GB2340213A - Water heater featuring controls for temperature and water level and including water conditioning means for reducing scale build-up - Google Patents

Abstract

A water heater (10) has a vessel (11) for holding water to be heated, a heating element (12), at least one temperature sensor (21, 22), one or more level sensors (19, 20) and a control circuit (15). The water heater (10) includes a water conditioner (23) which is operable via the control circuit (15) to prevent or reduce the precipitation of limescale from the water. This is to reduce limescale build-up within the heater, thereby increasing its efficiency and prolonging its useful life. The water is conditioned by generating a conditioning signal in the water, the conditioning signal being varied in frequency and optionally varied in intensity for greater volumes of water to be conditioned.

Description

2340213 WATER HEATER HAVING MULTI-PARANIETER CONTROL

Field of the Invention

The present invention relates to water heaters., particularly to those common],,, known as vented water heaters. More particularly, the invention relates to control of parameters such as water temperature, water level and limescale precipitation.

Background to the Invention

Water heaters typically incorporate a vent either to allow surplus liquid to run off or to prevent excess vapour pressure from the heated water causing the vessel holding the water to rupture. Conventional vented and non-vented heaters are furnished with means to control two parameters, namelNI the,vater level within a vessel for containing the water to be heated and the temperature of that ivater. By implementing control over these parameters, vater heaters can be provided from which small quantities of hot water can be removed at irregular intervals, for example, to prepare beverages. Replacement cold water is subsequently admitted to restore the level to its desired position but alters the temperature of the water in the vessel. Heating, is then applied to counteract the cooling effect of the introduced cold water, to restore the temperature to a predetermined value.

Mechanical control of the level can be achieved usino various means such as a float operated valve. Electro-mechanical means such as a rod, capillary or bimetallic disk type thermostat may be used for level and temperature control.

More recently, electronic circuits controlling, via suitable electronic sensing devices, the temperature, water level or both are used Conventional water heaters suffer from a further drawback in that heatina of the I water v,,III cause precipitation of limescale (principalIN calcium carbonate), particularly onto the water heatimz element With time this can lead not on]y to cloudiness of the,vater-as the precipitate breaks free into the bulk of the liquid but also heating efficiency is reduced In order to reduce this, a number Of methods have been attempted to remove or alter the chemical species involved in limescale before they enter the heater. For example, water softeners which remove ions such as calcium have been employed These are not however suitable for drinkincy water applications Sequestrants such as polyphosphates can also be used, although here care must be taken not to change the character of the Nvater. bN altering for example the acidity. Furthermore. magnetic conditioners, electronic conditioners and electrolytic conditioners have also been employed. In the case of these latter three devices, the water is not "softened", the hardness salts are modified to reduce precipitation and adhesion to the internal hot surfaces of the heater and pipes. To produce a single intearated xvater heater comprising a level and temperature control and has limescale control.,,-,h1ch can be installed safe]y in anNr location havina a water and power supply, has not been achieved heretofore The present invention has as its object, the provision of such a water heater The object of the present invention is to provide an improved water heater v.-hich -)o includes both level and temperature control of water held in a heating vessel for subsequent dispensing. To maintain the efficiency of the heater, prevention or reduction of limescale build-up within the heater is required.

It is thus the preferred object of the invention to provide a water heater having an inteual limescale reducina means vvithout addina sianificantIN, to the cost. size or weight of the preferably compact heater.

=1 - It is further an object of the invention to realise a Nvater heater having inte'Fal limescale reducing means without alterina the water chemically, so that palatable water for bevera2es is available.

Summary of the Invention

AccordinaINI, the present invention provides a water heater having a vessel for holdina water to be heated, a heatin2 element, at least one temperature sensor, one or more level sensors and a control circuit, wherein the water heater includes means for conditioning water to be heated, said means being operable via the control circuit, to prevent or reduce the precipitation of limescale from the water, so as to reduce limescale build-up NvIthin the heater, thereby increasing its efficiency and prolonging, its useful life.

The means for conditioning water comprises an induction coil or closed loop antennae coiled about a water inlet pipe, the water being conditioned by inducino a conditioning signal in the water.

Preferably, the conditioning signal comprises electromagnetic ener2v, the frequency and intensity of which is variable.

