AU2004297288A1 - Hot water supply system - Google Patents

Description

WO 2005/057086 PCT/AU2004/001576 HOT WATER SUPPLY Related Applications This application claims priority from US Application 5 60/529898 filed 16 December 2003, and Australian Provisional Application 2003906902 filed 12 December 2003. Field of the Invention This invention relates to a water supply system and, in 10 particular, to a hot water supply system for supplying hot water in a domestic residence or commercial or industrial environment. Background Art 15 Hot water supply systems generally include a water heater of some description which heats water and then supplies the hot water through a hot water supply line to a plurality of hot water outlets. Typically, in a domestic dwelling, the hot water outlets may be located in a 20 kitchen, bathroom, laundry and the like. If hot water has not been used for some time, the hot water in the supply line can cool, and when it is next desired to use the hot water, it is generally necessary to turn on the hot water outlet and allow the cool water in the line to exit the 25 line until hot water reaches the outlet from the water heater. Therefore, a significant amount of water is wasted whilst waiting for hot water to arrive at the outlet. This problem is exacerbated in large residential dwellings where a significant distance may be present 30 between the water heater and the outlets. The problem is even further exacerbated in commercial and industrial environments because the distance between the water heater and the outlets can be even greater. 35 Thus, a significant amount of water is lost each year simply by people turning on a hot water outlet and WO2005/057086 PCT/AU2004/001576 - 2 allowing cool water to flow out of the outlet until hot water arrives. Summary of the Invention 5 The object of the invention is to provide a water supply system which overcomes this problem. The invention provides a hot water supply system having a hot water line for supply of hot water to at least one hot 10 water outlet, comprising: a hot water heater for heating water; a hot water supply circuit having said hot water heater and said hot water supply line; a pump for circulating water through the hot water 15 supply circuit; means for activating the pump so that when water is circulated around the supply circuit the water heater heats the water in the supply circuit, and therefore the supply line, before the hot water outlet is opened; 20 a temperature sensor for sensing the temperature of the water in the circuit; and an indicator for providing to a user an indication that the temperature of the water is sufficiently high for substantially immediate supply of hot water to the hot 25 water outlet upon opening of the hot water outlet. The water in the hot water supply circuit, and therefore the hot water line is heated by circulating the water through the supply circuit and the heater so that when the 30 indicator indicates the water has reached the sufficiently high temperature, a user knows that the hot water outlet can be opened and hot water will be immediately supplied. Thus, water is not wasted by the need to allow cold water to flow out of the hot water supply line until hot water 35 arrives at the outlet.

WO2005/057086 PCT/AU2004/001576 -3 In one embodiment of the invention, the water heater comprises a primary water heater for the supply of hot water to the hot water supply line, the primary water heater having a cold water inlet for receiving cold water 5 from a cold water supply, and wherein prior to the hot water outlet being opened, water is circulated only through the circuit and water heater to heat the water in the circuit and supply line, and wherein upon opening of the hot water outlet, water is drawn through the cold 10 water inlet and through the heater and supplied into the hot water supply circuit as hot water so a continuous supply of hot water is supplied to the hot water outlet until the hot water outlet is closed. 15 Preferably the temperature sensor causes the pump to switch off after the water in the circuit reaches the sufficiently high temperature. Preferably the system includes a control unit for 20 receiving a signal from the temperature sensor indicative of the water temperature in the circuit, and wherein the control unit is for determining whether the signal represents the sufficiently high temperature and, if so, the control unit switches off the pump. 25 In one embodiment the control unit maintains operation of the pump for a predetermine time period after receipt of the signal indicative of the predetermined temperature, so the water is continued to be circulated about the hot 30 water supply circuit by the pump for that predetermined time period. In one embodiment the circuit includes a flow sensor for monitoring flow of water through the circuit to provide an 35 indication that the pump is operating.

