BS 7074-1-1989 Application selection and installation of expansion vessels and ancillary equipment for sealed water systems - Code of practice for domestic heating and hot water su.pdf

1、BRITISH STANDARD BS 7074-1: 1989 Application, selection and installation of expansion vessels and ancillary equipment for sealed water systems Part 1: Code of practice for domestic heating and hot water supply UDC 621.642.3:644.62:697.43:001.4:620.1:006.76(083.75)BS7074-1:1989 This British Standard,

2、 having been prepared under the directionof the Refrigeration, Heating and Air Conditioning Standards Policy Committee, waspublished under the authorityof the Board of BSI andcomes into effect on 31 July 1989 BSI 06-1999 The following BSI references relate to the work on this standard: Committee ref

3、erence RHE/7 Draft for comment 87/73419 DC ISBN 0 580 17145 0 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Refrigeration, Heating and Air Conditioning Standards Policy Committee (RHE/-) to Technical Committee RHE/7 upon which the foll

4、owing bodies were represented: Associated Offices Technical Committee Association of Consulting Engineers Association of Manufacturers of Domestic Unvented Supply Systems Equipment (MODUSSE) British Marine Equipment Council Building Services Research and Information Association Chartered Institution

5、 of Building Services Engineers Heating and Ventilating Contractors Association HEVAC Association Institute of Domestic Heating Engineers Sealed Expansion Vessel Association Waterheater Manufacturers Association Amendments issued since publication Amd. No. Date of issue CommentsBS7074-1:1989 BSI 06-

6、1999 i Contents Page Committees responsible Inside front cover Foreword ii Section 1. General 1 Scope 1 2 Definitions 1 3 Symbols, designations and units 2 4 Testing and commissioning 2 5 Maintenance and servicing 2 6 Workmanship2 Section 2. Heating systems 7 Design considerations 3 8 System filling

7、 and make-up 5 9 Ancillary equipment7 Section 3. Hot water supply systems 10 General 9 Figure 1 Location of connection of expansion vessel in a system 3 Figure 2 Non-automatic filling and make-up 6 Figure 3 Automatic filling and make-up 6 Figure 4 Semi-automatic make-up 7 Table 1 Symbols, designatio

8、ns and units 2 Table 2 Capacities of expansion vessels 4 Table 3 Expansion percentages (e) for various system flow temperatures. Base temperature 4 C 5 Publications referred to Inside back coverBS7074-1:1989 ii BSI 06-1999 Foreword This British Standard code of practice has been prepared under the d

9、irection of the Refrigeration, Heating and Air Conditioning Standards Policy Committee. The code complements BS 4814 and gives recommendations in its three Parts for the installation of expansion vessels in domestic heating and supply systems (Part 1); low and medium temperature hot water heating sy

10、stems (Part 2); chilled water and condenser systems (Part 3) and boosted hot water supply systems 1) . The code deals with the work involved in the general planning, designing and installation of the various systems when the expansion and contraction of the system water is catered for in a sealed di

11、aphragm type vessel. In all other respects the customary design process should be followed for the appropriate system. 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

12、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 and ii, pages1 to 10, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amend

13、ments incorporated. This will be indicated in the amendment table on theinside front cover. 1) Planned.BS7074-1:1989 BSI 06-1999 1 Section 1. General 1 Scope This Part of BS 7074 gives recommendations on the application of expansion vessels for use in individual domestic premises. It includes descri

14、ption, design considerations and types of application. Sections 1 and 2 cover domestic heating systems using expansion vessels complying with BS4814 and include recommendations on: a) the application and use of ancillary equipment and b) testing, commissioning and maintenance. Section 3 makes refere

15、nce to domestic hot water supply systems. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this Part of BS 7074 the following definitions apply. 2.1 charging pressure the initial pressure to which the gas/air side

16、of the vessel is charged which is equal to the initial system design pressure 2.2 design acceptance factor (a) the ratio of the volume of water due to expansion, to total vessel volume 2.3 diaphragm (or membrane) the flexible means by which the chamber of an expansion vessel is partitioned to mainta

17、in separation between the expanding hot water and the gas or air which in consequence becomes compressed. It may be either a literal diaphragm clamped between two parts (or halves) of the vessel, or a bag located by its mouth which is secured to the point of the water connection to the vessel 2.4 ex

18、pansion percentage (e) the expansion percentage increase in volume when water is heated to maximum design system temperature 2.5 expansion volume (V a ) the increase in volume of water due to expansion when heated to the maximum design system temperature 2.6 final system design pressure (P f ) the p

