Method for Controlling a Heating System Component for a Simple and Safe Operation and a Heating System Component Therefore

Abstract

The invention relates to a heating system component for a heating system for heating a fluid medium, with a carrier unit, and a heating unit coupled to said carrier unit, and a controller; wherein said carrier unit comprises a wet side and a dry side, wherein said wet side corresponds to a surface of said carrier unit configured to be in contact with said fluid medium, wherein said dry side is located on a surface opposite to said wet side. A temperature sensor, in particular an NTC thermistor, is effectively in thermal contact with at least a part of an upper surface of said dry side of the carrier unit, the method comprising: receiving a starting signal at the controller for starting the heating system component; carrying out a test routine for at least the at least one temperature sensor; and in case the test routine is not successful: entering a safe state of the heating system component.

Claims

1. A method for controlling a heating system component of a heating system for heating a fluid medium, said heating system component comprising: a carrier unit; a heating unit coupled to said carrier unit; and a controller; wherein said carrier unit comprises a wet side and a dry side, wherein said wet side corresponds to a surface of said carrier unit configured to be in contact with said fluid medium, wherein said dry side is located on a surface opposite to said wet side; and further comprising at least one temperature sensor, in particular an NTC thermistor, wherein said temperature sensor is effectively in thermal contact with at least a part of an upper surface of said dry side of the carrier unit, the method comprising: receiving a starting signal at the controller for starting the heating system component; carrying out a test routine for at least the at least one temperature sensor; and in case the test routine is not successful: entering a safe state of the heating system component.

2. The method of claim 1, wherein the test routine includes: sending a test signal from the controller to said at least one temperature sensor.

3. The method of claim 1, wherein the test routine includes: powering the heating unit with a predetermined test power level for a predetermined test time period; obtaining a temperature test value measured by said at least one temperature sensor; and comparing the obtained temperature test value with a predetermined temperature threshold.

4. The method of claim 3, wherein the test power level is 100% or less of a maximum power level, preferably 50% or less.

5. The method of claim 3, wherein the test power is supplied in a pulsed manner.

6. The method of claim 1, wherein the test routine includes: powering the heating unit with a predetermined test power level at a test start time; obtaining a temperature test value measured by said at least one temperature sensor; determining that a predetermined test temperature threshold is reached at a test end time; and comparing a duration from the test start time to the test end time with a predetermined time period threshold.

7. The method of claim 1, wherein the test routine includes: powering the heating unit with a predetermined heat quantity.

8. The method of claim 7, comprising: determining a supply voltage of the heating unit; and calculating by the controller a start up supply time necessary to obtain the supply of the predetermined heat quantity.

9. The method of claim 3, wherein multiple temperature test values are obtained, and further comprising the step: calculating one single heating curve based on the multiple temperature test values, or calculating individual temperature curves for each temperature test value.

10. The method of claim 1, comprising: providing for the heating system component a second temperature sensor which is positioned distal from said first temperature sensor, preferably near the first temperature sensor.

11. The method of claim 1, comprising: providing a connection between the controller and said at least one temperature sensor via a primary connection and providing a second temperature sensor by using a redundant connection.

12. The method of claim 1, comprising, recessing said heating unit in a groove provided on said dry side of the carrier unit.

13. A heating system component of a heating system for heating a fluid medium, said heating system component comprising: a carrier unit; a heating unit coupled to said carrier unit; and a controller; wherein said carrier unit comprises a wet side and a dry side, wherein said wet side corresponds to a surface of said carrier unit configured to be in contact with said fluid medium, wherein said dry side is located on a surface opposite to said wet side; and further comprising at least one temperature sensor, in particular a NTC thermistor, wherein said temperature sensor is effectively in thermal contact with at least a part of an upper surface of said dry side of the carrier unit, wherein said controller comprises a memory and a processor, the memory comprises software code, which, when run on the processor, causes the controller to carry out the method of claim 1.

14. The heating system component of claim 13, wherein the heat conducting plate comprises a part with thermal connection to said heating unit and a part with thermal connection to said carrier unit distal from the connection to said heating unit providing a mixing temperature of this two temperature levels on said heat conducting plate, wherein the at least one temperature sensor is attached in a position ensuring the intended mixing temperature on one side and keeping the temperatures of the at least one temperature sensor within the specified operation temperature range of said at least one temperature sensor which is significantly lower than the maximum temperature of said heating unit.

