GB2428285A

GB2428285A - Instantaneous water heater control

Info

Publication number: GB2428285A
Application number: GB0514292A
Authority: GB
Inventors: Phil Capon
Original assignee: Aqualisa Products Ltd
Current assignee: Aqualisa Products Ltd
Priority date: 2005-07-12
Filing date: 2005-07-12
Publication date: 2007-01-24
Anticipated expiration: 2025-07-12
Also published as: GB2428285B; GB0514292D0

Abstract

The apparatus includes a cold water inlet 2, a hot water outlet 4, and a heater can 6 with an upstream end 10 and a downstream end 16. The heater can defines a heater flow path from the upstream end to the downstream end to heat water according to the flow rate of water through the heater flow path. An over-temperature valve 24 enables an additional flow of cold water from the cold water inlet to the upstream end of the heater can in response to the temperature of water in the heater flow path of the heater can exceeding a predefined normal working range. A temperature control valve 18 is located between the cold water inlet and the hot water outlet for adjusting the flow rate of water through at least one flow path between the cold water inlet and the hot water outlet so as to adjust the temperature of water at the hot water outlet. The apparatus may be used in a method of protecting a heater can from overheating.

Description

INSTANTANEOUS WATER HEATER

The present invention relates to an instantaneous water heater and a method of protecting a heater can of an instantaneous water heater from overheating.

Instantaneous water heaters are well known having heater cans for heating water. The heater cans receive a supply of cold water at an upstream end and provide hot water from their downstream end. The heater can is provided with a power source, such as an electric heater coil, within the flow path of the heater can and the outlet temperature is determined by the rate of flow of water.

Where the user reduces the flow rate unduly, the outlet temperature can rise unacceptably.

To overcome this problem, it has been proposed, in response to temperatures detected at the outlet of the heater can, to introduce additional cold water at the downstream end of the heater can. In this way, the temperature of the water provided at the hot-water outlet of the instantaneous water heater is reduced to an acceptable level. It will be appreciated, however, that the temperature within the heater can still rises excessively.

It is also known to provide a temperature sensor in or immediately adjacent the heater can and to shut down the instantaneous water heater in response to detected high temperatures.

Two stages of thermal protection are known. The first stage is to stop the shower from exceeding a predefined temperature of, for example 55 C, for a period of time (self- resetting). The second stage (permanent) is set at much higher level in order to stop the unit from burning, for instance in the event of a switch failure. The first stage can be very inconvenient for the user and, furthermore, has been found not to be responsive enough. It often allows temperature spikes way in excess of the predefined (55 C) temperature.

It is an object of the present invention to provide a system that reduces excessive temperatures in the heater can and provides protection for the user.

According to the present invention, there is provided a method of protecting a heater can of an instantaneous water heater from overheating, the heater can having a heater flow path extending from an upstream end to a downstream end, the heater flow path heating water according to flow rate of water through the heater flow path, the method including: providing an additional flow of cold water from a cold water inlet of the instantaneous water heater to the upstream end of the heater can in response to the temperature of water in the heater flow path of the heater can exceeding a predefined normal working range.

According to the present invention, there is also provided an instantaneous water heater including a cold-water inlet; a hot-water outlet; a heater can having an upstream end connecting with the coldwater inlet and a downstream end connecting with the hot-water outlet, the heater can defining a heater flow path from the upstream end to the downstream end and being arranged to heat water in the heater flow path according to the flow rate of the water through the heater flow path; a temperature control valve between the cold-water inlet and the hot-water outlet for adjusting a flow rate of water through at least one flow path between the cold-water inlet and the hot-water outlet so as to adjust the temperature of water at the hot-water outlet; and an over-temperature valve for enabling additional flow of cold water from the cold-water inlet to the upstream end of the heater can in response to the temperature of water in the heater flow path of the heater can exceeding a predefined normal working range.

Hence, when the outlet temperature rises excessively, additional cold water is provided to the upstream end of the heater can such that there is an additional flow of water through the heater can and the overall heating effect of the heater can is reduced. In this way, not only is the outlet temperature reduced for the safety of the user, but the temperature of water within the heater can is reduced for the safety of the heater can itself The present invention can be provided in addition to either or both of the two stages of thermal trip mentioned above. It has the added advantage of improving the life of the heater element.

The temperature control valve can be arranged to control temperature by varying a mix of water from the downstream end of the heater can and from the cold-water supply directly.

Although this might indirectly vary the flow rate of water through the heater can, it is also possible to provide arrangements where the temperature control valve only varies the flow rate of water through the heater can. The temperature control valve could be positioned upstream or downstream of the heater can and water from the heater can may optionally be mixed with water directly from the cold-water supply.

Preferably, the temperature control valve includes a valve portion for varying the flow rate of water in the heater flow path and the overtemperature valve selectively connects an upstream side of the valve portion to a downstream side of the valve portion so as to bypass the valve portion and enable additional flow of water through the heating flow path.

