EP0175716A1

EP0175716A1 - Control means for hot water systems

Info

Publication number: EP0175716A1
Application number: EP85901311A
Authority: EP
Inventors: Andrew Strange
Original assignee: Actrol Industries Pty Ltd
Current assignee: Actrol Industries Pty Ltd
Priority date: 1984-03-20
Filing date: 1985-03-19
Publication date: 1986-04-02
Also published as: IT8519980A0; IT1185094B; ZA852054B; WO1985004239A1; JPS61501520A

Abstract

Dispositif de commande pour un système d'eau chaude comportant un microprocesseur doté d'une mémoire programmable (15) et d'un circuit logique (10) recevant des données du système et répondant d'une manière indiquée par la mémoire. La réponse peut comporter une modification des paramètres de fonctionnement du système ou l'émission d'un signal indiquant la présence d'un défaut dans le système. Le dispositif de commande est actionnable pour réguler le cycle de chauffage du système de manière à ne commencer que lorsque les conditions de température du système le rend nécessaire et que les autres facteurs auxquels il est soumis sont satisfaisants, par exemple la charge sur l'alimentation du secteur utilisée pour mettre le système sous tension.A controller for a hot water system comprising a microprocessor having a programmable memory (15) and a logic circuit (10) receiving data from the system and responding in a manner indicated by the memory. The response may include changing the operating parameters of the system or issuing a signal indicating the presence of a fault in the system. The controller is operable to regulate the heating cycle of the system so as to start only when the temperature conditions of the system make it necessary and other factors to which it is subjected are satisfactory, for example the load on the power supply power used to turn on the system.

Description

This invention relates to hot water systems and is particularly concerned with the control of such systems. The invention is applicable to hot water systems in which the

' heating source is electrically energized or includes a fuel

(e.g., gas) burner.

Hot water systems of the foregoing kind have been progressively developed to include a variety of safety devices such as valves which open automatically to relieve the system in the event of excessive temperature and/or pressure being 10 generated within the system. Such safeguard devices and other control aspects of hot water systems have traditionally operated in relative isolation so that the failure or operation of one aspect will not necesarily influence operation of the total system. In the result, such systems continue to operate in a relatively inefficient and perhaps dangerous manner.

It is an object of the present invention to provide control means for a water heater or hot water system which enables the system to respond to any of a plurality of 20 circumstances such that the safety and efficiency of the system is improved. It is another object of the invention to provide a water heater or hot water system including such control means.

According to the present invention, there is provided a r control means for a hot water system including, storage means for storing a set of pre-established instructions, and responder means for receiving and responding to data received from said system and being connected to said storage means so that said instructions at least influence the nature of said 30 response, and said response is operable to either influence the operation of the system or generate an indication of a condition of said system.

The essential features of the invention, and further optional features, are described in detail in the following passages of the specification which refer to the accompanying drawings. The drawings however, are merely illustrative of how the invention might be put into effect, so that the specific form and arrangement of the features (whether they be essential or optional features) shown is not to be understood as limiting on the invention.

In the drawings: - Figure 1 is a schematic view of a conventional electric hot water system;

Figure 2 is a schematic view showing one form of control means according to the present invention as applied to a hot water system of the general kind shown in figure 1;

Figure 3 is a diagrammatic layout of a surveillance sequence which may be used with the arrangement shown in figure 2; Figure 4 is a schematic view of a possible application of the control means to a solar heating system which operates as an adjunct to the electrically energized heating system as shown in figure 2.

Control means according to the invention is electronic in nature and includes a micro-processor or other means for storing a set of instructions and responding as those instructions require to input data derived from the associated system. The control means can serve any of a plurality of different functions and its form may alter accordingly. It will be convenient to hereinafter describe the control means as applied to a particular example form of hot water system, but that is not to be undeerstood as limiting on the invention.