15. The heating system component of claim 13, wherein said heating unit is recessed in a groove provided on said dry side of the carrier unit.

16. The heating system component of claim 13, wherein said heating unit is in the form of quartzite heaters, flow through heaters, flat-plate heaters, thick film and thin film heaters.

17. The method of claim 6 wherein multiple temperature test values are obtained, and further comprising the step: calculating one single heating curve based on the multiple temperature test values, or calculating individual temperature curves for each temperature test value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In the following drawings:

[0051] FIG. 1 shows schematically and exemplarily an embodiment of a heating system component;

[0052] FIGS. 2a and 2b show schematically and exemplarily cross-section views of the heating system component according to FIG. 1;

[0053] FIG. 3 shows schematically and exemplarily an embodiment of a method for controlling a heating system component;

[0054] FIG. 4 shows schematically and exemplarily an embodiment of a controller;

[0055] FIG. 5a shows schematically and exemplarily a first diagram of a heating process;

[0056] FIG. 5b shows schematically and exemplarily a second diagram of a heating process;

[0057] FIGS. 6a and 6b show schematically and exemplarily a further embodiment of a heating system component;

[0058] FIG. 7 shows schematically and exemplarily a further embodiment of a heating system component;

[0059] FIGS. 8a and 8b show schematically and exemplarily a further embodiment of a heating system component;

[0060] FIGS. 9a and 9b show schematically and exemplarily a further embodiment of a heating system component;

[0061] FIG. 10 shows schematically and exemplarily a further embodiment of a heating system component;

[0062] FIGS. 11a to 11c show schematically and exemplarily a further embodiment of a heating system component; and

[0063] FIG. 12 shows schematically and exemplarily possible temperature measuring points on a heating system component.

DETAILED DESCRIPTION OF EMBODIMENTS

[0064] FIG. 1 shows schematically and exemplarily an embodiment of a heating system component 100. Heating system component 100 comprises a carrier unit 110 and a heating unit 120.

[0065] Heating system component 100 may be connected to, e.g., a conveyor pump of a domestic appliance such asbut not limited toa dishwashing machine. Heating system component 100 can be attached to the conveyor pump or to a conveyor pump housing during assembly of the domestic appliance. In another example, heating system component 100 can form a pre-assembled structural unit together with the conveyor pump.

[0066] As can be seen from FIG. 1, carrier unit 110 is a circular disc. In concentric relationship with its central axis (not shown), carrier unit 110 has a circular hole 111, through which a suction pipe of the conveyor pump is passed in sealing integrity in relation to the medium. At its outer peripheral edge, carrier unit 110 may engage over the edge of the conveyor pump's housing in sealing integrity in relation to the medium. That backside of carrier unit 110, as shown in FIG. 1, is in direct contact with the medium to be heated in the installed condition of the pump and can therefore be referred to as the wet side 101, whereas the side of carrier unit 110 shown in FIG. 1 does not come into contact with the medium and can thus be referred to as the dry side 102.

[0067] Heating unit 120 is arranged on dry side 102 of carrier unit 110 as shown in FIG. 2a illustrating the cross sectional view along line A-A in FIG. 1. Heating unit 120 is coupled to carrier unit 110 by means of a coupling step. The coupling step may comprise any one of a soldering step, a laser welding step, a gluing step, an ultrasonic welding step, and/or a friction welding step.

[0068] Carrier unit 110 may comprise a composite material. The composite material comprises at least an aluminum layer and a stainless steel layer. The stainless steel layer is arranged on wet side 101 of carrier unit 110. The aluminum layer is arranged on dry side 102 of carrier unit 110. In an example, the composite material may be produced by means of a cold roll bonding process.

[0069] In the embodiment illustrated in FIG. 1, carrier unit 110 further comprises groove 112. Groove 112 is configured to receive heating unit 120. Heating unit 120 comprises a first cross section which is perpendicular to an axial direction of heating unit 120. The first cross section may have a rectangular shape, a hat-like trapezoid with rounded edges, a bell-like trapezoid with rounded edges.

