Heating Services in Buildings E-Book

David E. Watkins

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 1070

Veröffentlichungsjahr: 2011

Beschreibung

Water based heating systems are efficient, flexible, versatile and offer many advantages over other heating systems. These advantages (fast response, good controllability, efficient zonal heating and largely silent operation) all require that initial design, installation, commissioning and maintenance be carried out to a high standard by competent engineers.

Heating Services in Buildings provides the reader with a detailed and thorough understanding of the principles and elements of heating buildings using modern water based heating systems. A key theme of the book is that there is little difference, in the approach to the design and engineering, between domestic and commercial installations. The author’s detailed but highly practical approach to the subject ensures there is sufficient information for students from both a craft background and those with more academic backgrounds to understand the material. This approach is complemented by straightforward, easy-to-use diagrams.

Heating Services in Buildings supports a range of educational courses, including degree level building services engineering; NVQ Level 4 Higher Professional Diploma in Building Services Engineering; City & Guilds supplementary heating course and the Heating Design and Installation Course accredited by the European Registration Scheme (ERS).  

Leseprobe

Table of Contents

Cover

Title page

Copyright page

Preface

1 Introduction to Heating Services

2 Wet Heating Systems

TEMPERATURE AND PRESSURE

CIRCULATION

PIPING DISTRIBUTION ARRANGEMENT

ONE OR SINGLE PIPE SYSTEM

TWO PIPE SYSTEM

MICRO BORE PIPING SYSTEM

TWO PIPE RADIAL SYSTEM

HYBRID (MIXED) SYSTEMS

OPEN VENTED HEATING SYSTEMS

FEED AND EXPANSION (F&E) CISTERN

OPEN VENT PIPE AND COLD FEED AND EXPANSION PIPE

INTRODUCTION TO AND HISTORY OF SEALED HEATING SYSTEMS

SEALED HEATING SYSTEMS

EXPANSION VESSELS

AIR SEPARATION

SYSTEM CHARGING

SIZING THE EXPANSION VESSEL

GRAVITY CIRCULATION HEATING SYSTEMS

EXPLANATION OF GRAVITY CIRCULATION

3 Materials

PIPING MATERIALS FOR HEATING APPLICATIONS

LIGHT GAUGE COPPER TUBE

CURRENT EUROPEAN BRITISH STANDARD – COPPER TUBE

COATED COPPER TUBE

FORMING BENDS IN COPPER TUBE

JOINTING COPPER TUBE

PROPRIETARY MADE PIPE FITTINGS

MECHANICAL COMPRESSION TYPE FITTINGS

CAPILLARY TYPE FITTINGS

FLAME-FREE JOINTS

PUSH FIT RING SEAL JOINTS

CRIMPED OR PRESSED COPPER JOINTS

STAINLESS STEEL TUBE

STAINLESS STEEL IDENTIFICATION

LIGHT GAUGE STAINLESS STEEL TUBE

STEEL PIPE

LOW CARBON MILD STEEL TUBE

FORMING BENDS IN STEEL TUBE

JOINTS FOR LOW CARBON MILD STEEL TUBE

MECHANICAL TYPE JOINTS FOR STEEL TUBE

MALLEABLE IRON

PLASTICS

CROSS-LINKED POLYETHYLENE (PEX)

POLYBUTYLENE (PB)