In a typical electrical hot water system as shown in figure 1, there will be switch means 1 for the heating element 2 and temperature sensing means 3 to determine when electrical energy should be supplied to and disconnected from the element 2. Such systems may include a booster element 4 which is controlled by a switch 5 and which enables accelerated heating ° of the water stored in the tank 6 in times of peak demand on the system. Furthermore, the system will normally include valve means 7 which opens in response to detection of excessive pressure or temperature within the system and thereby relieve the system from a potentially dangerous overload situation. Another facility commonly included in such systems is a selector switch 8 which is adjusted according to whether the system is to operate - i.e., heat the stored water - during daytime or night time periods. A master switch 9 may control the total system. Figure 2 shows, in diagrammatic form, control means according to the invention applied to a system of the foregoing kind. The control means may be programmed in an appropriate manner to provide the necessary responses to information received by the control means. It is usually preferred however, to embody the logic of the control means in micro-circuitry such as a silicon chip or a plurality of such chips. That circuitry is represented by the block bearing reference numeral 10 in figure 2 and can be arranged to respond in a predetermined manner to any one of a variety of different circumstances and the following description deals with one example only.

The system may include a master switch 11 which can be operated according to whether the control means is to be active or inactive. In the inactive state, the system is preferably inoperable. Also, means (not shown) may be -provided to enable manual .override of any of the functions of the control means.

In the arrangement shown, the line 12 represents a connection to the heating period selector 8 and other information sources such as a zellweger circuit, peak load sensor, time clock, etc. When in the active state, the control means is thereby able to sense whether the system is to operate during daytime or night time periods and will preferably sense when there is a^' change in the selection of the operating period. Furthermore, instead of supplying energy to the heater element 2 at a preset time as in current systems, the control means is able to respond to data automatically fed to it from the system so as to select an appropriate time for commencement of the heating operation. For example, the control means may receive data concerning the volume and temperature of the stored water and the unexpired time of the operating period, and from that data automatically compute an appropriate time for commencement ofenergization of the heating element 2. That energization will then commence automatically at the selected time.

Such automatic selection of energization time enables the system to minimize surge loading on the associated mains power supply. That aspect may be further enhanced by having the control means sense the load on the mains supply at the selected time and defer energization of the element 2 if the load is excessive.

Temperature control can be achieved through use of suitable temperature responsive means. For example, sensors 13 may be arranged to detect the upper and lower levels of the selected temperature range and the control means responds to those sensors 13 to energize or de-energize the element 2 as appropriate.

Relief means is preferably provided to take care of excessive temperature conditions and that means may include a sensor and a solenoid valve 7. When the sensor detects an over-temperature condition the control means responds by causing the solenoid valve 7 to open and thereby relieve the system. Similar means can be adopted to cope with excessive pressure conditions.

If the control means operates to relieve an over-temperature or an over-pressure condition, it may function to automatically reset the system to normal operation when the relevant condition no longer exists. Alternatively, manual resetting may be required to ensure that the failure does not go undetected. In the event of automatic resetting, the control means may produce a visual or other signal to indicate thata failure has ocurred and manual intervention may be required to terminate that signal. For example, an LED display 14 may remain steady if the system is operating satisfactorily and may flash if a fault has been detected.

The same kind of fault indicating facility and resetting may be adopted for any other failure or malfunction within the system which the control means is arranged to detect.

With regard to the foregoing, the control means may have a diagnostic function and may continuously or periodically survey the associated system for that purpose. Some of the diagnostic functions may be to detect failure or malfunction of the heating element 2, earth leakage, out of tolerance rate of change of water temperature, and the electroylsis level of the stored water. The latter information can be relvant to the condition of a sacrificial anode as sometimes used in hot water systems. Appropriate displays and/or responses can be included to reveal and/or cope with aberrations or failures within the system. The control means preferably responds to at least one condition to shut down the system until the relevant aberration or fault is rectified. In that regard, it is preferred that the various functions of the heater or system are interrelated through the control means so that the control means will operate to shut-down the heater or system if a particular sequence of functions is not achieved or if any function is not commenced or completed.

The control means may be arranged to automatically reset the system in the event of temporary shut-down due to failure of the mains power supply for example. The same may apply in the event of termination of an aberration in the system to which the control means has responded by shutting down the system.

Figure 2 shows one possible circuit arrangement in which the basic set of instructions for the control means is stored in a memory 15 connected to the logic circuit 10. The memory 15 can be programmed in any suitable manner and the arrangement is such that the logic circuit 10 functions in a manner dictated by the memory 15. That is, the logic circuit 10 receives data from the system and then responds to the received information in a manner as controlled by the memory 15. The resulting response of the logic circuit 10 may be to cause generation of a fault indication at the display 14 and/or to cause a change in the operating parameters of the system - e.g., energize or de-energize the element 2.

