BS-6880-1-1988.pdf

BRITISH STANDARD BS 6880-1: 1988 Code of practice for Low temperature hot water heating systems of output greater than 45 kW Part 1: Fundamental and design considerations UDC 621.18.04:621.181.25:621.18.064:697.27:697.326:614.8 Licensed Copy: London South Bank University, London South Bank University, Thu Dec 07 06:40:59 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6880-1:1988 This British Standard, having been prepared under the direction of the Refrigeration, Heating and Air Conditioning Standards Committee, was published under the authority of the Board of BSl and comes into effect on 29 February 1988 © BSI 02-1999 The following BSl references relate to the work on this standard: Committee reference RHE/23 Draft for comment 85/70687 DC ISBN 0 580 16026 2 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Refrigeration, Heating and Air Conditioning Standards Committee (RHE/-) to Technical Committee RHE/23, upon which the following bodies were represented: Association of Consulting Engineers British Combustion Equipment Manufacturers Association British Gas plc Building Services Research and Information Association Chartered Institution of Building Services Engineers Department of Health and Social Security Department of the Environment (Property Services Agency) Electricity Supply Industry in England and Wales Health and Safety Executive Hevac Association Institute of Refrigeration Institution of Gas Engineers Ministry of Defence Royal Institute of British Architects Sealed Expansion Vessel Association Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: London South Bank University, London South Bank University, Thu Dec 07 06:40:59 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6880-1:1988 © BSI 02-1999i Contents Page Committees responsibleInside front cover Forewordiii Section 1. General 1.1Scope1 1.2Definitions1 Section 2. Fundamental considerations 2.1General2 2.2Comfort factors2 2.3Application factors6 2.4Statutory, structural and safety factors15 2.5Energy conservation and energy management23 2.6Quality and reliability25 Section 3. Design considerations 3.1Types of systems28 3.2Basis of design29 3.3Energy conversion subsystem design34 3.4Distribution subsystem design48 3.5Corrosion control and water treatment61 3.6Thermal insulation64 3.7Plant room ventilation64 3.8Automatic controls65 3.9Electrical requirements73 3.10 Noise and vibration75 3.11 General layout and operational facilities76 Appendix A Bibliography78 Figure 1 Typical 24 h load profile and temperature decay curve (based on 9 am to 5 pm occupancy)33 Figure 2 Principal flue types44 Figure 3 Simplified representation of principal system temperature relationships49 Figure 4 Principal circuit arrangements52 Figure 5 Typical air vent arrangements56 Figure 6 Pump and feed location59 Figure 7 Vent arrangement for multiple boilers60 Figure 8 Typical multiple boiler control arrangements68 Figure 9 HWS control72 Figure 10 Location of sensors in pipes and ducts74 Table 1 Recommended design values for resultant temperature, tc (heating season)3 Table 2 Levels of relative humidity, for an internal temperature of 21 °C, at which condensation will occur at various outside temperatures5 Table 3 Air temperatures for educational accommodation8 Table 4 Recommended resultant temperatures for industrial work14 Table 5 Recommended temperatures for storage spaces15 Licensed Copy: London South Bank University, London South Bank University, Thu Dec 07 06:40:59 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6880-1:1988 ii © BSI 02-1999 Page Table 6 Recommended minimum oil storage and handling temperatures for classes E, F and G fuel oils38 Table 7 Typical ranges of excess air41 Table 8 Thermal expansion characteristics of piping materials56 Publications referred to80 Licensed Copy: London South Bank University, London South Bank University, Thu Dec 07 06:40:59 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6880-1:1988 © BSI 02-1999iii Foreword This Part of BS 6880 has been prepared under the direction of the Refrigeration, Heating and Air Conditioning Standards Committee. BS 6880 is published in three Parts which together form a full technical revision of CP 341.300-307:1956 which is withdrawn. This Part gives recommendations on the design of low temperature hot water heating systems. The other two Parts are: Part 2: Selection of equipment; Part 3: Installation, commissioning and maintenance. The policy adopted when writing this code has been to avoid repetition of material for which other bodies are the accepted authority, except in so far as limited extraction assists the understanding of this code. Consequently the code provides general recommendations only on certain topics. References in this category are as follows. a) For detailed procedures: 1) publications of the Chartered Institution of Building Services Engineers (CIBSE), particularly: i) CIBSE Guide 1; ii) CIBSE Building Energy Code 2; iii) technical memoranda relating to fire in buildings; iv) practice notes relating to provision of combustion and ventilation air for boiler installations; 2) handbooks published by the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE). b) For detailed commissioning arrangements: 1) CIBSE commissioning codes; 2) application guides published by the Building Services Research and Information Association (BSRIA). It should be noted that references to such applications are deemed to refer to the current edition, whereas specific extracts reproduced in this code are from the edition current at the time of preparation of this code. Whilst the recommendations made in this code generally relate to current practice, they are not intended to inhibit the use of innovative systems or equipment which an experienced designer considers appropriate to the application, and which meet all statutory requirements and the safety and general good practice recommendations of this code. It is desirable that the principal interested parties should be made aware of such proposals at the design stage. Reference is made in the text to a number of Acts of Parliament and to various regulations made under them. Such lists are necessarily incomplete, and in any particular circumstance the users of this code should acquaint themselves with the relevant regulations in force at the time. Attention is drawn to the requirements of the Building Regulations of England and Wales, of Scotland, Northern Ireland and of Inner London. Licensed Copy: London South Bank University, London South Bank University, Thu Dec 07 06:40:59 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6880-1:1988 iv © BSI 02-1999 A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages 1 to 80, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: London South Bank University, London South Bank University, Thu Dec 07 06:40:59 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6880-1:1988 © BSI 02-19991 Section 1. General 1.1 Scope This Part of BS 6880 gives recommendations regarding the fundamental considerations and the design considerations which need to be taken into account in the design of low temperature hot water (see 1.2.1) heating systems of output greater than 45 kW, open vented or sealed. It is primarily intended for use by building owners, building managers, installers and associated professionals. It is not intended to serve as a detailed design guide (see foreword). The recommendations recognize the need to optimize the use of energy, reduce hazards and minimize effects detrimental to the environment. Solar heating is outside the scope of this code. NOTEThe titles of the British Standards publications referred to in this standard are listed on the inside back cover. References in the text to other publications are identified in the text by numbers in square brackets, and are listed in Appendix A. 1.2 Definitions For the purposes of this Part of BS 6880 the definitions given in BS 1523, BS 3533 and BS 5643 apply together with the following. NOTESee also the CIBSE Building Energy Code 2. 