JOINTING PEX AND PB TUBES

VALVES

STOPCOCK PATTERN STOPVALVE

GATEVALVES

BUTTERFLY VALVES

DIAPHRAGM VALVE

PLUG VALVES AND COCKS

NON-RETURN AND CHECK VALVES

NON-RETURN VALVES

CHECK VALVES

DOUBLE CHECK VALVE

NON-VERIFIABLE DISCONNECTOR VALVE

REDUCED PRESSURE ZONE (RPZ) VALVE

VACUUM BREAKING VALVE

FLOATVALVES

GLOBE VALVES

4 Heat and Heat Transfer

HEAT

TEMPERATURE

SPECIFIC HEAT CAPACITY

LATENT HEAT

SENSIBLE HEAT

HEAT TRANSFER

CONDUCTION

CONVECTION

RADIATION

HUMIDITY

5 Heat Emitters

PRESSED STEEL PANEL RADIATORS

CONVECTOR RADIATOR

LOW SURFACE TEMPERATURE (LST) RADIATORS

CAST IRON PANEL RADIATORS

COLUMN RADIATORS

ALUMINIUM RADIATORS

NATURAL CONVECTORS

FLOOR TRENCH CONVECTOR

FAN, OR FORCED CONVECTORS

SKIRTING HEATING

RADIANT PANELS

EMBEDDED RADIANT PANELS

RADIATOR FIXING AND SHELVES

EXAMPLES OF CONVECTION STAINING

RADIATOR ENCLOSURES

RADIATOR CONNECTIONS

ROOM HEIGHT EFFECT

LOCATION OF HEAT EMITTERS

RADIATOR ACCESSORIES

DESIGNER RADIATORS AND TOWEL RAILS

6 Underfloor Heating

OPERATING PRINCIPLES

UFH PIPING MATERIALS

PIPING ARRANGEMENTS

TRANSITING PIPEWORK

FLOOR STRUCTURES AND FINISHES

FLOOR FINISHES

ASSESSMENT OF FLOOR HEAT EMISSION

UNDERFLOOR HEATING COMPONENTS

UFH WATER TEMPERATURE CONTROL

SYSTEM TESTING AND COMMISSIONING

7 Heat Requirements of Buildings

INTERNAL DESIGN TEMPERATURES

EXTERNAL TEMPERATURE (BASE DESIGN TEMPERATURE)

THERMAL PROPERTIES OF BUILDINGS

‘U’ VALUES (THERMAL TRANSMITTANCE COEFFICIENT)

AIR INFILTRATION

HEAT GAINS

BUILDING TIME-LAG

HEAT LOSS CALCULATIONS

WORKED ENGINEERING HEAT LOSS CALCULATION

EXPLANATION OF EXAMPLE CALCULATION

BOILER SIZING

CUBE X NUMBER METHOD

8 Heat Emitter Selection and Sizing

MEAN WATER TEMPERATURE AND DELTA T

CONDENSING BOILER SYSTEMS MODE

CORRECTION FACTORS

EXAMPLE OF CORRECTION FACTOR USE

SIZING AND SELECTION PROCEDURE FOR HEAT EMITTERS

HEATING SURFACE

9 Pipe Sizing

FLOW OF HEAT IN PIPES

VELOCITY

FRICTIONAL RESISTANCE

INDEX PIPE CIRCUIT

PIPE SIZING DATA

PIPE SIZING PROCEDURE

SIMPLER PIPE SIZING EXAMPLE

BOILER BYPASS FLOW ALLOWANCE

APPROXIMATION OF PIPE SIZES

OTHER PIPING ARRANGEMENTS

10 Electricity

HISTORY AND NATURE OF ELECTRICITY

DEFINITIONS OF ELECTRICAL TERMS

ELECTRICAL GENERATION, SUPPLY AND DISTRIBUTION

DIRECT CURRENT (DC)

CABLE IDENTIFICATION COLOURS

VOLTAGE DEFINITIONS

BUILDING WIRING CIRCUITS

CONSUMER UNIT

RING CIRCUITS

SPUR POINTS

LIGHTING RADIAL CIRCUITS

IMMERSION HEATER WIRING

EARTHING

11 Controls, Components and Control Systems

CONTROLS FOR SAFETY

SYSTEM SAFETY RELIEF VALVES

CONTROLS FOR COMFORT AND ENERGY EFFICIENCY

BASIC SYSTEM OF THERMOSTAT CONTROLLING PUMP

ROOM THERMOSTATS

ROOM THERMOSTAT LOCATION

MIXING CONVECTORS AND RADIATORS

TEMPERATURE SENSING VALVE

CYLINDER THERMOSTAT ARRANGED FOR DOMESTIC HOT WATER PRIORITY

CYLINDER THERMOSTATS

CURRENT CONTROL SCHEMES

ZONE CONTROL BY TWO-PORT MOTORISED VALVE

MOTORISED VALVES

SELECTIVE DIVERTER CONTROL BY THREE-WAY MOTORISED VALVE

SHARED FLOW BY THREE-WAY MOTORISED VALVE

WEATHER COMPENSATING CONTROL SYSTEM

TWIN-PUMP CONTROL SCHEMES

WIRELESS CONTROLS

THERMOSTATIC FROST PROTECTION

AUTOMATIC SPACE TEMPERATURE REDUCTION

AUTOMATIC BYPASS VALVE

THERMOSTATIC RADIATOR VALVES (TRVs)

