GB2330649A

GB2330649A - A water heating arrangement

Info

Publication number: GB2330649A
Application number: GB9722679A
Authority: GB
Inventors: Alistair David Sivill
Original assignee: ALPHA THERM Ltd
Current assignee: ALPHA THERM Ltd
Priority date: 1997-10-27
Filing date: 1997-10-27
Publication date: 1999-04-28
Also published as: GB9722679D0

Abstract

A water heating arrangement comprises a combination boiler and an associated hot water storage tank (24). In an initial state water circulates between the heat exchanger (17) of the boiler and the storage tank (24) so that the temperature of the storage tank is raised. When a tap connected to an outlet pipe (21) is opened to draw hot water, hot water from the storage tank flows (24) to the tap and also, water passing through the heat exchanger (17) of the combination boiler passes to the tap. A thermostatically controlled arrangement (29,30) shuts off the flow of water to the tap from the tank (24) when all of the hot water has been discharged from the tank. Subsequently, it is only water passing through the heat exchanger (17) that is directed to the tap.

Description

"IMPROVEMENTS IN OR RELATING TO A WATER HEATING ARRANGEMENT" THE PRESENT INVENTION relates to a water heating arrangement.

A typical modern water heating arrangement utilises a "combination boiler" to provide hot water for a domestic heating system as well as for domestic consumption. Various arrangements of combination boilers exist as is explained in greater detail below. However, a feature of combination boilers is that hot water for domestic consumption is generated by passing cold water, at mains pressure, through a heat exchanger, in which the water is heated, and then passing the heated water directly to the taps. Consequently there is no need for a hot water storage tank.

Since the water is supplied at mains pressure and is heated to an appropriate temperature during the time that it passes through the heat exchanger, a continuous supply of hot water is provided indefinitely. However, a problem with a typical water heating arrangement utilising a "combination boiler" is that the rate of supply of hot water is relatively low. While the rate of water supply is typically sufficient for supplying a single hot water tap, there is an insufficient supply of hot water should several taps simultaneously be turned on. Similarly, if a bath tub is to be filled with hot water, then the relatively low rate of hot water supply results in a rather lengthy filling process.

The present invention seeks to provide an improved water heating arrangement.

According to this invention there is provided a water heating arrangement comprising a heat exchanger having an inlet pipe for mains pressure cold water and having an outlet pipe to be connected to a hot water tap, the heat exchanger being adapted to receive heat from the heat source of a combination boiler, either directly or indirectly; the inlet pipe and the outlet pipe being in fluid communication with a hot water storage tank, pump means being provided so that, in a first state, water may circulate between the heat exchanger and the storage tank in a closed loop, the water being heated as it passes through the heat exchanger; the arrangement also comprising thermostatically controlled means so that when said hot water tap is opened the arrangement is initially in a second state, in which water from the inlet pipe flows through the heat exchanger and out of the outlet pipe and also water from the inlet pipe flows into the storage tank so that hot water from the storage tank flows to the outlet pipe; the thermostatically controlled means being such that a third state is subsequently entered in which the flow of water from the inlet pipe passes solely through the heat exchanger and out of the outlet pipe, with the flow of water from the storage tank being halted.

Preferably a spur pipe which branches from the inlet pipe extends to the said hot water storage tank, and the storage tank is provided with an exit pipe which is connected to said outlet pipe, the thennostatically controlled means being present in the exit pipe, there being a re-circulation pipe connected to the outlet pipe, the re-circulation pipe extending into the hot water storage tank, a pump being provided to circulate water through the heat exchanger and through the outlet pipe and the re-circulation pipe into the tank and thus through the spur pipe and part of the inlet pipe back to the heat exchanger again.

Conveniently the re-circulation pipe is provided with a non-return valve.

A preferred embodiment of the invention provides a combination boiler in conjunction with a tank to store hot water heated by the boiler, thus enabling a very high flow rate of hot water to be achieved when a tap is first turned on.

Hot water flow is taken both from the combination boiler and from the tank to achieve this high flow rate. Once the store of hot water within the tank is exhausted, and the temperature of water within the tank has fallen below a predetermined level, the flow of water from the tank is terminated. However, the mains water continues to be heated by the combination boiler and delivered to the tap.