The electromagnetic energy alters the characteristics of "hard ivater" to reduce scale precipitation from the water and accumulation of that scale on hot surfaces within the heater.

Preferablv, the conditioninc, si-nal is intensified for greater volumes of Nvater Z) ID drawn through the inlet pipe.

The conditionina si2nal aenerated cyclically sweeps through a range of frequencies The frequency sweep is non-continuous in that pre-selected frequencies are applied to the water for longer periods than other frequencies.

The control circuit is housed within the water heater and includes means for correlatina level and temperature signals so as to maintain substantialiv a pre Z - selected volume of water at a predetermined temperature. Release of water from the heater may be restricted until the predetermined temperature is achieved Conveniently, the control circuit is governed by a microprocessor which reads sensor signals from the level and temperature sensors to control pararneters of temperature and level within the heater. When fresh water is introduced into the heater from the inlet pipe the conditioning means is enabled.

A preferred embodiment of water heater has a vessel for holding water to be heated, a heating element, a first temperature sensor located adjacent the heating element, a second temperature sensor at or towards the top of the vessel to detect steam, a "half-full" level sensor, a "full" level sensor and a control circuit "N-herein the water heater includes a coil or antenna connected to the control circuit which induces throuah the loop or antenna a conditionina sicynal in water drawn throu-h an inlet pipe, the conditioning signal preventing or reducing the precipitation of limescale from the water.

Brief Description of the Dra-,vinas

The invention will now be described more particularly with reference to the accompanying drawings which show, bv way of example only, one embodiment of a water heater havina multi-parameter control In the drawings zn Flaure I is a schematic representation of the water heater, and Flaure 2 is a schematic circuit dia2ram of a control circuit in accordance,vith the invention Description of the Preferred Embodiment

Fi-ure I shows a heater, Lenerally referenced 10, comprising a vessel I I which -'0 water is heated b-, a heatim: element 12 The vessel is connected bN inlet pipe 13 to a water supply. Control of the rate of inflow of water is by means of inlet solenoid valve 14 which is coverned bv the control circuit I-S The heater 10 also comprises an outlet pipe 16, allowing heated water to be drawn off to prepare bevera,es and throucyh which flow is manuallv reaulated bv means of outlet valve 2 5 17. The vessel I I further comprises a vent IS through which excess pressure created by the increasinq vapour pressure of the water as It is heated, is released A level sensor 19 detects when the water level has reached a certain predetermined height and when it has, causes the inlet solenoid valve 14 to close off the water inlet pipe 13 A ftirther sensor 20, is positioned to detect whether vessel I I is less than half full. In such a situation it causes, via the control circuit 15, the heating element 12 to be switched off In this way. the risk of over heating the element 12, due to an insufficient volume of water being present is reduced.

Z The heating element 12 is further controlled by means of the temperature control sensor 21, which operates such that when the water temperature drops below a pre-set level, the element 12 is activated. Similarly when the ternperature exceeds, a further pre-set level then power to the element 12 is switched off, thus causing the water temperature to fall. Boiling of the'water is detected by steam thermistor 10 22, which is positioned above the maximum pre-set water level and which measures the temperature of the vapour above the water The circuit is also equipped with a boll interval timer such that, should heatina not occur for a defined period, a boll sequence is initiated. The control circuit 15 may also be desHined such that the power supply to the 15 heating element is varied as a function of the difference between two pre-set temperature levels, and additionally or alternatively to take into account the rate of heating for a alven value of power supplied. Such a facility would be able to maintain a relatively constant water temperature and also optimise power consumption 20 The heater 10 further comprises a closed loop antennae 23 which imparts to the water being admitted to the vessel I I by inlet point 13, electromagnetic radiation L,enerated in circuit 15. Such electroma!netic radiation can reduce deposition of limescale (chiefly calcium carbonate), particularly around heating elements, by altering the solution characteristics of the dissolved salts such that precipitation is 25 reduced. Typical frequencies generated by the circuit 15 to prevent scaling, all Nvith a 50' 0' duty cycle, are 1.5, 2.0, 2.5, 3.0, and 4.0 kHz. In use this range of frequencies sweeps sequentially backwards and forwards at a rate of approximately 16 milliseconds per frequency. Operation of the frequency aenerator can take place 30 either permanently, whilst the heater is in operation, or -,vhen the inlet solenoid valve is open.