12 Oil Firing

OIL

OIL BURNER FUELS

EXPLANATION OF CHARACTERISTICS

OIL STORAGE

OIL STORAGE TANKS

BUNDED OIL CATCHMENT AREAS

STORAGE TANK LOCATION

OIL HANDLING AND DISTRIBUTION

OIL FIRE VALVE

DOMESTIC OIL FIRED HEATING FIRE VALVES

OIL FILTERS AND STRAINERS

OIL LINE PIPE SIZING

OIL PRE-HEATING

CENTRAL OIL STORAGE

OIL BURNERS

PRESSURE JET OIL BURNER

ROTARY CUP BURNER

ROTARY VAPORISING OIL BURNERS

ROTARY VAPORISING DYNAFLAME BURNER

CONSTANT LEVEL CONTROL UNIT

13 Natural Gas Firing

GAS

NATURAL GAS

ODOUR

TOXICITY

CALORIFIC VALUE

RELATIVE DENSITY

COMBUSTION AIR

WOBBE NUMBER

BURNING VELOCITY

GAS MODULUS

SUPPLY PRESSURE

OTHER GASES

GAS SUPPLY AND DISTRIBUTION

GAS METERS

METER COMPARTMENT

GAS BOOSTING

GAS SUPPLY PIPEWORK

DOMESTIC PIPE SIZING

FLOW OF GAS IN PIPES

GAS BURNERS

NATURAL DRAUGHT BURNERS

GAS SAFETY SOLENOID SHUT-OFF VALVE

THERMOCOUPLE ASSEMBLY

BOILER THERMOSTAT AND MAIN GAS SOLENOID CONTROL VALVE

MAIN BURNER GAS PRESSURE GOVERNOR/REGULATOR

MULTIFUNCTIONAL GAS CONTROL VALVE

IGNITION METHODS

FAN-ASSISTED NATURAL DRAUGHT BURNERS

FORCED DRAUGHT GAS BURNER

PULSE COMBUSTION FURNACE

14 Liquefied Petroleum Gas Firing (LPG)

PROPERTIES OF LIQUEFIED PETROLEUM GAS

EXPLANATION OF PROPERTIES

LIQUEFIED PETROLEUM GAS STORAGE

CYLINDER INSTALLATIONS

BULK LPG STORAGE INSTALLATION

STATIC ELECTRICITY

FIRE PROTECTION

LPG STORAGE LOCATION

LPG DISTRIBUTION SYSTEMS

DISTRIBUTION PIPING MATERIALS

LPG GAS BURNERS

15 Alternative Fuels and Energy

WOOD BURNING

ELECTRICAL ENERGY

ELECTRIC HEAT GENERATORS

NEW ALTERNATIVE FUELS, ENERGIES AND SYSTEMS

SOLAR HEATING

COMBINED HEAT AND POWER (CHP)

MICRO-COMBINED HEAT AND POWER

BIOFUELS

BIOMASS

BIOMASS BOILERS

BIO-OIL

BIOGAS

HEAT PUMPS

HEAT PUMP REFRIGERANT

HEAT PUMP TYPES AND APPLICATIONS

AIR SOURCE

AIR-TO-AIR HEAT PUMPS

AIR-TO-WATER HEAT PUMPS

WATER SOURCE

WATER-TO-AIR AND WATER-TO-WATER HEAT PUMPS

GROUND SOURCE HEAT PUMPS

SOLAR ENERGY HEAT PUMPS

COEFFICIENT OF PERFORMANCE (COP)

HEAT RECOVERY

16 Combustion, Flues and Chimneys

AIR

COMBUSTION AND COMBUSTION REACTION

INCOMPLETE COMBUSTION

CARBON MONOXIDE (CO)

