WO2010031994A2

WO2010031994A2 - An improved water heater

Info

Publication number: WO2010031994A2
Application number: PCT/GB2009/002178
Authority: WO
Inventors: Mark Storey
Original assignee: Baxi Heating (Uk) Limited
Priority date: 2008-09-17
Filing date: 2009-09-14
Publication date: 2010-03-25
Also published as: WO2010031994A3; EP2338006A2

Abstract

A water heater for supplying hot water, to a domestic or office environment, the heater comprising a storage vessel (10) to retain water, a plurality of heating elements (14-16) within the storage vessel said elements (14-16) being spatially separated from each other in a vertical direction; a plurality of temperature sensors (17-19) within the storage vessel (10) measuring the water temperature a heating element (14-16) being associated with at least one sensor (17-19); a control unit operably linked to each element and each sensor, the control unit comprising data receiving means to receive data from the sensors, a storage area to store system data, processing means to compare the sensor data with the system data, a decision making means to determine activation or de-activation of the elements (17-19).

Description

AN IMPROVED WATER HEATER

Field of the Invention

The present invention relates to a water heater for supplying domestic and industrial premises with hot water, for washing or for a central heating system etc. In particular a heater with a control system to monitor and evaluate water usage and to make heating predictions based thereon is disclosed.

Background to the Invention

In the past ten to fifteen years, the consumer has become increasingly concerned about the energy efficiency of household appliances. To satisfy the increased demand for information and guidance on this topic, an energy rating system can frequently be seen by which an appliance is given a rating from A to G, with "A" being the most efficient and "G" the least efficient category.

A rating system is now being devised at European Commission Level for electric hot water systems and a report was presented to the Commission in September 2007. Whilst discussions about the final test parameters still continue, it is likely that one parameter will be an indicator of how the heater copes with different draw-off profiles (also known as tapping patterns): the comparison being against theoretical energy demand. Systems governing the operation of a heater, particularly those which are based on electro-mechanical controls with only limited or no time control are likely to be deemed inefficient and achieve a poor rating. Although water heating systems presently enable a user to choose the temperature of the water in the tank and to set timings so that energy is not expended outside preset times, the control over these parameters has been relatively crude. Moreover the heating applied to a volume of water in a hot water tank acts, in the prior art to heat the whole volume of water to the same temperature.

It is an object of the present invention to provide a hot water tank and a heating system which addresses the above problems.

Summary of the Invention

According to a first aspect of the invention there is provided a water heater for supplying hot water, to a domestic or office environment, the heater comprising a storage vessel to retain water,

a plurality of heating elements within the storage vessel said elements being spatially separated from each other in a vertical direction;

a plurality of temperature sensors within the tank measuring the water temperature a heating element being associated with at least one sensor;

a control unit operably linked to each element and each sensor, the control unit comprising data receiving means to receive data from the sensors, a storage area to store system data, processing means to compare the sensor data with the system data,

a decision making means to determine activation or de-activation of the elements.

The system described is a able therefore, by being able to determine when the water is required and also being able to heat only a fraction of the water within the tank to the hottest designated temperature, to save energy. Optionally, the heater includes further heating elements which are in the same or substantially the same place as said plurality of heating elements.

Conveniently, the heater has three heating elements to provide efficient heating without increasing too far the complexity. Preferably the heating elements are vertically arranged above and below each other to simplify construction.

Brief Description of the Drawings

The invention will now be described with reference to the accompanying drawings which show two embodiments of a heater and system for control therefor. In the drawings:

Figure 1 is a diagrammatic illustration of a tank: Figure 2 is an image of heat distribution within a tank: and

Figure 3 is a diagram of a system for monitoring and controlling temperature

Detailed Description of the Invention

The system described herein acts to optimise the energy usage in dealing with the hot water requirements of a household or premises. In order to achieve this a means of accumulating, storing and processing data is incorporated into the heating circuit of a hot water heater: and the embodiments described, an electric hot water heater. In order to implement the control system advantage has been taken of the surprising discovery that heated water within an electric boiler can accumulate into distinct and measurable layers, each layer being at a different temperature to its neighbour and that, moreover, these layers are stable over an extended time period, at least long enough to assist in lowering energy consumption.