The circuit is further equipped to deactivate the frequency aeneration should a critical fault occur.

The heater can also be pro-vided with a start up sequence of events In this sequence, water is admitted via inlet pipe 13. Once the water le-vel has reached the half wav sensor 20, the heater element 12, is activated alon2 v\,Ith a 1121-it-emitting diode (LED) display to indicate this to the user- The inflo,,v of water is continued until the full level sensor 19 'is activated, causina the inlet solenoid valve 14 to be closed. Once the vater temperature has reached a pre-set idle value, often 88C, then a boll timer is initiated Should the water then reach a temperature - just below the boilincy point N-vithin a certain pre-set time, the circuit 15 will cause the power to the heatine element 12 to be switched off Furthermore, once the water has reached a temperature close to boiling point, the steam thermistor 22 assesses the steam temperature. Once this sensor detects a rapid rise in the stearn temperature, this is taken as an indication that the v.-ater is bolllnu and the heat1nQ element Is then switched off Once the boll time has expired, the water thermistor is calibrated. Calibration provides data for both normal and standby operation.

On completion of the above stages, the commissioning sequence is then at an end, and the water heater enters its idle stage An LED display then indicates to the user that the water is readv to be drawn off Typically, the circuit will be designed such that until the heater has under!one this commissioning sequence, the indicator wIII not be illuminated In normal usage. the It,-ht will be on when the temperature of the water is above the minimum usable temperature of 92C Should the water temperature drop below the pre-set value, normafly 98C-/- I C, at which the temperature is to be maintained, then the circuit 15 Nvill activate the heater. Conversely, should the temperature exceed the threshold, the heater will be deactivated Typically a small amount of hysteresis Nvill be introduced In this manner the heater Nvill not be switched on and off in rapid succession The circuit 15 mounted on a printed circuit board (PCB) detects, whether water has been drawn off during a certain defined period, perhaps by means of a timer connected to the inlet solenoid valve 14. If no water has been drawn off, then the heater can enter a standby phase, in which the water temperature is maintained at the calibrated or fixed standby reference. This can again be set at 98C plus or minus I C, or whatever temperature is desired or permitted by regulation Certain safety features can also be introduced into the heater to mininlise the risk of overheatina, of the element, or boll off of the water, and also to prevent the 11> water beincy maintained at too low a temperature which can introduce health risks.

For example, if the half level switch is deactivated vk-hilst the full level switch is sill active, and indicating that maximum normal level of water is present, then ti I I 1 11 ID this will result in the heater element bein2 switched off and the inlet solenoid valve bein- closed, preventing further water from entering the vessel Also, a timer can operate, to monitor the length of time that the inlet valve is open, and if me is exceeded, cause shutdown of the heater When other faults occur, a pre-set ti 1 the heater can continue to function, but at a less optimurn level. Such non-critical faults are indicated to the user by, for example, an LED light flashing An example of a non-critical fault is failure to detect boiling during the commissioning sequence. In this case water temperatures are maintained using non-calibrated settings. Dufing non-critical fault conditions, bolling is terminated either bv the water temperature reaching a pre-set level, or bv the boil tinier expiring ReferrinQ now to Ficure 2, the control circult 15 comprises a power supply, a power circuit for the heating element and inlet solenoid valve of the water heater under control of a valve drive circuit and a signal processor for reading sensor supplied signals and interpreting those signals accord' -programmed ing to Pre criteria.