EFFECTS OF CARBON MONOXIDE POISONING

CARBON MONOXIDE DETECTORS

INCORRECT BURNER PRESSURES

FLAME IMPINGEMENT

PRODUCT OF COMBUSTION STANDARDS

NITROGEN OXIDE

NOx

FLUES AND CHIMNEYS

DESIGN PERFORMANCE FACTORS

DRAUGHT

COMBUSTION AND VENTILATION AIR

TEMPERATURE DIFFERENTIAL

FLUE OR CHIMNEY HEIGHT

COMBUSTION STACK EFFECT

ADVERSE PERFORMANCE FACTORS

FLUE AND CHIMNEY TERMINATIONS AND TERMINALS

DRAUGHT DIVERTERS, BREAKS AND STABILISERS

THERMAL INVERSION

FLUE PRINCIPLES, CONSTRUCTION AND MATERIALS

USE AND LINING OF EXISTING MASONRY CHIMNEYS

BALANCED FLUES

ROOM SEALED APPLIANCES

BALANCED FLUE TERMINATIONS

FLUE BOOSTING

FLUES FOR HIGH-RISE BUILDINGS

SE-DUCT AND ‘U’ DUCT FLUE SYSTEMS

FLUE DILUTION

ASSESSMENT OF CONVENTIONAL FLUE PIPE SIZES

CONDENSATION WITHIN FLUES

PSYCHROMETRICS

CONDENSING BOILERS

SEDBUK

DEVELOPMENT OF CONDENSING BOILERS

CONDENSING HEATING SYSTEMS

PLUMING

CONDENSATE DRAIN

BOILER EFFICIENCY

17 Combustion Efficiency Testing

BURNER EFFICIENCY

COMBUSTION EFFICIENCY TESTING

FLUE GAS TEMPERATURE

DEW POINT TEMPERATURE

CARBON DIOXIDE (CO2) CONTENT

SMOKE TEST

FLUE DRAUGHT TEST

NITROGEN OXIDES (NOx)

ELECTRONIC FLUE GAS ANALYSERS

18 Circulating Pumps

CENTRIFUGAL ACTION

CENTRIFUGAL PUMPS

CIRCULATING PUMPS

DOMESTIC INLINE CIRCULATORS

PUMP SELECTION

FIXED OR VARIABLE PERFORMANCE PUMPS

PUMP EFFECTS

PUMP POSITION

CIRCULATING PUMPS FOR SEALED HEATING SYSTEMS

CAVITATION

EFFECTS OF CAVITATION

PUMP ARRANGEMENTS

ELECTRIC MOTORS

INDEX OF PROTECTION (IP RATING)

