Table Of ContentNon-domestic hot water
heating systems
CIBSE AM14: 2010
Engineering a sustainable
built environment
The Chartered Institution of Building Services Engineers
222 Balham High Road, London SW12 9BS
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© January 2010 The Chartered Institution of Building Services
Engineers London
Registered charity number 278104
ISBN 978-1-906846-12-1
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Cover: The Boilersuit, Guy’s Hospital, London (architect:
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Note from the publisher
This publication is primarily intended to provide guidance to those responsible for the
design, installation, commissioning, operation and maintenance of building services. It is
not intended to be exhaustive or definitive and it will be necessary for users of the guidance
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Foreword
When first published in 1989, CIBSE Applications Manual AM3 provided guidance on a
novel form of boiler for heating systems and domestic hot water — the condensing boiler.
In the intervening period, the place of the condensing boiler in heating and hot water
systems has changed to the point where, in almost all cases, they are now required by the
Building Regulations. Standards for such systems have evolved from the old British
Standards into new European Standards, which focus far more on removing barriers to
trade than overcoming barriers to understanding how to install and commission modern
boilers, heating and control systems.
Other regulations have also emerged in that time, notably the Boiler Efficiency Directive,
as well as the Energy Using Products Directive. The environmental agenda has also
travelled far in that time, from Rio to Kyoto and then on, via Bali, to Copenhagen.
From a position of self sufficiency in oil and gas from the harsh operating conditions of the
North Sea, and a quarter of UK electricity generated from nuclear plant, we now have
dwindling nuclear supplies as our aging reactors reach the end of their working lives, and
are increasingly dependent on gas from the harsher political climate east of the Urals.
There is no avoiding the need for the United Kingdom to reduce its energy use by all
economically effective means. Doing so is essential to improve the security of our supplies,
and to minimise the huge capital costs of the next generation of electricity plants, whatever
fuel they use. Taking these actions now will also help us to reduce man-made emissions of
carbon dioxide into the atmosphere.
The politics of CO emissions may be clouded, but the chemistry is very simple. The bond
2
between carbon and oxygen absorbs radiation at a certain wavelength, so that carbon
dioxide traps radiation and prevents it leaving the atmosphere — the ‘greenhouse gas’
effect. If there is more CO in our atmosphere, it will retain more heat. This fact was
2
established by the Swedish chemist Arrhenius in the late 19th century.
It is also increasingly clear that the existing building stock needs considerable investment
to reduce its energy consumption, and replacement of heating systems will play a significant
role in achieving this. There is a pressing need to provide advice on the refurbishment of
existing buildings and retrofitting of heating systems within them.
It is therefore timely for CIBSE, working with ICOM Energy and experts from the
manufacturing, design, and installation and commissioning sectors, to produce this new
Applications Manual, giving comprehensive guidance on the design, installation, commis-
sioning and operation and maintenance of heating systems. It also addresses the two very
different aspects of design: that intended for a new building, and that for a refurbishment
or retrofit project.
This publication should be widely read and used by all those responsible for heating
systems in non-domestic buildings, and should contribute significantly to providing better
heating in many buildings.
This publication would not have been possible without the tireless efforts of the volunteers
on the Steering Group, as well as the contracted authors from BSRIA, and the professional
editorial and publishing team at CIBSE. The Institution and the wider readership are
indebted to them.
Dr Hywel Davies
CIBSE Technical Director
Principal author
Arnold Teekaram (BSRIA Ltd.)
AM14 Steering Committee
Arnold Teekaram (BSRIA Ltd.) (Chair)
Keith Brant (Exhausto Ltd.)
David Davies (CIBSE)
Hywel Davies (CIBSE)
Yan Evans (Baxi Heating UK Ltd.)
Peter Gammon (Modular Heating Group plc)
Barry Gregory (Riello Ltd.)
Malcom Gunn (Hamworthy Heating Ltd.)
David Hughes (ICOM Energy Association)
Fiona Lowrie (BSRIA Ltd.)
Stephen Laws (Clyde Energy Solutions Ltd.)
George Moss (Burgess Group)
Keith Nelson (Broag Ltd.)