WO2005/057086 PCT/AU2004/001576 -4 Preferably the means for activating the pump comprises a controller for controlling the primary water heater which can be activated by a user, a switch for activation by the user, or a occupancy sensor for sensing the presence of a 5 user in proximity to the hot water outlet. In another embodiment the hot water heater comprises a secondary hot water heater provided in the circuit for heating water in the circuit prior to opening of the hot 10 water outlet, the secondary hot water heater being activated by a primary water controller, a switch or a proximity sensor, and switched off after the temperature sensor senses the water in the hot water supply circuit has reached the sufficiently high temperature, and wherein 15 the system still further includes a primary hot water heater for heating water and supplying water to the circuit when the hot water outlet is opened. Preferably the secondary heater is provided in a water 20 tank arranged in the circuit for heating water in the tank, and hence water in the circuit. Preferably the indicator comprises a visual indicator. However, in other embodiments, other forms of indicators 25 such as audible indicators or the like could be used. Most preferably the visual indicator comprises a light. The visual indicator may operate in a number of ways in 30 order to provide an indication that hot water is ready for delivery. In one embodiment, upon actuation of the means for activating the pump, the visual indicator can be 35 illuminated until the temperature reaches the predetermined temperature, and then is switched off to WO2005/057086 PCT/AU2004/001576 5 thereby provide an indication that the user can now use the hot water. In other embodiments, the light can be illuminated only 5 when the temperature reaches the predetermined temperature, and will remain illuminated for a certain period of time, thereby indicative of the fact that hot water is ready for delivery. 10 In still further embodiments, the light can be continuously illuminated until the means for activating the pump is activated. The light is illuminated and the water heater 15 automatically switches on and off to maintain the water temperature at the required temperature for delivery. This latter alternative enables a standby condition to be achieved whereby the water can be preheated before it is used and then be ready for delivery when required by the 20 user. The invention also provides a hot water supply system having a hot water line for supply of hot water to at least one hot water outlet, comprising: 25 a hot water supply circuit including said hot water supply line; a secondary heater in the circuit; a pump for pumping water through the circuit so that water circulating through the circuit is heated by the 30 secondary heater; means for switching on said pump and said secondary heater for heating the water in the circuit, and therefore the hot water supply line prior to opening of the hot water outlet, so that upon opening of the hot water 35 outlet, hot water is substantially immediately supplied to the hot water outlet; and WO2005/057086 PCT/AU2004/001576 - 6 a primary hot water heater having a cold water inlet branch for supply of cold water, and a hot water outlet branch connected to said circuit, so that upon opening of the hot water outlet, cold water is able to pass from the 5 cold water branch through the primary heater for heating by the primary heater so that hot water is supplied from the hot water branch into the circuit to provide a continuous supply of hot water to the circuit and therefore the hot water outlet, until the hot water outlet 10 is closed. Thus, according to this invention, the water in the supply line is heated before the hot water tap is opened so that hot water is immediately supplied from the outlet. Thus, 15 water is not wasted by the need to have to turn the tap on and wait for cold water to drain out of the hot water line before hot water arrives from the heater. The preheating of the circuit is performed by the secondary heater, but when the normal demand for hot water is required by way of 20 opening the hot water outlet, the primary hot water heater heats cold water coming into the system to thereby provide the continuous supply of hot water until the outlet is turned off. 25 Preferably a temperature sensor is provided for sensing the temperature of water in the circuit so that after the temperature of the water reaches a predetermined temperature, the pump and secondary heater are switched off. 30 Preferably the system includes a control unit for receiving a signal from the temperature sensor indicative of the water temperature in the circuit, and wherein the control unit is for determining whether the signal 35 represents a temperature at or above the predetermined temperature and, if so, the control unit switches off the pump.

WO2005/057086 PCT/AU2004/001576 7 In one embodiment the control unit maintains operation of the pump for a predetermine time period after receipt of the signal indicative of the predetermined temperature, so the water is continued to be circulated about the hot 5 water supply circuit by the pump for that predetermined time period. In one embodiment the circuit includes a flow sensor for monitoring flow of water through the circuit to provide an 10 indication that the pump is operating. Preferably the means for switching on said pump and said secondary heater comprises a means for providing a signal indicative of the need for supply of hot water to the hot 15 water outlet. Preferably the signal providing means comprises a controller for controlling the primary water heater which is actuatable by a user, a switch for activation by the 20 user, or a occupancy sensor for sensing the presence of a user in proximity to the hot water outlet. Preferably the secondary heater is provided in a water tank arranged in the circuit for heating water in the 25 tank, and hence water in the circuit. Preferably the system includes an indicator for providing an indication, in response to the temperature sensed by the temperature sensor, that the water temperature has 30 reached the predetermined temperature ready for substantially immediate supply from the hot water outlet. Preferably the indicator comprises a light. 35 The invention also provides a hot water supply system having a hot water line for supply of hot water to at least one hot water outlet, comprising: WO2005/057086 PCT/AU2004/001576 - 8 an instantaneous water heater for instantaneously heating water upon opening of a hot water outlet to supply hot water from the outlet; a hot water supply circuit including said hot water 5 supply line for receiving hot water from the heater; a cold water inlet for supplying cold water to the heater; a pump for circulating water through the circuit and the heater for heating water in the circuit, and therefore 10 in the supply line, prior to opening of the hot water outlet; a temperature sensor for sensing the temperature of the water in the circuit and for switching off the pump after the temperature reaches a predetermined temperature; 15 and wherein when the hot water outlet is opened, hot water is substantially immediately supplied from the hot water outlet because of the preheating of the circuit, and the opening of the outlet causes water to be drawn from 20 the circuit, which in turn causes water to be drawn into the heater through the cold water inlet to heat the water drawn through the cold water outlet for supply as hot water to the circuit and therefore to the hot water outlet. 25 Thus, the water in the supply line is heated before the water tap is opened, thereby preventing the waste of water, because it is not necessary for cold water to drain from the circuit or supply line before hot water arrives 30 at the outlet. Preferably the system includes a control unit for receiving a signal indicative of the need for hot water and for switching on the pump to cause heating of water 35 circulated through the circuit by the pump prior to opening of the hot water outlet.