METHODS OF STARTING ELECTRIC MOTORS

ANCILLARY EQUIPMENT FOR PUMPS

NOISE AND VIBRATION

19 Domestic Hot Water

CHOICE OF DOMESTIC HOT WATER SYSTEM

ASSESSMENT OF DOMESTIC HOT WATER STORAGE

RECOVERY TIME

DOMESTIC HOT WATER TEMPERATURE

DOMESTIC HOT WATER STORAGE VESSELS

DIRECT DOMESTIC HOT WATER SYSTEMS

INDIRECT DOMESTIC HOT WATER SYSTEMS

SINGLE FEED INDIRECT DOMESTIC HOT WATER SYSTEMS

UNVENTED DOMESTIC HOT WATER

PRINCIPLES OF UNVENTED DOMESTIC HOT WATER STORAGE SYSTEMS

DISCHARGE PIPES FROM SAFETY DEVICES

SUMMARY OF CONTROLS FOR UVDHWSS

UNVENTED DOMESTIC HOT WATER STORAGE VESSEL WITH INTERNAL EXPANSION CHAMBER

NON-STORAGE UNVENTED DOMESTIC HOT WATER SYSTEMS

DOMESTIC HOT WATER CYLINDER WITH TWIN HEAT EXCHANGERS

STRATIFICATION

BOILER LOADING/ELECTRICAL POWER FOR DOMESTIC HOT WATER

ELECTRIC IMMERSION HEATERS

COMBINATION BOILERS FOR HEATING AND DOMESTIC HOT WATER

20 Solar Energy for Water Heating

SOLAR ENERGY

SOLAR RADIATION INTENSITY

SOLAR THERMAL SYSTEMS

SOLAR THERMAL ENERGY FOR SPACE HEATING

SOLAR THERMAL ENERGY FOR HEATING SWIMMING POOLS

SOLAR ENERGY HEAT SOURCE FOR HEAT PUMPS

SOLAR THERMAL ENERGY FOR RAISING DOMESTIC HOT WATER TEMPERATURE

DIRECT SOLAR DOMESTIC HOT WATER SYSTEMS

INDIRECT SOLAR DOMESTIC HOT WATER SYSTEMS

SOLAR HEATED THERMAL STORE

FROST PROTECTION

DRAIN-BACK SOLAR HEATING SYSTEMS

SOLAR COLLECTOR PANELS

SOLAR COLLECTOR PANEL LOCATION

SOLAR COLLECTOR PANEL FIXING

SOLAR COLLECTOR PANEL SIZING

SOLAR HEATING CONTROL SCHEMES

21 Water Treatment

WATER SUPPLY

WATER TREATMENT

HARDNESS OF WATER

CLASSIFICATION OF HARDNESS

EFFECT OF HARD WATER

BASE EXCHANGE SOFTENING

INSTALLATION OF BASE EXCHANGE WATER SOFTENER

ELECTROLYTIC ACTION

DEZINCIFICATION

BLACK IRON OXIDE

HYDROGEN GAS

BACTERIAL ACTIVITY

OXIDIC CORROSION

OTHER FORMS OF CORROSION

ALUMINIUM HEAT EMITTERS

pH VALUE (POTENTIAL HYDROGEN)

CORROSION INHIBITION

APPLICATION OF THE INHIBITOR (NEW SYSTEMS)

APPLICATION OF THE INHIBITOR (EXISTING SYSTEMS)

NON-DOMESTIC HEATING SYSTEMS

SACRIFICIAL ANODES

SCALE REDUCERS/WATER CONDITIONERS

22 District Heating

THE DISTRICT HEATING SYSTEM

THE HEAT-GENERATING STATION

DISTRIBUTION HEATING MAINS

DISTRIBUTION PIPE MATERIALS AND INSTALLATION

HEAT METERS AND CONSUMER CONNECTIONS

23 Expansion of Pipework

COEFFICIENT OF LINEAR EXPANSION

CALCULATING EXPANSION

PROVISION FOR EXPANSION AND EXPANSION JOINTS

EXPANSION LOOPS

EXPANSION BELLOWS/COMPENSATORS

CYCLIC LIFE

BELLOWS APPLICATION

FORCES ON ANCHORS AND GUIDES

ANCHORS AND GUIDES

HINGED ANGULAR BELLOWS

ARTICULATED BELLOWS

GIMBAL EXPANSION BELLOWS

PACKED GLAND SLIDING EXPANSION JOINT

FLEXIBLE RUBBER EXPANSION JOINTS

24 Regulations, Standards, Codes and Guides

BUILDING REGULATIONS

WATER REGULATIONS

THE GAS SAFETY (INSTALLATION AND USE) REGULATIONS

BRITISH STANDARDS

COMPETENT PERSONS SCHEMES

PROFESSIONAL BODIES

25 Testing and System Commissioning

TESTING FOR SOUNDNESS

TESTING MEDIUM

TESTING METALLIC PIPING SYSTEMS

TESTING THERMOPLASTIC PIPING SYSTEMS

TESTING SYSTEMS COMPRISING MIXED RIGID AND ELASTOMERIC PIPING MATERIALS

PRE-COMMISSIONING ACTIVITIES

COMMISSIONING THE HEAT RAISING PLANT

COMMISSIONING THE CIRCULATORY SYSTEM

OPERATING AND MAINTENANCE REQUIREMENTS

26 Operating Costs and Whole Life Costing

CALORIFIC VALUE

SYSTEM EFFICIENCY

HEATING LOAD

HEATING SEASON/OPERATING PERIOD

DEGREE-DAYS

ANNUAL ENERGY CONSUMED

ANNUAL FUEL UTILISATION

ANNUAL AUXILIARIES RUNNING COSTS

WHOLE LIFE COSTING

Appendices

APPENDIX 1 COMPARATIVE TABLE OF SHEET METAL GAUGES

APPENDIX 2 TEMPERATURE COMPARISON AT ATMOSPHERIC PRESSURE

APPENDIX 3 MESH/MICRON RATING

APPENDIX 4 COPPER TUBE BS EN1057 (INTRODUCED 15/8/96, FORMERLY BS2871)

