1、BRITISH STANDARD BS 7478:1991 Guide to Selection and use of thermostatic radiator valvesBS7478:1991 This British Standard, having been prepared under the directionof the Refrigeration, Heating and Air Conditioning Standards Policy Committee, waspublished under the authorityof the Standards Boardand
2、comes into effecton 20December1991 BSI 08-1999 The following BSI references relate to the work on this standard: Committee reference RHE/16 Draft for comment 89/80536 DC ISBN 0 580 19988 6 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the
3、Refrigeration, Heating and Air Conditioning Standards Policy Committee (RHE/-) to Technical Committee RHE/16, upon which the following bodies were represented: Association of Manufacturers of Domestic Unvented Supply Systems Equipment (MODUSSE) BEAMA Ltd. Association of Control Manufacturers (TACMA)
4、 British Gas plc British Plumbing Fittings Manufacturers Association British Valve and Actuator Manufacturers Association Building Services Research and Information Association Department of the Environment (Property Services Agency) Hevac Association Institute of Domestic Heating Engineers Institut
5、e of Refrigeration Institution of Gas Engineers Society of British Gas Industries Amendments issued since publication Amd. No. Date CommentsBS7478:1991 BSI 08-1999 i Contents Page Committees responsible Inside front cover Foreword ii Section 1. General 1 Scope 1 2 Definitions and symbols 1 Section 2
6、. Domestic installations 3 General 3 4 Features 3 5 Valve selection 4 6 Checklist 6 7 Installation 6 8 Commissioning 7 9 User instructions 7 Section 3. Commercial installations 10 General 9 11 Valve selection 10 12 Features 10 13 Checklist 10 14 Installation 10 15 Commissioning 12 Figure 1 Typical f
7、low characteristics showing the two degree position 2 Figure 2 Typical two-pipe system installation 3 Figure 3 Principal components of thermostatic radiator valve 4 Figure 4 Valve position with respect to the radiator 5 Figure 5 Examples of radiator valve connections 6 Figure 6 Integral and remote s
8、ensor 7 Figure 7 Pipework configurations 9 Figure 8 Typical manufacturers flow capacity charts for two degree deviation 11 Figure 9 Sub-circuit pressure losses 12 Figure 10 Sub-circuit pressure losses 12 Publication(s) referred to Inside back coverBS7478:1991 ii BSI 08-1999 Foreword This guide has b
9、een prepared under the direction of the Refrigeration, Heating and Air Conditioning Standards Policy Committee to provide guidance to the user and installer of heating systems on thermostatic radiator valves. These temperature sensing valves are installed in place of manually operated radiator valve
10、s, enabling individual rooms to be controlled at different temperatures. Additionally thermostatic radiator valves (TRV) automatically compensate for heat gains from other sources, such as cooking, open fires, solar gain, additional occupancy, etc. Each TRV has its own temperature sensing actuator,
11、which enables the valve to admit more or less hot water to the radiator as the room temperature falls or rises, thereby maintaining comfort conditions and economizing on fuel. Since TRVs are entirely automatic, no manual adjustment is needed once the desired temperatures have been set. To obtain the
12、se benefits it is important that the guidelines given in this standard are adhered to. 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 i
13、tself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 12, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will b
14、e indicated in the amendment table on the inside front cover.BS7478:1991 BSI 08-1999 1 Section 1. General 1 Scope This British Standard gives guidance on the selection, application and use of thermostatic radiator valves (TRV) manufactured in accordance with BSEN215-1for use in domestic and commerci
15、al wet central heating systems up to a water temperature of120 C. This standard covers two areas of TRV use, these are domestic installation and commercial installation. It is assumed that the installations to which the TRV is to be added are installed in accordance with BS5449, for domestic heating
16、 systems and in accordance with BS6880and CIBSE Commissioning Code Series W “Water distribution systems” for commercial installations. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions and symbols 2.1 Definitions For the purposes of th
17、is British Standard the following definitions apply. 2.1.1 two degree deviation the temperature change in kelvins which, from the closed position, results in60% of maximum flow rate through the TRV NOTE 1A TRV generally moves from a closed to a fully open position for a temperature change of6K. This