An internal circulating pump is provided to circulate water between the tank and the combination boiler when there is no demand for hot water. Thus, the temperature of water within the tank is raised and the circulation can continue until the temperature of water within the tank has risen to a pre-set level.

In preferred embodiments of the invention the thermostatically controlled means comprise a thermostatically controlled valve in the exit pipe, the valve being adapted to close when the temperature of water flowing through the valve falls.

Preferably the thermostatically controlled valve comprises a solenoid valve in the exit pipe controlled by a thermostat attached to the tank.

Alternatively the thermostatically controlled valve is a wax valve which itself senses the temperature and shuts off the flow through the exit pipe.

Conveniently the spur pipe is configured to direct water flowing into the hot water storage tank against a wall of the hot water storage tank, a thermostatic switch being provided on the exterior of the hot water storage tank at that point, the thermostatic switch being adapted to activate the combination boiler in response to a fall in the temperature sensed by the thermostatic switch.

Preferably the thermostatic switch actuates the pump.

In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described, by way of example, with reference to the accompanying drawings in which: FIGURE 1 is a schematic view of a first type of combination boiler which may be used in a water heating arrangement according to the present invention; FIGURE 2 is a schematic view of a second type of combination boiler which may be used as part of a water heating arrangement according to the present invention; FIGURE 3 is a schematic view of a third type of combination boiler which may be used as part of a water heating arrangement according to the present invention, FIGURE 4 is a schematic view of a water heating arrangement according to one embodiment of the present invention, FIGURE 5 is a view corresponding to Figure 4 illustrating the arrangement in a first state, FIGURE 6 is a view corresponding to Figure 4 illustrating the arrangement in a second state, FIGURE 7 is a view corresponding to Figure 4 showing the arrangement in a third state, and FIGURE 8 is a schematic view of an alternative water heating arrangement in accordance with the invention.

Referring now to Figure 1 of the accompanying drawings, a combination boiler 1 comprises a casing 2 in which there is a provided a heat source 3. The heat source 3 is preferably a gas burner.

A domestic heating system 4 comprising a circuit through which water flows may be corrected to the combination boiler 1. The circuit comprises a cool water inlet pipe 5 which is connected to a pump 6 which pumps the cool water through a heat exchanger 7. The heat exchanger is within the casing 2, adjacent the heat source 3 so as to receive heat directly from the heat source The pump 6 is controlled by a thermostat located in the space which is heated by the domestic heating system.. Water passing through the heat exchanger 6 is thus heated. The heat exchanger 7 is, in turn, connected to a hot water outlet pipe 8 which carries heated water out from the heat exchanger 7. The water then passes through a series of radiators (not shown) in which the water becomes cooled and the water then passes back through the cool water inlet pipe 5 and is again pumped through the heat exchanger 7.

A hot water system 9 is also connected to the boiler. In the hot water system 9 cold water passes from a water mains supply through a cold water inlet pipe 10. The water then flows through a second heat exchanger 11, which is within the casing 2 adjacent the heat source 3 so as to receive heat directly from the heat source. Water passing through the heat exchanger 11 is thus heated. The heated water from the heat exchanger 11 then flows through a hot water supply pipe 12 and from there flows to taps (not shown). Thus the water in the hot water system is heated directly by the heat source 3.

The boiler 1 is activated when the temperature of water flows through the heat exchanger 7, or the heat exchanger 11, falls below a predetermined limit. Thus, the boiler is actuated when the pump 6 pumps cool water through the heat exchanger 7, or when a hot tap is turned on to cause water to flow through the second heat exchanger 11.

It is to be appreciated that, whilst Figure 1 illustrates a first type of a combination boiler 1, there are alternative types of combination boiler which are illustrated in Figures 2 and 3.

Referring to Figure 2, a combination boiler 1 is shown in which like components from Figure 1 are given identical numbers. In this embodiment of a water heating means, a domestic heating system 4 is again provided, comprising a circuit through which water is pumped by pump 6 from a cool water inlet pipe 5 and through a first heat exchanger 7. However, the water flows through the second heat exchanger 11, which is located within the casing, and which is connected in series with the first heat exchanger 6 before the water flows through a hot water outlet pipe 8. The heat exchanger 7 of the domestic heating system is, as in the previous embodiment, within the casing 2, adjacent the heat source 3, so as to receive heat directly from the heat source.