APPENDIX 5 DIMENSIONAL TOLERANCES OF LOW CARBON MILD STEEL TUBE CONFORMING TO BS EN10255, 2004. FORMERLY BS1387

APPENDIX 6 HYDROSTATIC DATA

APPENDIX 7 COMPOSITION OF COPPER ALLOYS (COMMON)

APPENDIX 8 COMPOSITION OF SOFT SOLDERS

APPENDIX 9 SI PREFIXES

APPENDIX 10 LIGHT GAUGE STAINLESS STEEL TUBE AUSTENITIC TYPE 304 OR 316 (BS EN10312)

APPENDIX 11 ELEMENTS AND CHEMICAL SYMBOLS

APPENDIX 12 BEAUFORT WIND SCALE

APPENDIX 13 COMPARISON OF BSP AND NPT THREADS

APPENDIX 14 PROPERTIES OF WATER

APPENDIX 15 TEMPERATURE CONVERSIONS

APPENDIX 16 METRIC CONVERSION FACTORS

APPENDIX 17 PRESSURE CONVERSION

APPENDIX 18 HEAT FLOW CONVERSION

APPENDIX 19 APPROXIMATE VISCOSITY CONVERSION

APPENDIX 20 VISCOSITY–TEMPERATURE RELATIONSHIP

APPENDIX 21 ALTITUDE AND PRESSURE CORRECTIONS

Index

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Library of Congress Cataloging-in-Publication Data

Watkins, David E.

Heating services in buildings : design, installation, commissioning & maintenance / by David E Watkins.

p. cm.

Includes bibliographical references and index.

ISBN 978-0-470-65603-7 (pbk. : alk. paper) 1. Heating. I. Title.

TH7121.W37 2011

697–dc22

2010051098

A catalogue record for this book is available from the British Library.

This book is published in the following electronic formats: ePDF 9781119971658; ePub 9781119971665; Mobi 9781119971672

Preface

There have been a number of books written on the subject of heating over the years, which would fill a sizable section of any notable library if collected together.

On examining the more recent of these books, that is those published over the last twenty years, it was found that they could be categorised as belonging to one of three groups. These are books written for the DIY market which are of little use to any student who is serious about studying to become a qualified heating professional. Alternatively, there are a number of books aimed at the craft level student concentrating only on the practical aspects of the subject. The third category of technical books, of which there are fewer available, has been written for the qualified professional engineer that assumes the student has previously obtained the basic engineering knowledge that is required to advance to a higher level of their education.

This observation becomes apparent when looking for a suitable technical book to support the NVQ Level 4 Higher Professional Diploma in Building Services Engineering and other design based engineering courses.

The search found that no single book was available to support these courses and the student would have to purchase a large number of publications to cover the subject to the extent required. This would also result in the student incurring a high financial cost to obtain copies of these publications.

The answer to this situation was to produce a number of supporting handout papers that expanded upon the course lectures that eventually developed over the years into a sizable set of notes when bound together.

During the course of developing these supporting notes, the subject of heating buildings, both for domestic residential properties and commercial buildings, has changed enormously, particularly with regard to the need to conserve energy, develop alternative forms of energy and provide controls that are suitable for the system’s needs.

This requirement has manifested itself in the form of increased mandatory regulations and improved technology that has been developed to meet these compulsory regulations and conservation targets.

It was that necessity to incorporate explanations and detailed information on these changes that led to the set of supporting notes being developed into the basis of this book.

The aim of this work is to provide in a text and illustrative form a complete guide from basic principles to an advanced level to all the elements that combine to impart the engineering knowledge required on the subject of hydronic heating systems.

The book has been arranged to present the subject matter in a logical order that builds on each preceding chapter and culminates to provide the complete informative material. The book also demonstrates that there is little difference between domestic and commercial heating systems in the approach to the engineering and design of the systems, but makes mention where there is a difference.

This book has been developed over many years from the collection of handout notes to its present volume, where it originally supported a City & Guilds supplementary heating course, which further developed to support the heating design and installation course accredited by the European Registration Scheme (ERS) and other similar academic courses presently run today.