As general background, and to deal with the prevailing supply characteristics in many countries, the systems include a water tank having at least one resistive heating element and where, when a plurality of heating elements is used, these elements are at different levels within the tank. The heating elements are held under the control of a switching system. The switching capability operates under 230-240 single phase AC supply, with each resistive heating element being suitable to take a loading of up to 6kW. In order to comply with, informal, customer standards the system and the component part should be capable of withstanding more than 100,000 switching cycles (not applicable to the over temperature cut out function). In addition other safety measures are included as described below.

The basis on which the heater and heater system operates is now described with reference to Figure 1. The tank 10 is of typical construction, usually of copper or stainless steel, and is housed within a casing 11 to provide the tank 10 with an improved appearance. The casing 11 also facilitates the provision of stable insulating material around the tank 10 to reduce heat loss from the water stored in the tank 10. Also, as with prior art tanks, a cold water inlet pipe 12, through which water from a mains supply enters the tank 10 to replace water drawn off, engages the tank 10 towards the tank's lower portion. A baffle (not illustrated) minimises mixing between the incoming cold water and water already in the tank

10. This facilitates the establishment and maintenance of layers of water of different temperature. A hot water outlet pipe 13 connects the water in the tank 10 with, for example, the hot water taps on the heating system supplied by the tank 10.

The tank 10 is in addition equipped with a plurality of heating elements 14-16, each separately operable to achieve maximum heating efficiency. The heating elements 14-16 are vertically separated from one another so that they each measure the water temperature at a different level of the tank 10. It should be clear that the elements 14-16 need not be directly above and below each other but can be spaced at different points around the tank. Nevertheless for ease of manufacture, the elements 14-16 are typically in line vertically. It should be appreciated that the illustration, using three elements is not to be interpreted in a restrictive manner but as illustrative of the principles. Larger tanks, for example, can be provided with a greater number of elements to suit the usage. Additional sensors at a particular level can be included to ensure that the reading is accurate and that an incorrect value is not obtained due to a sensor being too close to an element. For example, in the case of a 210 litre tank, three heating elements have been found to be suitable. For tanks of volume less than 210 litre two elements may be suitable.

In conjunction with a number of elements 14-16, sensors 17-19 measure the temperature of the water at that particular level within the tank 10.

Information from the sensors 17-19 is collected by a control unit 20 which in turn issues instructions to the elements 14-16 to heat the water. The positioning of the control unit 20 at the base of the tank 10 is for convenience of illustration and the control unit 20 can be located where suitable for the installer and user.

Selective operation of the elements 14-16 can lead to a number of situations developing within the tank 10. Firstly, operation of all of the elements 14-16 can lead to the water in the tank 10 being at a uniform temperature. For example this situation arises if the control unit 20 anticipates a large usage of hot water in the near future or if the user operates an override/continuous usage mode. In this case, depending on the user-defined temperature, the water can be at a temperature of from 10-70C, preferably 35-70C. Typically for domestic situations the standard setting is 6OC, which temperature sterilises the water from micro-organisms, but does not cause too much damage due to precipitation, largely of calcium salts.

Where only a limited hot water draw-off is anticipated by the control unit 20, then the elements are operated selectively. For a small volume of intended usage, the element 14 is activated which acts to heat the water in its vicinity, eventually stabilising the zone 21 of heated water, at for example 65C. Although heat exchange between the zone 21 and the zone 22 immediately beneath this obviously takes place, there remains nevertheless a distinct temperature difference.

Where anticipated usage is greater then the element 15 can be used additionally to element 14. In similar fashion to that outlined above, three zones of water 21-23 are established at for example; 65C, 55C and 45C respectively. A thermal image of this situation is shown in Figure 2.

By the above means, energy is saved by two routes. Firstly, where only a portion of the water in a tank is heated, then the energy consumed to heat the water is reduced in comparison to a conventionally heated tank. In addition, heat loss from the tank is minimised. As will be recognised, the rate of heat loss from a body is proportional to the difference in temperature between that body and its surroundings. As the temperature of much of the water in the tank can be lower than in conventional tanks, the rate of loss is therefore lower.