WO2005/057086 PCT/AU2004/001576 -9 Preferably the system includes a control unit for receiving a signal from the temperature sensor indicative of the water temperature in the circuit, and wherein the control unit is for determining whether the signal 5 represents a temperature at or above the predetermined temperature and, if so, the control unit switches off the pump. In one embodiment the control unit maintains operation of 10 the pump for a predetermine time period after receipt of the signal indicative of the predetermined temperature, so the water is continued to be circulated about the hot water supply circuit by the pump for that predetermined time period. 15 Preferably the system includes a means for providing a signal indicative of the need for hot water at the hot water outlet, said signal being supplied to said control unit to activate the pump and the heater. 20 Preferably the control unit is for providing a hot water ready signal when the temperature of the water sensed by the temperature sensor reaches the predetermined temperature, to thereby indicate to a user that hot water 25 is ready for supply from the hot water outlet. Preferably the signal is for activating a light emitting diode which is illuminated when the water temperature reaches the predetermined temperature. 30 However, other forms of signals such as an audible signal or other form of display could also be used. Preferably the signal providing means comprises a 35 controller for controlling the heater, which controller is operable by a user when hot water is required, a switch for activation by the user when hot water is required, or WO2005/057086 PCT/AU2004/001576 - 10 an occupancy sensor for sensing the presence of a user in proximity to the hot water outlet. Preferably the flow sensor is for providing an output 5 signal to the control unit to provide an indication that flow of water through the circuit and heater is taking place so that the unit can switch on the heater, and whereupon if the flow sensor indicates that there is no flow of water through the circuit and the heater, the 10 control unit prevents the heater from being switched on. Preferably the control unit comprises a first control section which forms part of the instantaneous water heater, and a second control section associated with the 15 pump and the temperature sensor, the first and second control sections being connected by a communication line, and wherein the signal providing means is connected to the second control section so the second control section operates the pump upon receipt of the signal to circulate 20 water through the circuit and the instantaneous heater, and whereupon the circulation of the water activates the instantaneous water heater to heat the water circulating in the circuit. 25 In one embodiment the signal providing means is provided in a controller for controlling operation of the instantaneous water heater, and whereupon control signals for operation of the instantaneous water heater are supplied from the controller to the second control 30 section, and from the section control section to the first control section via the communication line to control the operation of the instantaneous water heater in accordance with user input commands. 35 In one embodiment a flow sensor may be provided in the circuit for sensing flow of water through the circuit and WO2005/057086 PCT/AU2004/001576 - 11 for providing a signal to the second control section to indicate that the pump is operational. In one embodiment of the invention the second control 5 section is for supplying an error signal if the pump is switched on in response to the signal providing means and the flow sensor does not provide a signal to the second control unit indicative of flow of water through the circuit. 10 Brief Description of the Drawings Preferred embodiments of the invention will be described with reference to the accompanying drawings in which: Figure 1 is a diagram showing a first embodiment of 15 the invention; and Figure 2 is a diagram showing a second embodiment of the invention. Detailed Description of the Preferred Embodiments 20 With reference to Figure 1, a water supply system is shown which has a primary water heater 10 which is preferably an instantaneous water heater such as that sold by Rinnai Australia under the registered trade mark INFINITY. The water supply system has a cold water supply line 12 which 25 supplies cold water from a cold water supply such as mains 13, a water tank or the like. The supply line 12 has a plurality of cold water outlets 14 (only one shown) such as taps or the like, which may be provided around a premises such as in a kitchen, bathroom, laundry or the 30 like. The cold water supply line 12 also has a cold water inlet branch 15 for supplying cold water to