or to serve a wider area (district heating).

In addition, Heat Networks have the flexibility to incorporate other technologies which may appear in future and which would help to decarbonise. It is easy to build in hot water storage, smaller sizing is made possible by coincidence factors and CHP operation generates income, as well as heat.

Heating, Ventilation and Air Conditioning (HVAC)

HVAC is the collective term for heating, ventilating and air conditioning systems that maintain comfortable temperatures and indoor air quality in a building. The design of any HVAC system has a significant impact on the energy consumption and carbon emissions of the associated building.

There are many configurations of HVAC systems, ranging from separate arrangements for heating, ventilation and air conditioning, to integrated systems that handle all three. Not all buildings have the three systems.

Heating and cooling systems use hot / chilled water or warm / cooled air to maintain comfortable temperatures in a building. In ‘wet’ systems, water is distributed to terminal units throughout the building. Commonly used heating terminal units include radiators, radiant heating panels, fan coils, fan convectors and trench heaters. The amount of heating is controlled by the temperature and / or volume of the circulating hot water. Chilled beams are used for cooling only.

In air based systems, air is warmed or cooled in an air handling unit and supplied through ductwork to supply grilles. The extent of heating or cooling is controlled by the temperature and volume of supply air. In most cases, warm air supplied to a space is a mixture of external fresh air, and air which has been recirculated. The proportion of fresh air should always be sufficient to ensure adequate ventilation. At the same time, optimum use should be made of the heat contained in the recirculated air, so that ventilation levels are balanced with energy efficiency.

Some ventilation systems have no associated heating or cooling, so that their primary objective is to supply sufficient air to maintain acceptable indoor air quality. In some buildings it is possible to maintain indoor air quality solely by opening windows or using grilles. However, in most commercial buildings, mechanical ventilation is necessary.

Hep 20 piping & fittings

Hep20 is a leading brand of plastic (polybutylene) pipe used for a wide range of plumbing connections. It can be used with hot and cold potable water systems, as well as for those serving radiators and underfloor heating. Connections are made using push fittings, which are reliable and simple to make.

A key benefit of Hep20 is its flexibility, making it easier to install when compared to traditional copper pipework systems.

Hep2o is offered in 2 different types: Standard Piping (as recommended for potable water systems), where low levels of oxygen diffusion through pipe walls are tolerable. Alternatively, Barrier Pipe (as used for heating systems), contains an inner layer of ethylene vinyl which prevents any migration of oxygen through the walls.

Hep20 pipework is smooth bore and expands slightly when heated, helping installations to remain free of lime scale in hard water areas. The ability to expand also provides protection against rupture when pipes thaw after freezing. Hep20 systems tend to be quieter than traditional copper systems, as large radius bends minimise turbulence and the effects of water hammer are dissipated effectively.

Indoor Air Quality (IAQ)

Indoor Air Quality (IAQ) refers to the air quality in a space within a building, with particular reference to its potential impact on the health of occupants. There are many factors that can affect IAQ, including volatile compounds from furniture and fittings, microbial contaminants and carbon dioxide (CO₂).

As carbon dioxide is a by-product of respiration and is exhaled as a waste product, it is a good indicator of occupancy and the level of physical activity within a ventilated space. For that reason, the CO2 level as measured by sensor is often used as the primary measure for Demand Controlled Ventilation, producing a corresponding increase in ventilation rate with rising CO2 levels.

Raised levels of carbon dioxide have an adverse effect on alertness, whereas very high concentrations can give rise to health problems.

Effects of CO2 levels :

  • 400-1000 ppm – Normal conditions
  • 1200-2000ppm – Fatigue, lack of concentration
  • 2000-5000ppm – Fatigue, headaches, general discomfort
  • >5000ppm – Increased heart rate, nausea, oxygen deprivation
Mechanical Ventilation with Heat Recovery (MVHR)

Mechanical ventilation systems are those which incorporate a fan or similar device to assist air movement.

An important subset of this main category is mechanical ventilation with heat recovery (MVHR).  These systems extract heat from exhaust air and transfer it to incoming fresh air, greatly reducing the heat energy which would otherwise be lost from a building. Energy is transferred via a heat exchanger, of which there are several designs on the market. Contraflow heat exchangers are amongst the most efficient.

M-Bus Wiring

M-Bus (short for Meter-Bus), is a European standard (EN 13757-2 for physical and link layer, EN 13757-3 for application layer) developed for the remote reading of utility meters. M-Bus is designed to facilitate the monitoring and measurement of energy consumption to assist with energy conservation. The M-Bus interface is designed to use two wires, though there is also a wireless version (EN 13757-4).

M-Bus, uses a hierarchical system controlled by a master (e.g. a PC) connected to a number of slaves (meters), using M-Bus two-wire cable.

The transfer of information from master to slave uses voltage level shifts, whereas that from slave to master is by modulation of current.


A manifold is a pipe or chamber that branches into several openings. It is used as a distribution hub and can be selected with integral isolators at each branch.

Manifolds reduce the number of connections to be made on site and thus have excellent time-saving potential. Factory-made assemblies often include fittings such as air vents, drain valves, temperature gauges and DPCVs.

Mechanical Ventilation

Mechanical ventilation systems use fans to supply fresh or tempered air to a space, and can also extract stale air from it. They can be designed as a centralised facility to supply ducted air throughout a building, or as discrete units selected to ventilate single rooms at a time.

(Natural ventilation methods, on the other hand, use either wind pressure or the building stack effect for air movement. There are no fans involved).


Monolinks are small manifolds which enable connections to be made simply and effectively to fan coil and air handling units. They each include a full-bore bypass which significantly reduces commissioning time.

