BG 31/2017 the Illustrated Guide to Mechanical Building Services

BG 31-17 illustrated mechanical guide third edition cover_BSRIA Pubs cover 02/05/2017 09:11 Page 1

A BSRIA Guide www.bsria.co.uk

The Illustrated Guide to Mechanical Building Services

Third Edition

By David Bleicher

BG 31/2017

ACKNOWLEDGEMENTS

The first edition of this publication (AG 15/2002) was written by Tom de Saulles and included considerable contribution from Gay Lawrence Race. The second edition (BG 31/2012) was written by David Bleicher. This third edition was updated by David Bleicher and James Parker. BSRIA would also like to thank the following organisations that kindly provided the photographs or diagrams which have made this illustrated guide possible:

Airedale International Air Conditioning Ltd. Albion valves (UK) Ltd. Alfa Laval Ltd. Altecnic Ltd. AmbiRad Ltd. Armstrong Integrated Ltd. Clivet UK Ltd. Colt International Ltd. Crane Fluid Systems Daikin UK Ltd. DE-VI Electroheat Ltd. Displacement Design Ltd. Dravo Environmental Services Ltd. Elster Metering Ltd. - Now part of Honeywell Frenyer Ltd. Geoff Sumner Honeywell International Inc. Hudevad Ltd. Kamstrup Kensa Heat Pumps Kohlbach Holdings GmbH Marflow Hydronics Mitsubishi Electric Ormandy Ltd. Peter Brotherhood Ltd. Powrmatic Ltd. S&P Coil Products Siemens Building Technologies Spirotech UK Toshiba Air Conditioning Trox UK Ltd. TSI Instruments Ltd. Vortice Ltd. This publication was designed and produced by Joanna Smith. Final editorial control rested with BSRIA.

The guidance given in this publication is correct to the best of BSRIA’s knowledge. However BSRIA cannot guarantee that it is free of errors. Material in this publication does not constitute any warranty, endorsement or guarantee by BSRIA. Risk associated with the use of material from this publication is assumed entirely by the user.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means electronic or mechanical including photocopying, recording or otherwise without prior written permission of the publisher.

THE ILLUSTRATED GUIDE TO MECHANICAL BUILDING SERVICES © BSRIA BG 31/2017

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PREFACE This illustrated guide provides basic reference information on mechanical building services systems for construction clients and professionals in other areas of the construction industry. The topics covered are:

¾¾ Heating ¾¾ Ventilation ¾¾ Air-conditioning ¾¾ Controls.

For construction clients, this guide provides a simple insight into the main system options discussed during the briefing process and can consequently assist dialogue with the design team. It can also help clients to identify and raise technical questions which they feel are relevant to their organisation’s specific needs. For construction professionals, the guide provides a quick reference to building services systems and can assist their working knowledge of the subject.

To ensure the guide is simple and quick to use, a brief introduction to each system is provided, followed by a list of key points. Photographs and simple drawings are used to help explain the appearance and operation of each system.

It is acknowledged that the design team’s role includes assessing and recommending appropriate design solutions for a given project. This guide does not aim to provide a route for system selection other than pointing out typical applications for many of the systems covered.

Since the previous edition of this guide, further information has been added on pumps, pipework, valves, heat networks, gas systems, ductwork, air handling units and commissioning along with updates of the original information.

BSRIA has also published a companion guide BG 32/2014, The Illustrated Guide to Electrical Building Services – Third edition. This provides information on electrical systems including power supply and distribution, fire detection and alarm systems, security systems, lighting systems, uninterruptible power supplies and structured cabling. More detailed information on systems covered in this guide can be found in the following publications:

¾¾ BG 2/2009 The Illustrated Guide to Ventilation ¾¾ BG 1/2010 The Illustrated Guide to Mechanical Cooling ¾¾ BG 1/2008 The Illustrated Guide to Renewable Technologies ¾¾ BG 33/2014 The Illustrated guide to Hot and Cold Water Services ¾¾ BG 7/2009 Heat Pumps ¾¾ BG 2/2007 CHP for Existing Buildings.

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CONTENTS Page

OVERVIEW 1 Building design and building services 1 Location of building services 3 Thermal comfort 4

HEATING 5 Air and dirt removal 6 Pipework 7 Typical systems 8 Valves 10 Heat networks 12 Gas systems 13 Boilers 14 Low carbon heat 15 Radiators 16 Convectors 17 Underfloor heating 18 Radiant heating 19 Warm air unit heaters 21

VENTILATION 22 Natural ventilation 22 Powered window actuators 23 Single-sided ventilation 24 Cross ventilation 24 Stack ventilation 25 Stack and wind ventilators 26 Mechanical ventilation – Extract only 27 Mechanical ventilation – Supply only 28 Supply and extract systems 29 Mechanical ventilation with heat recovery 30 Ductwork 31 Air handling units 32

AIR-CONDITIONING SYSTEMS 33 Constant volume (CV) 36 Variable air volume (VAV) 37 Displacement ventilation 38 Fan coil units 39 Chilled ceilings 41 Chilled beams 42 Room-based heat pumps (Versatemp system) 43 Split systems 44 Variable refrigerant flow systems (VRF) 45 Chillers, dry coolers and cooling towers 46 Air diffusers 47

CONTROL SYSTEMS AND COMPONENTS 48 Analogue and direct digital control (DCC) systems 51 Building management systems (BMS) 52 Integrated control systems 53

COMMISSIONING, HANDOVER AND EVALUATION 54

INDEX 56

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BSRIA ILLUSTRATED GUIDE SET – SAVE OVER 45%

BSRIA publishes a range of illustrated guides on key building services topics. They are ideal for those new to the industry, as an easy reference for experienced engineers or an aid to assist dialogue in project teams.