the primary hot water heater 10. The water heater 10 is provided with a flow sensor (not 35 shown) which forms an integral part of the heater 10 for detecting flow of water through the heater from the cold water inlet 15. Thus, when an outlet is turned on water WO2005/057086 PCT/AU2004/001576 - 12 is supplied from the circuit and replaced by water entering the heater through the inlet 15, and the flow sensor senses the flow of water and activates the heater 10 so the water is heated as it passes through the heater 5 10. The heater 10 also has its own control unit 30 which controls operation of the heater 10 to activate the heater so as to heat water in response to the flow of water through the heater, and also to control the heater 10 in accordance with user input commands provided from a 10 controller 32. The controller 32 can typically switch on and off the heater 10 and also set the temperature of water a user requires. The heater 10 has a hot water outlet branch 16 which 15 supplies hot water to a hot water supply circuit 18. The circuit 18 includes a hot water supply line 19 which has a plurality of hot water outlets such as taps or shower roses for supply of hot water to the premises. The circuit 18 reconnects with the primary water heater 10 so 20 as to provide a continuous circuit through the primary heater 10. The circuit 18 also includes a pump 22 for pumping water about the circuit 18 and through the heater 10, a 25 temperature sensor 24 for monitoring the temperature of the water in the circuit 18. A flow sensor 26 may also be provided for determining that there is flow through the circuit 18. 30 The controller 32 may include an additional preheating switch 35 which is pressed by a user when a user enters a room and requires hot water. As will be explained below, this will cause the water in the circuit 18 to be heated so that as soon as an outlet 20 is opened, hot water is 35 immediately supplied, and it is not necessary for the user to wait until cold water drains out of the supply line 19 and is replaced by hot water from the heater 10, and WO2005/057086 PCT/AU2004/001576 - 13 therefore water is not wasted whilst waiting for hot water to arrive at the outlet 20. Rather than the controller 32 being activated to cause the 5 preheating of the water in the line 19, a separate switch or button 37 could be provided, or alternatively a proximity sensor 38 could be provided which senses the arrival of a user into a room or in proximity to an outlet 20, thereby immediately causing the water in the line 19 10 to be heated to the required temperature before opening of the outlet 20. Thus, either the controller 32, the switch 37 or the proximity sensor 38 can be used as a device to provide an 15 indication of the need for hot water from one of the outlets 20 and to initiate preheating of the water in the circuit 19 so that when the user opens the outlet 20, hot water is immediately supplied. 20 When either the controller 32, the switch 37 or the sensor 38 receives an indication of a requirement for hot water, such as by a user pressing the switch 37 or the button 35 on the controller 32, or just arriving in proximity to the tap 20 as sensed by the sensor 38, a signal is output on 25 line 33 to a second control unit 40 of a pre-heating device 41. The second control unit 40 is connected by a line 39 to the first control unit 30 of the heater 10. When the second control unit 40 receives a signal on line 30 33 indicative of the requirement for hot water, the second control unit 40 activates the pump 22 so that water is pumped about the circuit 18 through the heater 10. The control unit 30 in the heater 10 also activates the heater 10 in response to the flow of water through the heater, so 35 that the heater operates to heat the hot water which circulates through the line 18 and the heater 10. Thus, if the water in the circuit 19 has gone cold because hot WO2005/057086 PCT/AU2004/001576 - 14 water has not been used for some time, the heater 10 will heat the hot water circulating through the circuit 18 and therefore in the branch 19. The flow sensor 26 may be provided to measure flow of water through the circuit 18 5 and provides a signal to the control unit 40 indicative of the fact that the pump 22 is therefore operating. If the flow sensor 26 does not indicate that flow is occurring through the circuit 18, thereby indicating that the pump 22 is possibly not working properly, the second control 10 unit 40 may supply a signal to indicate an error condition. The error signal is provided from the second control unit 40 on line 33 back to controller 32 so that an error message can be displayed indicating that the system has malfunctioned and may require maintenance. 