Control of the heating pattern is governed by the control unit 20. The control unit 20 comprises a number of features which enable the central unit 20 to acquire and process information and to issue instructions based thereon. For example, information is received from a flow meter (not illustrated) as to how much hot water is drawn off and the time that this takes place, which information is stored in a storage area in the unit 20. The processor, from the information required over a 7 day period, calculates likely water consumption and issues instructions to the elements 14-16 which are required to heat sufficient water to satisfy the expected consumption.

However, functionality is also provided to enable a user to override these learned settings and also to display information to the user on water availability, status etc. Said interface and information display can be provided as part of the control unit and integrated as part of the tank and casing units. This can be achieved as part of the manufacturing procedure to minimise time and knowledge therefore required by an installer. Alternatively, the interface on display can be remote from a control unit for ease of access. In addition, facility can be included to allow control from a distance by means of a wireless control facility, mobile telephone or computer. Where an in-house interface is used then programming can be mediated through a touch-screen facility or through buttons such as soft touch rubber, hard plastic, membrane or touch sensitive buttons. Information can be displayed through an LCD display or other means well known in the art.

Of the type of information to be supplied to a user through the display, the following can be contemplated. Firstly, energy usage: information on the energy usage over a specified period can be provided to assist the user in monitoring consumption and expected bills. If tariff information is entered into the unit then the amount expected to be due can be calculated by the unit and display. The unit can also be provided with a processing means to enable, where the information is supplied, optimal heating patterns to ensure that this is achieved at minimum cost.

Secondly, water usage: the number of baths or showers available from the water presently in the tank can be displayed. The user is also enabled, should it be necessary, to input any additional baths/showers required and also when. Additionally, if a user is expecting guests this information can also be intput and used by the unit to calculate expected usage.

A further facility enables a user to set a holiday period for the heating system when the water temperature remains low at around 1OC. For example, periods of from 2-21 days may be input. In order to reduce the risk of legionella or other micro-organism growth within the tank, at the end of the pre-defined period, the control unit initiates a function which raises the temperature of all the water in the tank to around 6OC and holds the water at this temperature for a pre-set time.

As well as the above energy saving and safety functions the control unit also governs other safety functions such as monitoring the water level to ensure the tank is not dry during element heating. Also, the unit monitors the water temperature to ensure it does not rise over a pre-set safety value and if it does so, initiates a safety procedure such as water drain. *^• The flow chart of Figure 2a illustrates the functionality of the heating system and the interactions between elements of the system set up to carry out the function stated. In Figure 2a, a directed arrow indicates input from one element to another element.

Figure 3 illustrates diagrammatically a system incorporating some of the features described above, the tank in this embodiment having five heating elements. In Figure 3, a tank 30 has five vertically arrayed heating elements 31a-e under control of a unit 32. The control unit 32 receives information on the status of the water in the tank 30 from an array of sensors 33.

Cold water from the mains supply, enters the system through a pipe 34 via a stopcock 35. The mains water supply typically also supplies other areas of the house such as the kitchen 36. The cold water is brought below a standard pressure and checked for extraneous material in a series of valves or a combination valve 37. The water then passes through pipes 38 to enter the tank 30 via the inlet pipe 39. Hot water is drawn off the top region of the supply held in the tank 30 through the outlet pipe 40. From here, along with cold water led off the pipes 38, hot water is supplied to the household. In the event of hot water needing to be discharged from the tank 30 on safety grounds, the temperature, pressure relief valve 40 is included through which hot water is vented to drain to a tun dish.

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

1. A water heater for supplying hot water, to a domestic or office environment, the heater comprising a storage vessel (10) to retain water,

a plurality of heating elements (14-16) within the storage vessel said elements (14-16) being spatially separated from each other in a vertical direction;

a plurality of temperature sensors (17-19) within the storage vessel (10) measuring the water temperature a heating element (14-16) being associated with at least one sensor (17-19);

a decision making means to determine activation or de-activation of the elements (17-19).

2. A heater according to Claim 1, wherein each element comprises a plurality of heating element.

3. A heater according to Claim 1 or Claim 2, wherein the heater has three heating elements.

4. A heater according to any preceding claim, wherein the heating elements are vertically arranged above and below each other to simplify construction.

5. A heater according to any preceding claim including a flow meter to determine the volume of water leaving the tank 10.

6. A heater according to any preceding claim, wherein the control unit includes a learning module, said module storing heating usage obtained over a defined time period, and subsequently setting heating patterns to match said usage.