[0070] In the embodiment illustrated in FIG. 1, a cross section of groove 112 corresponds to said first cross section of heating unit 120. In particular, heating unit 120 is arranged in groove 112 as shown in FIG. 2a. The cross section of groove 112 and the cross section of heating unit 120 are chosen such that at least a part of a surface of heating unit 120 and a part of said dry side 102 form a flat face. In FIG. 2a all three sides of heating unit 120 are welded or soldered to the surfaces of groove 112 of carrier unit 110. The necessary close contact between the surfaces of heating unit 120 and carrier unit 110 may be achieved by applying a press preload to heating unit 120 during the coupling step. Optionally, a thermally conducting paste 122 may be applied to one or both of the surfaces of carrier unit 110 and heating unit 120. By employing a thermally conducting paste, problems associated with an occurrence of voids between carrier unit 110 and heating unit 120 may be avoided.

[0071] Another possibility for addressing problems associated with an occurrence of voids between carrier unit 110 and heating unit 120 is to arrange a phase change compound between carrier unit 110 and heating unit 120. Such a compound changes its phase state above its phase change temperature and is thereby able to fill cracks, voids, slits, etc. In an embodiment, the phase change compound is applied to the surfaces of carrier unit 110 and/or heating unit 120 by means of a dispensing step. Dispensing typically implies that the phase change compound dries within a short period of time.

[0072] In the embodiment illustrated in FIG. 1, heating system component 100 further comprises a temperature sensor 170a, preferably a NTC (Negative Temperature Coefficient) thermistor, connectable to a processing unit of the domestic appliance and in particular to a controller 30 as explained below in order to measure the temperature of the fluid circulating on the wet side of the heating system component 100. NTC thermistors provide a cost effective way of determining the temperature. However, such common inexpensive NTC thermistors only sustain continuous operation in a temperature regime of up to 100 C. Since heating unit 120 usually reaches temperatures above 100 C., NTC thermistor 170a must be thermally shielded from heating unit 120 in order to ensure a certain durability while avoiding to use more expensive NTC thermistors which sustain higher temperatures. Therefore, heating unit 120 is covered by a heat conducting plate 140 at an outer circumferential part of carrier unit 110 covering groove 112. Heat conducting plate 140 may comprise a projecting part 141 extending towards an inner circumferential part 113 of carrier unit 110. This projecting part 141 is in direct contact with the dry side 102 of carrier unit 110. Since at the opposite side of carrier unit 110, wet side 101, the fluid is circulated in operation, the temperature of carrier unit 110 and thus the temperature of projecting part 141 of heat conducting plate 140 approximately reflects the temperature of the fluid. In order to measure the fluid temperature, NTC thermistor 170a is thus mounted at projecting part 141 of heat conducting plate 140. In order to control the heat transfer from heating unit 120 to projecting part 141 on which the NTC is mounted, heat conducting plate 140 may provide a detached portion 142 at an outer circumferential part above heating unit 120 under the same angle as projecting part 141 extends towards the centre. FIG. 2b shows a cross sectional view along the line B-B in FIG. 1. FIG. 2b shows that there is a space between detached portion 142 of heat conducting plate 140 and heating unit 120. Projecting part 141 is in contact with detached portion 142, but is declined towards the upper surface of carrier unit 110. Preferably, the angular expansion of detached portion 142 is slightly broader than the angular expansion of projecting part 141. Heat conducting plate 140 may additionally be provided with trenches 143 at detached portion 142 provided towards both sides of the angular expansion of detached portion 142, wherein the length of trenches 143 influences the amount of heat conducted from non-detached portion 144 of heat conducting plate 140 to the projecting portion 141.

[0073] Optionally, a second NTC thermistor may be provided, either at a further detached portion 142 in order to determine the fluid temperature, such that the first and second NTC thermistor measurements can be averaged in order to increase the liability. Alternatively, second NTC thermistor 170b may be mounted at non-detached portion 144 of heat conducting plate 140 in order to determine the temperature of heating unit 120 itself to prevent, for instance, that the pump is running dry. In the latter case, an NTC thermistor sustaining the resulting temperatures reachable by heating unit 120 must be chosen.

[0074] When heating unit 120 is powered, it might happen that there is no water present at wet side 101, which could result in a quick overheating of the heating system component. According to the present invention, the at least one temperature sensor 170a, 180a, 270a, 370a, 460, 470a, 480, 770 is used to determine whether the heating system component is overheating or if a safe operation is possible. In this regard, FIG. 3 illustrates a method 1 for controlling heating system component 100. Method 1 shown in FIG. 3 basically comprises three sections, wherein in a first section a receiving step 2 is carried out. In receiving step 2, a starting signal S1 (see FIG. 4) at a controller 30 for starting heating system component 100 is received. Controller 30 may be a controller of the appliance in which heating system component 100 is used. In the case of, e.g., a start up test, the starting signal S1 is usually a signal provided by e.g. a starting switch, which can be manually operated by a user, or an automatically generated signal provided by a higher level control.