Brian Price (Broag Ltd.)
Peter Roge (Exhausto Ltd.)
Wayne Rose (Armstrong Holden Brooke Pullen Ltd.)
Claire Ruston (CIBSE) (Secretary)
Acknowledgements
CIBSE gratefully acknowledges the contribution of material for inclusion in this
publication by the following: Mike Campbell (AECOM), Robin Curtis and Don Sullivan
(Earth Energy Ltd.), Guy Hundy (Institute of Refrigeration) and Rosemary Rawlings.
The Institution also gratefully acknowledges the following for permission to reproduce
graphs, text and illustrations: AECOM, Aqua Environmental Ltd., Armstrong Holden
Brooke Pullen Ltd., Armstrong Integrated Systems Ltd., Baxi Commercial Division, Broag
Ltd., BSRIA Ltd., Clyde Energy Solutions Ltd., Dresser-Rand Ltd., Earth Energy Ltd.,
Econergy Ltd., Exhausto Ltd., Fröling GmbH., Hamworthy Combustion Engineering
Ltd., Hoval Ltd., Institution of Gas Engineers and Managers, Kensa Engineering Ltd., Dr
Steve Lo, MHS Boilers Ltd., Minikin and Sons Ltd., Riello Ltd., Spirotech Ltd., Trent
Concrete Ltd., Viessmann Ltd.
The Institution is grateful to Mike Campbell (AECOM), Ian Richardson (NG Bailey Ltd.)
and Andy Sneyd (Crown House Ltd.) for kindly reviewing the draft prior to publication.
Editor
Ken Butcher
CIBSE Technical Director
Hywel Davies
CIBSE Director of Information
Jacqueline Balian
Contents
1 Introduction 1-1
1.1 Background 1-1
1.2 How to use this Applications Manual 1-1
1.3 Sources of further information 1-3
References 1-4
2 Design decisions and criteria: new buildings 2-1
2.1 Introduction 2-1
2.2 Strategic design decisions 2-1
2.3 Design criteria for boilers in new buildings 2-12
References 2-22
3 Design decisions and criteria: refurbishment 3-1
3.1 Introduction 3-1
3.2 Drivers for refurbishment 3-1
3.3 Scope for refurbishment 3-2
3.4 Constraints 3-4
3.5 Statutory regulations and guidance 3-5
3.6 Identification of existing heating types 3-6
3.7 Evaluation of existing heating systems 3-7
3.8 Evaluation of heating loads 3-10
3.9 Reducing energy consumption 3-10
3.10 Options for refurbishment using low carbon technologies 3-11
3.11 Whole life costs and payback 3-17
3.12 Performance criteria for replacement boiler plant 3-18
References 3-21
4 Major components of heating systems 4-1
4.1 Introduction 4-1
4.2 Heat sources (boilers) 4-1
4.3 Distribution network 4-24
4.4 Heat emitters 4-35
4.5 Flue and chimney design 4-39
4.6 Air supply and ventilation 4-45
4.7 Fuel storage 4-49
References 4-52
5 Controls 5-1
5.1 Introduction 5-1
5.2 Circuit design 5-1
5.3 Boiler controls 5-3
5.4 Avoiding excessive boiler cycling 5-3
5.5 Demand-based boiler control and system inhibit 5-3
5.6 Boiler sequence control 5-3
5.7 Burner controls 5-4
5.8 Time controls 5-4
5.9 Temperature controls 5-5
5.10 Hot water controls 5-7
References 5-7
6 Installation 6-1
6.1 General 6-1
6.2 Legislation and guidance 6-1
6.3 Site facilities 6-1
6.4 On-site storage and protection of equipment 6-2
6.5 Installation of equipment 6-4
6.6 Installation of circulation and distribution equipment 6-5
6.7 Installation of heat emitters 6-7
References 6-8
7 Testing, commissioning and maintenance 7-1
7.1 Introduction 7-1
7.2 System testing 7-1
7.3 System cleaning, flushing and water treatment 7-2
7.4 Pre-commissioning 7-4
7.5 Commissioning 7-4
7.6 Final reporting and documentation 7-6
7.7 Continued evaluation and record keeping 7-7
References 7-7
8 Troubleshooting for hot water heating systems 8-1
8.1 Introduction 8-1
Reference 8-4
Index I-1
1-1
1 Introduction
1.1 Background Existing heating systems are highly diverse in design and
this can mean that some are relatively simple to upgrade
whilst others present much more of a challenge.