In the arrangement of figure 2 the logic circuit is powered through a voltage regulator 16 and the connections 17 and 18 respectively provide an earth reference and a signal representing -the AC mains supply level. An adjustable selector 19 is operable to establish the upper level of the temperature of the stored water, although the setting of that selector 19 cannot exceed the maximum possible temperature as determined by a limiting resistor 20. The various temperature sensors 13 are located as required within the tank 6 and each transmits its respective signal to the logic circuit through an analogue/digital converter 21.

A third heating element 22 is shown in the figure 2 arrangement and that may be used as a substitute for, or in addition to, the normal element 2 when a particular heating rate is required. The elements 2, 4 and 22 are controlled by respective switches 23, 24 and 25 which are in turn controlled by the logic circuit 10.

The particular circuit shown also includes a thermistor 26 which functions as a low water detector. In addition an anode 27 is connected to the thermister 26. The anode 27 is not a sacrificial anode as would normally be included in a hot water tank, but is arranged to pass a low current into the surrounding body of water and that current has an inhibiting effect on electrolysis at the walls of the tank 6. Current is fed to the anode 27 from the logic circuit 10 through the connection 28 and the thermistor 26. When the thermistor 26 is immersed in the tank water there will be a constant voltage drop across it which is detected by the logic circuit 10 through the connection 29 and transistor 30. Should the level of water fall below the thermistor 26 there will be a change in the voltage -drop across the thermistor 26 which is detected but the current defect device 32. The logic circuit 10 responds to a signal generated by the device 32 by preventing power supply to the elements 2, 4 and 22. In the event of failure of the thermistor 26, the anode 27 will function as a low water detector. When the water level drops below the anode 27, current bleed from the anode 27 will cease and that is detected by the logic circuit 10 which responds in a manner such as to inactivate the elements 2, 4 and 22.

A manually operable boost switch 31 is also shown in the figure 2 arrangement. The logic circuit 10 detects when the switch 31 is. activated to the on position and responds by causing subsequent actuation of that switch 31 to have an "off" function. The reverse also applies. Figure 3 shows a- possible surveilance sequence as applied to the figure 2 arrangement, and that sequence involves 12 cycles or pulses. During cycles 1, 3, 5 and 7 the logic circuit 10 receives data from a respective one of the four sensors 13 through the A/D convertor 21 and responds as necessary to the data received. During cycles 2, 4, 6, 8, 10 and 12 the control means resets the A/D convertor 21, checks the condition of the boost switch 31 and reads the external control function as provided through the connection line 12. During cycle 8 the control means may also check the condition of the low water level detector 26 and possibly the anode 27 also. Cycle 9 may be used to check the condition of the heating elements 2, 4 and 22 and may also check any internal clock pulse as may be used. Apart from the previously referred to checks made during cycle 10, that cycle might also be used to check the condition of the mains supply. Cycles 11 and 12 may also provide a catch up function if the control means has been programmed for a 50Hz system for example but is used with a 60Hz system.

It.will be appreciated that the sequence described is repeated during operation of the system and that the logic circuit 10 responds to data received during each surveillance sequence to cause any change as may be necessary to the operating parameters of the system.

Figure 4 shows a possible arrangement in which the control means as previously described is applied to a solar heating system. The tank 6 as shown in figure 4 may also include electrical heating elements in which case the control means may be arranged as shown in figure 2 in addition to the arrangement shown in figure 4. That is, the figure 4 circuit arrangement is an addition to and not a substitute for the arrangement shown in figure 2.

In the figure 4 arrangement, water from the tank 6 is circulated through solar panels 33 by operation of a pump 34. The logic circuit may be arranged to cause periodic operation of the pump 34 so that it will push a slug of water through the panels 33 and sensors 35 and 36 function to detect the water temperature at different parts of the panels 33. A sensor 37 also functions to detect the temperature of pump motor, and data from each sensor 35, 36 and 37 is fed to the logic circuit through an analogue to digital convertor 38. Flow through the panels 33 is detected by the flow sensor 39.

A keyboard 40 may be provided as shown to enable the system to be set up to run between preselected parameters. The keyboard 40 also enables selection of data to be displayed at the display 41, which can be a device of any appropriate form. For example, the display 41 might provide information such as the number of times that the panel temperature reached or fell to a certain level in a predetermined time span, or it might indicate how often and/or for how long the pump 34 operated in a predetermined time span. In the arrangement shown, the display 41 is energized direct from a transformer 42 provided in the mains supply connection to the logic circuit 10, but other arrangements are possible.