The second heat exchanger is also within the casing 2 but is not adjacent the heat source 3. In this embodiment, in the hot water system 9, water flows firstly through a cold water inlet pipe 9, then through the second heat exchanger 11, and then the water passes through the hot water supply pipe 12.

In the second heat exchanger 11 there is a transfer of heat from the hot water in the domestic heating system 4 to the water of the hot water system 8. Thus the water which flows through the hot water system 8 is heated only indirectly by the heat source 3.

A controlled diverter valve 13 is provided in the hot water outlet pipe 8 of the second heat exchanger 11 which is connected to a pipe which leads directly to the cool water inlet to the first heat exchanger 7. The diverter valve 13 may cause the water in the heating system to flow solely through the heat exchangers 7 and 11 so that heat from the heat source 3 is directed preferentially to the hot water supply.

Referring to Figure 3 of the drawings, a further embodiment of a combination boiler 1 is shown. Like components from the previous two embodiments are given identical numbers in this embodiment. Functionally this embodiment is identical to the embodiment of Figure 2, except that the heat exchanger 11 is not within the casing of the boiler, but may be located at any convenient position outside the boiler.

It is to be appreciated that the three embodiments of a combination boiler described above will provide a means for supplying hot water at mains pressure suitable for use in the invention.

Referring now to Figure 4 of the accompanying drawings, a water heating arrangement 14 is illustrated. The water heating arrangement incorporates a boiler 15 which is illustrated as being equivalent with the boiler shown in Figure 2, with the diverter valve causing the water in the heating system to flow solely through the heat exchanger.

The boiler 15 incorporates a first heat exchanger 16 which receives heat from a heat source, and a second heat exchanger 17. Water is pumped solely between the heat exchanger 16 and 17 by means of a pump 18.

The heating arrangement 14 has a cold water inlet 19, the cold water inlet 19 being connected to the inlet of a pump 20, the outlet of the pump 20 being connected to a cold water inlet of the heat exchanger 17. A hot water outlet of the heat exchanger 17 is connected to an outlet a pipe 21, which extends to a tap.

A spur pipe 23 from the inlet pipe 19, which extends from the water inlet pipe 19 at a point up-stream from the pump 20, extends through the base of an insulated storage tank 24. The spur pipe 23 terminates within the storage tank 24 just above the base immediately adjacent a point on the side wall of the storage tank where a thermostatic switch 25 is provided on the exterior of the storage tank. The thermostatic switch 25 is responsive to a fall in temperature below a predetermined threshold. The thermostatic switch 25 is connected, by means of a cable 26, to the pump 20, and activates the pump 20 when the temperature sensed by the thermostatic switch 25 falls below the threshold.

A re-circulation pipe 26 is provided which is connected to the outlet pipe 21 connected to the water outlet of the heat exchanger 17. The recirculation pipe 26 incorporates a non-return valve 27 and extends into the storage tank 24.

A hot water exit pipe 28 is provided which has an open end within the hot water storage tank 24 adjacent the top of the hot water storage tank 24. The hot water exit pipe 28 is provided with a thermostatically controlled valve 29.

The thermostatically controlled valve 29 is controlled by a thermostat 30 which is connected to an upper part of the storage tank 24. The hot water exit pipe 28 is connected to the outlet pipe 21. In the illustrated embodiment the connection of the re-circulation pipe 26 with the outlet pipe 21 is located between the heat exchanger 17 and the connection of the exit pipe 28 and the outlet pipe 21.

In use of the water heating arrangement 12 there are three possible states, as shown in Figures 5 to 7.

Firstly, as shown in Figure 5, there is the state in which there is no demand for hot water via the hot water outlet pipe 21. In this state, if the thermostatic switch 25 is below a predetermined temperature, the pump 20 is activated. When the pump 20 is actuated water flows from the outlet of the pump 20 through the cold water inlet of the heat exchanger 17, through the heat exchanger and out of the hot water outlet of the heat exchanger, and thus through part of the pipe outlet 21. The water then flows through the recirculation pipe 26, past the non-return valve 27 and into the hot water storage tank 24. Water also flows from the hot water storage tank through the spur pipe 23 and thus to the inlet of the pump 20. As the water flows through the heat exchanger 17, the water is heated.

