AU2016253669B2

AU2016253669B2 - Water heating system

Info

Publication number: AU2016253669B2
Application number: AU2016253669A
Authority: AU
Inventors: Ravindra Hiremath; Shalitha Lokuliyana
Original assignee: Pump and Electrical Engineering Services Pty Ltd
Current assignee: Pump and Electrical Engineering Services Pty Ltd
Priority date: 2015-11-05
Filing date: 2016-11-04
Publication date: 2022-08-11
Anticipated expiration: 2036-11-04
Also published as: AU2016253669A1

Abstract

A water heating system for a building, comprising: a plurality of water heaters; a water supply circuit for supplying water from the heaters to a plurality of outlets for heated water in the building; at least one pump for pumping water through the system; and at least one storage tank configured to supply water to the heaters and receive heated water not used at the outlets from the supply circuit through a heated water return line; wherein the at least one storage tank is also configured to supply water into the supply circuit without passing through the heaters via a bypass circuit in response to demand at the outlets for heated water exceeding a heating capacity of the heaters. C)D 0 U)Y C) C 0 NoIt '?.--C -- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ---.. .... ..... .T m.. ....0::. El C) t CID a)e 022 -00 CO zJ -o CDz 0L LO 02 I .1 .. ..

Description

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WATER HEATING SYSTEM FIELD OF THE INVENTION

The present invention relates to a water heating system. More particularly, but not exclusively, the invention relates to heating potable water and supplying heated water to a building in which relatively large numbers of outlets for heated water are required and which may be dispersed over a considerable distance.

BACKGROUND OF THE INVENTION

Conventional hot water systems for domestic dwellings generally comprise either a hot water storage tank in which hot water is heated and stored for use or continuous flow heaters for heating water on demand. In domestic environments, the water is distributed to hot water outlets which are relatively close together.

In larger buildings such as apartment blocks, office buildings and the like, outlets for hot water can be distributed over a considerable distance. Conventional systems for delivering hot water in these environments comprise a plurality of heaters which heat water and supply the water to a water storage vessel. Cold water is supplied to the heaters by a primary pump. The water storage vessel also includes a cold water inlet. Water is discharged from the hot water vessel and distributed to the outlets in the building by a circuit which may include a secondary circulating pump which return water to the hot water storage vessel. The reason for this is to maintain hot water in the circuit so that when a user turns on a tap, which may be a considerable distance from the hot water storage vessel, hot water can be delivered almost instantaneously. If the water is not returned to the vessel to recover the heat using a secondary pump the following may result: water in the return circuit will cool down; considerable delay in delivering the hot water to the outlets can occur; water and energy can be wasted; and a real possibility of proliferation of legionella bacteria within the return circuit.

Under applicable Australian regulations, the temperature of water delivered from the hot water storage vessel should always be above 60 degrees Celsius. The primary pump which pumps the water through the heaters to the storage vessel, is controlled dependent on the temperature of water in the storage vessel. Water is pumped through the heaters when hot water is supplied from the vessel to the hot water outlets in the building and the temperature of the hot water in the vessel drops due to addition of cold water to the vessel. Hot water is also circulated from the vessel through the heaters by the primary pump if the water temperature in the vessel drops due to cooling. The Primary pump size is chosen such that the same supplies sufficient flow rate & pressure to meet maximum demand of the water heaters. Hot water supply pressure from a storage vessel is the same as that of a cold water inlet pressure, however, a drop in outlet temperature is possible due to an increase in hot water demand at the outlets in the building beyond the capabilities of water heaters. This is in view of cold water being supplied to the hot water storage vessel.

For a designer of a heated water system, to increase efficiency, reduce space occupied and minimise costs it is desirable to reduce the number of pumps and eliminate hot water storage vessels used while meeting the probable simultaneous flow demand requirements stipulated for a building. Designers accustomed to the use of the above described conventional systems and the applicants have found a general market reluctance to rely solely on continuous flow water heaters for heating water on demand.

The present applicant's Australian Patent nos. 763394; 2007201101 and Patent Application no. 2015903715 disclose a 'tankless' hot water system. These systems work very well in most applications for supplying hot water to a building in which relatively large numbers of hot water take-off points are required and which may be dispersed over a considerable distance. However, it is desirable to provide a system that can meet peak probable simultaneous flow demand with a lower size water heating means, and a choice of either tankless hot water system and/or a storage tank hot water system.

Examples of the invention seek to solve, or at least ameliorate, one or more disadvantages of previous hot water systems, or at least provide a useful alternative.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided a water heating system for a building, comprising: a plurality of water heaters; a water supply circuit for supplying water from the heaters to a plurality of outlets for heated water in the building; a pump for pumping water through the system; and a storage tank configured to supply water to the heaters and receive heated water not used at the outlets from the supply circuit through a heated water return line; wherein the storage tank is also configured to supply water into the supply circuit without passing through the heaters via a bypass circuit in response to demand at the outlets for heated water exceeding a heating capacity of the heaters, and wherein the at least one storage tank is upstream of the pump and receives, through an inlet, water from the heated water return line and a cold water inlet.

The bypass circuit may have a flow compensation valve mounted therein for encouraging flow through the heaters. The flow compensation valve can be a variable resistance spring loaded flow/pressure compensating valve which favours the water supply to the heaters thereby reducing the size of the circulation pump. Another bypass loop may be provided with a one-way flow/pressure regulating device mounted therein and configured for flow from the water supply circuit to the heated water return line.

According to a preferred embodiment of the present invention, the system can further comprise a controller for operating the pump in response to a drop in temperature in the water supply circuit.

The pump may be disposed between the at least one storage tank and the water heaters. A temperature sensor may be provided, in embodiments having a controller, so that the controller can determine the temperature of water entering the storage tank and the water heaters.

