GB2272105A

GB2272105A - Water heating system

Info

Publication number: GB2272105A
Application number: GB9307226A
Authority: GB
Inventors: Houghton Ainsworth Gledhill
Original assignee: Gledhill Water Storage Ltd
Current assignee: Gledhill Water Storage Ltd
Priority date: 1992-09-22
Filing date: 1993-04-05
Publication date: 1994-05-04
Anticipated expiration: 2013-04-05
Also published as: GB9220022D0; GB9307226D0; GB2272105B

Abstract

In a temperature control system for a thermal storage water heating system, the temperature of the water in the storage tank is controlled by a thermostat having an adjustment pointer 60, which can be set to, for example, "Winter" or "Summer". The pointer 60 controls the displacement of a diaphragm 46 which is displaced by expansion of gas or liquid in a bulb 38 of the thermostat which is connected to the diaphragm 46 by a capillary tube 44. The adjustment pointer 60 adjusts the thermostatically controlled temperature of the water in the storage tank and can be prevented from being moved to a maximum position by a lock or catch 62 to prevent the user from setting the thermostat at too high a temperature which could result in the boiler "cycling" because its maximum output could never satisfy the maximum thermostat setting. In effect therefore the user is prevented from decommissioning the installation. The thermostat is carried by an electric immersion heater. <IMAGE>

Description

Improvements Relating to Water Heating Apparatus and Electric Element Heaters Therefor This invention relates to water heating apparatus, particularly but not exclusively, water heating apparatus for domestic purposes, and concerns the form of water heating apparatus which is identified by the description "thermal storage11.

In thermal storage water heating apparatus, a water tank contains a substantial body of water which is heated to form a thermal store, and the heat from that body of water is utilised for two purposes, namely for the space heating of the building by, in one example, circulating water from the thermal store through a central heating radiator system, and the heat of the water in the thermal store is also used by heat exchange to heat incoming mains pressure water to provide the secondary heated water for domestic washing purposes.

The temperature of the water in the thermal store is controlled by a temperature sensitive device which may be electronic in nature, or may comprise a thermostat, and the temPeratufe control device is arranged to control the operation of a boiler which serves to heat the water in the thermal store. Typically, the boiler will be of the gas fired type and will be arranged to heat the water in the thermal store by circulation of the water from the store through the boiler and back to the store by means of a boiler pump.

Gas boilers also usually have their own thermostat to prevent the boiler from discharging heated water at anything above a pre-set temperature.

Because there are two controls operating on the actuation of the boiler, these controls being the temperature sensitive element of the thermal store, and the thermostat of the boiler, problems can sometimes be encountered in commissioning the installation insofar as if the boiler thermostat and the store temperature sensitive device are not correctly set, the boiler may well fire when the thermal store is in fact satisfied by operating on its own thermostat. It may well therefore cycle when it is unnecessary so to do, and this can lead to an increase in the cost of fuel bills to the consumer, which is unnecessary, and can also cause considerable annoyance particularly if the boiler switches on and off during the night.

In our co-pending Patent Application No. 9013643.3, we have provided an arrangement for the commissioning of the installation whereby this disadvantage can be overcome, and this arrangement works efficiently.

However, there is now a demand of thermal storage installations, which have only relatively recently been adopted in large numbers in the United Kingdom, to provide that the thermal store should be capable of running at at least two different store temperatures corresponding to (i) winter demand, when there is a greater demand for space heating, and (ii) summer demand when the demand is mainly for the secondary hot water for washing purposes, the heating requirement being minimal or not required at all.

Initial proposals to meet this requirement have suggested the utilisation of two separate temperature sensitive devices which monitor the temperature of the store, such devices being set to operate at different temperatures, for example in the order of 780C in winter, and 680C in summer. Such an arrangement requires the utilisation of a switch which may be manual or automatic, but the utilisation of two temperature sensitive devices for the thermal store, especially when the devices are thermostats, means that the construction of the store tank is complicated and the tank becomes correspondingly more expensive. Additionally, the commissioning of the installation can be disturbed leading to the undesirable effects described above.