This flow will continue until the thermostat 25, which is located adjacent the base of the tank 24, senses that the temperature has risen above a predetermined threshold. Under the control of the thermostat the pump will be stopped and thus the described flow stops.

Although the storage tank 24 is thermally insulated, the temperature of water within the tank will gradually fall. The warmer water will stay towards the top of the storage tank and the cooler water will amass in the lower part of the storage tank. The temperature sensed by the thermostat 30 will be such that the thermostat valve 29 will be open. When the temperature sensed by the thermostat 25 falls below the predetermined threshold, the pump 20 will again be activated.

It is to be appreciated that when the pump 20 is activated, cool water will be caused to flow into the inlet of the heat exchanger 17, causing the temperature of the heat exchanger 17 to fall. Thus the pump 18 within the boiler will be activated causing water to circulate between the heat exchanger 16 and the heat exchanger 17. If the temperature of the heat exchanger 16 falls below a predetermined threshold, the heat source present within the boiler 15 will be activated.

It is to be appreciated that the water in the hot water storage tank 24 is thus maintained at a substantially constant temperature. The temperature of water in the tank may be relatively high as the water in the tank may be circulated through the heat exchanger several times until the water has reached the maximum practicable temperature.

Should a hot tap connected to the water outlet pipe 21 be turned on, a second state is reached, which is illustrated in Figure 6. In the second state, water will flow out of the cold mains supply and will pass inwardly through the inlet pipe 19, and hot water will flow out of the outlet pipe 21. Some of the water flowing through the inlet pipe 19 will pass through the spur pipe 23 and into the hot water storage tank 24. Simultaneously, because the thermostatic valve 29 will be open, water will flow, from the hot water storage tank 24, through the hot water exit pipe 28 and through the hot water outlet pipe 21.

As the cold water from the spur pipe 23 enters the hot water storage tank 24, the temperature in the vicinity of a thermostatic switch 25 will fall, and the thermostatic switch 25 will close thus activating the pump 20. Cold water from the cold water inlet pipe 19 is then also directed to flow through the pump 20 and consequently into the cold water inlet of the heat exchanger 17. As the cold water flows through the heat exchanger 17, it is heated. The heated water flows through the hot water outlet of the heat exchanger 17 to flow through the hot water outlet pipe 21, where it is joined by water flowing from the tank through the hot water exit pipe 28.

Thus, in the second state, some of the water flowing through the cold water inlet is directed to the storage tank displacing hot water which flows through the hot water outlet, and the remainder of the water flowing through the cold water inlet flows through the heat exchanger 17, that water being heated and being directed to the hot water outlet. Thus, a substantial flow rate is achieved at the hot water outlet, and the water supplied is at a relatively high temperature.

If water continues to flow through the outlet pipe, a third state may be reached, as shown in Figure 7. When the store of hot water within the tank is displaced, so that cold water is present in the upper part of the storage tank adjacent the thermostat 30, the thermostat 30 will respond by closing the thermostatically controlled valve 29. The thermostat 30 is so located that the thermostat 30 will close the thermostatically controlled valve 29 before any cold water from the storage tank starts to flow downwardly through the hot water exit pipe 28.

When the thermostatically controlled valve 29 is closed, if there is still a demand from hot water through the hot water outlet pipe 21, the heating system enters a third state. In the third state, the pump 20 is still activated, because the water in the tank 24, adjacent the thermostatically controlled switch 25 is at a low temperature. Thus water flowing through the inlet 19 is directed through the heat exchanger 17 where the water is heated, and the heated water flows out through the outlet pipe 21. Because the valve 29 is closed, no water can flow from the tank 24 through the hot water exit pipe 28 and the non-return valve 27 prevents water flowing out of the tank 24 through the re-circulation pipe 26.

Thus, it is only water that has passed through the heat exchanger 17 that flows out through the hot water outlet pipe 21 when the arrangement is in the third state. The rate of flow of water will fall, as compared with when the arrangement is in the second state, but the water will still be at an appropriate high temperature.

