Cibse how to design a heating system.pdf

CIBSE KNOWLEDGE SERIES

How to design a heating

system

Direct and accessible guidance from key subject

overviews to implementing practical solutions

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No part of this publication may be reproduced, stored in a retrieval system or transmitted

in any form or by any means without the prior permission of the Institution.

Registered charity number 278104

ISBN-10: 1-903287-79-0

ISBN-13: 978-1-903287-79-8

This document is based on the best knowledge available at the time of publication.

However no responsibility of any kind for any injury, death, loss, damage or delay however

caused resulting from the use of these recommendations can be accepted by the

Chartered Institution of Building Services Engineers, the authors or others involved in its

publication. In adopting these recommendations for use each adopter by doing so agrees to

accept full responsibility for any personal injury, death, loss, damage or delay arising out of

or in connection with their use by or on behalf of such adopter irrespective of the cause or

reason therefore and agrees to defend, indemnify and hold harmless the Chartered

Institution of Building Services Engineers, the authors and others involved in their

publication from any and all liability arising out of or in connection with such use as

aforesaid and irrespective of any negligence on the part of those indemnified.

Typeset by CIBSE Publications

Printed in Great Britain by Latimer Trend & Co. Ltd., Plymouth PL6 7PY

How to design a

heating system

CIBSE Knowledge Series: KS8

Principal author

Gay Lawrence Race

Editor

Helen Carwardine

CIBSE Knowledge Series — How to design a heating system

Contents

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

1.1 Use of this guidance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

2 The heating design process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

2.1 The design process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

2.2 Heating system design process . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

2.3 Key heating design calculation sequence . . . . . . . . . . . . . . . . . . . .8

2.4 Thermal comfort . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

3 Key design steps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

3.1 Step 1: pre-design and design brief . . . . . . . . . . . . . . . . . . . . . . .10

3.2 Step 2: gather design information . . . . . . . . . . . . . . . . . . . . . . . . .11

3.3 Step 3: design data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

3.4 Step 4: building thermal performance analysis . . . . . . . . . . . . . . .13

3 . 5 Step 5: heating system option analysis and selection . . . . . . . . . .15

3.6 Step 6: space heat losses and heat load . . . . . . . . . . . . . . . . . . . .20

3.7 Step 7: equipment sizing and selection . . . . . . . . . . . . . . . . . . . . .23

3.8 Step 8: heating load analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

3.9 Step 9: plant sizing and selection . . . . . . . . . . . . . . . . . . . . . . . . .27

3.10 Step 10: system analysis and control performance . . . . . . . . . .27

3.11 Step 11: Final value engineering and energy targets assessment 29

3.12 Step 12: design review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29

4 Developing the design — key issues . . . . . . . . . . . . . . . . . . . . . . .31

4.1 Design data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

4.2 Design margins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

4.3 Energy efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

4.4 Quality control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

CIBSE Knowledge Series — How to design a heating system

Introduction

In cooler climates the provision of heating is an essential part of creating

comfortable internal environments, and therefore heating system design is a

fundamental part of building services design.

Heating

In 2005:

Heating is a major sector within mechanical building services. There are some

21 million domestic properties in the UK with gas-fired central heating, and a

further 200,000 commercial properties with heating. The UK market for

heating systems is substantial, with around 1.65 million new domestic boilers

installed per year and around 23,500 commercial boilers. There are around 9

million radiators installed per year with a further 22 million metres of

underfloor heating pipe (2005 figures) (1) .

1.65 million new domestic boilers

23,500 commercial boilers

9 million radiators

22 million metres of underfloor

heating pipe

were installed in the UK alone.

Sources: BSRIA domestic boiler

marketing report March 2006, BSRIA

commercial boiler marketing report

March 2006.

Heating is also a major consumer of energy within the UK, with space heating

accounting for over 40% of all non-transport energy use and over 60% of

domestic energy use (2) , rising to over 80% if hot water is included (see Figure

1). As major energy users, heating and hot water also generate a substantial

proportion of CO 2 emissions, delivering almost half the CO 2 emissions from

non-domestic buildings.

Given the current requirements to limit energy consumption and CO 2

production, good design of heating systems is essential to ensure that systems

operate efficiently and safely and make effective use of energy. Historically

there have been problems with oversizing of heating systems which can lead

to inefficient operation, particularly at part load operation, to control

problems and to a reduction in plant operating life (3) . The energy

consumption for oversized plant can be 50% more than necessary.

Figure 1:

UK non-transport energy

use (2002 figures) million

tonnes of oil equivalent

11·8

Although heating is often considered to be a simple, basic system, there are

many options and permutations to be considered. The majority of UK

buildings will require heating but different building types and locations will

have very different requirements and constraints — consider for example the

choices possible for a small ground floor flat in a city centre development

against those for a holiday cottage in one of the National Parks, or the

choices for an urban industrial unit against those for a rural agricultural unit

and farm shop.

4·4

41·4

15·0

9·7

12·9

Space heating

Water

Cooking/catering

Lighting appliances

Process use

Motors/drivers

Drying/separation

Other non-transport

The fundamental components of any heating system are:

—

a means of generating heat, i.e. the heat source

—

a means of distributing the heat around the building or buildings, i.e.

the distribution medium and network

Source: DTI Energy consumption tables:

overall energy consumption. URN No:

05/2008 Table 1.2 Non-transport energy

consumption by end use, 1990, 2000, 2001

and 2002

—

a means of delivering the heat into the space to be heated, i.e. the

heat emitter .

CIBSE Knowledge Series — How to design a heating system

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