1.2.1 low temperature hot water (LTHW) water used as the heating medium such that its temperature does not exceed 100 °C at any point in the system, whether open or sealed NOTEVarious safety considerations may require that the actual design flow temperature of an LTHW system should be significantly less than 100°C (see Section B.1 of the CIBSE Guide 1, Health and Safety Executive (HSE) Guidance Note PM5 3 and section three of this Part of BS 6880. 1.2.2 boiler an appliance designed for heating water either for space heating or for space heating combined with hot water supply 1.2.3 heat emitters equipment emitting heat for the purpose of space heating NOTEThis equipment includes radiators, convectors, skirting heating and radiant panels. 1.2.4 radiator a unit for space heating that warms the air by convection and provides radiation Licensed Copy: London South Bank University, London South Bank University, Thu Dec 07 06:40:59 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6880-1:1988 2 © BSI 02-1999 Section 2. Fundamental considerations 2.1 General The object of providing heating facilities in buildings is to provide (during periods when heating is appropriate) thermal conditions under which people can live in comfort and work safely and efficiently, and also to contribute to the protection of the building fabric and its contents from deleterious effects of cold weather. The purpose of this section is to relate the various controllable factors to the comfort and well-being of the people using the building, and to certain aspects of the building fabric and its contents. Thus the requirements of the system can be clearly established sufficiently early in the design process that those aspects of building design and use which affect its thermal performance can be developed together. The thermal conditions within a building may not be entirely determined by the heating system, since they depend on the interaction of various other factors with the heating system. These include the thermal inertia of the building fabric, natural and artificial ventilation, extraneous air leakage into the building, solar effects, evaporation of moisture and heat produced from other sources within the building. It is therefore important that the heating system design takes account of such factors to the extent that they can be evaluated at the design stage, and that those concerned with other aspects of the building design, and with its use, should appreciate these effects if a satisfactory and energy efficient system is to be achieved. Detailed guidance for the designer on these matters is given in the CIBSE Guide 1 and the CIBSE Building Energy Code 2. Further information in respect of ventilation and air conditioning is given in BS 5720 and BS 5925. Certain industrial process and storage situations may impose particular requirements on the heating system. While this code does not refer in detail to such situations, or to other applications which impose requirements additional to those of occupant comfort, some general recommendations are given in 2.3.3. 2.2 Comfort factors 2.2.1 General A wide range of external environmental conditions can be accepted by varying clothing or the degree of physical activity. Such comfort conditions, the lack of which can affect the welfare of people, are provided by controlling temperature, air movement and humidity. A heating system alone may enable all or some of these conditions to be controlled during those periods of the day or year when external temperature and humidity conditions are lower than the required comfort conditions. It is considered impractical to cover all aspects of comfort conditions in this code of practice and therefore it is recommended that reference be made to the CIBSE Guide 1. The factors that affect comfort and that are relevant to the design of heating systems are: a) resultant temperature (2.2.2); b) air movement and draught (2.2.3); c) infiltration and natural ventilation (2.2.4); d) humidity (2.2.5); e) solar effects (2.2.6); f) noise and vibration (2.2.7). 2.2.2 Temperature 2.2.2.1 General considerations. Certain minimum temperatures are required by legislation and by local regulations. Maximum permitted heating temperatures may be stipulated by legislation relating to energy conservation (see 2.4 and 2.5). From the comfort aspect, it is important to take into account the effect of radiant temperature in fixing the desired air temperatures to maintain comfortable conditions. When heating is provided from radiating floors, ceilings, walls or other radiating surfaces, air temperatures may be reduced. Radiation losses to large windows or cold external walls may require an upward adjustment in air temperature. A persons overall heat loss, and hence his feeling of warmth, depends not only on air temperature, but also on heat lost or gained by the body through radiation to or from the surroundings (radiant heat gain), air movement and the humidity of the air. Many attempts have been made to devise a single index that combines the effect of two or more of these separate variables. In practice the difference between these indices is small, provided that the various parameters do not vary beyond certain limits. Licensed Copy: London South Bank University, London South Bank University, Thu Dec 07 06:40:59 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6880-1:1988 © BSI 02-19993 In some situations it may be necessary to provide shading to protect the occupants from heat gain due to solar radiation, as when large windows are used. It is not practical to compensate fully for solar heating purely by lowering air temperature, due to its intermittent nature. 2.2.2.2 Resultant temperature. The resultant temperature index is recommended for use in the UK and is widely used in the rest of Europe. It combines inside air temperature, mean radiant temperature and air velocity to form a single index known as dry resultant temperature, hereafter referred to as resultant temperature. This relationship is described fully in the CIBSE Guide 1. 2.2.2.3 Design air temperature. It should be noted that, despite the relevance of resultant temperature to establishing comfort conditions and heating requirements, the inside air temperature selected as the basis for design should be stated. The air temperature is e