Mains power is supplied across mains supply connectors (CN5-1, CN6-1) to a mains transformer (TXI, TT1808) via a fiise (Fl, 200mA).A varistor (R30, 265VRMS) is provided to protect the power supply from mains borne transients A 12 volt ac output from the transformer (TX I) is rectifi ed throu Lh a di ode bri d!e (D19 to D22, IN4007) and regulated through a circuit centred about a standard re!aulator confiauration including a switching transistor (TS, BC817) and zener diode (Z2,, 5NII, BZV55C) to -5 volts for the logic circuitry. On power up, the voltage across a base connected resistor (R32) causes one of a pair of Darlington coupled transistors J9, BC847) to turn "ON" turning "OFF" the other of the coupled transistors (TIO, BC847) and allowina an accumulatino capacitor (C16) to charae from the recyulator output via a series coupled resistor R34 This provides the required reset signal to the microcontrollei (IC 1, 68HC70-5P6ACD'NV). A diode (D-23, PN4007) allows rapid discharE-,e of the capacitor (C16) during po,,ver-doNvn Smoothinu capacitors (05, C17) are provided to eliminate supply ripple The microcontroller (ICI) performs control functions for water heating and temperature maintenance, water fillino, LED status indication and water treatment A cr%,stal (YI, 4,T\,IHz) and associated capacitors (Cl, C2) form part of an oscillator circuit which operates at an overall frequency of 4T\,IHz A bank of unit status LEDs are fed throuLh LED driver circuits and fed via a connector (CN4-12CNT4-5) The LED indicators are mounted on a separate PCB and are confiaured to operate in common anode mode from a rectified but unretwlated 12 volt feed taken from the secondary Nvindingo of the transformer (TXI) Switching of the LEDs is performed under the control of the microcontroller ICI vla switching transistors (T] to T4, BC847) provided i I in an emitter follower confiouration in the driver circuits This confi(, uration prevents variations in the unregulated supply from affecting the LED current and hence the intensity of the LEDs. Resistors (R19, R21 R23, R225) set the LED operating current at approximately 9mA A relay (R-LI, GHP-I I I IP-12NIT)C) and its associated switching transistor J6, BC817) control power to the heating element (,,,-ia connectors C\7-1, CN8-1) auain under control of the microcontroller (IC 1 1), A snubber network (C 18, R3 5) is formed across the relav contacts to reduce switching interference. The voltaLe developed across a ground connected resistor- (R5 I) can be used bv the 3 0 microcontroller (IC I) to measure the relay current.

An optical coupler (IC-5, TLP30621) and associated components (transistors T7, BC847 and T12, BCS57) provide water inlet solenoid valve control. As the first solenoid driver transistor J7) is turned "ON", so the second driver transistor (T12) is driven "ON" supplyinQ current to the optical coupler IC-5 allowing current to flow throu-ch to the valve connector (CN10-1, CN9-1) A snubber network (C19, R44) is provided to help reduce switching interference. The optical coupler circuit includes a detector that only allows switchincy to occur at the mains waveform zero crossing point.

Input signals from the full and half full float switches across float signal connectors (CNI-5 and CNI-10, CNI-4 and CNI-3) are presented to the microcontroller (ICI) via series resistors (R2, R4). The active state for the float switches is normally closed. In this condition, current floxvs to ground (GND) from optical coupler (IC5) via series resistor (R39) for the full float sN-,,7]tch and via a resistor (R45), coupled to the 12 volt rail, for the half-full float sNvitch. The full float switch completes the current path for the water solenoid valve optical coupler (IC5). This ensures that a failure of the microcontroller (ICI) NvIll not cause an over-fill condition. The 12 volt rail coupled resistor (IR45) provides a vhettina current when the half-full float switch closes. Steering diodes (D9 and D10, IN4007) provide a path to ground (GN-D) via pull up resistors (R". R5) on the full float and half-full float switch Circuits, respectively. This aFFarioement allows the microcontroller (ICI) to detect float switch activation at a low louic level (at PCO and PC 1).

The steam thermistor input is presented also across a connector (CN 1-6. CN 1 -7) for feedinc, data to the microcontroller (ICI). The thermistor and a resistor (RI 1) tied to the 5 volt rail together form a potential divider to PFOVIde a control voltage to one part of a conditioning operational amplifier (10A, LN12904) The cTain of the thermistor signal is increased here and the voltage span is reduced to allovv the microcontroller (ICI) to monitor (at PC5/ANI) a relati-vely small temperature range- The water thermistor input is taken across its respective connector (CN I -S, CNI-9) and is conditioned in an identical vvaN, to the second part of the conditioning operational amplifier (IC33B) but includes a sN,,,Itcli[nQ transistor (Tll BC847) in the circuit. In the present embodiment of the invention, Vvo temperature ranges may be measured by shortine out a resistor (R43) bv s-, vitching the transistor (TI 1) via the microcontroller (IC], at PA-7). Sirn1laFlv, the transistor (T I I) can be turned "OFF" to provide extended water temperature coverage The Z4 outputs of both parts of the conditioning operational amplifier (IC3A, IC313) are fed via protection resistors (R48, R49) to ADC channels 0 and I (PC6/ANO, PC5/'A-Nl) on the microcontroller (ICI). Capacitors (C7, CS, C9, CIO) are provided to help increase noise immunity.