[0075] When starting signal S1 is received in receiving step 2, subsequently a test routine 3 as a second section is carried out. It shall be noted that in general there are three different options for carrying out test routine 3. One first option is carrying out test routine 3 on demand without any further heating step. A second option is carrying out test routine 3 after starting the appliance. A third option is carrying out test routine 3 during the regular operation of the appliance. It shall be understood that all three options are contemplated within the scope of the present invention, even though in the embodiment described in the following only the second option is described in detail.

[0076] According to this embodiment (FIG. 3), in test routine 3 first of all the operation of the at least one temperature sensor 170a, 180a, 270a, 370a, 460, 470a, 480, 770 is tested, in that a test signal S2 is sent from controller 30 to the at least one temperature sensor 170a, 180a, 270a, 370a, 460, 470a, 480, 770 in a sending step 4. This test signal S2 (see FIG. 4) is sent from controller 30 to the at least one temperature sensor 170a, 180a, 270a, 370a, 460, 470a, 480, 770 and temperature sensor 170a, 180a, 270a, 370a, 460, 470a, 480, 770 may respond with a respective response signal S2R, indicating that it is operating in a normal condition. When this response signal S2R is received, test routine 3 can be further carried out. According to this embodiment (FIG. 3) a powering step 6 is carried out next and heating unit 120 is powered with a predetermined test power level Wt (cf. FIG. 5a) for a predetermined test time period Th. This test time period Th is shown in FIG. 5a, which is also explained in detail below. Thus, controller 30 sends power S3 to heating unit 120 for a short time of the test time period Th. Predetermined test power level Wt preferably is 50% or less.

[0077] When test power level Wt is 50% or less of the maximum power level, the risk of overheating just in test routine 3 is lowered. Other preferred values are 20% or less, 25% or less, 40% or less. Preferably, test power level Wt is not lower than 10%, since then test routine 3 will not provide exact results.

[0078] After heating unit 120 has been powered with test power level Wt for the predetermined test time period Th (see FIG. 5a), a temperature test value S4 is measured by the at least one temperature sensor 170a, 180a, 270a, 370a, 460, 470a, 480, 770. This step 8 of determining is preferably carried out at a determination time Td, which is shortly later than the end of test time period Th, as can be inferred from FIG. 5a. That means that after test time period Th has lapsed, it is preferably waited for a short time (e.g. 1 to 10 seconds) as heater unit 120 has a heater lag time and responds in a delayed manner. To take into account this heater lag time, the step of determining is carried out at determination time Td.

[0079] Moreover, in a comparing step 10, obtained temperature test value S4 is compared with a predetermined temperature threshold Tt (see FIG. 5a), depending on heating time Th, determination time Td, test power level Wt and the overall construction of heater unit 120, in particular the heater lag time.

[0080] In FIG. 5a, lower graph 40 shows a temperature curve, which would be typical for a heating unit 120 with enough water at wet side 101. Upper graph 42 in FIG. 5 shows a temperature curve which would be typical for a heater unit 120 with not enough water at wet side 101 and with the risk of running dry. As can be inferred from FIG. 5, graph 42 is much steeper than graph 40 during heating time Th. At determination time Td, the temperature is measured using the at least one temperature sensor 170a, 180a, 270a, 370a, 460, 470a, 480, 770. For graph 40, temperature value Tf is determined, which is lower than predetermined temperature threshold Tt. For graph 42, temperature Te is determined, which is above predetermined temperature threshold Tt.

[0081] Based on this comparison, a decision 12 is made after test routine 3 has been carried out. When the determined temperature value is below predetermined temperature threshold Tt (as e.g. value Tf), it is determined that test routine 3 is successful and the normal starting procedure can be continued in step 14. Normal operation of heating unit 120 is carried out.

[0082] When in decision step 12, it is found that the measured temperature value is above predetermined temperature threshold Tt (as e.g. the value Te), it is considered that test routine 3 is not successful and subsequently a safe state 16 is entered.