The present invention seeks to provide an alternative arrangement for providing for different running conditions of the water heating system as related to for example different seasonal requirements.

According to the present invention in one aspect, the thermal storage water heating system has the temperature of its water controlled by means of a thermostat of the type comprising a temperature sensitive bulb including a liquid or gas which expands under the influence of heat, the bulb being connected by a capiliary tube which leads to a pressure displacement member such as a diaphragm whose displacement can be adjusted by the turning of an adjustment device, whereby the adjustment device can set the temperature at which the thermostat operates, and wherein the adjustment device has a means whereby following the commissioning of the system, the installer can position a lock or catch means which limits the extent of movement of the adjustment means, preventing the user who can move the adjustment means to suit different seasonal conditions, from moving the adjustment means to such a position whereby the installation could become decommissioned.

In a preferred arrangement, the adjustment means comprises an adjustment knob which is adapted to be turned for adjustment purposes, and the knob is associated with a pointer to register with a labelling arrangement, indicating on a support surface different seasonal conditions, for example "summer' and "winter".

The lock or catch means may comprise simply a peg which is pushed into one of a range of apertures surrounding the knob which apertures lie in a curved arc so as to be traversed by the said pointer when the knob is turned, the peg forming an obstruction to the turning of the knob to a particular position.

The thermostat bulb may be of such size and capacity and the capiliary tube may be of such length and inner bore size as related to the angular adjustment of the knob such that an adjustment of the knob through an angle approaching 1800 represents an 80C variation in the response of the thermostat.

By making a thermostat arrangement such that a large degree of angular movement of the adjustment knob gives only a relatively small temperature drop in the response, e.g. 80C, adjustment of the thermal storage operating conditions by the user is made particularly simple.

In the commissioning of the installation of the particular arrangement indicated above, the installer will initially fire the boiler with the knob and pointer at the maximum temperature response condition of the thermostat which may be for example representative of 780C in the thermal store.

Where the arrangement as described in our co-pending patent application No 9013643.3 is employed, the installer will run the installation until such times as the boiler switches off when the store is satisfied, indicating that the installation has been correctly commissioned. The indicator light remains illuminated. Next the installer turns the pointer so as to sweep over one or two of said apertures, in a direction effectively setting the thermostat to run at a slightly lower temperature than the commissioning temperature, until the indicator light is extinguished, following which the lock or catch means in the form of the locking peg is inserted in the appropriate aperture preventing the pointer from being turned back to the initial commissioning position.This will prevent the user from decommissioning the apparatus, but will still enable the user to move the pointer through the remainder of its possible sweep in order to set the apparatus for different climatic conditions such as winter and summer.

The utility and novelty of the first aspect of the present invention leads to a second aspect of the invention which relates to an electric element heater for a thermal store.

A conventional electric element heater comprises a head which is adapted to be received in an aperture in the store tank wall and an electric heating element extends therefrom so as in use to be immersed in the water to be heated.

A thermostat tube containing the temperature sensitive bulb and capillary tube as abovementioned also extends from the head into the crater so that the bulb will experience the water temperature for the operation of the pressure displacement member which is contained in the head.

By this arrangement only electrical connections are required to the heater head.

In accordance with the second embodiment of the invention, the head of an electric element heater for a thermal store is provided with the adjustment means as aforesaid, and in this aspect of the invention the provision of the lock or catch means is optional, although preferred.

The adjustment means, as abovementioned,is preferably associated with a labelling arrangement indicating different seasonal conditions, covered by the heater head.

Preferably, the adjustment means is an adjustment knob having a pointer to register with different seasonal conditions indicated on said labelling arrangement.

When the lock or catch means is provided in the second aspect of the invention, said lock or catch means is of the same form as in the first aspect of the invention.