The water treatment driver circultrNr comprises a switching transistor (T';, BCS 17) and associated components. A current is unlimited by a protection resistor (R-27) to approximately 70mA. The driver of the circuit Is controlled bv the microcontroller (ICI) which generates a variable frequency square-wave output.

The resulting output current flovvs through a wire loop provided across the descaler connector (CNI-1, CNI-2) to PF0Vide conditioning of the incomine water flow. The frequency and amplitude of the electromagnetic Nvave induced in the wire loop is controlled by the microcontroller (ICI, at TCNfP).

The microcontroller (ICI) is provided with pre-selected program instructions to read, interpret and act upon level and temperature parameters. The programming includes initialisation procedures and fault condition contin'oencies. The overall operation of the programming is indicated below The water heater always assumes that the tank is empty whenever the unit is powered up. If the tank is not empty but full then the inlet solenoid for valve is deactivated.

The folloAin(y processes shall operate during the commissioning phase - 0 The "POWER" LED flashes until unit commissioning is complete Forwater heatin2 and water boilinE4 the following processes are followed For water heat, the heater does not activate until the water level has activated the half full float switch and the steam theri-nistor has reached a minimurn 2 5 temperature. This ensures that the unit cannot heat an empty tank or continue to boll if power is removed during the boll stage A timer operates to determine the maximum time allowed for the steam and water temperatures to reach their idle states Failure of the steam thermistor to reach an idle state shall be determined as a non-critical fault condition. The unit waits for the water tank thermistor to begin rising from the idle value (approx 88 Centig,rade). A timer shall operate during this period and if allowed to expire shall cause a critical fault condition. The water tank temperature is monitored from the minimum setting until the temperature reaches a point Just below boilinsz. Note, this setting can only be approximate A rise in temperature shall be expected throughout this period with the unit entering a critical fault condition if this is not achieved. This enables correct water tank thermistor operation to be determined. If the water temperature has reached near boiling point at power on the unit shall proceed to check for the steam condition.

For water boil, the unit normally expects to see a rapid rise in steam temperature to indicate the start of a boiling condition. Once boillne has been detected the unit switches off the heater. Water thermistor calibration takes place afier expiry of the boil timer.

The above event indicates the end of the initialisation sequence The. vaier heater enters the idle state. The ready LED illuminates indicating that the unit is readN for use. The water tank thermistor is calibrated to provide the tank- temperature maintenance points for both normal and standby operation Failure to detect boiling shall result in a non-critical fault condition being Renerated and termination of the initialisation sequence. The normal and standby water temperatures are maintained using a non-calibrated setting.

n If water bolls during, fault condition, a boil timer shall operate during this condition. If allowed to expire the unit terminates boiling The normal and standby water temperatures are maintained usina a non-calibrated settin- Boiling nated when the water temperature reaches a pre-set boiling point.

is termi The following processes operate during water tank filling - The tank fills from empty and when the water level has risen the required amount to activate the half full level float switch, the half full LED illuminates The half full LED extinoulshes as water is drawn frorn the unit below the level of the half full level float switch.Activation of the full level float sv,-Itch without corresponding activation of the half level float s,.vItch shall cause the unit to enter a critical fault condition.

The water level is expected to rise and activate the full level float switch at which I I The water inlet soleno'd s 'mmed'atelv time the fall level LED 'llum'nates, I I 1 1 deactivated A boll sequence is initiated if the unit was in standby mode when water was requested.