The valve portion of the temperature control valve will limit the flow of water through the heater flow path. By bypassing that valve portion with the over-temperature valve, additional flow is provided through the heater can, thereby reducing the water temperature at the downstream end of the heater can.

Although the valve portion could be located at the downstream end of the heater can, preferably, the valve portion is connected between the coldwater inlet and the upstream end of the heater can and is arranged to control the flow of cold water from the cold-water inlet to the heater can. Preferably, then, the over-temperature valve selectively connects the cold-water inlet to the upstream end of the heater can so as to bypass the valve portion and enable additional flow of cold water from the cold-water inlet to the upstream end of the heater can.

With additional cold water supplied to and flowing through the heater can, the temperature of water in the heater can and at its downstream end will be reduced.

Preferably, the instantaneous water heater further includes a flow controller having first and second chambers with respective first and second ports, the valve portion and the over- temperature valve both being formed as part of the flow controller and each individually connecting selectively the first and second chambers.

Flow of water to or from the heater can passes between the first and second ports via the first and second chambers. The valve portion of the temperature control valve varies this flow by controlling flow between the first and second chambers. However, the over- temperature valve can separately connect the first and second chambers so as to bypass the valve portion and allow additional flow to or from the heater can.

Preferably, the instantaneous water heater further includes a thermomechanical actuator in thermal contact with water in the heater flow path and providing movement in response to temperature changes of water in the heater flow path, a connecting mechanism for transferring the movement of the thermomechanical actuator to the over-temperature valve such that the over-temperature valve selectively enables additional flow of control water to the upstream end of the heater according to movement of the thermomechanical actuator.

Although the over-temperature valve could be operated electrically in response to detected temperatures, use of the thermomechanical actuator and connecting mechanism provides a simple and reliable means of operation.

The thermomechanical actuator may be a wax-stat.

It is possible for the over-temperature valve merely to switch between closed and open states. However, preferably, the over-temperature valve is arranged to enable varying amounts of additional flow of cold water according to the extent by which the temperature of water in the heater flow path of the heater can exceeds the predefined normal working range.

In this way, as the temperature of water in the heating flow path starts to exceed the predefined normal working range, the over-temperature valve acts to reduce it to a predetermined temperature, usually the upper limit of the normal working range. As the temperature continues to rise, so the over-temperature valve continues to open more. By means of the feedback ioop formed in this way, the over-temperature valve can operate to stabilise the temperature at the predetermined temperature.

Preferably, the over-temperature valve comprises walls defining a valve opening and a conical valve member movable axially within the valve opening so as to create a space between the walls and the valve member of variable cross-sectional area.

This is a convenient and effective way of variably controlling the additional amount of water flowing through the heater can.

It will be appreciated that the over-temperature valve is closed and inoperative whilst the temperature of water in the heater flow path of the heater can is within the predefined normal working range.

Preferably, the temperature control valve is operable by a user to select a required water temperature at the hot-water outlet.

The temperature control valve may be operated manually by the user or by a control system operating in response to a temperature selected by the user.

The temperature control valve may be responsive to a temperature sensor to adjust the flow rate through said at least one flow path to maintain a selected water temperature at the hot-water outlet.

Preferably, the temperature control valve adjusts the temperature of water at the hot-water outlet by adjusting the flow rate of water along the heating flow path.

Preferably, the heater can includes an electric heating coil within the heating flow path.

The invention will be more clearly understood from the following description, given by way of example only, with reference to the accompanying drawings, in which: Figure 1 illustrates an instantaneous water heater according to the present invention; Figure 2 illustrates a flow controller for use in an instantaneous water heater; and Figures 3(a) to (d) illustrate various alternative arrangements.

In one type of instantaneous water heater, all of the flow passes through the heater can and the outlet temperature is controlled merely by controlling the flow rate through the instantaneous water heater and, hence, the heater can. A preferred embodiment of the present invention is illustrated in Figure 1 as part of a schematic representation of such an instantaneous water heater.

The instantaneous water heater has a cold-water inlet 2 and a hot-water outlet 4. A heater can 6 is provided for heating the water flowing from the cold-water inlet 2 to the hot-water outlet 4. In the illustrated embodiment, the heater can 6 is provided with a outlet duct 8.

The outlet duct 8 defines, with the inner walls of the heater can 6, a heater flow path which extends from an upstream end 10 at the bottom of the heater can 6 (as illustrated in Figure 1) to an intermediate portion 12 at the top of the heater can 6 (as illustrated in Figure 1). In the illustrated embodiment, this heater flow path has an annular form around the outside of the outlet duct 8. The annular space outside the outlet duct 8 and inside the inner walls of the heater can 6 contain an electric heater coil 14. Hence, water flowing from the upstream end 10 of the heater can 6 to the intermediate portion 12 is heated by the electric coil 14.