Again the thermostat bulb and capillary tube preferably are of such size, length and inner bore that adjustment of the adjustment knob through an angle approaching 1800 represent an 80C variation in the response of the thermostat.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, wherein: Fig. 1 is a layout diagram showing a thermal storage apparatus equipped with thermostatic control according to the invention; Fig. 2 is a perspective view illustrating the thermostatic control arrangement of Fig. 1; and Fig. 3 is a perspective view of an electric element heater according to a second aspect of the invention, and useable in the apparatus of Fig. 1.

Referring to the drawings, the components of the system are illustrated in Fig. 1 and comprise the storate tank 10 which is supplied under gravity with water from a feed and expansion tank 12, the feed and expansion tank being supplied from a mains supply line 14 through a float controlled valve 16. The flow of water from tank 12 to tank 10 is via feed pipe 18, whilst expansion pipe 20 serves as a means for returning expanded water from tank 10 back to the tank 12, in conventional fashion.

Inside the tank 10 is a heat exchanger 22 through which mains water pressure is fed via pipe 24, and heated water is discharged from pipe 26 and eventually is delivered to user points such as taps 28. A branch line 30 between line 24 and line 26 leads to a mixing valve 32 in line 26 in order to mix some cold water with the issuing hot water on line 26 to provide temperate water at the taps 28, in accordance with the temperature control setting of the mixing valve 32. The mixing valve 32 is of the adjustable type so that the water which flows from taps 28 can be adjusted to the appropriate temperature.

The water in the tank 10 is heated by circulation through a boiler 34, and the boiler has its own thermostat 36 which senses the temperature of heated water issuing from the boiler into the store 10 to control same to a predetermined boilerstat maximum.

The boiler is also under the control of a thermostat 38 and control means 40 via electrical lines 42 so that the thermostat 38 is in fact the overriding control for the boiler 34 should it be that thermostat 38 and thermostat 36 are competing. In other words if thermostat 38 indicates that the store is satisfied, the boiler will not switch on even though thermostat 36 indicates that there is demand for a boiler to be switched on. If the store 10 indicates that heat is demanded, the boiler will switch on and will deliver hot water to the store, but it will not deliver water any hotter than the maximum temperature as set by the thermostat 36, and therefore in the heating up process the boiler may well switch on and off until the store thermostat 38 is satisfied.

As indicated in said co-pending application 9013643.3 (publication No. 2234050) commissioning of the installation can cause problems if for example the boiler thermostat 36 is not operating sufficiently accurately and there is some variation between the respective demands of the store thermostat and the boiler thermostat. As explained in said co-pending application the method of overcoming this difficulty is to provide an indicator means for example in the form of a neon indicator light 40A which is extinguished when the store thermostat is satisfied and if the light 40A is extinguished when the boiler eventually switches off, the installer knows that the system has been correctly commissioned.

As explained herein, the conventional thermal storage systems are designed to operate to control the store 10 to be at a fixed store temperature, regardless of the seasonal conditions. This has been shown to be something of a disadvantage, because for example in summer the demand for heat is much less, and if the store is maintained at the fixed single temperature which is usually geared to the temperature required from the heating circuit, then in fact the water can be maintained at too high a temperature with the consequent heat wastage and the need to dilute the hot water with cold water to provide suitable water for the taps 28.It is desirable therefore that the system should be capable of some adjustment in order to allow that it operates for example in summer at a lower temperature than it does in winter although the temperature differential between winter and summer is in fact in practise relatively small, for example of the order of 80C.

The system of the present invention provides for this adjustment, and in the arrangement shown in Fig. 2, the thermostat 38 is in the form of an elongated metallic bulb of conventional construction but perhaps of larger than normal size, which is filled with an expandable gas or liquid which responds to changes in temperature by expanding to a greater or lesser degree. The bulb 38 is coupled to a capiliary tube 44 which in turn is connected to a control diaphragm 46 which is displaced by the increase in pressure resulting from expansion of the gas or liquid in the bulb 38. The resistance to displacement of the diaphragm is controlled by means of an adjustment knob 48 whereby by adjustment of knob 48 angularly as indicated by arrow 50, the diaphragm displacement can be controlled.The diaphragm in turn is connected to an electrical switch which operates when the diaphragm reaches a predetermined position, and the throwing of this switch by the displacement of the diaphragm causes a signal to be issued on output wire 42 which in turn as described herein effects control of the operation of the boiler 34.