According to another aspect of the present invention there is provided a water heating system for a building, comprising: a plurality of water heaters;

a water supply circuit for supplying water from the heaters to a plurality of outlets for heated water in the building; at least one pump for pumping water through the system; and at least one storage tank configured to supply water to the heaters and receive heated water not used at the outlets from the supply circuit through a heated water return line; wherein the at least one storage tank is also configured to supply water into the supply circuit without passing through the heaters via a bypass circuit in response to demand at the outlets for heated water exceeding a heating capacity of the heaters, and wherein the at least one storage tank is upstream of the pump and receives water from the heated water return line and a cold water inlet, the system being configured so that heated water flowing from an outlet of the at least one storage tank mixes with water flowing from the cold water inlet before entering the pump.

A controller may be provided, the controller being configured for operating the pump in response to a drop in temperature in the water supply circuit. A temperature sensor may be provided in the supply circuit so that the temperature of water entering the storage tank and the water heaters can be determined by the controller, where provided. Preferably, the pump is disposed between the storage tank and the water heaters.

According to another aspect of the present invention there is provided a water heating system for a building, comprising: a plurality of water heaters; a water supply circuit for supplying water from the heaters to a plurality of outlets for heated water in the building; at least one pump for pumping water through the system; and at least one storage tank configured to supply water to the heaters and receive heated water not used at the outlets from the supply circuit through a heated water return line; wherein the pump is disposed upstream of the at least one storage tank and in the heated water return line, wherein the at least one storage tank is also configured to supply water into the supply circuit without passing through the heaters via a bypass circuit in response to demand at the outlets for heated water exceeding a heating capacity of the heaters, and wherein the at least one storage tank receives water from the heated water return line and a cold water inlet, the at least one storage tank being configured to supply water directly to a single water heater and to each subsequent water heater via a respective staging valve mounted between the at least one storage tank and each subsequent heater, whereby the water heaters are sequentially operable in response to increasing demand from the outlets for heated water.

The system can further comprise a controller for operating the pump in response to a drop in temperature in the water supply circuit. A temperature sensor may be provided in the supply circuit so that the temperature of water entering the storage tank and the water heaters can be determined by the controller, where provided.

Any of the above described water heating systems may include other features, such as a pressure sensor upstream of the pump for halting operation of the pump in response to a loss of inlet pressure. The water heating systems may further comprise a check valve on the suction side of the pump and the pump may be positioned in the system to prevent gravitational draining of the system. Preferably, the pressure sensor is immediately downstream of the cold water supply. Also, the water heaters may be mounted in parallel and the heated water return line may be of an equal or smaller diameter than the water supply circuit. Further the systems may also include an automatic electricity supply interruption, operable for a brief period to reset and/or reboot the water heaters, each water heating means being reset and/or rebooted independently of the other water heating means and on a randomly selected and/or randomly timed basis.

The above described systems may also include a plurality of storage tanks mounted in parallel, the tanks being hydraulically balanced. A temperature sensor may be provided for monitoring the temperature of water upstream of the water heaters, the pump being configured to shutdown once a predetermined temperature has been exceeded. Also, the water temperature stored in the at least one storage tank may be maintained and controlled automatically by the set temperature of the water heating means.

In the embodiments where a storage tank is included in the water heating system, on the top of the storage tank an air bleed valve can be provided to expel air displaced by water and two one-way flow devices, one duty and one standby (or vice versa), acting as air inlet valves can be installed in series to prevent vacuum related crushing of the storage tank membrane due to drainage of water.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will be further described, by way of non-limiting example only, with reference to the accompanying drawings in which:

Figure 1 is a schematic diagram of a traditional/conventional hot water system with a storage tank; Figure 2 is a schematic diagram of a traditional/conventional tankless hot water system as per Australian Patent nos. 763394; 2007201101 and Patent Application no. 2015903715; Figure 3 is a schematic diagram of a water heating system of one embodiment of the invention;

Figure 4 is a schematic diagram of a water heating system of another embodiment of the invention; and

Figure 5 is a schematic diagram of a water heating system of another embodiment of the invention.

DETAILED DESCRIPTION

Figures 1 and 2 illustrate convention prior art hot water systems 10, 20, respectively, with Figure 1 illustrating a system 10 including a storage tank 80 and Figure 2 illustrating a tankless system 20. Each system includes a plurality of water heaters 16, a supply circuit 12b for supplying water to outlets for heated water 36 and a hot water return 12c.

Conventional hot water system 10 with storage tank System 10 of Figure 1 includes a primary pump 22 and a continuously operable secondary pump 90, with the primary pump 22 being provided for pumping water through heaters 16a, 16b, 16c (together referred to as 16) and the secondary pump 90 being provided to draw water through a hot water return 12c. Once water is heated by the heaters 16 it is stored in the storage tank 80 ready for use. Although shown as having a single storage tank 80, multiple tanks mounted in parallel may be used. It will be appreciated that the flow capacity of system 10 for supplying heated water to the outlets for heated water is limited by the output of the heaters and storage tank 80. Storage tank 80 is configured to store heated water downstream of the heaters 16.

System 10 of Figure 1 also includes a water supply circuit 12 and a cold water inlet 13 in which cold water from a cold water supply is provided to intersection U. The cold water inlet 13 may also have an isolation valve 113 to provide for maintenance. A downstream portion of circuit 12 forms a building reticulated hot water supply circuit 12b which is downstream from a hot water storage tank 80 and the heaters 16. Downstream portion 12b is configured for supplying hot water from the storage tank 80 and the heaters 16 to a plurality of water outlets 36 (all of which are schematically represented by block 36) in the building.

A plurality of water heaters 16 in parallel are provided upstream of the storage tank 80. Inlet and outlet branches 18 are provided for supplying water to and from the water heaters 16.

A primary pump 22 is provided for supplying water through the plurality of water heaters 16 and through storage tank 80. A control system 50 and water temperature sensor 151 mounted in or on the storage tank 80 may be provided for monitoring the temperature of water stored in a storage tank 80. At a predetermined temperature a signal is provided for switching on or off the primary pump 22.

Secondary hot water circulation pump 90 is provided to circulate the hot water from storage tank 80 through the building reticulated hot water supply circuit 12b through to 12c so that hot water is always available on demand to water outlets 36.