19、ressure occurring at the mid-height of the expansion vessel at the maximum design system temperature 2.7 initial cold water fill temperature (t i ) the basic reference temperature is taken to be 4 C 2.8 initial system design pressure (P i ) the pressure occurring at the mid-height of the expansion v

20、essel at cold fill. This is equal to the static height pressure plus the pressure margin 2.9 lowest working pressure component (LWPC) the component having the lowest working pressure in the system 2.10 maximum acceptance factor (A) the ratio of maximum acceptance volume of the system to total volume

21、 2.11 maximum acceptance volume (V) the volume of water which the vessel may be allowed to contain 2.12 maximum vessel temperature the maximum water temperature at which the vessel may be allowed to operate continuously 2.13 maximum vessel working pressure the maximum pressure that the vessel may be

22、 allowed to contain in operation 2.14 pressure depth (P d ) the vertical distance between the component being considered and the mid-height of the expansion vessel situated above it 2.15 pressure margin (P s ) the additional pressure imposed on the circuit to prevent water vaporizing or boiling and/

23、or to exclude air from the system at the highest point 2.16 safety valve set pressure (P max ) the pressure at which the safety valve is set for operationBS7074-1:1989 2 BSI 06-1999 2.17 static height pressure (P h ) the pressure created by the column of water between the uppermost part of the heati

24、ng circuit and the mid-height of the expansion vessel 2.18 system flow temperature (t f ) the maximum designed temperature of the water circulating in the system 2.19 total system volume (V s ) the total volume of water in the complete system 2.20 total vessel volume (V t ) the volume occupied by ga

25、s/air when the vessel is empty of water 3 Symbols, designations and units The symbols for physical quantities, their designations and units used in this code of practice are given in Table 1. Table 1 Symbols, designations and units 4 Testing and commissioning 4.1 Testing the system The completed ins

26、tallation, as well as being checked for leaks, should be rinsed to minimize presence of solid particles and chemical residues which may cause damage within the system. The following procedure should be followed: a) fill system and vent all high points, pump and radiators; b) examine for leaks and re

27、ctify where necessary. 4.2 Commissioning the system The boiler and pump should be put into operation and the system allowed to heat up to normal operating temperature for 1 h. After this period the boiler and pump should be turned off and the system allowed to cool. Further checks should be made for

28、 any leakages. Any water loss should be made up thus ensuring the system design pressure is restored. 5 Maintenance and servicing It is necessary that procedures for maintenance and servicing of the system be explained to the user and confirmed in writing. 6 Workmanship All work on domestic premises

29、 systems as described in this Part of the code of practice should be carried out by competent persons. Symbol Designation Unit A Maximum acceptance factor a Design acceptance factor e Expansion percentage P d Pressure depth bar gauge P f Final system design pressure bar gauge P h Static height press

30、ure bar gauge P i Initial system design pressure bar gauge P max Safety valve, set pressure bar gauge P s Pressure margin bar gauge t f System flow temperature C t i Initial cold water fill temperature C V Maximum acceptance volume L V a Expansion volume L V s Total system volume L V t Total vessel

31、volume LBS7074-1:1989 BSI 06-1999 3 Section 2. Heating systems 7 Design considerations 7.1 General Successful and continuing safe operation of a domestic heating system depends on the use of the correct equipment properly installed to a good design and effectively serviced and maintained. In additio

32、n to the customary design procedures applicable to small-bore or micro-bore systems, the following design considerations should be adhered to when a sealed diaphragm expansion vessel is incorporated. a) The preferred and the acceptable positions of the expansion vessel are shown in Figure 1. b) The

33、method of filling should be in accordance with the requirements of the local water authorities. c) System flow temperature (t f ). Whilst the normal operating temperature is limited to 82 C, a fault condition may occur with the safety devices enabling system temperature to rise to110 C and it is rec

34、ommended that this figure be used in the calculation of vessel sizes. Figure 1 Location of connection of expansion vessel in a systemBS7074-1:1989 4 BSI 06-1999 d) Static height pressure (P h ). e) Final system design pressure (P f ). f) Total water content of system. As an approximation of water co

35、ntent, where it is not feasible to make accurate calculation, a figure of12 L/kW output of the heat generator could be used. g) Capacity of expansion vessel. It is recommended that the method given in 7.2 for the accurate selection of the expansion vessel capacity be followed. Where design informati

36、on is not complete Table 2 can be used for selecting the size of the vessel; it should be noted that the sizes given in Table 2 take account of the fault condition temperature rise referred to in c) and other safety factors. h) Should it be considered necessary to use a chemical inhibitor to prevent

37、 corrosion in the system, care should be taken to ensure compatibility with the diaphragm, and other system components. i) Connection of the expansion vessel. The point of connection of the expansion pipework is the neutral point of the system and it is recommended that this is in the return pipewor