The diaphragm control unit 46 is located under a support plate 52 which has markings indicating an adjustment sweep limited by stops - not shown of the knob 48 by 1800, such markings being indicated by reference numerals 54 and 56.

The system is arranged such that the sweep of the knob 48 between position 54 and 56 represents a temperature response difference for the bulb 38 in the order of 80C and as indicated the sweep range of 1800 between 54 and 56 is subdivided into two quadrants indicating winter conditions and summer conditions. In the quandrant of the plate 52 indicating the winter conditions, there are holes 58 arranged in an arcuate path and which are swept over by a pointer 60 connected to the knob 48. It will be understood that the pointer 60 when in the winter quadrant sets the bulb 38 to operate in response to a higher temperature whereas when it is in the quadrant representing the summer conditions, the bulb will respond to a lower temperature of the water in store 10. This means provides the adjustment for the user so that the user can readily adjust between winter and summer running conditions.Typically, when the unit runs in winter conditions, the store will operate at a temperature in the order of 760C, whilst during summer conditions by adjustment of the knob 48, the unit will run at a temperature in the order of 680C.

The holes 58 in conjunction with a locking peg 62 provide a means for preventing the user from decommissioning the apparatus insofar as when the installation is first commissioned, the pointer 60 will be placed coincident with line 54 to set the store 10 to run at the maximum temperature. At this time the neon light 40A is illuminated. The boiler then switches off eventually on its own thermostat 36 and the installer then turns the knob 48 anticlockwise until the neon light is extinguished which sets the running temperature of the store at a level lower than the upper control temperature of the boiler thermostat which means that the store thermostat 38 will be satisfied before the boiler thermostat in normal operation.From this point the installer turns the knob 50 to an extent so that the pointer 60 passes over one or perhaps two of the holes 58, and then the peg 62 is inserted as indicated in Fig. 2 to prevent the pointer 60 from being turned back to the maximum position where the boiler thermostat could override the tank thermostat. The peg 62 which locks in the hole therefore prevents the user from decommissioning the apparatus although the user is still able to adjust between winter and summer conditions as desired.

Other embodiments of the locking device are possible.

Referring now to Fig. 3, which shows a practical embodiment of the invention, the figure shows an electric element heater 70 which is mounted on the wall of tank 10 so that a heating element 72 thereof projects into and is immersed in the water in the tank. The element is in this case screwed to the tank by means of a threaded sleeve portion 74, and a collar 76 with flats thereon is engagable by a wrench or other turning tool for the fitting of the heater.

A casing 78 houses various control elements including the diaphram 46, and as indicated the end of the casing 78 is made up by the plate 52 and in this regard it is to be mentioned that reference numerals already used in Fig. 2 are used to designate the same or equivalent parts in the arrangement of Fig. 3.

Thus, the control knob 48 is shown as mounted on the plate 52 and a label 80 carries the markings 54 and 56 and the quadrant labelling for winter and summer conditions.

The electric heating element 72 contains electric heating means, and a probe 82 contains the bulb 38 and the capillary tube 44.

With the heater shown in Fig. 3, it is simply a matter of making the electrical connections the appropriate wires 42 in order to couple the heater into the control system as shown in Fig. 1.

The particular arrangement in Fig. 3 operates in identical fashion to that described in relation to Fig. 2, the portability of the unit brings out another aspect of this invention in that with the arrangement of Fig. 3, it is not necessary to provide the lock out apertures 58, and the heater to be used simply as an electric immersion heater with a climatic condition control knob or other adjustment means.

Normally these immersion heaters are fixed for operating at a single temperature, and the adaptation according to this aspect of the invention for the adjustability constitutes a departure in the art.