As illustrated, the heater flow path then continues back down through the outlet duct 8 to a downstream end 16 of the heater can 6. However, since most of the heating occurs between the upstream end 10 and the intermediate portion 12 of the heater can 6, the intermediate portion 12 of the heater can 6 could be considered as the downstream end.

A temperature control valve 18 is provided for varying the flow rate of water along the heater flow path and, hence, varying the outlet temperature. In the illustrated embodiment, two conical valves 20a, 20b engage with opposite sides of a pinion 22. When the pinion 22 is rotated in one angular direction, the two conical valves 20a, 20b are moved linearly in opposite directions so as to open and both provide additional flow from the inlet 2 to the upstream end 10 of the heater can 6. By rotating the pinion 22 in the opposite angular direction, the two conical valves 20a, 20b close and reduce the flow from the inlet 2 to the upstream end 10 of the heater can 6.

As illustrated, in addition to the temperature control valve 18, an overtemperature valve 24 is provided between the cold-water inlet 2 and the upstream end 10 of the heater can 6.

By opening this over-temperature valve 24, an additional flow of cold water is provided from the cold-water inlet 2 to the upstream end 10 of the heater can 6. The rate of flow of water along the heater flow path past the coil 14 thus increases and the outlet temperature is reduced. The over-temperature valve 24 is able selectively to bypass the temperature control valve 18.

In the heater can 6, a thermomechanical actuator 26, such as a wax-stat, is provided.

A connecting mechanism 28, in this case, a simple rod, transfers movement of the thermomechanical actuator 26 to the over-temperature valve 24.

In the illustrated embodiment, the thermomechanical actuator 26 is positioned at the downstream end of the outlet duct 8, which might be considered to be substantially the downstream end of the heater can 6. The thermomechanical actuator 26 is arranged to provide movement in response to the temperature. In this embodiment, when the thermomechanical actuator 26 is exposed to a predetermined temperature above the predefined normal operating range of the heater can 6, it moves sufficiently to open the over-temperature valve 24 so as to allow additional flow of cold water through the heater flow path and hence reduce the outlet water temperature. As illustrated, the over- temperature valve is formed from a conical valve member 30 in a valve seat defined, for instance, by an 0-ring 32. A space may be formed between the conical valve member 30 and the 0-ring 32 and the cross- sectional area of this space varies with axial movement of the conical valve member 30. By varying the amount by which the over-temperature valve 24 opens in this way, a feedback loop is formed. In particular, as the thermomechanical actuator 26 is subjected to temperatures that exceed the predetermined temperature by greater amounts, the over-temperature valve will open more so as to allow a greater flow of cold water through the heater flow path of the heater can 6 and, hence, a greater cooling effect.

The arrangement thus tends to stabilise the outlet water temperature at the predetermined temperature.

The flow regulator (core) consists of 2 distinct portions. The first is a smooth cylinder which creates a seal against the flow regulating 0 ring. The second is a grooved portion where the grooves start shallow (low flow) and become progressively deeper (higher flow).

The valve remains sealed until the actuator (waxstat) has expanded by eg 1 mm or more.

The advantage of this is that the valve can be exercised by up to 1mm (shuffling slightly without adding water) within the normal showering temperature range of the product. In order to do this, the temperature at which the waxstat starts to move is typically a few degrees lower than the predetermined maximum working temperature of the shower. This helps to reduce problems due to stiction if the valve remains closed for long periods of time.

It will be appreciated that the temperature control valve and the overtemperature valve could be provided together as part of a flow controller separate to the heater can. This is illustrated in Figure 2.

The flow controller 40 includes a first port 42 to a first chamber 44 and a second port 46 to a second chamber 48. Both the temperature control valve 18 and the over-temperature valve 24 connect the first and second chambers. The flow controller can be used to control flow through the heater flow path of a heater can as described above.

The over-temperature valve can be used in other similar arrangements. Figures 3(a) to (d) illustrate schematically various alternatives.

In the arrangement of Figure 3(a), a heater can 106 is fed at its upstream end with cold water from a first valve 150 of the temperature control valve 118 with an over-temperature valve 124 connected as described above. In this arrangement, water from the downstream end of the heater can 106 is mixed with cold water supplied via a second valve 152 of the temperature control valve 118. The first valve 150 and second valve 152 of the temperature control valve 118 act to provide a mixed supply of hot and cold water at the outlet, but the over-temperature valve 124 is still effective to allow additional cold water through the heater can 106 when necessary.

In the arrangement of Figure 3(b), flow through the heater can 206 is controlled by a temperature control valve 218 at its downstream end. An over-temperature valve 224 is provided for bypassing the temperature control valve 218. It will be appreciated that, when the over-temperature valve 224 opens, flow increases through the heater can 206 such that additional cold water flows in through its upstream end.

