GB2442066A - Water heater with temperature control - Google Patents

Abstract

The water heater 10 includes a container 11 in which to store water. The container is provided with a water inlet 14 and a water outlet means 19, a heating element 17, activated by a control element, to raise the temperature of the water and a temperature measuring device. The heater includes a pressure sensor 22 to measure the atmospheric pressure and communicate the measured pressure to a calculation means 21 to calculate the boiling point of the water. A data linkage transmits the calculated boiling point to the control element. The control element maintains the water temperature at a preset temperature difference below the determined boiling point. The temperature measuring device may be a thermistor and more than one heating element with differing power ratings may be used.

Description

AN IMPROVED WATER HEATER

Field of the Invention

The present invention relates to a water heater to maintain a body of water at a predetermined temperature. The heaters contemplated are particularly suited for storing and dispensing drinking water at a temperature close to, but below the boiling point.

Back2round to the Invention Water heaters which provide a ready supply of hot water suitable for preparing beverages such as tea or coffee are established items in the workplace and at functions such as conferences or large meetings. Such heaters normally provide a reservoir of waler sufficient to supply the requirements of those present without recourse to continually having to boil a kettle.

A disadvantage of such heaters is however the need to maintain the water at a relatively consistent temperature close to the boiling point of water. Too low a temperature can impact the quality of the drink produced. A temperature above the boiling point can cause a dangerous situation to arise due to excess pressure from steam and is moreover wasteful of energy as a large amount of energy is required to convert water from the liquid to the vapour state.

Provision is therefore often made to contain any excess pressure and to include further safety features to ensure that the heaters do not become dangerous. For example, where steam is or may be present, then outlets are normally below the level of the hot water as otherwise steam might be drawn off and discharged through the outlet due to its lower density. Of course the facility to be able to draw off steam is actively used on certain devices such as are used in the preparation of drinks such as cappuccinos or expressos. -2..

Even when the safety considerations have been dealt with, the presence of steam often causes water discharge to be noisy. Moreover, uneven flow of water can occur due to pockets of gas or vapour within the liquid.

To ameliorate the above problems, pumps can be included in the heater to assist water flow, but this leads to an increase in the complexity and cost.

It would be advantageous therefore to provide a heater which addresses the above problems and allows for heaters which are quieter and which are more easily installed.

Summary of the Invention

According to the invention there is provided a water heater comprising; a container in which to store water, the container being provided with a water inlet and a water outlet means; a heating element, activated by a control element, to raise the temperatuie of the water; a temperature measuring device, and characterised in that the heater includes a pressure sensor to measure the atmospheric pressure, a calculation means to calculate the boiling point of the water from the measured pressure, communication means to pass the calculated boiling point to the control element to control the water temperature to below the determined boiling point.

The monitoring of the pressure provides a safe means of retaining the water close to its boiling point.

Preferably the temperature measuring device is a thermistor to provide rapid indication of temperature change which change can readily be forwarded to the control element.

Optionally, the heating element includes a plurality of heating devices, which further optionally are of differing power ratings.

Preferably, the container is surrounded by a layer of insulation.

Advantageously the outlet draws water from the upper regions of the water in the container, as this water is typically the hottest. Particularly advantageously the outlet is located above the level of the water in the container which allows for more compact heaters and also more flexibility in the location of the heater.

The pressure device preferably comprises an electronic chip to measure the pressure, which provides a reliable and means of accurately measuring the pressure and facilitates communication of the information to the calculation means.

Optionally, the heater includes means to determine the hardness of the water in the container. This allows for a more accurate calculation of the boiling point.

Brief Description of the Drawings

The invention will now be described with reference to the accompanying drawings which show by way of example only, one embodiment of a heater. In the drawings: Figure 1 is a perspective view of a heater; Figure 2a and 2b are respectively a side view and a top view of a heater; and Figure 3 is a section through A-A of Figure 2b.

Detailed Description of the Invention

Referring initially to Figure 1 a heater generally referenced 10 is shown which is suitable for maintaining water at a temperature just below its boiling paint.

It will be appreciated that the design of the outer tank is merely illustrative and that other configurations can be used without departing from the scope of the invention. Heaters within the scope of the invention are suitable for domestic use but find particular application when catering for large numbers such as in an office environment or in a conference facility. It is important that a reservoir of water at the correct temperature is readily available for use.

The heater 10 shown in the Figures has a tank 11 usually formed of metal to retain water. The tank 11 is open at one end which opening is covered by a sealing plate 12, sealed in position by conventional means such as nuts and bolts or rivets 13.

Where required, the tank wall is insulated, for example by including a vacuum within the wall to retain heat in the tank 11.

Water is introduced into the tank 11 through an inlet pipe 14, with the first end 15 of the pipe 14 being connected to the domestic water supply to enable the volume of water in the tank 11 to be replenished when required.