It is also intended that this volume will support Unit 11, ‘Space heating technology and design’, which is a module contained in the NVQ Level 4 Higher Professional Diploma in Building Services Engineering.

The book is aimed at both craft level plumbing students qualified to NVQ Level 3 standard aspiring to bridge the educational gap to an engineering career, plus school leavers with the necessary academic ‘A’ level qualifications and employed in a building services engineering consultancy.

Although this volume has been produced to support the NVQ Level 4 course and similar design/engineering courses, it is hoped that it will be of equal interest and use to anyone concerned with the design and installation of hydronic heating systems.

This book has resisted the inclusion of over explaining or illustrating elements in order to provide the information in an affordable manner to all those concerned. This gives the lecturer the opportunity to expand upon each subject and provide further examples in the classroom.

It is also correct to acknowledge that a work of this type has only been possible due to the encouragement and assistance of many other people, most notably Mr David Bantock, whose original set of notes I inherited when I started as a part-time lecturer delivering the course, and who has been instrumental in his encouragement during its development. Also my wife, Jenny Watkins, for proofreading and endless patience, and the many students who encouraged its eventual publication.

Special acknowledgement should also be mentioned for permission to reproduce Figure 5.23, Room Height Temperature Gradients, from Elsevier Publishing, which is based on a similar illustration in their book entitled Faber & Kell’s Heating & Air-conditioning of Buildings. Also, for permission granted by Baxi Heating to reproduce Figure 15.8, Illustration of a Micro-Combined Heat and Power Generating Unit and M H Mear Co. Ltd for permission to reproduce Figure 7.3, of a Mear’s Slide Rule Heating Calculator.

David E. Watkins

1

Introduction to Heating Services

The broad term ‘central heating’ is used to describe many types and forms of heating, and some usage is totally misleading and inaccurate, through ignorance of the subject. This chapter is a basic introduction to the mechanics of central heating, which is discussed in greater detail in the following chapters.

If we examine the term, it implies a system where heat is produced from a central source and distributed around the whole building. The method of heat generation and distribution may vary with the type of heating system employed.

Central heating is sometimes referred to as space heating. To be understood fully, this must be described by its type or system arrangement, and may be categorised as being either full, part or background heating.

Full central heating may be defined as being a system of heating from a central source where all the normally habitable or used rooms/spaces are heated to achieve guaranteed temperatures under certain conditions. By today’s standards, all heating systems installed in residential dwellings and most commercial buildings should conform to this category, unless there are acceptable reasons for not doing so.

Partial central heating is the term applied where only part of the building is to be heated, but even then the rooms or spaces that are heated should still have guaranteed temperatures under stated conditions. This form of central heating would be a rare occurrence for a residential dwelling but not so uncommon for some commercial buildings, especially where part of the building complex is not normally occupied.

The term ‘background heating’ is used to describe a form of central heating whereby lower than normal or standard recommended temperatures are aimed at for the type of building involved. The term is sometimes used to refer to heating systems installed in buildings where the room temperatures are not guaranteed. This form of heating is unacceptable by today’s standards on both environmental and efficiency grounds.

It should be noted that, unless otherwise specified, full central heating should normally be designed to current regulations and standards and installed in a professional manner. In some instances, usually due to a specific use or financial reasons, the client may only require or specify partial heating to be installed, sometimes with the request that safeguards are included to allow the system to be extended at a later date to achieve full central heating.

Background heating, where lower than normal or recommended temperatures are aimed at, should only be used when specifically requested by the client for some reason. Even then, agreed temperatures should be incorporated into the design and guaranteed before any installation work commences. Under no circumstances should any heating system be installed without first agreeing specific room temperatures to be achieved when certain conditions exist. These conditions are discussed in Chapter 2.

Having understood the extent of the heating system and its classification, be it full, part or background heating, heating systems may be further divided under the headings of ‘wet’ or ‘dry’ systems. The terms wet or dry refer to the medium used to convey the heat from its source of generation to its point of use. Wet systems may be further classified by the piping circulation arrangement, with dry systems being divided into warm air and electric heating.

Figure 1.1 indicates the broad classifications of heating systems.