Again, the bulb 38 and capillary 44 are set in relation to the adjustment means such that as between limits 54 and 56 and 80C temperature variation in response temperature is obtained.

The advantage of the described arrangement is that the immersion heater described is accessible to the householder for ready adjustment and is capable of precise setting. The immersion heater furthermore has general application to water heating where the stored water may not be in a thermal storage system.

The invention therefore provides a simple and effective means for providing for adjustment between different seasonal conditions whilst preventing the user from accidentally decommissioning the apparatus.

Claims

1. A thermal storage water heating system wherein the temperature of the heated stored water is controlled by means of a thermostat of the type comprising a temperature sensitive bulb including a liquid or gas which expands under the influence of heat, the bulb being connected by a capiliary tube which leads to a pressure displacement member such as a diaphragm, whose displacement can be adjusted by the turning of an adjustment device, whereby the adjustment device can set the temperature at which the thermostat operates, and wherein the adjustment device has a means whereby following the commissioning of the system, the installer can position a lock or catch means which limits the extent of movement of the adjustment means, preventing the user who can move the adjustment means to suit different seasonal conditions, from moving the adjustment means to such a position whereby the installation could become decommissioned.

2. A system according to Claim 1, wherein the adjustement means comprises an adjustment knob which is adapted to be turned for adjustment purposes, and the knob is associated with a pointer to register with a labelling arrangement, indicating on a support surface, different seasonal conditions, for example summer and winter.

3. A system according to Claim 2 wherein the lock or catch means comprises a peg which is pushed into one or a range of apertures surrounding the knob, which apertures lie in a curved arc so as to be traversed by said pointer when the knob is turned, the peg forming an obstruction to the turning of the knob to a particular position.

4. A system according to any preceding claim, wherein the thermostat bulb is of such size and capacity and the capiliary tube is of such length and inner bore size as related to the angular adjustment of the knob such that an adjustment of the knob through an angle approaching 1800 represents an 80 C variation in the response of the thermostat.

5. A control system for use in the thermal storage water heating system according to any preceding claim, wherein the control system is as set forth in Claim 1 or any claim dependant thereon.

6. An electric element heater for thermal store comprising a thermostat of the type comprising a temperature sensitive bulb including a liquid or gas which expands under the influence of heat, the bulb being connected by a capillary tube which leads to a pressure diplacement member such as a diaphram, whose displacement can be adjusted by the movement of an adjustment device, whereby the adjustment device can set the temperature at which the thermostat operates, said heater being of the immersion heater type comprising an element which is for immersion in the water to be heated, and the head for mounting on the wall of the water tank, said head carrying said adjustment device.

7. A heater according to Claim 6, including the adjustment device as a means whereby following the commissioning of the system in which the heater is used, the installer can position a lock or catch means which limits the extent of movement of the adjustment means, preventing the user who can move the adjustment means to suit different seasonal conditions, from moving the adjustment means to such a position whereby the installation could become decommissioned.

8. A system according to Claim 7 wherein the adjustment means comprises an adjustment knob which is adapted to be turned for adjustment purposes, and the knob is associated with a pointer to register with a labelling arrangement indicating on a support surface, different seasonal conditions, for example winter and summer.

9. A heater according to Claim 8 wherein the lock or catch means comprises a peg which is pushed into one or a range of apertures surrounding the knob, which apertures lie in a curved arc so as to be traversed by said pointer when the knob is turned, the peg forming an obstruction to the turning of the knob to a particular position.

10. A heater according to any of Claims 6 to 9, wherein the thermostat bulb is of such size and capacity and the capillary tube is of such length and inner bore size as related to the angular adjustment of the knob such that an adjustment of the knob through an angle approaching 1800 represents and 80C variation in the response of the thermostat.

11. An electric immersion heater substantially as hereinbefore described with reference to Fig. 3 of the accompanying drawings.

12. A thermal storage water heating system substantially as hereinbefore described with reference to the accompanying drawings.