A bypass circuit/loop 40 is provided to allow water flow from the cold water inlet 13 to the downstream location D through the hot water storage tank 80 when water flow requirements through the supply circuit 12b through to 12c exceed capability of supply through the water heaters 16. Bypass circuit 40 also allows water to flow from the hot water storage tank 80 through the primary pump 22 and the water heaters 16 and back to storage tank 80 to recover the lost heat during the hot water circulation process through the building reticulated hot water supply circuit 12b through to 12c.

Gas is supplied to the heaters 16a to 16c to fuel the heaters via gas inlet 140. Individually, heaters 16a to 16c will also require continuous single phase power for their normal operation, such as a 240V/lPh/5OHz power supply.

A controller 50, where used, may be a conventional controller and is connected by wires 120 to the pump 22, to operate the pump, and to the temperature sensor 151 so that the required signals are supplied to and from the controller 50 to operate the system. In the systems without such a controller, pump 22 will be continuously operating.

A pressure/temperature relief valve 70 is provided as part of a storage tank 80 to protect the system pressure rating. The suction side of pumps 22 and 90 may include a strainer 32 as protection against water borne particles. The discharge side of pumps 22 and 90 can include a one way flow valve/check valve to prevent reverse flow.

The intersection of the hot water return 12c and a bidirectional line 40 is marked as location U and indicates a point where water can flow either toward the primary pump 22 or toward the storage tank 80. Under operating conditions where there is no demand for hot water from the hot water outlets 36, the secondary pump 90 will draw unused hot water through the hot water return 12c and primary pump 22 will not be operational so that the unused hot water returns to the storage tank 80. The primary pump 22 is operable via controller 50 in response to temperature sensor 151 mounted in or on the storage tank 80 with its set value falling below a predetermined level, at which point the primary pump 22 is operable to pump water from storage tank 80 through heaters 16 so that the required increase in the water temperature within the storage tank 80 is achieved.

Conventional tankless hot water system 20 Figure 2 illustrates a tankless hot water system 20 as per the present applicant's Australian Patent nos. 763394; 2007201101 and Patent Application no. 2015903715. In system 20, a plurality of heaters 16a, 16b, 16c (together referred to as 16) supply water directly to outlets for heated water 36. A bidirectional line 40 is also provided to supply cold water to the outlets for heated water 36 in response to demand for hot water exceeding the heating capacity of the water heaters 16. This arrangement is fully described in the present applicant's Australian patent no. 2007201101, the contents of which are incorporated by reference herein. Controller 50 is electrically coupled to sensors 150 and 151 and the pump via wires 120 and is provided to operate primary pump 22 in response to a drop in temperature measured by temperature sensor 150. A pressure sensor 130 is also provided to prevent the pump running dry.

System 20 of Figure 2 includes a water supply circuit 12 and a cold water inlet 13 in which cold water from a cold water supply is received to intersection U. Cold water inlet 13 may also have an isolation valves 113 to provide for maintenance. Circuit 12 has inlet and outlet branches 18 for supplying water to and from the water heaters 16. Water supply circuit 12 includes a downstream portion 12b which is downstream from the heaters 16, which are mounted in parallel. A downstream portion 12b of the water supply circuit 12 supplies hot water from the heaters 16 to a plurality of water outlets 36 (all of which are schematically represented by block 36) in the building.

Water heaters 16a are mounted in parallel downstream of a pump 22, though multiple pumps may be provided. Pump 22 is located downstream of water supply circuit 13, located upstream of the water heaters 16. Pump 22 is configured for supplying water through the plurality of water heaters 16, and is configured to circulate hot water through the building reticulated hot water supply circuit 12b through to 12c so that hot water is always available on demand to water outlets 36.

A control system/controller 50 may be provided in communication with a water temperature sensor 150 mounted at intersection U. Controller 50 may be or may not be provided for monitoring the temperature and upon reaching a predetermined temperature a signal is provided for switching on or off the pump 22. Controller 50, where used, may be a conventional controller and is connected by wires 120 to the pump 22 to operate the pump 22, and to the temperature sensors 150 and/or 151 so that the required signals are supplied to and from the controller 50 to operate the system. In the systems without such a controller, pump 22 will be continuously operating.

A bidirectional bypass circuit/loop 40 is provided and located between intersection U and intersection D. Loop 40 is also located downstream of water supply circuit 13, located upstream of pump 22, located downstream of hot water return 12c, and located downstream of heaters 16.

Loop 40 is provided with a first one way flow/pressure regulating device 180, in the form of variable resistance spring loaded one way flow/pressure compensating valve 180, configured to allow flow from the cold water inlet 13 to the downstream location 12b and to open only once a predetermined pressure differential has been exceeded so as to create resistance within the bypass circuit 40 to encourage flow through the heaters 16 before flowing through the bypass circuit 40 when water flow requirements through the supply circuit 12b through to 12c exceed capability of supply through the water heaters 16.

Loop 40 is also provided with a second one way flow/pressure regulating device 190, in the form of variable resistance spring loaded one way flow/pressure compensating valve 190, for opening the loop circuit 40 when a predetermined pressure differential exists between the downstream location D and the upstream location U, for allowing water to flow between the downstream location D and the upstream location U for supplying sufficient amount of water to ignite one or more water heaters 16.

Pressure Relief Valve 70 is provided in the hot water circuit 12 to protect the system pressure rating. A loss of inlet pressure switch 130 is provided to act as a safety and prevent dry operation of the pump 22. Test gauge cock and plug 60 may also be provided in the hot water circuit 12. The suction side of pump 22 and hot water return 12c may include a strainer 32 as protection against water borne particles. Discharge side of pump 22 and hot water return 12c may include a one way flow valve / check valve to prevent reverse flow.

Hot water system 100 according to a first preferred embodiment With reference to Figure 3, there is shown a water heating system 100 according to a first preferred embodiment of the present invention. The water heating system 100 comprises a plurality of water heaters 116a, 116b, 116c (together referred to as 116) mounted in parallel, a water supply circuit 112 for supplying water from the heaters 116 to a plurality of outlets for heated water 136 in the building, a pump 122 for pumping water through the system 100, a storage tank 180 configured to supply water to the heaters 116 and receive heated water not used at the outlets 136 from the supply circuit 112 through a heated water return line 112c. Circuit 112 has inlet and outlet branches 118 for supplying water to and from the water heaters 116.