This new CIBSE Applications Manual has evolved as a
Knowledge of the types and designs of existing systems,
result of the following:
their initial design criteria and their limits will help the
— the need to revise CIBSE AM3: Condensing engineer to make the correct decisions.
boilers(1)
— the pending withdrawal of parts of BS 6880: Code 1.1.1 Purpose
of practice for low temperature hot water heating
systems of output greater than 45kW(2) This Applications Manual provides guidance on the
design, installation and commissioning of water based
— the implications of the changes to the Building
heating systems. It addresses both the design of heating
Regulations(3)introduced in 2006
systems for new buildings and the specific requirements
— the requirements of the Energy Performance in relating to the design of replacement systems, or
Buildings Directive(4) and its implementation in refurbishment of existing systems, in the existing building
the UK(5). stock. It does not cover medium temperature or high
temperature hot water systems (i.e. those having flow
temperatures above 90°C).
CIBSE Applications Manual AM3, first published in 1989,
dealt specifically with the application of condensing
boilers. At that time condensing boilers were the first high
1.1.2 Readership
efficiency boilers, mainly for natural gas, and were used in
the UK in small numbers. Their use was not encouraged
The guidance is intended for designers and those who
by legislation and, apart from a number of voluntary
install and commission heating systems and their
‘green’ schemes, there was little incentive to use them.
components. It is important that those who design
systems, particularly for existing buildings, have regard
Since the publication of CIBSE AM3, there have been
for the installation and commissioning requirem ents. Not
significant advances in technology and, with commit -
only do they and their employers have a statutory duty to
ments to reduce carbon emissions, legislation is now in
consider the safe construction and installation of their
place that prohibits the use of inefficient boilers for many
design, but it also yields benefits in terms of better
domestic and commercial space heating and hot water
performance, improved maintainability and lower costs
production/applications.
over the life cycle of the system. The guidance therefore
considers installation and commiss ioning alongside
BS 6880(2) was for many years a comprehensive guide for design requirements.
engineers involved in the design, installation and commis-
sioning of non-domestic heating systems. Its nominal
replacement, BS EN 12828(6) (published in 2003), only
covers system design and in far less detail than the earlier 1.2 How to use this
standard. Matters covered in BS 6880: Part 2: Selection of
Applications Manual
equipment and Part 3: Installation, commissioning and
maintenanceare not addressed in BS EN 12828.
This publication is intended to describe a logical sequence
The changes to the Building Regulations(3) in 2006 of processes for engineers to enable them to design
imposed more stringent requirements for energy efficient heating systems. It covers water based heating
efficiency and carbon emission reduction, which apply to systems for buildings other than dwellings with a total
both new and existing buildings. This imposes additional installed capacity from 45kW up to 2MW. Domestic hot
requirements for designers and installers who are water generation is outside the scope of this publication.
upgrading existing systems. What was once a simple boiler
replacement now needs more thought and detailed The design decisions and criteria for space heating and
knowledge of the building, the system and its controls to hot water systems for new buildings and existing building
enable the engineer not only to comply with the refurbishment projects are covered in chapters 2 and 3
Regulations, but also to implement an efficient and respectively of this Manual.
effective system. In addition, to ensure that boilers comply
with the Regulations, extra measures may need to be For new buildings, a number of key strategic design
taken, such as improvement in operating temperature decisions are outlined. These include planning and
controls and zoning. sustainability issues. ‘Sustainable development’ is now
1-2 Non-domestic hot water heating systems
becoming a major criterion underpinning planning. combined heat and power (CHP) and the application of
Specific targets for low carbon buildings and the use of biomass boilers. Life cycle analysis costs and payback are
renewable energy are being set by many local authorities. reviewed with respect to the replacement of plant. The
Examples of sustainability issues relating to the design of minimum efficiency and controls requirements for
the building, reduction in energy and CO emissions and replacement boiler plant are also included.