It is thus to be appreciated that in utilising the hot water arrangement as illustrated in Figures 4 to 7, when a tap is turned on, initially there will be a relatively high flow rate of very hot water, with the hot water coming from the storage tank and from the heat exchanger within the boiler, and when the supply of hot water within the hot water storage tank is exhausted, there will still be a flow of hot water, but that flow will comprise only water that has passed through the heat exchanger 17.

When the demand for hot water ceases, the apparatus will re-enter the first state. The pump 20 will operate causing water to circulate through the heat exchanger 17 and past the non-return valve 27, into the storage tank 24.

This flow of water will continue until the temperature of the water within the storage tank again reaches the predetermined threshold at which the thermostatically controlled switch 25 ceases operation of the pump 20.

Figure 8 illustrates a modified embodiment of the invention in which the hot water discharge pipe 28 is connected to a point adjacent the upper-most part of the hot water storage tank 24 by means of a wax thermostatic valve 31. In a wax valve a change of state of the wax, as a consequence of a change of temperature, causes a movement which actuates the valve. The wax thermostatic valve 31 is open whenever there is hot water present at the top of the storage tank 24 and closes whenever there is cold water present at the top of the hot water storage tank ; 24. The remaining parts of the arrangement shown in Figure 8 are the same as the corresponding parts of the arrangement shown in Figure 4, and the arrangement shown in Figure 8 operates in the same way as the arrangement shown in Figure 4 with the wax thermostatic valve 31 normally being open when the contents of the storage tank are hot and being closed as soon as cold water reaches the top of the hot water storage tank 24, at the end of the second state of operation of the arrangement.

Claims

CLAIMS: 1. A water heating arrangement comprising a heat exchanger having an inlet pipe for mains pressure cold water and having an outlet pipe to be connected to a hot water tap, the heat exchanger being adapted to receive heat from the heat source of a combination boiler, either directly or indirectly; the inlet pipe and the outlet pipe being in fluid communication with a hot water storage tank, pump means being provided so that, in a first state, water may circulate between the heat exchanger and the storage tank in a closed loop, the water being heated as it passes through the heat exchanger; the arrangement also comprising thermostatically controlled means so that when said hot water tap is opened the arrangement is initially in a second state, in which water from the inlet pipe flows through the heat exchanger and out of the outlet pipe and also water from the inlet pipe flows into the storage tank so that hot water from the storage tank flows to the outlet pipe; the thermostatically controlled means being such that a third state is subsequently entered in which the flow of water from the inlet pipe passes solely through the heat exchanger and out of the outlet pipe, with the flow of water from the storage tank being halted.
2. An arrangement according to Claim 1 wherein a spur pipe which branches from the inlet pipe extends to the said hot water storage tank, and the storage tank is provided with an exit pipe which is connected to said outlet pipe, the thermostatically controlled means being present in the exit pipe, there being a re-circulation pipe connected to the outlet pipe, the re-circulation pipe extending into the hot water storage tank, a pump being provided to circulate water through the head exchanger and through the outlet pipe and the re circulation pipe into the tank and thus through the spur pipe and part of the inlet pipe back to the heat exchanger again.
3. An arrangement according to Claim 2 wherein the re-circulation pipe is provided with a non-return valve.
4. An arrangement according to any one of the preceding claims wherein the thermostatically controlled means comprise a thermostatically controlled valve in the exit pipe, the valve being adapted to close when the temperature of water flowing through the valve falls.
5. An arrangement according to Claim 4 wherein the thermostatically controlled valve comprises a solenoid valve in the exit pipe controlled by a thermostat attached to the tank.
6. An arrangement according to Claim 4 wherein the thermostatically controlled valve is a wax valve.
7. An arrangement according to Claim 2 or 3 wherein the re-circulation pipe is configured to direct water flowing through the re-circulation pipe into the hot water storage tank against a wall of the hot water storage tank, a thermostatic switch being provided on the exterior of the hot water storage tank at that point, the thermostatic switch being adapted to activate the combination boiler in response to a fall in the temperature sensed by the thermostatic switch.
8. An arrangement according to Claim 7 wherein the thermostatic switch actuates the pump.
9. A water heating arrangement substantially herein described with reference to and as shown in the accompanying drawings.
10. Any novel feature or combination of features disclosed herein.