The solar heating aspect as described can be subjected to surveillance in the manner previously described. By way of example however, the surveillance sequence may involve six cycles rather than twelve as described in relation to the figure 2 circuit. According to one arrangement, the temperature of the pump motor is checked through sensor 37 during the irst half of cycle 1 and the second half of that cycle is used to reset the A/D convertor 38 and detect whether flow is occurring through the panels 33. The sensors 35 and 36 are interrogated during cycles 2 and 4 respectively and the A/D convertor 38 is next during cycles 3 and 5. Cycle 6 may provide a catch-up facility as previously described in relation to figure 3.

Once again the logic circuit 10 responds to input data so as to influence operation of the system as may be required. In particular, the logic circuit 10 controls operation of the pump 34 in accordance with information received during each surveillance sequence.

It will be apparent that the control means described can perform many functions other than the examples given. It can perform a time keeping function for example. Also, the control means may respond to remote switching such as through use of ripple switching or radio coded signals for example.

Although the control means has been described in relation to an electrically energized water heater, it is equally applicable to gas or other fuel fired heaters. Such a fuel-fired heater will usually employ an electrically energized spark ignitor and the control means can regulate operation of such an ignitor and also regulate the fuel supply through a solenoid valve or other means. The control means may have the facility to detect the presence of a flame at the burner and perhaps also indicate through an LED display or other means the condition of the flame - e.g., steady or flashing fast or slow. It is also preferred that the control means performs an automatic safety check of the system before giving the command to commence operation of the burner. If the burner is fed from an exhaustible fuel source such as an LP gas bottle, the control means may function to indicate the amount of fuel remaining in that bottle. If the system includes a flue, the control means may detect CO levels and respond ^"to ^"a predetermined level by shutting down the system until the level falls below the predetermined level. Other control and surveillance functions may be generally as previously described.

It will be clear from the foregoing that control means as described has many advantages in terms of economical and safe operation of hot water systems. Such control means can be arranged to simultaneously control and monitor a plurality of systems.

Various alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambit of the invention as defined by the appended claims.

Claims

1. Control means for a hot water system including, storage means for storing a set of pre-established instructions, and responder means for receiving and responding to data received from said system and being connected to said storage means so that said instructions at least influence the nature of said response, and said response is operable to either influence the operation of said system or generate an indication of a condition of said system.

2. Control means according to claim 1, wherein said storage means comprises the memory of a micro-processor and said responder means comprises the logic circuit of said micro¬ processor.

3. Control means according to claim 1 or 2, wherein said system includes a water storage tank and said responder means receives and responds to data concerning the temperature and level of the water in said tank.

4. Control means according to claim 3, wherein an anode is located within said tank and is operable to discharge a small current into a surrounding body of water so as to inhibit electrolysis, and said anode also functions as a low water detector.

5. Control means according to any preceding claim, wherein means is provided to effect a continual survey of said system, said survey comprises continually repeating series of sequential steps, each said series after the first immediately follows a preceding said series, each said step is performed in a predetermined time span, and at least some of the steps in each series involve deriving data from said system and passing that data to said responder means for response as necessary.

6. Control means according to any preceding claim, wherein the responder means is connectable into an electric mains supply and to an electrically energizable heating element of a said system, and is operable to detect the load on said mains supply and to control energization of said element accordingly.

7. - Control means according to any preceding claim, wherein said responder means is operable to detect the presence of a fault in said system and to generate a signal indicating the presence of that fault.

8. Control means according to any preceding claim when combined with an electrically energized hot water system.

9. Control means according to any preceding claim when combined with a said system including solar heating means.

10. The combination of claim 9, wherein the system includes a storage tank, at least one solar panel and a pump operable to circulate water from said tank through said panel and back to said tank, and said responder means is operable to control operation of said pump according to data received from at least said panel.

11. Control means according to any one of claims 1 to 7 when combined with a system having a water storage tank and a fuel fired heater which is operable to heat the water in said tank.

12. Control means substantially as herein particularly described with reference to what is shown in Figures 2 and 3, or 4, of the accompanying drawings.