2
NO pollution are given in section 2 of the guide.
x
Examples of other key strategic design decisions that need Guidance on the use of renewable and low carbon
to be considered in the early design stages of the project technologies is given in chapters 3 and 4. This is a
include the intended occupancy of the building and its changing field and there is currently little authoritative
use, thermal comfort, interaction with the building design, guidance available. This document therefore refers to the
building fabric, services and facilities, the client’s budget, various technologies and directs readers to more detailed
fuel supply and heat generators. guidance where this is available.
Guidance in these areas is given with additional references Chapter 4 describes the major components of the heating
for further reading. The operating strategy of the heating system, including a review of the technologies used by
plant is covered with specific reference to the use of different boilers. Recent advances in the field of
controls. Various strands of legislation that affect the renewables, such as biofuel boilers and heat pumps, are
design of the heating system are covered, such as Part L of covered. The majority of hot water heating systems
the Building Regulations(3). The standards and guidance currently installed in buildings are of the constant volume
documents that support the requirements, such as the Non type with fixed speed pumps for the primary and
Domestic Heating, Cooling and Ventilation Compliance secondary circuits. Developments in variable speed
Guide(7), CIBSE Guides and British and European pumping technology have since led to variable flow
Standards, are identified. heating systems as an alternative to the constant volume
heating system and are reviewed here.
The criteria for the design of heating systems for new
buildings are given in section 2.3. Heating systems are The main components within the distribution hot water
classified according to the temperature regime over which system such as pumps, flow measurement and regulating
they operate and the corresponding operating pressure. devices are also covered and guidance is given on
The guidance is aimed mainly at low temperature hot component selection. The different types of heat emitters
water (LTHW) systems with condensing boilers. The choice are reviewed and reference made to underfloor heating.
of the internal and external design temperatures, Detailed guidance is given on flue and chimney design
calculation of the fabric and ventilation heat loss and use with respect to natural and mechanical draught systems
of reheat factors are included. A simple methodology for with particular emphasis on condensation occurring
calculation of the total design building heat load using the within the flue or chimney. Requirements for combustion
steady state approach is given. air supply and ventilation are given, based upon the
guidance already given in published British Standards.
The minimum seasonal efficiency criteria and control Fuel storage, particularly that required for biomass and
requirements that must be met by boilers in new buildings liquid biofuels, and requirements for reheating and water
in order to comply with Building Regulations Approved removal are covered. The requirements for water treat -
Document L2A(8)are also reviewed. ment, safety controls and electrical installation are also
covered in detail.
An existing system presents more challenges than
designing a new system. Not only does the engineer need a Chapter 5 reviews the basic types of controls for heating
full understanding of the type of system installed, but also systems. This chapter is not intended to deal with the
an understanding of the logic and intent behind its design subject in great detail and reference is therefore made to
at the time of installation. Only with this knowledge can CIBSE Guide H(9), CIBSE KS4(10)and CIBSE Guide F(11),
reasonable decisions be made on upgrading. Chapter 3 has which offer extensive information. The minimum control
therefore been written specifically for refurbishment requirements required to meet the Building Regulations(3)
projects. The main drivers for refurbishm ent are are also included.
identified, including failed heating plant, improving
performance of existing heating plant etc. For the Chapter 6 seeks to offer guidance on the installation of
purposes of this document, the scope of refurbishment is LTHWsystems and ancillary equipment. These include the
defined at three levels: minor refurbishm ent, major installation considerations for principal items of equip-
refurbishment and complete refurbishment. A flowchart ment, including heat sources, water circulation and
for a major refurbishment is included. The refurbishment distribution systems, heat emitters, controls and other
of existing heating systems is often subject to constraints associated plant items.
and these are identified.
Chapter 7 provides an overview of the installation, testing,
There are various types of heating systems currently commissioning and maintenance of heating systems in
installed in buildings. These are described so that existing general. This subject covers everything from static testing
systems undergoing refurbishment can be easily iden - of newly installed pipework, through the flushing and
tified. Guidance is also given that will assist the evaluation cleaning and finally the testing and commissioning of the
of current systems so that logical decisions can be made systems. It should be noted that many documents exist
regarding the appropriate level of refurbishment. covering each aspect of this subject in detail. This chapter
Evaluation of the existing heating load is reviewed and therefore provides an overview of the process.
three methods are given to enable this to be determined.