Illustrated with simple line diagrams and photos, the guides demystify the subjects of:

¾¾ Mechanical Building Services ¾¾ Electrical Building Services ¾¾ Mechanical Cooling ¾¾ Ventilation ¾¾ Hot and Cold Water Services ¾¾ Renewable Technologies

AVAILABLE IN HARD COPY OR PDF FROM THE BSRIA BOOKSHOP www.bsria.co.uk/goto/ill6 or Tel: +44 (0) 1344 465 529

THE ILLUSTRATED GUIDE TO MECHANICAL BUILDING SERVICES © BSRIA BG 31/2017

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OVERVIEW – BUILDING DESIGN AND BUILDING SERVICES The design of a building will affect many of the costs which an operator will encounter during the life of a building. The building services can account for around 30% of the capital cost and 50% of the operating cost for a typical office building. It is therefore important that the services form OVERVIEW an integral part of the overall building concept to help ensure they will operate efficiently. Involving the specialist building services engineer at an early stage in the design process can help achieve this objective.

If the services are not considered until a later stage, problems which could have been overcome by simple measures may require a more complex technical solution. A well-designed building may cost a little more initially, but the overall cost of ownership should be reduced. Life cycle costs of building services systems should be considered, as the cost-in-use element can form a large proportion of the total cost, outweighing the initial capital cost.

Decisions about which services to incorporate into a building design require consideration of many factors including the following: ¾¾ Cost Both initial costs and life cycle costs. ¾¾ Level of thermal comfort required See overview: thermal comfort, page 4. ¾¾ Level of control required See control systems and components, page 48. ¾¾ Complexity What type of system is appropriate and will it be difficult to operate and maintain? For example a full air-conditioning system provides close control of air temperature and humidity, but this comes at a price. ¾¾ Noise levels Will heating, ventilation and air-conditioning plant adversely affect noise levels in occupied areas? What about noise from outside the building? The noise rating (NR) is a European measure of sound levels which relates to the sensitivity of the human ear. It is often used to specify an acceptable interior or exterior sound level, for example NR 35 to 40 for offices, NR 20 for a concert hall. ¾¾ Adaptability and flexibility To meet possible future requirements. ¾¾ Energy use Mechanical building services plant can account for a major part of a building’s energy use. ¾¾ Plant space Air-conditioning systems can require a large amount of space to accommodate the refrigeration and air handling plant. Access for operation, maintenance and replacement must be considered (see overview: location of building services, page 3). It is not always possible to design a building that can utilise all possible energy saving measures. Urban noise and pollution may dictate the need for sealed buildings incorporating mechanical ventilation or air- conditioning systems. The activities in some buildings can also necessitate air-conditioning to offset a high internal heat gain.

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HEATING - INTRODUCTION Buildings lose heat by three mechanisms: ¾¾ Fabric losses – heat that transfers through the floor, walls, roof and windows of a building. They can be reduced by providing insulation and double-glazing. ¾¾ Ventilation losses – heat that is lost when stale, warm air is exhausted from buildings. They can be reduced by only ventilating to the degree necessary for health and comfort of building occupants, and making use of heat recovery (see page 29). ¾¾ Infiltration losses – unintentional losses of warm air through gaps and cracks in the building envelope. They can be reduced by Thermography is a useful tool for identifying where designing and constructing the building fabric to be airtight. heat losses are occurring. In a thermal image, hot surfaces show up as brighter colours than Heating systems generally consist of a heat source such as a boiler, a means HEATING cold surfaces. This image shows both fabric and of heat distribution such as pipework with pumps, and heat emitters such as infiltration losses. radiators. Systems that use water in pipes for heat distribution are known as wet or hydronic systems.

Electrical resistance can be used for heating. However, in the UK this is generally associated with energy costs and carbon dioxide emissions being higher than for gas or oil-fired heating. This is because the UK’s electricity supply relies heavily on gas and coal-fired power stations, which emit most of the energy from their fuel through their cooling towers. There are further losses in transmission of electricity from power stations to end users. Electric heating is most commonly used in temporary buildings, as background (frost protection) heating and in areas without mains gas.