15 Alternatively, the error signal could be displayed on a display attached to the second control unit 40 or be output on a separate line (not shown) to a different remote display. Thus, in the unlikely event of malfunction, a message is immediately supplied to the user 20 so that appropriate remedial action can be taken. The temperature sensor 24 monitors the temperature of the water in the circuit 18, and supplies a signal to the control unit 40 indicative of the temperature of the 25 water. The control unit 40 then switches off the pump 22 when the signal from sensor 24 indicates the water temperature has reached the predetermined required temperature. When the pump 22 is switched off, the flow of water in the circuit 18 stops and therefore, the heater 30 10 detects that there is no flow of water and the first control unit 30 switches off the heater 10. Simultaneously, a signal is supplied on line 33 to light emitting diode 45 so the light emitting diode 45 is illuminated to show that the water temperature in the 35 supply line 19 is at the predetermined hot level ready for immediate use from one of the outlets 20. The light emitting diode 45 may be located in any convenient place, WO2005/057086 PCT/AU2004/001576 - 15 such as in proximity to one of the outlets 20 so it can be viewed by a user, or on the switch 37 or controller 32. When the light emitting diode 45 is illuminated, the user 5 knows that the outlet 20 can be turned on and hot water will be supplied. As soon as the outlet 20 is turned on, water begins to flow from the outlet 20 from the circuit 18 and this causes water to be drawn into the hot water heater 10 from the cold water branch 15, so cold water 10 flows into the heater 10. The control unit 30 of the heater 10 determines that flow of water is passing through the heater, and therefore activates the heater so that the cold water is heated by the heater 10 and then flows from the hot water branch 16 into the circuit 18 for continuous 15 supply of hot water to the opened outlet 20. In other embodiments, the availability of hot water ready for immediate supply can be signalled to a user in different ways to that described above. 20 In one embodiment, a standby mode is provided whereby, after the user activates the pump 22 by switching the switch 37 or the controller 32 or being sensed by the proximity sensor 38, the pump is switched on and the unit 25 40 outputs a signal on line 33 to illuminate the light emitting diode 45 to show that the system is in the preheat mode. In the standby mode, when the temperature reaches the predetermined temperature, the heater 10 can be switched off and then automatically again switched on 30 if the temperature in the circuit 19 drops below the predetermined temperature, so that the predetermined temperature of the water 19 is always maintained in the loop, thereby providing the standby mode. The light emitting diode 45 remains illuminated for the entire 35 period the system is in this mode. If the user wishes to end the standby mode, the user can again press the switch 37 or switch on the controller 32 or another switch (not WO2005/057086 PCT/AU2004/001576 - 16 shown) associated with the proximity sensor 38 to show that standby mode is no longer required. Light emitting diode 45 will then be extinguished. 5 In a further embodiment, after the user activates the switch 37 or the controller 32 or is sensed by the proximity sensor 38, the unit 40 immediately outputs a signal on line 33 to illuminate the light emitting diode 45 to show that the system is in the preheat mode. When 10 the temperature in the loop 19 reaches the predetermined temperature, the control unit 40 switches off the light emitting diode 45, thereby indicating to the user that the system is ready to deliver hot water. 15 In a still further embodiment, the light emitting diode is illuminated after the switch 37, or the controller 32 or the proximity sensor 38 is activated, and remains illuminated for a predetermined time period after the temperature sensor 24 detects that the temperature in the 20 circuit 19 has reached the predetermined temperature. In the latter two embodiments, when the light emitting diode switches off, this provides the signal to the user that the hot water is available for supply from one of the outlets 20. 25 Instill further embodiments, a flashing mode of the light emitting diode can be used to show that the system is in the preheat mode and the water is being heated, and either a continuous illumination or complete switching off of the 30 light emitting diode used to indicate that the water is ready for delivery at the predetermined temperature. In most environments, cold water is supplied from the branch 15 simply by mains pressure. However, in other 35 environments a pump (not shown) can be used to facilitate supply of cold water through the branch 15 to the heater 10.