The water inlet solenoid activates when water is drawn from the unit and the full level LED extin2ulshes indicating that the tank in no lon2er full. The xvater boll sequence is subsequently initiated on expiry of the boll duration timer The unit enters its standbN, mode if no water has been drawn off for a pre- selected period of time. De-activation of the half full level float switch -while the full level float switch is activated shall cause the unit to enter a critical fault condition A,vater boll sequence in progress terminates when water is drawn from the unit.

The unit enters normal operation when the normally active full level float switch is deactivated.

The water fill timer monitors all water fill activities and if allowed to expire, causes the unit to enter a critical fault condition. The timer settirl'a is selected to be sufficlentIv long in duration to a,,,-old -timin2 out" under normal use On expiry of the boll inter-,,al timer the unit initiates a boll sequence. Operation is similar to that used during unit commissioning with the exception that no check is made for the water level belnL, half full.

For heater control during normal operation, the water tank temperature is maintained at the calibrated or fixed workin!4 reference A small arnount of hysteresis is provided to prevent rapid heater switching Nkhere the water -)5 thermistor has been calibrated the maintained temperature is 98 +/- I Centigrade.

The heater is activated -when the water tank temperature drops beloxv the low threshold. The heater is deactivated when the water tank temperature rises above the hiah threshold.

For heater control during standby operation, the water tank temperature is maintained at the calibrated or fixed standby reference. A small arnount of hysteresis is again provided to prevent rapid heater switching. NA"here the -,vater thermistor has been calibrated the maintained temperature is 98 -/'- I Centigrade.

The heater is actl,,,,ated when the water tank temperature drops below the loxv threshold. The heater is deactivated when the water tank temperature rises above the h12h threshold.

Indications that the unit is ready for use or near ready are provided by panel front mounted LEDs The "READY" LED does not illuminate until the unit has completed the initialisation procedure.

The "READY" LED illuminates when the water tank is abo-,.-e the minimum useable temperature of 92 and extinguishes when the water tank drops belov, the minimum useable temperature.

Two types of system fault shall be catered for and indicated A non-critical fault is defined as a fault which does not affect unit operation from the user's perspective but should be rectified as soon as possible. A non critical system fault is indicated by briefly flashing the "RE.ADY" LED The indication operates in such a way as not to detract from the descale indication If the normal state of the LED is extin2ulshed then a fault condition shall cause a regular, brief illumination. The unit shall assume that all faults have been rectified when re-powered and enters the initialisation procedure.

The water conditioning circuit is active during normal unit operation but is I deactivated during a critical fault condition.

Where "hard" water is stored and heated a proportion of the "hardness salts" (for example calcium carbonate) precipitates out of the Nvater and adheres to hot surfaces within the water heater. This can lead to a reduction in efficiencN, of the heating means by effectively forming an insulating barrier of limescale on the surface of the heating means, and/or a reduction in flow performance by reducing ID I - the cross sectional bore of inlet and outlet pipes The proposed control is an electronic circuit that combines the temperature and level control functions with an electronic scale condltionln! device that can be incorporated into the,vater heater thus obviating the need for a number of separate devices.

The circuit controls 0 temperature by means of an electronic sensing device (tvpicallN, a therinistor) which provides a signal to the circuit to make or break an electrical supply to the heating means at a pre-settemperature The sensor detects whether the,vater ternperature is below its pre-set %allue. If it is a switchino means is enabled that provides electrical power to tile heating means and hence raisina the water temperature. W'hen the sensor detects the pre set temperature has been reached the switching means is disabled thus interrupting the electrical supply to the heating means and thus preventing any further temperature rise.

Water level bv means of a ftirther electronic sensinQ device or devices,hich provides a signal to the circuit when the water level vlthjn the heater reaches a Z predetermined level to make or break an electrical suppl-,., to a means of controlling the inlet water flo,v (typically a solenoid valve) Z - - If the water level within the water heater is below its "full" level the sensor pitioned at the "full" level will detect this and provide a signal to the control osi I I I circuit. This sional will enable a switching means to provide power to a flow control device and hence allow water to enter the heater from the water supply to replenish the heater. W'hen the -full" sensor level is reached by the "vater tile siznal to the circuit ivill be interrupted hence de-ener-isin the flow control device, stoppina, the inlet water floNv and consequently any further rise in water level within the heater A further sensor mav act as a "lox",'" level sensor to prevent the heating means beinE ener-ised should the water level be at a level where the heatino means was not immersed Other sensors may be incorporated at differing levels to give signals of vaFyinQ deiarees of fill level up to the "full" level, signals from these sensors can be used to switch visual indicators (typically an LED or neon) of the level of fill achieved Scale conditioning of the inlet water supply.