Each Monolink module is supplied as a single assembly and is connected to its terminal unit by just four unions, making it easy to fit and adjust in situ. Monolink design can be static (with flow established by commissioning set) or dynamic (where flow is controlled by a pressure independent control valve).

Each flow side isolation valve comes with an integral strainer, which can be removed and cleaned without having to drain down the whole system. A drain point is provided to assist with maintenance.

Monolinks are assembled and tested hydraulically at works, giving time savings to the contractor.

Radiant Panels

Radiant panels are heat distributors which use radiation as the predominant method of heat exchange. They are usually mounted on walls or attached to ceilings.

Radiation involves the transfer of heat across the intervening space between a hot body and an object at lower temperature, without the space itself being heated. Radiant energy will heat all surfaces which are in the direct line of sight from the panel, such as walls, floor, furniture and of course, the room occupants.

A small proportion of heat is passed to the air adjacent to panel surfaces, thus producing convection currents.

The amount of heat delivered by a radiator is largely determined by panel area and surface temperature. For domestic applications, radiator surface maximum temperatures are usually around 47-48°C. Where safety considerations apply, such as at NHS facilities, surface temperatures for wall-mounted radiators are limited to 43°C. Surface temperatures of ceiling radiant panels are higher.

Radiant panels are usually controlled by room thermostat. They can provide heat at different times to multiple zones, as described under SAV’s 2-Zone compliance kit.

Specific Fan Power (SFP)

The Specific Fan Power (SFP) of a fan driven system is a measure of the efficiency at the duty point by which it can move a unit volume of air. It is not a constant, but varies with air flow and system pressure differential. Specifications for air handling equipment often stipulate an allowable limit for SFP, which is usually expressed in watts per litre per second (W/l/s).

For combined supply and extract ventilation units with heat recovery, the SFP is calculated by the (total amount of electrical power supplied to fans, actuators and controls) divided by (the larger of supply or extract air flow rate, at design load).

Substation Heat Interface Units

SubStation HIUs are pre-engineered, factory-assembled heat exchange package plants used predominantly in district heating networks. They are designed to deal with large flows, such as those associated with whole blocks of apartments.

Each assembly is mounted on a robust frame, which simplifies handling arrangements at site. The layout of components makes them easily accessible for maintenance operations.

Each unit is tested at works, so that installation is easy to plan. Sufficient  instrumentation is provided for operational control and to enable commissioning to be carried out effectively.

Trench heating

Trench heating is the term which describes a heat source set in a floor trench, covered by a grille and almost always sited in front of glazed facades. The primary purpose of trench heating is to create convection currents that prevent heat loss through the glazing and condensation forming on the glass. Trench heating can be configured to also contribute to space heating, reducing demand on the primary space heating system.

Trench heating is often specified in buildings that are glazed from floor to ceiling, where other types of perimeter heating (such as radiators) would be unsightly and encroach on the views. Trench heating takes up less floor space, an important consideration in offices.

The heat source for trench heating may be hot water piping or electric elements. Heat distribution may rely solely on natural convection or be fan-assisted.

The positioning of the pipes or heating elements within the trench also influences the distribution of the warmed air. For example, positioning the heating element on the room side of the trench creates an air convection loop adjacent to the glazing, but contributes very little to room space heating. By contrast, location of the element on the window side of the trench encourages cold entrained air to be brought in from the room floor, thus encouraging a stronger convection loop for space heating. Mid-positioning of the element in the trench is effectively a compromise, contributing to both façade and space heating.

Underfloor Heating systems (UFH)

An underfloor heating (UFH) system is made up of a number of parallel underfloor heating circuits, which can be balanced to achieve an even heat distribution across a floor. The underfloor heating circuits can be zoned where necessary so as to serve more than one floor space.

Each underfloor heating circuit comprises a loop of flexible heating pipe connected at each end to an underfloor heating manifold, where control can be maintained over water flow rates and temperature. Underfloor piping is typically laid out within channels cut in an insulated base board, which enables rapid installation and ensures even separation between pipe runs.

Underfoor Heating manifolds

An underfloor heating (UFH) manifold is a compact multiport arrangement, which usually includes a series of thermostatically controlled 2-port valves, temperature gauges, a mixing valve and circulation pump.

Balancing between circuits is achieved using valves placed on the manifold return connections. A mixing valve introduces cold supply as necessary to the hot flow water as it arrives at the manifold, thus maintaining the required water temperature to the circuits. In the event that temperature to the circuits should go too high for any reason, a safety temperature override switch cuts in.

The concentration of valves at the manifold makes for ease of access during commissioning, and also for any rebalancing of circuits which may be required ubsequently.

Valve actuator

A valve actuator is attached to the valve spindle and enables control from a remote location. Actuators are classified according to their range of movement, or travel:

  • Multi-turn actuators – Used for control applications where accurate mid-range performance is required.
  • Part-turn actuators – Used for rapid shut off, such as with butterfly or ball valves.

Actuators are usually driven by electric motors, although some systems are still based on pneumatic actuation.

Ventilation louvre

A ventilation louvre is an opening protected by slats in a wall or window. It allows the ingress of fresh air to a building but excludes birds and rain. The slats may either be fixed or adjustable to suit required ventilation levels.

Ventilation louvres are used in a wide range of buildings, often with the purpose of ensuring at least a minimum level of ventilation at all times. The higher the standard of thermal insulation used in a building, the more important this ventilation becomes. Louvres may also be used for additional purposes, such as for controlling the amount of sunlight reaching a space and for attenuating noise ingress from outside.

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