38、k close to the heat generator. The fill position should be between the expansion vessel connection point and the inlet of the circulation pump. The point of connection of the expansion vessel into the system having been clearly defined, the physical location of the vessel can be anywhere. Table 2 Ca

39、pacities of expansion vessels Safety valve setting (bargauge) 3.0 2.5 2.0 Vessel charge and initialsystem pressure (bargauge) 0.5 1.0 1.5 0.5 1.0 1.5 0.5 1.0 Total water content ofsystem Vessel volume L L L L L L L L L 25 2.1 2.7 3.9 2.3 3.3 5.9 2.8 5.0 50 4.2 5.4 7.8 4.7 6.7 11.8 5.6 10.0 75 6.3 8.

40、2 11.7 7.0 10.0 17.7 8.4 15.0 100 8.3 10.9 15.6 9.4 13.4 23.7 11.3 20.0 125 10.4 13.6 19.5 11.7 16.7 29.6 14.1 25.0 150 12.5 16.3 23.4 14.1 20.1 35.5 16.9 30.0 175 14.6 19.1 27.3 16.4 23.4 41.4 19.7 35.0 200 16.7 21.8 31.2 18.8 26.8 47.4 22.6 40.0 225 18.7 24.5 35.1 21.1 30.1 53.3 25.4 45.0 250 20.8

41、 27.2 39.0 23.5 33.5 59.2 28.2 50.0 275 22.9 30.0 42.9 25.8 36.8 65.1 31.0 55.0 300 25.0 32.7 46.8 28.2 40.2 71.1 33.9 60.0 325 27.0 35.7 50.7 30.5 43.5 77.0 36.7 65.0 350 29.1 38.1 54.6 32.9 46.9 82.9 39.5 70.0 375 31.2 40.9 58.5 35.2 50.2 88.8 42.3 75.0 400 33.3 43.6 62.4 37.6 53.6 94.8 45.2 80.0

42、425 35.4 46.3 66.3 39.9 56.9 100.7 48.0 85.0 450 37.5 49.0 70.2 42.3 60.3 106.6 50.8 90.0 475 39.6 51.8 74.1 44.6 63.6 112.5 53.6 95.0 500 41.6 54.5 78.0 47.0 67.0 118.5 56.5 100.0 Multiplying factors for other system volumes 0.0833 0.109 0.156 0.094 0.134 0.237 0.113 0.2BS7074-1:1989 BSI 06-1999 5

43、7.2 Expansion vessel size calculation The accurate size of the expansion vessel is calculated as follows. a) Establish. 1) The water content of the system in litres (V s ) (this to include circulatory pipework, heat emitters and heat generators). 2) The system flow temperature (t f ) in C. 3) The ex

44、pansion percentage (e) (see Table 3). NOTEThe addition of anti-freeze or similar fluid will affect the expansion percentage co-efficient and may also affect the diaphragm material. 4) The static height pressure (P h ) in bar gauge. NOTEExpansion vessels supplied into the domestic central heating mar

45、ket are filled at factory to pressures of0.5 bar; 1.0 bar; 1.5 bar equating to the average P h . 5) The initial system design pressure (P i ) in bar gauge. The margin normally added to the static height pressure is 0.3 bar 2) . This added pressure margin (P s ) is necessary to expel air from the sys

46、tem, also to permit system control pressure differentials. P i= P h+ P s The minimum value of P ishould be0.7 bar. 6) The final system design pressure (P f ) in bar gauge. This pressure has to be less than the set pressure of the safety valve by 0.3 bar. 7) The design acceptance factor (a): where P

47、f+ 1 and P i+ 1 expresses P fand P irespectively in absolute units. b) The total vessel volume (V t ) in L, can now be calculated from: where V a= V s e To allow for contingencies and operational variances a margin should be added. It is recommended that this should be at least 10 %. The vessel sele

48、cted needs to have a volume equal to or greater than the final vessel volume (V t+ 10 %). Table 3 Expansion percentages (e) for various system flow temperatures. Base temperature 4 C 8 System filling and make-up 8.1 System initial fill connection To facilitate the initial filling of the system a tem

49、porary hose connection may be made from a water mains supply in accordance with water byelaws. For protection to the installation when filling from a temporary connection to the mains supply, a non-return valve and an air-inlet valve (see Figure 2) should be incorporated at the point of filling. The temporary hose connection has to be removed after the system has been filled. Care should be exercised to ensure that the fill pressure does not exceed the calculated value of P i . 8.2 Automatic make-up unit Automatic make-up may