Most hydronic systems in buildings are low temperature hot water (LTHW), also referred to as low pressure hot water (LPHW). Medium and high temperature/pressure systems are sometimes used in heat networks (see page 12). These require pressurisation to prevent the water turning to steam. An in-line circulator pump of the type commonly used in domestic and small Category Water Water pressure commercial heating systems. temperature (°C) (bar absolute) (Picture courtesy of Armstrong Integrated Ltd.) LTHW/LPHW 40 – 85 1 – 3 MTHW/MPHW 100 – 120 3 – 5 HTHW/HPHW >120 5 – 10

Pumps Hot water is moved through a hydronic heating system by means of one or more pumps. These are nearly always centrifugal pumps, and nearly always driven by electric motors. In applications where demand on the system is variable, pumps are fitted with variable speed drives. This method of controlling flow rates is much more energy-efficient than older methods, which involved increasing the system’s resistance to flow, thereby reducing flow rates.

In-line circulator pumps are low pressure devices used to keep fluids flowing around a circuit. They are available in twin head variants to provide built in back-up. For higher pressure requirements, such as pumping water up tall buildings, different pumps are required such as the multistage in-line centrifugal pump. These have multiple impellers to increase the pressure. Other specialist pumps are available for certain processes. One example is the sump pump. Designed to operate submerged, they are used for pumping drainage water, from within tanks or from flooded areas.

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AIR-CONDITIONING SYSTEMS – INTRODUCTION Heat gains In hot weather, buildings can gain heat by the same mechanisms through which they lose heat in cold weather (fabric, ventilation and infiltration, see heating – introduction, page 9). Buildings can also gain heat by the following mechanisms: ¾¾ Solar gain: Sunlight falling directly on windows and other glazed elements causes the inside of the building to be heated. This can occur even on very cold days. Solar gain can be reduced by avoiding large areas of south-facing glazing, providing shading over this glazing, or selecting glazing that reduces solar gains. ¾¾ Metabolic gains: People produce heat as part of their normal bodily process. In densely-occupied buildings, this can be the largest component of heat gain. ¾¾ Equipment gains: All electrical energy used by equipment such as lighting, computers and appliances gets turned in to heat. This component of heat gain can be reduced by selecting energy-efficient equipment and ensuring it is switched off when not in use. This building makes use of solar shades (sometimes known as brise soleil) and solar Passive cooling control glazing to reduce solar gains. Buildings with high thermal mass, such as those constructed primarily with heavy masonry or concrete, are able to absorb heat gains during the day and cool off again at night.

Natural and mechanical ventilation systems can be used to cool buildings – a technique known as free cooling (see ventilation – introduction, page 22).

Passive cooling measures cannot be applied to all buildings, so air- AIR conditioning is often used as a means to offset heat gains and maintain

acceptable levels of thermal comfort. CONDITIONING

Comfort cooling and air-conditioning A true air-conditioning system provides full control of air temperature, humidity, freshness and cleanliness. In practice, the term is often misused to describe systems that do not provide full control of humidity. These are more correctly known as comfort cooling systems. However, since the term air-conditioning is already taken to mean both types of system in general parlance, this guide has adopted this approach.

Systems that provide heating, ventilation and air-conditioning are often referred to as HVAC systems.

Zoning Buildings are often divided into a number of zones for the purposes of system control. The way in which a building is zoned depends on factors such as:

costs and complexity ol, ¾¾ Varying solar loads - at certain times of the day the south side of a building can have high solar gains and require easing contr more cooling than the north side. Incr ¾¾ Varying internal conditions - zoning may be used when two or more internal spaces require different conditions. Natural Mechanical Comfort Air ¾¾ Internal partitions - Internal work areas or partitioning ventilation ventilation cooling conditioning can determine the boundaries for zones.

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CONTROL SYSTEMS AND COMPONENTS – INTRODUCTION What controls do There are two basic functions which building controls perform: ¾¾ Switching equipment on and off ¾¾ Adjusting the output of equipment to maintain the required operating conditions.

There are various ways of switching plant on and off, and for simple systems, manually operated controls can be the best option. As systems become more complex, devices such as time switches, optimisers and programmable controllers are needed. In recent years the development of computerised control devices and new types of sensors have enabled more complex plant control and greater energy efficiency. However, over-specified control systems that are excessively sophisticated for their application are a common source of complaint and should be avoided. It is important that the type/ level of control selected matches the requirements of the building systems and the abilities of the individuals who will operate them. In many instances, relatively simple stand-alone controls can be the most appropriate choice.

Control components Time switches For buildings with a fixed occupancy pattern, time switches enable plant to be switched on and off at the appropriate time. Basic time switches are electromechanical, and are generally very simple, reliable and easy to use. For systems requiring more complex programming, electronic time switches are available which offer greater flexibility and a longer programmable period.

Time switch Turns boiler on and off at pre-set times Boiler The boiler has inbuilt 8:32

CONTROLS controls which regulate water temperature.

Room thermostat Adjusted to control the required space temperature. The thermostat senses the space temperature and automatically switches the circulation pump on and off to maintain the selected setting.

Circulation pump

Radiator

Example of simple controls (domestic heating).

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