[0083] Such a safe state could be e.g. cutting the power supply to heating unit 120, while the appliance still is switched-on. A test result signal S5 may be provided by controller 30 to the operator, or to a higher level control unit of the appliance.

[0084] FIG. 5b shows an alternative diagram which illustrates embodiments using a slope of a first heating curve 44 of a first temperature sensor and a second heating curve 46 of a second temperature sensor. In FIG. 5b, the first temperature sensor is indicated by NTC1, and the second temperature sensor is indicated by NTC2, even though the first temperature sensor may be any of the temperature sensors 170a, 180a, 270a, 370a, 460, 470a,480, 770 and the second temperature may be any of the temperature sensors 170b, 180b, 270b, 370b, 470b, 480 (positioned near NTC1), 770 (positioned near NTC1). For example, first temperature sensor NTC1 may be mounted preferably in a first mounting place 840 (or 842) and second temperature sensor NTC2 may be mounted preferably in a second mounting place 842 (or 844) as shown in FIG. 12, which will be described in more detail below.

First ExampleRunning Dry Failure

[0085] In a first example, the two temperature sensors NTC1, NTC2 can be used to detect dry run failure. For this application, two temperature sensors NTC1, NTC2 are necessary to achieve a redundancy. In this example, the method preferably comprises determining a first slope Y1 of first heating curve 44 for first temperature sensor NTC1. First slope Y1 is defined by T/t measured beginning at determination time Td. Then, this determined first slope Y1 is compared with a first slope threshold YT1, which might be in the range of 12 to 40 K/s, dependent on the physical inertia of heating unit 120. Preferably, the method also comprises determining a second slope Y2 of second heating curve 46 for second temperature sensor NTC2. Second slope Y2 is defined by T/t measured beginning at determination time Td. Then, this determined second slope Y2 is compared with a second slope threshold YT2, which might be in the range of 1 to 10 K/s, dependent on the physical inertia of heating unit 120, as the second mounting position 842 is in the mixed area and therefore it is assumed that temperature rises slower there.

[0086] Furthermore, the method may comprise determining a difference T.sub.NTC1T.sub.NTC2 with a predetermined threshold, wherein T.sub.NTC1 is the temperature measured at the determination time Td using the first temperature sensor NTC1 and T.sub.NTC2 is the temperature measured at the determination time Td using second temperature sensor NTC2. The threshold in this case may in the range of 80 to 120 C. Of course, also a comparison with a fixed predetermined threshold of only one temperature test value may be provided. For example, it may be determined whether the temperature test value of first temperature sensor NTC1 is above a predetermined threshold in the range of 180 to 220 C.

[0087] In case one or more of the above four tests are positive, i.e. the respective value is above the respective threshold, test routine 3 is not successful.

Second ExampleBoiled to Dry

[0088] In a second example in which two temperature sensors are necessary, a so called boiled to dry procedure is carried out. During a boiled to dry procedure, heating unit is started while a maximum water level is present at wet side. Heating unit is then powered until all water is boiled and wet side is dry. Such a process may e.g. beneficially be carried out with an electric kettle.

[0089] In this process, similar steps as defined in the above first example are carried out, but the following threshold values are used: [0090] Second slope Y2 (T/t); second slope threshold YT2: 1-10 K/s [0091] First slope Y1 (T/t); first slope threshold YT1: 12-40 K/s [0092] T.sub.NTC1T.sub.NTC2, Threshold: 80-120 C.; [0093] temperature test value NTC1: 180-220 C.

Third ExampleCalcification/Lime Scaling

[0094] In this process, similar steps as defined in the above first example are carried out. This process is carried out to test whether there is lime on surfaces of heating system component 100. The following threshold values are used:

[0095] In this process, the method preferably comprises the step of determining a difference T.sub.NTC1T.sub.NTC2 with a predetermined threshold, wherein T.sub.NTC1 is the temperature measured at determination time Td using first temperature sensor NTC1 and T.sub.NTC2 is the temperature measured at determination time Td using second temperature sensor NTC2.

[0096] However, the determined difference preferably is compared with a first lime threshold YL1 and a second lime threshold YL2. First lime threshold YL1 may be in the range of <50 to 60 C. Second lime threshold YL2 may be in the range of 80 to 120 C. When the determined difference is between the two lime thresholds YL1, YL2, it may indicate that lime is present on surfaces (wet side 101) of heater unit 120. A respective notice may be give to the operator.