The system 100 can also include an optional controller 150 for operating the pump 122 in response to a drop in temperature in the water supply circuit 112. In embodiments without a controller, it will be appreciated that pump 122 will be continuously operable.

Although depicted and referred to as a single tank, storage tank 180 may also be a plurality of tanks mounted in parallel. Where a plurality of tanks are used, they are hydraulically balanced to prevent idling of any one tank. The storage tank 180 is configured to also supply water without passing through the heaters 116 or, in other words, directly into the supply circuit 112 via a bypass circuit 140 in response to demand at the outlets for heated water 136 exceeding a heating capacity of the heaters 116.

Storage tank 180 is configured to store heated water and is located downstream of cold water supply circuit 113, located downstream of hot water return 112c and located upstream of the pump 122 and the heaters 116.

Pump 122 is provided for supplying water through the water heaters 116 and for circulating the hot water through supply circuit 112b through to 112c. Pump 122 is located downstream of storage tank 180 and located upstream of the water heaters 116.

In the embodiment shown in Figure 3, the storage tank 180 is upstream of the pump 122 and configured so that water supplied to the heaters 116 is fed from the storage tank 180.

The storage tank 180 receives, through an inlet, water from the heated water return line 112c and a cold water inlet 113. A temperature sensor 1150 is positioned proximal to the junction of a cold water inlet 113 and the hot water return 112c, so as to measure the temperature of water entering the storage tank 180 so that the controller (where provided) can operate circulation pump 122 as required. It will be appreciated that the position of the temperature sensor may be varied and still measure the temperature of water entering the storage tank 180. The location of sensor 1150 is selected so as to reflect the lowest temperature of water in system 100 to prevent water anywhere in the circuit 112 falling below the minimum required temperature of 60 degrees C. In the illustrated embodiment, a second sensor 1151 is provided within the supply circuit near a junction between the supply circuit 112 and bypass circuit 140. The second sensor is provided to show the temperature of water being supplied to the outlets 136. For convenience, the second sensor may be close to the heaters 116 and pump 122, though it will be appreciated that the second temperature sensor may be located closer to the outlets for heated water 136 so as to more accurately reflect the temperate of water near the outlets for heated water 136.

The bypass circuit 140 has a first one way flow/pressure regulating device 1180, in the form of variable resistance spring loaded one way flow/pressure compensating valve 1180 mounted therein for encouraging flow through the heaters 116. In this regard, flow compensation valve 1180 creates artificial friction within the bypass circuit 140 so that water, which will follow the path of least resistance, first flows toward pump 122 and not directly into the bypass circuit 140. Valve 1180 is located downstream of storage tank 180, upstream of pump 122, downstream of water heaters 116 and located in the bypass circuit 140. Valve 1180 is configured to allow flow from the cold water inlet 113 to the downstream location D and to open only once a predetermined pressure differential has been exceeded so as to create resistance within the bypass circuit 140 to encourage flow through the heaters 116 before flowing through the bypass circuit 140 when water flow requirements through the supply circuit 112b through to 112c exceed capability of supply through the water heaters 116.

To provide return flow to the tank 180 and water heaters 116 in the event of no return from the outlets 136, a second one way flow/pressure regulating device 1190, in the form of variable resistance spring loaded one way flow/pressure compensating valve 1190 is provided between the bypass circuit 140 and the heated water return line 112c to return flow to the heaters. The heated water return line 112c is preferably of a smaller diameter than the water supply circuit so as to minimise the energy required to keep the hot water supply circuit 112b through to 112c above 60°C in times of low use. Valve 1190 is located downstream of the water heating means 116, downstream of hot water return 112c, and in loop circuit 1140. Valve 1190 is configured for opening the loop circuit 1140 when a predetermined pressure differential exists between the downstream location D and the upstream location U, for allowing water to flow between the downstream location D and the upstream location U for supplying a sufficient amount of water to ignite one or more water heaters 116.

In use, the embodiment illustrated in Figure 3 operates in the following manner. During times of no demand at the outlets for heated water 136, water circulation ceases until the temperature measured at point U falls below a predetermined threshold due to heat losses within the building supply circuit 112b through to 112c, at which point the controller triggers operation of pump 122 to circulate water within the supply circuit 112 to maintain a desired temperature at the outlets for heated water 136. In embodiments without a controller, pump 122 will operate continuously.

As water is used within the building, cold water is introduced into the storage tank 180, which causes the temperature measured at location U to decrease. The amount of temperature decrease at location U will depend on the flow rate and temperature of water returning from the hot water return 112c and the flow rate at the building outlets 136 and temperature of water entering through the cold water inlet 113. Once the temperature of water at location U drops below a predetermined level, which is above 60 degrees, the pump 122 is operated to pump water through heaters 116 to increase the temperature of water flowing into the supply circuit 112. Also, if the temperature of water at location U rises above a predetermined temperature, a signal is provided to controller 150 for switching off the pump 122.

In embodiments without a controller 150 for switching on/off pump 122 is response to temperature variations, the temperature within system 100 is controlled automatically by the set temperature of the water heaters 116.

In the event that the use of heated water in the building exceeds the heating capacity of the heaters 116, cold water flows directly from the storage tank 180 and into bypass circuit 140 to meet the additional demand with the end result of a drop in temperature at outlets 136.

In a preferred embodiment, system 100 is configured so that the heated water return line 112c is of an equal or smaller diameter than the water supply circuit 112b. Also, the cold water inlet 113 preferably comprises part of the water supply circuit 113 upstream of the heating means 116. The cold water supply inlet 113 may also have an isolation valve 1113 and a Y-strainer 132 to provide for maintenance and a one-way flow device 130 to prevent accidental draining of the storage tank because of a drop in pressure upstream of isolation valve 1113.

