GB2073372A

GB2073372A - Thermostatic radiator valves and control system therefor

Info

Publication number: GB2073372A
Application number: GB8011298A
Authority: GB
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC
Priority date: 1980-04-03
Filing date: 1980-04-03
Publication date: 1981-10-14
Also published as: GB2073372B

Abstract

A thermostatic valve for a space heating system and a heating system employing said valves are described. Each valve (14) is of the type in which movement of a thermally responsive member, e.g. a fluid filled bellows (25) controls the position of a valve member (23) thus determining the blocking factor of the valve at any given temperature. An adjustable "off set" of the operation temperature profile of the valve is provided via a heater element (29) located adjacent or with the bellows. Each valve is fitted to a radiator or the like. The valves (14) are operated from a central control unit (not shown) which determines the operating temperature profile of each valve. <IMAGE>

Description

SPECIFICATION Thermostatic radiator valves and control system therefor This invention-relates to space heating systems in which thermostatic valves are used to vary, in accordance with ambient temperature, a flow of hot water through a plurality of radiator panels so as to maintain a desired temperature level.

According to one aspect of the invention there is provided a thermostatic fluid control valve of the type in which movement of a thermally responsive element determines the position of a valve member relative to a valve seat, the valve including a heater element and whereby the operating temperature of the valve can be controlled.

According to another aspect of the invention there is provided a space heating system, including a boiler, a plurality of radiators each coupled to the boiler via a thermostatic valve, heaters one associated with each said valve, and a central control unit coupled to each said heater, the arrangement being such that the control unit supplies each said heater selectively with a steady or non-steady current thereby determining the operating temperature profile of that valve.

Embodiments of the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a schematic diagram of a space heating system; Figure 2 is a cross-section of a thermostatic valve for the use in the system of Fig. 1; and Figure 3 is a cross-section of an alternative thermostatic valve construction.

Referring to Fig. 1, the system includes a boiler 11 coupled to a plurality of radiators 1 2 via pipes 1 3. The radiators are connected e.g.

in parallel and the flow of hot water through each is controlled by a respective thermostatic valve 14. In a one pipe system the radiators will of course be connected in series. The system may also include solenoid valves 1 5 whereby one or more portions of the system may be isolated from the boiler. A heat exchanger 1 6 may also be provided to supply hot water. Alternatively the solenoid valves 1 5 may be used for sharing the flow between the heat exchanger 1 6 and the radiators or for mixing hot water from the boiler with cooler water from the return pipe to maintain a certain pipe flow temperature.Control of the system is effected from a central control unit 1 7 which unit operates the boiler 11 and operates the various valves 1 4 and 1 5 in accordance with timing signals from a timer 1 8 and temperature information from a temperature sensitive device 19.

One type of thermostatic valve 1 4 for use in this system is shown in Fig. 2. The valve has inlet and outlet pipes 21 and 22, the water flow therebetween being controlled by a mushroom headed valve member 23 which is moveable relative to a valve seat 24. The valve member 23 is urged towards the seat by a bellows 25 secured to the far end of the valve and acting in opposition to coil spring 20 mounted inside the bellows. The bellows 25 is mounted within a sealed fluid containing chamber 26. The temperature of the fluid in the chamber 26 determines its volume and hence the equilibrium position of the bellows 25. Changes in ambient temperature cause heating or cooling of the fluid in the chamber 26 and consequent changes in the fluid volume.This moves the valve member 23 towards or away from the valve 24 thus determining the flow of water' through the valve.

Adjustment of the operating temperature range of the valve is effected by rotating the chamber 26 relative to a screw cap 27 fitted with a sealing gasket 28 thus altering the effective volume of the chamber 26.

Control of the valve by the central control unit 1 7 is provided via a resistive heater element 29 mounted within the chamber 26, the element 29 advantageously being of cylindrical form and surrounding the bellows 25.

The heater termination 30 may take the form of insulation piercing (insulation displacement) connection. By passing an electric current through the heater element 29 the fluid in the chamber 26 is heated to above ambient temperature and its volume is increased. This compresses the bellows and partially closes the valve member thus restricting the water flow through the valve. In an alternative ar rangement (not shown) the heater element may be immersed in the fluid inside the bellows.