Figure 3(c) illustrates an arrangement similar to that of Figure 3(b), but including an additional cold-water flow path which mixes with water from the heater can 206. The cold-water feed to the mixed output is preferably restricted. This may take the form of a valve which operates in conjunction with the valve on the hot-water outlet as part of the temperature control valve.

Figure 3(d) illustrates an arrangement where cold water is fed to the upstream end of the heater can 306 and to a mixer valve forming the temperature control valve 318. Hot water from the heater can 306 is also fed to the mixer valve 318. The over-temperature valve is provided to connect selectively the downstream end of the heater can 306 with the outlet of the instantaneous water device so as to bypass the mixer valve 318 of the temperature control valve 318. When the over-temperature valve 324 opens, it allows additional flow through the heater can 306 and thereby enables an additional flow of cold water into the upstream end of the heater can 306.

Claims

1. An instantaneous water heater including: a cold-water inlet; a hotwater outlet; a heater can having an upstream end connecting with the cold-water inlet and a downstream end connecting with the hot-water outlet, the heater can defining a heater flow path from the upstream end to the downstream end and being arranged to heat water in the heater flow path according to the flow rate of the water through the heater flow path; a temperature control valve between the cold-water inlet and the hotwater outlet for adjusting a flow rate of water through at least one flow path between the cold-water inlet and the hot-water outlet so as to adjust the temperature of water at the hot-water outlet; and an over-temperature valve for enabling additional flow of cold water from the cold- water inlet to the upstream end of the heater can in response to the temperature of water in the heater flow path of the heater can exceeding a predefined normal working range.

2. An instantaneous water heater according to claim 1 wherein: the temperature control valve includes a valve portion for varying the flow rate of water in the heater flow path; and the over-temperature valve selectively connects an upstream side of the valve portion to a downstream side of the valve portion so as to bypass the valve portion and enable additional flow of water through the heater flow path.

3. An instantaneous water heater according to claim 2 wherein: the valve portion is connected between the cold-water inlet and the upstream end of the heater can and is arranged to control the flow of cold water from the cold-water inlet to the heater can; and - 12 - the over-temperature valve selectively connects the cold-water inlet to the upstream end of the heater can so as to bypass the valve portion and enable additional flow of cold water from the cold-water inlet to the upstream end of the heater can.

4. An instantaneous water heater according to claim 2 or 3 further including: a flow controller having first and second chambers with respective first and second ports, the valve portion and the overtemperature valve both being formed as part of the flow controller and each individually connecting selectively the first and second chambers.

5. An instantaneous water heater according to any preceding claim further including: a thermomechanical actuator in thermal contact with water in the heater flow path and providing movement in response to temperature changes of water in the heater flow path; and a connecting mechanism for transferring said movement of the thermomechanical actuator to the overtemperature valve such that the over-temperature valve selectively enables additional flow of cold water to the upstream end of the heater according to movement of the thermomechanical actuator.

6. An instantaneous water heater according to claim 5 wherein: the thermomechanical actuator is a wax-stat.

7. An instantaneous water heater according to any preceding claim wherein: the over-temperature valve is arranged to enable varying amounts of additional flow of cold water according to the extent by which the temperature of water in the heater flow path of the heater can exceeds the predefined normal working range.

8. An instantaneous water heater according to claim 7 wherein the valve comprises: walls defining a wall opening and a conical valve member movable axially within the valve opening so as to create a space between the walls and the valve member of variable cross-sectional area.

- 13 -

9. An instantaneous water heater according to any preceding claim wherein: the over-temperature valve is closed and inoperative whilst the temperature of water in the heater flow path of the heater can is within the predefined working range.

10. An instantaneous water heater according to any preceding claim wherein: the temperature control valve is operable by a user so as to select a required water temperature at the hot-water outlet.

11. An instantaneous water heater according to any preceding claim wherein: the temperature control valve is responsive to a temperature sensor to adjust the flow rate through said at least one flow path to maintain a selected water temperature at the hot-water outlet.

12. An instantaneous water heater according to any preceding claim wherein: the temperature control valve adjusts the temperature of water at the hot-water outlet by adjusting the flow rate of water along the heater flow path.

13. An instantaneous water heater according to any preceding claim wherein: the heater can includes an electric heating coil within the heater flow path.

14. A method of protecting a heater can of an instantaneous water heater from overheating, the heater can having a heater flow path extending from an upstream end to a downstream end, the heater flow path heating water according to flow rate of water through the heater flow path, the method including: providing an additional flow of cold water from a cold water inlet of the instantaneous water heater to the upstream end of the heater can in response to the temperature of water in the heater flow path of the heater can exceeding a predefined normal working range.

15. An instantaneous water heater constructed and arranged substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.

16. A method of protecting a heater can substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.