WO2005/057086 PCT/AU2004/001576 - 17 It will be apparent from the above description that hot water only ever circulates through the circuit 18 and never is supplied through the cold water supply line 12. 5 Thus, it is not necessary to interfere with the plumbing of the cold water supply line 12, nor to be concerned that hot water has been provided into the cold water line. Thus, when one of the cold water outlets 14 is opened, fresh cold water is always supplied without any fear of 10 contamination from water which has been heated in the hot water circuit 18. Figure 2 shows a second embodiment of the invention in which like reference numerals indicate like parts to those 15 previously described. In this embodiment, a secondary water heater 50 is provided which is most preferably in the form of an electrical heating element provided in a relatively small 20 tank 52. The circuit 18 in this embodiment includes the tank 52 and the heater 50, but the primary water heater 10 is external of the circuit 18 and connected to the circuit 18 by the hot water outlet branch 16. Thus, in this embodiment, when water is circulating through the circuit 25 18 for preheating, the water does not pass through the primary hot water heater 10. This embodiment operates in substantially the same way as the previous embodiment, in that when the signal is 30 received on line 33, indicating the requirement for hot water, the second control unit 40 operates the pump 22 to pump water through the circuit 18, and also activates the heater 50. In this embodiment, the water passes through the tank 52 having the heater 50 and is heated by the 35 heater 50 to thereby preheat the water in the circuit 18 and hot water supply line 19. The sensor 24 supplies a signal to the unit 40 indicative of the temperature of the WO2005/057086 PCT/AU2004/001576 - 18 water, and when the temperature reaches the predetermined temperature, the unit 40 switches off both the pump 22 and the heating element 50. At the same time, the light emitting diode is illuminated as in the earlier embodiment 5 to show that hot water is ready for supply from one of the outlets 20. When the user opens the outlet 20, water is supplied from the outlet 20 and this causes water to flow from the inlet 10 branch 15 through the heater 10, the outlet branch 39 and into the circuit 18 for supply to the outlet 20. Again, as soon as water flows through the inlet branch 15, this is sensed by the heater 10 and the control unit 30 activates the heater 10 to switch the heater on to heat 15 the water so that the continuous supply of hot water is supplied at the opened outlet 20. In the embodiments described above, the pump 22 is switched off as soon as the signal from the temperature 20 sensor 24 indicates that the temperature of the water in the circuit 18 has reached the predetermined temperature. However, in other embodiments, the second control unit 40 may be programmed so that the pump 22 is maintained operating for a short period, such as 5-10 seconds after 25 the temperature reaches the predetermined temperature. This therefore maintains circulation of water about the circuit 18 after the temperature reaches the predetermined level, so that when the hot water outlet is opened and cold water is drawn through the inlet 15 into the heater 30 10, the circulation of the hot water about the circuit 18 will mix with any plug of cold water which passes through the heater at the point A in Figures 1 and 2. The mixing of any plug of cold water and the hot water at point A warms the plug of cold water. Thus, this reduces the 35 likelihood of a small volume of cold water exiting the hot water outlet 20 a short time after the outlet 20 is turned WO2005/057086 PCT/AU2004/001576 - 19 on in response to illumination of the light emitting diode 45. In a still further embodiment, the second control unit 40 5 may be provided with dip switches (not shown) which can be operated by an installer to set the predetermined temperature which is to be achieved in the circuit 18 by the preheating before the light emitting diode 45 is illuminated to indicate that hot water is ready for 10 delivery at the outlet 20. Furtherstill, the dip switches may be set so as to respond to the temperature which is set by a user at the controller 32 if the controller 32 is used, so that the predetermined temperature in the circuit 18 will be the temperature selected by the user by input 15 into the controller 32. Furtherstill, the temperature sensed by the temperature 24 can be used to cause shut off of the element 52 at a predetermined high temperature level to ensure that there 20 is no attempt to overheat the water in the circuit 18 beyond a safe level. The temperature sensor 24 which supplies a signal indicative of the temperature of the water in the circuit 25 18 may supply a continuous signal indicative of water temperature, and the control unit 40 can monitor that signal so that when the signal equates to a reference signal indicative of the predetermined temperature, the control unit 40 recognises that the predetermined 30 temperature has been reached. Alternatively, the sensor 24 may simply supply a signal 24 only when the predetermined temperature is reached, so that when any signal is received from the sensor 24, the unit 40 recognises that the water temperature has reached the 35 predetermined temperature. In the claims which follow and in the preceding WO2005/057086 PCT/AU2004/001576 - 20 description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise", or variations such as "comprises" or "comprising", is used in an inclusive 5 sense, ie. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. Since modifications within the spirit and scope of the 10 invention may readily be effected by persons skilled within the art, it is to be understood that this invention is not limited to the particular embodiment described by way of example hereinabove.