The central control unit 1 7 may operate each valve in one of two ways. Firstly the heater element 29 may be supplied with a steady current, not necessarily the same for each valve, that results in a temperature set back of that valve; i.e. there is provided a step reduction of the ambient operating temperature below the temperature for which the valve is currently set. This mode of operation can given local temperature control together with a variable remotely controlled set back e.g. to provide a temperature reduction at night.

In the second mode of operation each valve is provided either with no local adjustment or only with sufficient local adjustment to balance the various portions of the heating system. In this case the local ambient temperature depends entirely on the power fed to the heater elerNents from the central control unit.

As the valves have a relatively slow response to temperature changes, the power fed to the heaters 29 may be varied by switching the heater current on and off with a duty cycle dependent on the desired operating temperature. Even with a relatively long duty cycle period, typically 1 to 10 seconds, each valve controls the water flow in an analogue manner dependent on the mean power level supplied to its heater. Electrical waveforms suitable for driving the heaters may be generated e.g. by a microprocessor (not shown) fitted to the central control unit. The switching elements may be bi-polar transistors or power MOS devices such as VMOS transistors.

Fig. 3 shows an alternative valve construction in which a snap action may optionally be provided. In this construction, as before, the valve includes inlet and outlet pipes 31 and 32, the water flow therebetween being controlled by movement of a valve member 33 relative to a valve seat 34. The valve member 33 is urged towards the valve seat 34 by flexure of a bimetal strip 35 which strip may be additionally counterbalanced by a .compres- sion spring 36. The strip 35 and spring 36 are mounted in chamber 37 forming part of the valve assembly.

The bimetal strip 5 is constructed so that an increase of ambient temperature causes the strip to bend towards the valve member 33 this urging the valve member against the seat 34. Fine adjustment of the operating range of the valve is provided by an adjustable screw cap 38 fitted to the tail end of the valve member 33. As before, control of the valve from the central control unit 1 7 is effected by passing an electric current through a resistance heater element 39 mounted adjacent the bimetal strip. Snap operation of the bimetallic strip may be provided e.g. by forming a domed portion (not shown) in the strip.

Claims

1. A thermostatic fluid control valve of the type in which movement of a thermally responsive element determines the position of a valve member relative to a valve seat, the valve including a heater element disposed adjacent the thermally responsive element and whereby the operating temperature of the valve can be adjusted.

2. A thermostatic valve as claimed in claim 1, and wherein the thermally responsive element comprises a pressure responsive bellows to which the valve member is coupled.

3. A thermostatic valve as claimed in claim 2, and wherein the heater element is substantially circular in cross section and surrounds the bellows.

4. A thermostatic valve as claimed in claim 2, wherein the heater elements is immersed in the fluid within the bellows.

5. A thetmostatic valve as claimed in claim 1, and wherein the thermally responsive element comprises a bimetallic strip.

6. A thermostatic valve as claimed in claim 3, and wherein the strip is profiled so as to provide a snap action.

7. A thermostatic valve as claimed in any one of the preceding claims, wherein said heater element is provided with terminations of the insulation displacement type.

8. A thermostatic valve substantially as described herein with reference to Fig. 2 or Fig. 3 accompanying claims.

9. A space heating system including a plurality of radiators at least some of which are provided with a thermostatic valve as claimed in any one of claims 1 to 8, and a central control unit whereby an electric current may be supplied to each said valve so as to determine its operating temperature.

10. A space heating system as claimed in claim 9 and wherein said control unit supplies said current in digital pulse form.

11. A space heating system as claimed irr claim 9 or 10, wherein said control unit is a microprocessor control unit.

1 2. A space heating system, including a boiler, a plurality of radiators each coupled to the boiler via a thermostatic valve, heaters one associated with each said valve, and a central control unit coupled to each said heater, the arrangement being such that the control unit supplies each said heater selectively with a steady or non-steady current thereby determining the operating temperature profile of that valve.

1 3. A space heating system substantially as described herein with reference to Fig. 1 together with Fig. 2 or Fig. 3 of the accompanying drawings.

1 4. A method of controlling a space heating system which method is substantially as described herein with reference to the accompanying drawings.