Options for refurbishment using low carbon technology A ‘troubleshooting’ guide is given in chapter 8. This
are given, including the use of solar thermal technology, identifies typical problems, causes of failure and solutions
Introduction 1-3
relating to hot water heating systems. It covers typical — CIBSE Guide A: Environmental design: chapter 3:
problems relating to the heat generator, flue, system Thermal properties of building structures.
hydraulics, controls and commissioning
— CIBSE Guide B: Heating, ventilating, air conditioning
and refrigeration: chapter 1: Heating
— CIBSE Guide C: Reference data: chapter 4: Flow of
1.3 Sources of further
fluids in pipes and ducts
information
— CIBSE Guide F: Energy efficiency in buildings
— CIBSE Guide H: Building control systems
1.3.1 Building Regulations
— CIBSE Commissioning Code B: Boilers
The Building Regulations(3) set requirements for — CIBSE Commissioning Code C: Automatic controls
minimum levels of energy efficiency. They are supported
by Approved Documents and other publications: — CIBSE Commissioning Code M: Commissioning
management
— Building Regulations Approved Document L2A:
— CIBSE Commissioning Code W: Water distribution
Conservation of fuel and power for new buildings other
systems
than dwellings
— CIBSE TM27: Flexible building services for office-
— Building Regulations Approved Document L2B:
based environments: principles for designers
Conservation of fuel and power for existing buildings
other than dwellings
— CIBSE. TM29: HVAC strategies for well-insulated
airtight buildings
— Non Domestic Heating, Cooling and Ventilation
Compliance Guide
— CIBSE TM31: Building log book toolkit
— Low or Zero Carbon Energy Sources: Strategy Guide
— CIBSE TM38: Renewable energy sources for buildings
The above documents may be downloaded free of charge — CIBSE TM39: Building energy metering.
from the government’s ‘Planning Portal’ website (http://
www.planningportal.gov.uk). It should be noted that a new The CIBSE Knowledge Series gives straightforward,
edition of Part L of the Building Regulations is likely to practical advice for engineers and the following titles are
be published in 2010. particularly relevant to this Applications Manual:
— CIBSE KS2: Managing your building services
The procedure for demonstrating compliance with the
Building Regulations for buildings other than dwellings is — CIBSE KS4: Understanding controls
by calculating the annual energy use for a proposed
— CIBSE KS5: Making buildings work
building and comparing it with the energy use of a
comparable ‘notional’ building. The calculation may be
— CIBSE KS6: Comfort
carried out either using approved simulation software, or
by a simplified tool developed by BRE called the — CIBSE KS7: Variable flow pipework systems
‘Simplified Building Energy Model’ (SBEM) with its
— CIBSE KS8: How to design a heating system
associated basic user interface (iSBEM). The following
documents provide guidance: — CIBSE KS9: Commissioning variable flow pipework
systems
— User guide to iSBEM (Simplified Building Energy
Method) — CIBSE KS10: Biomass heating.
— A Technical Manual for SBEM.
CIBSE Briefings give an overview of topical subjects and
may be downloaded free of charge from the CIBSE
These documents may be downloaded free of charge from
website. Although some date back to 2002, they offer
the ‘National Calculation Method’ website (http://www.
useful background information to more current guidance.
ncm.bre.co.uk).
Those relevant to this document are listed below:
— CIBSE Briefing 6: The Energy Performance in
1.3.2 CIBSE guidance
Buildings Directive
The following CIBSE documents give further detailed — CIBSE Briefing 7: Energy efficiency in refurbishment
guidance on the design decisions, system design, controls,
— CIBSE Briefing 8: Reducing emissions through energy
commissioning and maintenance for energy efficient
efficiency
systems and building. Details of these and other CIBSE
publications may be found on the CIBSE website (http:// — CIBSE Briefing 10: Thermal comfort in a 21st century
www.cibse.org/publications). climate.