Claims (34)

1. A hot water supply system having a hot water line for supply of hot water to at least one hot water outlet, 5 comprising: a hot water heater for heating water; a hot water supply circuit having said hot water heater and said hot water supply line; a pump for circulating water through the hot water 10 supply circuit; means for activating the pump so that when water is circulated around the supply circuit the water heater heats the water in the supply circuit, and therefore the supply line, before the hot water outlet is opened; 15 a temperature sensor for sensing the temperature of the water in the circuit; and an indicator for providing to a user an indication that the temperature of the water is sufficiently high for substantially immediate supply of hot water to the hot 20 water outlet upon opening of the hot water outlet.

2. The system of claim 1 wherein the water heater comprises a primary water heater for the supply of hot water to the hot water supply line, the primary water 25 heater having a cold water inlet for receiving cold water from a cold water supply, and wherein prior to the hot water outlet being opened, water is circulated only through the circuit and water heater to heat the water in the circuit and supply line, and wherein upon opening of 30 the hot water outlet, water is drawn through the cold water inlet and through the heater and supplied into the hot water supply circuit as hot water so a continuous supply of hot water is supplied to the hot water outlet until the hot water outlet is closed. 35 WO2005/057086 PCT/AU2004/001576 - 22

3. The system of claim 1 wherein the temperature sensor causes the pump to switch off after the water in the circuit reaches the sufficiently high temperature. 5

4. The system of claim 1 wherein the system includes a control unit for receiving a signal from the temperature sensor indicative of the water temperature in the circuit, and wherein the control unit is for determining whether the signal represents the sufficiently high temperature 10 and, if sd, the control unit switches off the pump.

5. The system of claim 4 wherein the control unit maintains operation of the pump for a predetermine time period after receipt of the signal indicative of the 15 predetermined temperature, so the water is continued to be circulated about the hot water supply circuit by the pump for that predetermined time period.

6. The system of claim 1 wherein the circuit includes a 20 flow sensor for monitoring flow of water through the circuit to provide an indication that the pump is operating.

7. The system of claiml wherein the means for activating 25 the pump comprises a controller for controlling the primary water heater which can be activated by a user, a switch for activation by the user, or a occupancy sensor for sensing the presence of a user in proximity to the hot water outlet. 30

8. The system of claim 1 wherein the hot water heater comprises a secondary hot water heater provided in the circuit for heating water in the circuit prior to opening of the hot water outlet, the secondary hot water heater 35 being activated by a primary water controller, a switch or a proximity sensor, and switched off after the temperature sensor senses the water in the hot water supply circuit WO2005/057086 PCT/AU2004/001576 - 23 has reached the sufficiently high temperature, and wherein the system still further includes a primary hot water heater for heating water and supplying water to the circuit when the hot water outlet is opened. 5

9. The system of claim 8 wherein the secondary heater is provided in a water tank arranged in the circuit for heating water in the tank, and hence water in the circuit.

10 10. The system of claim 1 wherein the indicator comprises a visual indicator.

11. The system of claim 10 wherein the visual indicator comprises a light. 15

12. A hot water supply system having a hot water line for supply of hot water to at least one hot water outlet, comprising: a hot water supply circuit including said hot water 20 supply line; a secondary heater in the circuit; a pump for pumping water through the circuit so that water circulating through the circuit is heated by the secondary heater; 25 means for switching on said pump and said secondary heater for heating the water in the circuit, and therefore the hot water supply line prior to opening of the hot water outlet, so that upon opening of the hot water outlet, hot water is substantially immediately supplied to 30 the hot water outlet; and a primary hot water heater having a cold water inlet branch for supply of cold water, and a hot water outlet branch connected to said circuit, so that upon opening of the hot water outlet, cold water is able to pass from the 35 cold water branch through the primary heater for heating by the primary heater so that hot water is supplied from the hot water branch into the circuit to provide a WO2005/057086 PCT/AU2004/001576 - 24 continuous supply of hot water to the circuit and therefore the hot water outlet, until the hot water outlet is closed. 5

13. The system of claim 12 wherein a temperature sensor is provided for sensing the temperature of water in the circuit so that after the temperature of the water reaches a predetermined temperature, the pump and secondary heater are switched off. 10

14. The system of claim 12 wherein the system includes a control unit for receiving a signal from the temperature sensor indicative of the water temperature in the circuit, and wherein the control unit is for determining whether 15 the signal represents a temperature at or above the predetermined temperature and, if so, the control unit switches off the pump.

15. The system of claim 14 wherein the control unit 20 maintains operation of the pump for a predetermine time period after receipt of the signal indicative of the predetermined temperature, so the water is continued to be circulated about the hot water supply circuit by the pump for that predetermined time period. 25

16. The system of claim 12 wherein the circuit includes a flow sensor for monitoring flow of water through the circuit to provide an indication that the pump is operating. 30

17. The system of claim 12 wherein the means for switching on said pump and said secondary heater comprises a means for providing a signal indicative of the need for supply of hot water to the hot water outlet. 35

18. The system of claim 17 wherein the signal providing means comprises a controller for controlling the primary WO2005/057086 PCT/AU2004/001576 - 25 water heater which is actuatable by a user, a switch for activation by the user, or a occupancy sensor for sensing the presence of a user in proximity to the hot water outlet. 5

19. The system of claim 12 wherein the secondary heater is provided in a water tank arranged in the circuit for heating water in the tank, and hence water in the circuit. 10

20. The system of claim 12 wherein the system includes an indicator for providing an indication, in response to the temperature sensed by the temperature sensor, that the water temperature has reached the predetermined temperature ready for substantially immediate supply from 15 the hot water outlet.