Individually, heaters 116a to 116c will also require continuous single phase power for their normal operation, such as a 240V/lPh/50Hz power supply. Gas is supplied to the heaters 116a to 116c to fuel the heaters via gas inlet 1140.

System 100 may include an auto electricity power supply interruption, for a brief period, to reset and/or reboot the water heating means 116. Preferably, each of the water heating means 116 are reset and/or rebooted independently of the other water heating means 116 on a randomly selected and/or randomly timed basis. Controller 150, where used, may be a conventional controller and is connected by wires 1120 to the pump 122 to operate the pump 122, and to the temperature sensors 1150 and/or 1151 so thatthe required signals are supplied to and from the controller 150 to operate the system.

A pressure/temperature relief valve 170 is provided as part of a storage tank 180 to protect the system pressure rating. System 100 may include a pressure sensor 1130 for halting operation of the pump 122 in response to a loss of inlet water supply 113 pressure. A test gauge cock and plug 160 may also be provided in the hot water circuit 112.

A suction side of pump 122 and hot water return 112c may include a strainer 132 as protection against water borne particles. A discharge side of pump 122 and hot water return 112c may include a one way flow valve/check valve 130 to prevent reverse flow.

The embodiment illustrated in Figure 3 provides the advantage of a storage tank to meet sudden increases in demand and customer's expectations, without requiring a continuously operable pump or a secondary pump to maintain the required temperature within the hot water supply circuit 112b through to 112c, thus reducing the cost of installing and maintaining such a system.

Hot water system 200 according to a further preferred embodiment With reference to Figure 4, there is shown a water heating system 200 according to another embodiment of the present invention. The water heating system 200 comprises a plurality of water heaters 216a, 216b, 216c (together referred to as 216), a water supply circuit 212 for supplying water from the heaters 216 to a plurality of outlets for heated water 236 in the building, at least one pump 222 for pumping water through the system 200, a storage tank 280 configured to supply water to the heaters 216 and receive unused water from the supply circuit 212 through a heated water return line 212c. Cold water is introduced by cold water supply inlet 213, which may also have an isolation valve 2113 and a Y-strainer 232 to provide for maintenance and a one way flow device 230 to prevent accidental draining of the storage tank because of a drop in pressure upstream of isolation valve 2113.

The system 200 also includes an optional controller 250 for operating the pump 222 in response to a drop in temperature at location U which is upstream of the heaters 216.

Circuit 212 has inlet and outlet branches 218 for supplying water to and from the water heaters 216.

Although depicted and referred to as a single tank, storage tank 280 may also be a plurality of tanks mounted in parallel. Where a plurality of tanks are used, they are hydraulically balanced to prevent idling of any one tank. The storage tank 280 is configured to also supply water into the supply circuit 212 without passing through the heaters 216 via a bypass circuit 240, in response to demand at the outlets for heated water 236 exceeding heating capacity of the heaters 216.

Storage tank 280 is configured to store heated water and is located downstream of hot water return 212c, located in the hot water return bidirectional flow line 212d before intersection U, located downstream of cold water supply circuit 213 and located upstream of pump 222.

Pump 222 is configured for supplying water through the water heaters 216, for circulating the hot water through supply circuit 212b through to 212c. Pump 222 is located downstream of cold water supply circuit 213 and location U, located downstream of hot water return bidirectional flow line 212d and location U and located upstream of the water heaters 216.

Again, the storage tank 280 is upstream of the pump 222 and receives water from the heated water return line 212c. The system 200 is configured so that heated water flowing from an outlet of the storage tank 280 mixes with water flowing from a cold water inlet 213 before entering the pump 222. A temperature sensor 2150 is located at location U so that the temperature of water entering the pump 222 can be determined by the controller and so that the controller can operate circulation pump 222 as required. The position of the temperature sensor 2150 is selected so as to prevent water anywhere in the circuit 212 falling below the minimum required temperature of 60 degrees C. Again, it will be appreciated that the position of the temperature sensor may be varied and still measure the temperature of water entering the storage tank 280.

In the illustrated embodiment, a second temperature sensor 2151 is provided within the supply circuit 212 near a junction between the supply circuit 212 and bypass circuit 240. The second sensor is provided for displaying the temperature of water flowing to the outlets 236. For convenience, the second sensor may be close to the heaters 216 and pump 222, though it will be appreciated that the second temperature sensor may be located closer to the outlets for heated water 236 so as to more accurately reflect the temperate of water near the outlets for heated water 236.

System 200 includes a first one way flow/pressure regulating device, in the form of variable resistance spring loaded one way flow/pressure compensating valve 2180. Valve 2180 is located downstream of hot water return 212c and bidirectional flow line 212d intersection, located downstream of water heating means 216 and located in the bypass circuit 240. Valve 2180 is configured to allow flow from the cold water inlet 213 to the downstream location D and to open only once a predetermined pressure differential has been exceeded so as to create resistance within the bypass circuit 240 to encourage flow through the heaters 216 before flowing through the bypass circuit 240 when water flow requirements through the supply circuit 212b through to 212c exceed capability of supply through the water heaters 216.

To provide return flow to the tank 280 and water heaters 216 in the event of no return from the outlets 236, the loop circuit 2240 having a second one way flow/pressure regulating device 2190 will allow flow from the downstream location D to upstream location U. The second one way flow/pressure regulating device 2190 is also in the form of variable resistance spring loaded one way flow/pressure compensating valve 2190. Valve 2190 is located downstream of the water heating means 216, downstream of bypass circuit 240, downstream of intersection D, downstream of hot water return 212c and located in the loop circuit 2240. Valve 2190 is configured for opening the loop circuit 2240 when a predetermined pressure differential exists between the downstream location D and the upstream location U, for allowing water to flow between the downstream location D and the upstream location U for supplying a sufficient amount of water to ignite one or more water heaters 216.