CIBSE Guides are regarded as the most authoritative The above CIBSE Briefings may be downloaded free of
publications produced by the Institution and numerous charge from the CIBSE website (https://www.cibse.org/
references to these Guides will be found in other membersservices/downloads). It is necessary first to log-in,
documents mentioned below: either as a member or non-member.
1-4 Non-domestic hot water heating systems
1.3.3 HVCA guidance 2 BS 6880: Code of practice for low temperature hot water heating
systems of output greater than 45kW: Part 1: 1988: Fundamental
and design considerations; Part 2: 1988: Selection of equipment;
The Heating and Ventilating Contractors’ Association
Part 3: 1988: Installation, commissioning and maintenance
(HVCA) offers guidance for heating and ventilation
(London: British Standards Institution) (1988)
contractors on various topics associated with health and
safety, site management and installation. 3 The Building Regulations 2000 Statutory Instruments 2000 No
2531 as amended by The Building (Amendment) Regulations
Generally, published guidance on pipework installation 2001 Statutory Instruments 2001 No. 3335 and The Building
and testing is very limited. The following are the most and Approved Inspectors (Amendment) Regulations 2006
relevant parts of HVCA TR20: Installation and Testing of Statutory Instruments 2006 No. 652 (London: The Stationery
Pipework Systems: Office) (dates as indicated) (available at http://www.opsi.gov.uk/
stat.htm) (accessed August 2009)
— HVCA TR20: Part 1: Low temperature hot water
heating 4 Directive 2002/91/EC of the European Parliament and of the
Council of 16 December 2002 on the energy performance of
— HVCA TR20: Part 9: Natural gas buildings (‘The Energy Performance of Buildings Directive’)
Official J. of the European Communities L1/65 (4.1.2003)
— HVCA TR20: Part 10: Fuel oil.
(Brussels: Commission for the European Communities) (2003)
(available at http://ec.europa.eu/energy/demand/legislation/
Details of these and other HVCA publications may be
buildings_en.htm) (accessed August 2009)
found on the HVCA website (https://shop.welplan.co.uk).
5 The Energy Performance of Buildings (Certificates and
Inspections) (England and Wales) Regulations 2007 Statutory
1.3.4 Further guidance
Instruments 2007 No. 991 (London: The Stationery Office)
(2007) (available at http://www.opsi.gov.uk/stat.htm) (accessed
Although published some years ago, the following British August 2009)
Standards offer sound and practical advice:
6 BS 12828: 2003: Heating systems in buildings. Design for water-
— BS 6644: 2005 + A1: 2008: Specification for based heating systems(London: British Standards Institution)
installation of gas-fired hot water boilers of rated inputs (2003)
of between 70kW (net) and 1.8 MW (net) (2nd and
7 Non Domestic Heating, Cooling and Ventilation Compliance Guide
3rd family gases)
(London: NBS/Department of Communities and Local
— BS 6880: Code of practice for low temperature hot Government) (2006) (available at http://www.planningportal.
water heating systems of output greater than 45kW gov.uk/uploads/br/BR_PDF_PTL_NONDOMHEAT.pdf)
(3parts) (accessed August 2009)
— BS 5410: Code of practice for oil firing. Installations 8 Conservation of fuel and power in new buildings other than dwellings
up to 45kW output capacity for space heating and hot Building Regulations 2000 Approved Document L2A (London:
water supply purposes(2 parts). The Stationery Office) (2006) (available at http://www.planning
portal.gov.uk/england/professionals/en/1115314231806.html)
Details of British Standards may be found on the BSI (accessed August 2009)
website (http://www.bsigroup.com).
9 Building control systemsCIBSE Guide H (London: Chartered
Institution of Building Services Engineers) (2009)
10 Understanding controls CIBSE KS4 (London: Chartered
References Institution of Building Services Engineers) (2005)
1 Condensing boilersCIBSE AM3 (London: Chartered Institution 11 Energy efficiency in buildings CIBSE Guide F (London:
of Building Services Engineers) (1989) (out of print) Chartered Institution of Building Services Engineers) (2004)