I - A range of electromagnetic waves of varying frequency are generated "vithin the control circuitry and are imparted to the water supply by a closed loop antenna, the antenna being coiled around the inlet pipe of the,vater heater such tat water flowina into the heater is conditioned. Application of the electromagnetic fields has been shown the alter the characteristics of the "hardness salts" such that thev do not precipitate out of the water and adhere to hot surfaces withlin the heater.

The control circuitry may also include safeguards to ensure the heatina means is not enerulsed unless a predetermined water level has been achieved, user selection of differing control temperatures, other indications of Nvater heater status e.2 mains power on, correct storage temperature has been achieved, scale conditioning is operating, etc.

Temperature control, level control and scale conditioning are achieved bv using one control circuit rather than several discrete de%-I'ces.

Scale conditioning does not remove the hardness salts from the water thus retaininc, beneficial trace elements.

A"ater remains suitable for drinking purposes making this type of control especially suitable for use in water heaters for dispensing hot,vater for beverage making Z Maintenance of the water heater is reduced in hard water areas due to the reduction in scale formation within the heater.

It will of course be understood that the invention is not limited to the specific details described herein, which are aiven b-,,,vav of example only, and that various modification and alteration are possible within the scope of the appended claims.

Claims (9)

1. Claims

   I A water heater having a vessel for holdincy water to be heated, a heat'ing, element, at least one temperature sensor, one or more level sensors and a control circuit, wherein the water heater includes means for conditioning Z water to be heated, said means being operable via the control circuit to prevent or reduce the precipitation of limescale from the vater, so as to reduce limescale build-up within the heater, thereb%increasing its efficiency and prolonging its useful life.
2. 2. A water heater according to claim 1, vherein the means for conditionino water comprises an induction coil or closed loop antennae coiled about a water inlet pipe, the water being conditioned by inducInEz a condt'on' i i ing sicynal in the water.
3. A water heater according to claim /2, wherein the condition'InL, slunal I - - comprises electromagnetic energy the frequency and intensity of 711' N ich 'IS variable.
4. 4. A water heater accordina to claim 3, wherein the electronia!anetic energy alters the characteristics of "hard water" to reduce scale precipitation from the water and accumulation of that scale on hot surfaces,\,Ithin the heater
5. 5. A water heater according to an), one of claims 2 to 4, wherein the z:I conditioning signal is intensified for greater \Iolumes of.vater dravm through the inlet pipe.
6. 6. A water heater according to any one of claims _2 to 5, wherein the conditioning, signal generated cyclically sweeps through a range of frequencies
7. 7. A water heater according to claim 6, wherein the frequency sweep is non continuous in that pre-selected frequencies are applied to the water for longer periods than other frequencies.
8. 8. A water heater according to any preceding claim, wherein the control circuit is housed within the water heater and includes means for correlatina level and temperature signals so as to maintain substantially a pre-selected volume of water at a predetermined temperature, release of water from the heater beinQ restricted until a predetermined temperature is achieved.
9. 9. A water heater accordinu to any prececlim,, claim. wherein the control circuit is cyoverned bv a microprocessor which reads sensor signals frorn the level and temperature sensors to control parameters of ternper;ItUFe and level within the heater the conclitionina means beinu enabled when fresh water is introduced into the heater.

   M A water heater according to claim 1, vhereln the water heater has a vessel for holdinu water to be heated, a heatina element, a first temperature sensor located adjacent the heating element, a second temperature sensor at or towards the top of the vessel to detect steam, a "half-full" level sensor, a "full" level sensor and a control circult wherein the "vater heater includes a coil or antenna connected to the control circuit which induces through the loop or antenna a conditioning s'Qnal in water drawn through an inlet pipe, the conditioning signal preventing or reducing the precipitation of If mescale from the water 1. A water heater substantialk, as herein described with reference to and as shoNvn schematicalk, in the accompanying drawings.

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