As is common for certain types of water heater, water exits the pipe 14 through one or more holes 16 in the pipe 14, said holes 16 being situated towards the bottom of the tank 11. The incoming cold water from the water supply does not therefore cool down the hottest water at the top of the tank 11, which in the present invention can be drawn directly by the user.

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If required, the pipe 14 can be insulated or formed of a material of low co-efficient of heat conduction to ensure that cooling of the upper regions of the water is kept to a minimum.

In order to heat the water a heating element 17 is included and is located within the body of the water. The element 17 is electrically powered and of a resistance type. In the embodiment shown, the element 17 has a U-shaped configuration, but the particular shape can be tailored for the heater 10 in which the element is to be installed.

An outlet pipe 18 enables hot water to be drawn from the tank 11. Control of the water outlet is provided by an outlet tap or valve 19 so that the desired amount of hot water can be removed.

In order to control the temperature of the water, the heating element 17 is connected to and controlled by a control system. The control system includes a number of features to ensure that water is retained within the heater 10 close to the desired temperature. The water can thereby be delivered, if required, close to the boiling point of water.

A first feature of the control system is a thermometer 20, which passes through the tank 11 and measures the temperature of the water within the tank 11.

Typically the thermometer 20 is located such that it measures the temperature around the mid-point of the depth of the tank 11. The temperature in this region should give an indication of the mean overall temperature of the water, although it is recognised that the water at the top and the bottom of the tank 11 is likely to be hotter and colder respectively compared to the mean temperature.

The thermometer 20 is a resistance thermometer such as a thermistor. The temperature is therefore obtained as an electrical signal which is passed to an integrated circuit processor 21 through the connection 25.

The control system further includes a pressure sensor 22 integrated into a semi conductor chip which is mounted on a printed circuit board 24. The pressure sensor 22 determines the pressure of the ambient atmosphere around the heater 10. Again the measured pressure is communicated to the processor 21.

The processor 21 performs a number of functions in determining the energy required to be input to the water in the tank 11. Firstly, the information received from the pressure sensor 22 is used to calculate the boiling point of water at the particular pressure under consideration. The boiling point so calculated is used by the processor 21 to control the temperature of the water to a pre-set temperature around 0.1 C below the calculated boiling point. It will be appreciated however, that where required the temperature can be controlled to any desired temperature below the boiling point, suitable for preparing beverages. To achieve the control, the heating element 17 is also under the control of the processor 21 which determines the amotmt of heat required and activates the element 17 accordingly.

To provide a more compact structure, the wires 23 connecting the element 17 to the electricity supply pass through the board 24 on which the processor 21 and pressure sensor 22 are mounted.

By using the above heated water can be stored at pressures of typically from 0.5 bar -10 bar, which allows for widespread use of a single heater design.

The number and power output of the heating elements depends upon the use to which the heater 10 is to be put and the volume of water which the tank 11 can hold. Therefore heaters can be contemplated having a plurality of heating elements: not only to increase the heating output but also to enable heaters to be spread through the water volume to provide more even heating, which is less reliant on convection. Moreover, whcrc a plurality of elements is used, the individual elements can have different power ratings to enable stepwise and more controlled heating to take place and heating which is less likely to impose a too large step change on the load put on the electricity supply.

As the temperature of the boiling point of water also depends upon the salts dissolved in the water, provision can be made to take account of this within the heater. For example, the processor 21 can include information on the water hardness in the particular region in which the heater 10 is to be used. The influence of the hardness is then included in the calculation of the boiling point.

Alternatively, the heater 10 can include a further sensor to determine the calcium or magnesium ion concentration in the water which information is passed to the processor 21. The information is again included in the boiling point calculation.

It will of course be understood that the invention is not limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible within the scope of the invention. .

Claims (10)

1. Claims 1. A water heater comprising; S a container in which to store

   water, the container being provided with a water inlet and a water outlet means; a heating element, activated by a control element, to raise the temperature of the water; a temperature measuring device, and characterised in that the heater includes a pressure sensor to measure the atmospheric pressure, said sensor communicating the measured pressure to a calculation means to calculate the boiling point of the water, a data linkage for transmission of the calculated boiling point to the control element the control element maintaining the water temperature at a preset temperature difference below the determined boiling point.
2. 2. A heater according to Claim 1, wherein the temperature measuring device is a thermistor.
3. 3. A heater according to Claim 1 or Claim 2, wherein the heating element includes a plurality of heating devices.
4. 4. A heater according to Claim 3, wherein the heating elements are of differing power ratings.
5. 5. A heater according to any preceding claim, wherein the container is surrounded by a layer of insulation.
6. 6. A heater according to any preceding claim, wherein the outlet draws water from the upper regions of the water in the container.
7. 7. A heater according to Claim 6, wherein the outlet is located above the level of the water in the container.
8. 8. A heater according to any preceding claim, wherein the pressure sensor comprises an electronic chip to measure the pressure.
9. 9. A heater according to any preceding claim, wherein the heater includes means to determine the hardness of the water in the container.
10. 10. A heater substantially as herein described with reference to and as illustrated by the accompanying drawings.