In use, the embodiment illustrated in Figure 4 operates in the following manner. During times of no demand at the outlets for heated water 236, water circulation ceases until the temperature measured at point U falls below a predetermined threshold due to heat losses within the building supply circuit 212b through to 212c, at which point the controller triggers operation of pump 222 to circulate heated water within the supply circuit 212 to maintain a desired temperature at the outlets for heated water 236. In embodiment without a controller, pump 222 will operate continuously.

As water is used within the building, cold water is introduced into the supply circuit 212, which causes the temperature measured at location U to decrease. Initially the cold water flows into the storage tank 280 so that heated water is supplied to the outlets for heated water 236 under mains pressure. The amount of temperature decrease at location U will depend on the flow rate at the building outlets 236 and temperature of water entering through the cold water inlet 213. Once the temperature at location U drops below a predetermined level, which is above 60 degrees, the controller triggers operation of the pump 222 to pump water through heaters 216 to increase the temperature of water flowing into the supply circuit 212. If the temperature of water at location U rises above a predetermined temperature, a signal is provided for switching off the pump 222.

In embodiments without a controller 250 for switching the pump 222 on and off with respect to temperature of stored water, water temperature stored in storage tank 280 is maintained and

controlled automatically by the set temperature of the water heaters 216.

In the event that the use of heated water in the building exceeds the heating capacity of the heaters 214, cold water can flow directly from the storage tank 280 and into bypass circuit 240 to meet the additional demand with the end result a of drop in temperature at outlets 236.

The system 200 includes a hot water return line 212c from the supply circuit 212b to the upstream intersection U and downstream of cold water supply circuit 213. The heated water return line 212c is of an equal or smaller diameter than the water supply circuit 212b.

The system 200 may include an auto electricity power supply interruption, for a brief period, to reset and/or reboot the water heating means 216. Preferably, each of the water heating means 216 are reset and/or rebooted independently of the other water heating means 216 on a randomly selected and/or randomly timed basis.

Individually, heaters 216a to 216c will also require continuous single phase power for their normal operation, such as a 240V/lPh/5OHz power supply. Gas is supplied to the heaters 216a to 216c to fuel the heaters via gas inlet 2140.

Controller 250, where used, may be a conventional controller connected by wires 2120 to the pump 222 to operate the pump 222, and to the temperature sensors 2150 and/or 2151 so that the required signals are supplied to and from the controller 250 to operate the system.

The system 200 may also include pressure/temperature relief valve 270 as part of a storage tank 280 to protect the system pressure rating, along with a pressure sensor 2130 for halting operation of the pump 222 in response to a loss of inlet water supply 213 pressure. A test gauge cock and plug 260 may also be provided in the hot water circuit 212.

On a suction side of pump 222 and hot water return 212c a strainer 232 may be provided as protection against water borne particles. Pump 222 discharge and hot water return 212c may include a one way flow valve/check valve 230 to prevent reverse flow.

The embodiment illustrated in Figure 4 provides the advantage of a storage tank to meet sudden increases in demand and customer's expectations, without requiring a continuously operable pump or a secondary pump to maintain the required temperature within the hot water supply circuit 212b through to 212c, thus reducing the cost of installing and maintaining such a system.

Hot water system 300 according to a further preferred embodiment With reference to Figure 5, there is shown a water heating system 300 according to another embodiment of the present invention. The water heating system 300 comprises a plurality of water heaters 316a, 316b, 316c (together referred to as 316) which are hydraulically staged, a water supply circuit 312 for supplying water from the heaters 316 to a plurality of outlets for heated water 336 in the building, at least one pump 322 for pumping water through the system 300, and a storage tank 380 configured to supply water to the heaters 316 and receive unused water from the supply circuit 312 through a heated water return line 312c. In the embodiment of Figure 5, a controller 350 is provided for operating the pump 322. In other embodiments, controller 350 may be omitted and pump 322 operates continuously.

Circuit 312 has inlet and outlet branches 318 for supplying water to and from the water heaters 316. Cold water is introduced by supply inlet 313, which may also have an isolation valve 3113 and Y-strainer 332 to provide for maintenance and a one-way flow device 330 to prevent accidental draining of the storage tank because of a drop in pressure upstream of isolation valve 3113.

Although depicted and referred to as a single tank, storage tank 380 may also be a plurality of tanks mounted in parallel. Where a plurality of tanks are used, they are hydraulically balanced to prevent idling of any one tank. The storage tank 380 is also configured to supply water without passing through the heaters 316 or directly into the supply circuit 312 via a bypass circuit 340 in response to demand at the outlets for heated water 336 exceeding a heating capacity of the heaters 316.

Storage tank 380 is configured to store heated water and is located downstream of hot water return 312c and hot water circulation pump 322, located downstream of cold water supply circuit 313 and located upstream of hydraulically staged heaters 316.

Pump 322 is configured for supplying water through only one of heater 316a, 316b, 316c and configured for circulating the hot water through supply circuit 312b through to 312c. Pump 322 is located downstream of hot water return 312c and in the circuit 312c, located downstream of hot water bypass loop 3340, located downstream of cold water supply circuit 313, located upstream of the intersection U, and located upstream of the hot water storage tank 380.

In the embodiment shown in Figure 5, a first temperature sensor 3150 is positioned proximal to the junction of a cold water inlet 313 and the hot water return 312c, so as to measure the temperature of water entering the storage tank 380 so that the controller (where provided) can operate circulation pump 322 as required. It will be appreciated that the position of the temperature sensor 3150 may be varied and still measure the temperature of water entering the storage tank 380. The location of sensor 3150 is selected so as to reflect the lowest temperature of water in system 300 to prevent water anywhere in the circuit 312 falling below the minimum required temperature of 60 degrees C.

In the illustrated embodiment, location D is shown within the supply circuit 312 after a junction between the supply circuit 312 and bypass circuit 340 and a second temperature sensor 3151 is provided at this point for displaying the temperature of water flowing to outlets 336. For convenience, the sensor may be close to the heaters 316, though it will be appreciated that the second temperature sensor 3151 may be located closer to the outlets for heated water 336 so as to more accurately reflect the temperate of water near the outlets for heated water 336.