18、 magnitude of temperature change would obviously be unsuitable for controlling space temperature. For this reason a smaller deviation is normally chosen, typically2K. NOTE 2It can be seen from the graph inFigure 1 that more than60% of the maximum flow through the valve occurs with a temperature chan
19、ge of2K from the closed position. This valve characteristic has been found to give the optimum control. 2.1.2 maximum K I(K Is ) a means of identifying the maximum capacity of a TRV in the fully open position, in terms of flow (m 3 /h) at a differential pressure of1bar 1) NOTEThis enables the capaci
20、ty of one valve to be compared with another. This position is normally reached for a temperature change of 6 K. 2.1.3 differential pressure (p) the difference in pressure between the valve inlet and the valve outlet 2.1.4 static pressure the pressure existing in a central heating system when no wate
21、r is flowing 2.1.5 maximum working pressure the sum of the static and the differential pressures 2.1.6 valve authority (N) the ratio between the pressure loss across the valve when in the two degree position and the total pressure loss in the circuit NOTEThe ratio is used to determine the suitabilit
22、y of a valve for a particular purpose. Typical ratios for TRVs lie between0.3and0.5. 2.2 Symbols For the purposes of this British Standard the following symbols apply: 1) 1 bar = 10 5N/m 2= 100 kPa. a) two-port thermostatic radiator valve (straight pattern) b) two-port thermostatic radiator valve (a
23、ngle pattern) c) four-port thermostatic radiator valve d) isolation valve e) lockshield regulating valve (angle pattern) f) lockshield regulating valve (straight pattern) g) double regulation valve (regulation and isolation with adjustable regulation stop) h) isolation valve with calibrated orifice
24、and pressure tappings for flow measurements i) two-port motorized valve j) circulation pumpBS7478:1991 2 BSI 08-1999 k) radiator l) direction of flow Figure 1 Typical flow characteristics showing the two degree positionBS7478:1991 BSI 08-1999 3 Section 2. Domestic installations 3 General Figure 2 sh
25、ows diagrammatically a typical two-pipe system heating installation showing TRVs and omitting all other controls. 4 Features 4.1 Typical thermostatic radiator valve The arrangement and principal components of a typical thermostatic radiator valve are shown inFigure 3. 4.2 Temperature selector scale
26、Most TRVs have a graduated temperature selector scale. The relationship between the temperature at the thermostatic head assembly and the temperature at the centre of the room will vary between installations. NOTEIt is important that an appropriate setting should be selected on the temperature selec
27、tor scale to give comfort conditions in the room. (See clause8.) 4.3 Manual shut-off TRVs designed in accordance with BS EN215-1are either capable of positively shutting-off the valve by means of the thermostatic head assembly or a manual cap is provided to obtain a positive shut-off. 4.4 Seal chang
28、e TRVs designed in accordance with BS EN215-1incorporate a facility which enables the seal to be replaced without draining the system. 4.5 Frost protection Most TRVs include a frost position signified by a star, snowflake or other symbol. When the system is operating the frost position will give a r
29、oom temperature of approximately10 C which is intended to protect against freezing. 4.6 Range limiting Range limiting enables the user to restrict the movement of the temperature selector scale to a chosen range. 4.7 Lock setting The lock setting enables the user to lock the temperature selector sca
30、le to a chosen position. 4.8 Vandal guard Some TRVs can be provided with a protective device to render the valve tamper-proof or vandal-proof. NOTEIn a commercial situation this is an important consideration when ordering a valve. Figure 2 Typical two-pipe system installationBS7478:1991 4 BSI 08-199
31、9 5 Valve selection 5.1 Types of valve and pipe connections Different valve patterns are available to suit installation positions. These are shown inFigure 4. Types of valve connections are shown inFigure 5. They are available in straight or angled patterns. Typical connections for use in domestic i
32、nstallations where copper pipe is commonly used are shown in Figure 5(b) and Figure 5(d). NOTEIn retrofit applications it is sometimes possible to replace a manual radiator valve without removing the existing tailpiece and nut. 5.2 Valve sizing Examples of manufacturers sizing charts are shown in11.