21. The system of claim 20 wherein the indicator comprises a light. 20

22. A hot water supply system having a hot water line for supply of hot water to at least one hot water outlet, comprising: an instantaneous water heater for instantaneously heating water upon opening of a hot water outlet to supply 25 hot water from the outlet; a hot water supply circuit including said hot water supply line for receiving hot water from the heater; a cold water inlet for supplying cold water to the heater; 30 a pump for circulating water through the circuit and the heater for heating water in the circuit, and therefore in the supply line, prior to opening of the hot water outlet; a temperature sensor for sensing the temperature of 35 the water in the circuit and for switching off the pump after the temperature reaches a predetermined temperature; and WO2005/057086 PCT/AU2004/001576 - 26 wherein when the hot water outlet is opened, hot water is substantially immediately supplied from the hot water outlet because of the preheating of the circuit, and the opening of the outlet causes water to be drawn from 5 the circuit, which in turn causes water to be drawn into the heater through the cold water inlet to heat the water drawn through the cold water outlet for supply as hot water to the circuit and therefore to the hot water outlet. 10

23. The system of claim 22 wherein the system includes a control unit for receiving a signal indicative of the need for hot water and for switching on the pump to cause heating of water circulated through the circuit by the 15 pump prior to opening of the hot water outlet.

24. The system of claim 22 wherein the system includes a control unit for receiving a signal from the temperature sensor indicative of the water temperature in the circuit, 20 and wherein the control unit is for determining whether the signal represents a temperature at or above the predetermined temperature and, if so, the control unit switches off the pump.

25 25. The system of claim 24 wherein the control unit maintains operation of the pump for a predetermine time period after receipt of the signal indicative of the predetermined temperature, so the water is continued to be circulated about the hot water supply circuit by the pump 30 for that predetermined time period.

26. The system of claim 22 wherein the system includes a means for providing a signal indicative of the need for hot water at the hot water outlet, said signal being 35 supplied to said control unit to activate the pump and the heater. WO2005/057086 PCT/AU2004/001576 - 27

27. The system of claim 25 wherein the control unit is for providing a hot water ready signal when the temperature of the water sensed by the temperature sensor reaches the predetermined temperature, to thereby indicate 5 to a user that hot water is ready for supply from the hot water outlet.

28. The system of claim 27 wherein the signal is for activating a light emitting diode which is illuminated 10 when the water temperature reaches the predetermined temperature.

29. The system of claim 26 wherein the signal providing means comprises a cntroller for controlling the heater, 15 which controller is operable by a user when hot water is required, a switch for activation by the user when hot water is required, or an occupancy sensor for sensing the presence of a user in proximity to the hot water outlet. 20

30. The system of claim 22 wherein the flow sensor is for providing an output signal to the control unit to provide an indication that flow of water through the circuit and heater is taking place so that the unit can switch on the heater, and whereupon if the flow sensor indicates that 25 there is no flow of water through the circuit and the heater, the control unit prevents the heater from being switched on.

31. The system of claim 25 wherein the control unit 30 comprises a first control section which forms part of the instantaneous water heater, and a second control section associated with the pump and the temperature sensor, the first and second control sections being connected by a communication line, and wherein the signal providing means 35 is connected to the second control section so the second control section operates the pump upon receipt of the signal to circulate water through the circuit and the WO2005/057086 PCT/AU2004/001576 - 28 instantaneous heater, and whereupon the circulation of the water activates the instantaneous water heater to heat the water circulating in the circuit. 5

32. The system of claim 31 wherein the signal providing means is provided in a controller for controlling operation of the instantaneous water heater, and whereupon control signals for operation of the instantaneous water heater are supplied from the controller to the second 10 control section, and from the section control section to the first control section via the communication line to control the operation of the instantaneous water heater in accordance with user input commands. 15

33. The system of claim 22 wherein a flow sensor is provided in the circuit for sensing flow of water through the circuit and for providing a signal to the second control section to indicate that the pump is operational. 20

34. The system of claim 31 wherein the second control section is for supplying an error signal if the pump is switched on in response to the signal providing means and the flow sensor does not provide a signal to the second control unit indicative of flow of water through the 25 circuit.