The storage tank 380 receives water from the heated water return line 312c and a cold water inlet 313. The storage tank 380 is configured to supply water directly to one of the water heaters, such as 316a for example, and then to each subsequent water heaters 316b & 316c via a respective staging valves 324a, 324b & 324c mounted between the storage tank 380 and each of the water heaters 316a, 316b & 316c respectively. Owing to this arrangement, the water heaters 316a, 316b, 316c are sequentially operable in response to increasing demand from the outlets for heated water 336. To equalise usage time of the heaters, the staging valves 324a, 324b, 324c resistance may be varied so as to select the operational order of the heaters.

A water supply inlet of each of water heater 316a, 316b, 316c is fitted with a variable resistance spring loaded one way flow/pressure compensating valve 324a, 324b, 324c respectively, being configured to facilitate staged operation of each respective water heater 316a, 316b, 316c upon increasing flow demand. By changing the spring resistance of each of these valves 324a, 324b, 324c, equal operational time of the hydraulically staged water heaters 316 is possible.

In this embodiment, the bypass circuit 340 is in the form of a further branch having a variable resistance spring loaded one way flow/pressure compensating valve 3180 in parallel to staging valves 324a, 324b, 324c to open only once a predetermined pressure differential has been exceeded so as to create resistance within the bypass circuit 340 to encourage flow through the heaters 316 before flowing through the bypass circuit 340 when water flow requirements through the supply circuit 312b through to 312c exceed capability of supply through the hydraulically staged water heaters 316 and water can flow through this branch 340 from the cold water inlet 313 through storage tank 380 to meet the increased demand requirements at outlets 336. In this embodiment, the pump 322 is disposed upstream of the storage tank 380 and operates to push water through the only one water heater 316.

System 300 also includes a second one way flow/pressure regulating device 3190, in the form of variable resistance spring loaded one way flow/pressure compensating valve 3190. Valve 3190 is located downstream of the water heaters 316, downstream of hot water return 312c, located upstream of hot water circulation pump 322, and located in the bypass loop circuit 3340. Valve 3190 is configured for opening the bypass loop circuit 3340 when a predetermined pressure differential exists between the downstream location D and the upstream location U, for allowing water to flow between the downstream location D and the upstream location U for supplying a sufficient amount of water to ignite only one of the hydraulically staged water heaters 316.

Optionally, a water temperature sensor 3150 and a controller 350 may be provided for monitoring the temperature of water upstream of the water heaters 316 so that if the temperature of the water

upstream of the water heater 316 rises above a predetermined temperature, a signal is provided to a controller 350 for switching off the pump 322. Optionally, a water temperature sensor 3150 and a controller 350 may also be provided for monitoring the temperature of water upstream of the water heaters 316 so that if the temperature of the water upstream of the water heaters 316 falls below a predetermined temperature, a signal is provided to a controller 350 for switching on the pump 322.

When a controller 350 is not provided for switching the pump 322 on and off with respect to temperature of stored water, water temperature stored in storage tank 380 is maintained and

controlled automatically by the set temperature of any one off the water heaters 316.

Controller 350, where used, may be a conventional controller and is connected by wires 3120 to the pump 322 to operate the pump 322, and to the temperature sensors 3150 and/or 3151 so that the required signals are supplied to and from the controller 350 to operate the system.

The hot water supply circuit 312b through to 312c includes a return line 312c from the water outlets 336 to the upstream intersection U and downstream of cold water supply circuit 313. The heated water return line 312c is of an equal or smaller diameter than the water supply circuit 312b.

Wherein the cold water inlet 313 comprises part of the water supply circuit 313 upstream of the hydraulically staged heating means 316. Cold water supply inlet 313 may also have an isolation valve 3113 to provide for maintenance.

The system 300 may include an auto electricity power supply interruption, for a brief period, to reset and/or reboot the hydraulically staged water heating means 316. Preferably, each of the water heating means 316 are reset and/or rebooted independently of the other water heating means 316 on a randomly selected and/or randomly timed basis.

Individually hydraulically staged heaters 316a to 316c will also require continuous single phase power for their normal operation, such as a 240V/lPh/50Hz power supply. Gas is supplied to the hydraulically staged heaters 316a to 316c to fuel the heaters via gas inlet 3140.

Pressure/temperature relief valve 370 may be provided as part of a storage tank 380 to protect the system pressure rating, along with a test gauge cock and plug 360 in the hot water circuit 312. System 300 may also include a pressure sensor 3130 for halting operation of the pump 322 in response to a loss of inlet water supply 313 pressure. On a suction side of pump 322 and hot water return 312c a strainer 332 may be provided as protection against water borne particles. Pump 322 discharge and hot water return 312c may include a one way flow valve/check valve 330 to prevent reverse flow.

In use, the embodiment illustrated in Figure 5 operates in the following manner. During times of no demand at the outlets for heated water 336, water circulation is through a single water heater 316 and returns to pump 322 via return line 312c. As water is used within the building and the pressure differential increases across the staging valves 324, they progressively open to allow flow through additional water heaters to meet the increasing demand.

In the event that the use of heated water in the building exceeds the heating capacity of the heaters 316, water can flow directly from the storage tank 380 and into bypass circuit 340 to meet the additional demand with the end result of a drop in temperature at outlets 336.

The embodiment illustrated in Figure 5 provides the advantage of a storage tank to meet sudden increases in demand and customer's expectations, without requiring a large additional pump, such as a primary pump as is in a conventional system to pump water through all the heaters 316 to their full capacity, thus reducing the cost of installing and maintaining such a system.

General description of common features in preferred embodiments In the described preferred embodiments, heaters 116, 216, 316 are of the continuous type and operable by gas fed from a gas inlet 1140, 2140, 3140 and provide heated water at above 60 degrees. The inventors have found that the lifespan of water heaters of this type is improved by operating on high burner capacity. In this regard, the inventors have found that when heaters of this type are operating under low load conditions, i.e. under a low gas flow rate, condensation forms on the heat exchanger due to vaporising gas and there is insufficient heat to evaporate this condensation, leading to corrosion of heater's heat exchanger and a reduced lifespan. By operating the described systems on high burner capacity, this problem can be avoided.