33、2. Valves of15mm body diameter give adequate control for most domestic installations up to an output of4kW. Figure 3 Principal components of thermostatic radiator valveBS7478:1991 BSI 08-1999 5 Figure 4 Valve position with respect to the radiatorBS7478:1991 6 BSI 08-1999 6 Checklist The purchaser sh
34、ould ensure that all the design requirements are specified when purchasing TRVs. The following list includes the main points and should be read in conjunction with7.1: a) compliance with BS EN 215-1; b) body type; c) size of valve; d) type and size of pipe connection; e) range limiting; f) range set
35、ting; g) lock setting; h) vandal guard; i) sensor type; j) length of capillary, if remote sensor used. 7 Installation 7.1 Siting To obtain the best performance from a TRV ensure the following. a) Integral sensor type 1) The temperature selector scale and temperature reference point are easily visibl
36、e. 2) A free flow of convected air, i.e.avoid siting behind curtains, furniture or other obstruction which will prevent free flow of convected air over the sensor. 3) Avoid direct sunlight falling on the sensor. 4) Avoid fitting the valve in draughty locations. 5) Allow space to adjust temperature s
37、elector and remove and replace the thermostatic head of the valve body. b) Remote sensor type If the conditions given in a)2) to a)4), cannot be achieved using an integral sensor, a remote sensor should be used (seeFigure 6). It is usual to mount the sensor on the wall, but if this is not possible o
38、r is undesirable, it is permissible to fit it beneath, but not touching, the radiators, as there is normally a convective flow of air in this position. When inaccessiblity of the valve to the user is unavoidable, e.g.when the radiator and valve are located behind a decorative grille, valves with com
39、bined remote temperature sensors and adjusters should be used. Figure 5 Examples of radiator valve connectionsBS7478:1991 BSI 08-1999 7 7.2 Fitting the valve It is essential to ensure that the direction of flow through the valve corresponds to the direction of the arrow on the valve body. The valves
40、 should be fitted in accordance with the manufacturers instructions. NOTEIn retrofit installations where the direction of water flow is not known, it can be determined by first cooling the radiator by closing the valve and then re-opening the valve and identifying which connection to the radiator he
41、ats up first. This is the flow connection and water flows from this connection through the radiator and out through the return connection. 7.3 Absence of by-pass In systems without a by-pass between the flow and return pipes, TRVs should not be fitted to all radiators. A radiator or radiators should
42、 be left without a TRV sufficient to provide the necessary minimum flow rate through the boiler and/or pump. This is often done using the smallest radiator or towel rail, in which case it should be fitted with two lockshield valves to prevent it from being manually turned off. 7.4 Room thermostat Wh
43、en the over-riding space heating control is by a room thermostat, TRVs should not be fitted to radiators in that same room or space. 7.5 Flushing It is essential that all systems are flushed to remove all debris left after installation and prior to commissioning. This should be done with all TRV sen
44、sor heads removed and valves fully open. 8 Commissioning 8.1 Balancing When hydraulically balancing the system the thermostatic heads should be removed from all the TRVs to prevent changes in room temperature affecting the balancing procedure. 8.2 Temperature setting Fit all the thermostatic heads a
45、nd set the temperature selector scales to the mid-position. Bring the heating system into operation and wait until the room temperatures remain constant. If the temperatures achieved are not satisfactory the TRV temperature selectors should be adjusted up or down as appropriate. At least2h should be
46、 allowed after making the adjustments before re-measuring the room temperatures. When the required temperatures have been achieved the TRV temperature selectors should be left in their final positions. If lock or range setting devices are provided, these may now be set if desired. 9 User instruction
47、s The end-user should be informed of the following: a) that when the TRVs are correctly set they should not normally require further adjustment; but turning the temperature selector anti-clockwise increases the temperature and clockwise reduces the temperature; Figure 6 Integral and remote sensorBS7
48、478:1991 8 BSI 08-1999 b) that if the room overheats during the heating season through the effects of sunshine etc., the TRV will automatically turn the radiator off and it will feel cold to the touch; c) that if the house is left unoccupied for a period during cold weather, when freezing conditions
49、 may occur and there is a risk of the system freezing: 1) ensure that the heating system is on, to maintain a temperature of approximately10 C; and 2) the TRV temperature selectors should be set to the frost position, after noting the normal setting.BS7478:1991 BSI 08-1999 9 Section 3. Commercial installations 10 General In the commercial/industrial sector the two principal pipework configurations in common use are shown inFigure 7. A third system is sometimes used as shown inFigure 7(c) and requires a four-port valve. Many fac