Figure 1.1 Heating system categories

Heating systems can be sub-divided even further, but this will be explained in Chapter 21.

Wet Heating Systems

All wet types of heating systems employ a liquid as a medium to convey the heat from its source of generation. It is then distributed around the system to each heat emitter, where it transfers part of that heat through the heating surface of the heat emitters. Finally, the liquid is returned to the source of generation for the process to cycle continuously. The source of heat is commonly referred to as a boiler.

In all domestic heating systems, and most heating systems for other types of buildings, water is chosen as the medium for conveying the heat due to its low cost and being readily available. However, water does have the disadvantages of a low boiling point and high freezing point; it can also be corrosive to metallic materials and has a limited heat carrying capacity. The corrosive nature of the water can be reduced by water treatment, which is discussed later in this volume.

The temperature limitations and heat carrying capacity of water will have to be accepted unless we change the atmospheric conditions of the system, or we can change the liquid. Liquids known as ‘thermal fluids’ are available and have been used successfully on larger commercial type heating installations. They possess different properties to water, such as being less aggressive to common materials, having higher boiling points and lower freezing points, a greater heat carrying capacity than water and, in some cases, a lower viscosity. The merits of thermal fluids are much superior to those of water but are generally discounted for all domestic heating systems owing to their higher capital cost and not being readily available. They are also rarely used on larger commercial systems for the same reasons, but when conditions are right they can be considered attractive. The difficulty of availability can cause problems when replacement fluid is required immediately, following any emergency maintenance work. Thermal fluids have been used for domestic applications on limited occasions in countries that experience much lower temperatures than in the UK, as the lower freezing point of the fluid can be an important advantage when sub-zero ambient temperatures are experienced for prolonged periods with the heating system in a non-operating mode. They have also been employed as the heat carrying medium for some solar heating systems.

The purpose of the water used in heating systems differs from that used in domestic hot and cold water installations. In those systems, water is the end product or consumable item and after it has been used, it is discharged to waste. The water employed in a heating system is a non-consumable substance. It is the medium used to carry the heat required and, after it has transferred some of the heat, it is returned to the boiler to be re-used over and over again.

Dry Heating Systems (Warm Air)

Warm-air dry-type heating systems differ from wet-type heating systems insofar as the fluid employed is not only the medium used to convey the heat, but is also the end product. As the name implies, air is the fluid used to carry the heat from its source of generation, a warm air heater. It is then distributed, usually through a network of ducting, where it is arranged to enter directly into the room under controlled conditions to displace the cooler air. Finally, a mixture of the two is partly returned to the warm air heater for the process to be repeated.

Warm-air heating systems are generally disliked by many occupants of dwellings that have such systems installed, but this is usually because the systems are either not designed correctly, not installed correctly or are, in many cases, incomplete. This is mainly down to ignorance of the fundamental principles of warm air heating, which, if given the respect deserved, can be a very good form of heating. This work exclusively concentrates on wet-type heating systems since it is aimed at students and engineers in the plumbing industry.

Dry Heating Systems (Electricity)

Electrical heating systems may technically be classified as dry systems, but they do not employ a medium as they generate their heat at the point of use. For this reason, electrical heating systems are not included in this book, with the exception of heating systems that use electricity as the source of power to heat the water. Here they are classified as being wet or hydronic heating systems.

Supplementary Heating

This is a term applied to describe heating appliances, either fixed or portable, that are used to supplement the central heating system – either during extreme cold spells when the outside air temperature falls well below the base design temperature, or during the heating-off season in spring or autumn, when the outside temperature drops to below that considered comfortable.

Examples of such heating appliances include:

Radiant electric fires, portable and fixedOil filled radiatorsOil room heatersLPG room heatersGas firesOpen solid fuel fires.

The list is not intended to be exhaustive, but meant to serve as a general representative selection of supplementary heating appliances.

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Wet Heating Systems

Wet heating systems, commonly referred to as hydronic heating systems because they use a liquid as a medium, nearly always employ water as the medium to convey the heat from its source of generation, a boiler. This is rather a misnomer, as a boiler must be designed to avoid boiling the water, but is probably a leftover term from the days of raising steam. The heated water is circulated around the system, transferring part of its heat, and returns back to the boiler for the process to be repeated.