In the described embodiments, the pump is preferably positioned in the system to prevent gravitational draining to reduce the chances of the pump running dry and becoming damaged. Furthermore, the check valve on the pressure side of the pump may be replaced with a check valve on the suction side of the pump to prevent gravitational draining, thereby trapping water within the pump to prevent damage from dry running of the pump.

In the described embodiments, on the top of the storage tank an air bleed valve 185, 285, 385 is provided to expel air displaceable by water and two one-way flow devices 130, 230, 330, one duty and one standby (or vice versa), acting as air inlet valves can be installed in series to prevent vacuum related crushing of the storage tank membrane due to drainage of water.

The embodiments have been described by way of example only and modifications are possible within the scope of the invention disclosed.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Claims

1. A water heating system for a building, comprising: a plurality of water heaters;

a water supply circuit for supplying water from the heaters to a plurality of outlets for heated water in the building; at least one pump for pumping water through the system; and at least one storage tank configured to supply water to the heaters and receive heated water not used at the outlets from the supply circuit through a heated water return line; wherein the at least one storage tank is also configured to supply water into the supply circuit without passing through the heaters via a bypass circuit in response to demand at the outlets for heated water exceeding a heating capacity of the heaters, and wherein the at least one storage tank is upstream of the pump and receives, through an inlet, water from the heated water return line and a cold water inlet.

2. A water heating system as claimed in claim 1, further comprising a controller for operating the pump in response to a drop in temperature in the water supply circuit.

3. A water heating system as claimed in claim 1 or claim 2, wherein a temperature sensor is provided in the supply circuit so that the temperature of water entering the at least one storage tank and the water heaters can be determined by the controller.

4. A water heating system as claimed in any preceding claim, wherein the pump is disposed between the at least one storage tank and the water heaters.

5. A water heating system for a building, comprising: a plurality of water heaters;

6. A water heating system as claimed in claim 5, further comprising a controller for operating the pump in response to a drop in temperature in the water supply circuit.

7. A water heating system as claimed in claim 5 or claim 6, wherein a temperature sensor is provided in the supply circuit so that the temperature of water entering the at least one storage tank and the water heaters can be determined by the controller.

8. A water heating system as claimed in any one of claims 5 to 7, wherein the pump is disposed between the at least one storage tank and the water heaters.

9. A water heating system for a building, comprising: a plurality of water heaters;

a water supply circuit for supplying water from the heaters to a plurality of outlets for heated water in the building; at least one pump for pumping water through the system; and at least one storage tank configured to supply water to the heaters and receive heated water not used at the outlets from the supply circuit through a heated water return line; wherein the pump is disposed upstream of the at least one storage tank and in the heated water return line,

wherein the at least one storage tank is also configured to supply water into the supply circuit without passing through the heaters via a bypass circuit in response to demand at the outlets for heated water exceeding a heating capacity of the heaters, and wherein the at least one storage tank receives water from the heated water return line

and a cold water inlet, the at least one storage tank being configured to supply water directly to a single water heater and to each subsequent water heater via a respective staging valve mounted between the at least one storage tank and each subsequent heater, whereby the water heaters are sequentially operable in response to a fall in pressure in the water supply circuit due to increasing demand from the outlets for heated water.

10. A water heating system as claimed in claim 9, further comprising a controller for operating the pump in response to a drop in temperature in the water supply circuit.

11. A water heating system as claimed in claim 9 or claim 10, wherein a temperature sensor is provided in the supply circuit so that the temperature of water entering the at least one storage tank and the water heater can be determined by the controller.

12. A water heating system according to any preceding claim, wherein the bypass circuit has a one-way flow/pressure regulating device mounted therein for encouraging flow through the heaters before the bypass circuit and into plurality of outlets for heated water in the building exceeding the heating capacity of the heaters.

13. A water heating system according to any preceding claim, further comprising a oneway flow/pressure regulating device mounted between the water supply circuit and the bypass circuit and the heated water return line to direct water into the heated water return line for

allowing flow between the downstream location and the upstream location.

14. A water heating system according to claim 12 or claim 13, wherein either or both of the one way flow/pressure regulating devices is a variable resistance spring loaded one way flow/pressure compensating valve.

15. A water heating system according to any preceding claim, further comprising a pressure sensor for halting operation of the pump in response to a loss of inlet pressure.

16. A water heating system according to any preceding claim, further comprising a check valve on the suction side of the pump and wherein the pump is positioned in the system to prevent gravitational draining of the system.

17. A water heating system according to claim 15, wherein the pressure sensor is immediately downstream of the cold water supply.

18. A water heating system according to any preceding claim, wherein the water heaters are mounted in parallel

19. A water heating system according to any preceding claim, wherein the heated water return line is of an equal or smaller diameter than the water supply circuit.

20. A water heating system according to any preceding claim, comprising a plurality of storage tanks mounted in parallel, the tanks being hydraulically balanced.

21. A water heating system according to any preceding claim, further comprising a temperature sensor for monitoring the temperature of water upstream of the water heaters, the pump being configured to shutdown once a predetermined temperature has been exceeded.

22. A water heating system according to any preceding claim, further comprising an automatic electricity supply interruption, operable for a brief period to reset and/or reboot the water heating means, each water heating means being reset and/or rebooted independently of the other water heating means and on a randomly selected and/or randomly timed basis.

23. A water heating system according to any preceding claim, wherein the water temperature stored in the at least one storage tank is maintained and controlled automatically by the set temperature of the water heating means.

24. A water heating system according to any preceding claim, wherein a cold water inlet is provided, having an isolation valve and Y-strainer to provide for maintenance and a one-way flow device to prevent accidental draining of the storage tank because of a drop in pressure upstream of the isolation valve.

o

25. A water heating system according to any preceding claim, wherein on the top of the storage tank an air bleed valve is provided to expel air displaced by water and two one-way flow devices, one duty and one standby, acting as air inlet valves are installed in series to prevent vacuum related crushing of the storage tank membrane due to drainage of water.