[0097] When the second threshold is exceeded, this may indicate that there is a relatively high amount of lime at heater unit 120, and test routine 3 is considered not successful. Safe state 16 may be entered in this event.

[0098] One of the two temperature sensors NTC1, NTC2 may be formed as a safety-related sensor, while the other one is formed as a non-safety-relevant sensor.

Fourth ExampleRunning Dry with Only One Temperature Sensor

[0099] In this fourth example, a running dry failure may be detected based on either first or second temperature sensor NTC1, NTC2. The method in this embodiment preferably comprises determining a first slope Y1 of first heating curve 44 for first temperature sensor NTC1. First slope Y1 is defined by T/t measured beginning at determination time Td. Then, this determined first slope Y1 is compared with a first slope threshold YT1, which might be in the range of 15 to 40 K/s, dependent on the physical inertia of heating unit 120.

[0100] In a second step, an absolute temperature test value at determination time Td is measured and compared to a respective threshold. In this case, the threshold may be in the range of 180 to 220 C.

[0101] Alternatively, second temperature sensor NTC2 is used. The respective thresholds of the difference and the absolute temperature test value are: 1 to 10 K/s, and 80 to 120, in this case.

[0102] When both, the threshold for the difference and the threshold of the absolute temperature test value are exceeded, test routine 3 is considered not to be successful and the safe state 16 is entered.

Fifth ExampleBoiled to Dry with Only One Temperature Sensor

[0103] This procedure is carried out identically to the fourth example.

Sixth ExampleCalcification with Only One Temperature Sensor

[0104] In this example, only the absolute temperature test value measured at determination time Td is used. The threshold for first temperature sensor NTC1 may be set to 120 to 150 C. and the threshold for a second temperature sensor NTC2 may be set to 60 to 80.

[0105] In an alternative, the procedure of the sixth example is carried out using a further temperature sensor, which is already present in the appliance in which the heating system component is used. By means of this further sensor, the temperature of the water can be determined accurately and by this additional value, the amount of lime may be determined properly.

[0106] Moreover, it is preferred that the method in this embodiment comprises the steps: storing the measured temperature test value in a memory of the controller; and comparing the measured value with at least one previously stored value, preferably with a plurality of previously stored values.

[0107] The previously stored values may be used to calculate a curve and the slope of this curve may also be used to carry out an analysis of lime at the heater unit. Dependent on the slope a specific notice may be provided to the operator.

Seventh ExampleCalcification with One Temperature Sensor

[0108] The seventh example is based on the fourth example and again used to determine lime.

[0109] In this embodiment, a second temperature test value after an additional waiting time after determination time Td is obtained. The additional waiting time preferably is chosen such that the temperature measured by first and/or second temperature sensor NTC1, NTC2 substantially equals the temperature of the water present at the wet side.

[0110] Then, this second value may be used as described in the third example.

[0111] Now FIGS. 6 to 9 show additional variations and embodiments of heating system component 100 and, in particular, different places for mounting the at least one temperature sensor.

[0112] In the embodiment schematically illustrated in FIG. 6a, a heating system component 100 is shown which provides one or more temperature sensors, preferably NTC thermistors 180, inside groove 112. Heating unit 120 inserted in groove 112 of carrier unit 110 provides connecting pins 123 at both ends of heating unit 120.

[0113] These connecting pins 123 are not located inside groove 112, but project towards an axial direction to be connected to a power source. Temperature sensor 180 is therefore preferably provided in the portion of groove 112 which is not covered by heating unit 120 and is located below connection pins 123. In order to shield the temperature sensor 180 from heating unit 120, a shielding unit 181 is provided inside and preferably form-fit to the walls of groove 112. Shielding unit 181 is made of a heat insulating material such asbut not limited tostainless steel. As shown in cross-sectional view of FIG. 6b, shielding unit 181 provides a hollow chamber 182 into which temperature sensor 180a, preferably in form of an NTC pill, is inserted. In order to fix the NTC thermistors inside hollow chamber 182, an epoxy resin is injected into chamber 182, preferably a temperature resistant two-component resin. Again, optionally a second NTC thermistor 180b may be provided inside hollow chamber 182 in order to determine an average temperature of the fluid circulating at wet side 101 of carrier unit 110. The compact, yet cost-efficient design provided by this embodiment allows a reliable measurement of the fluid temperature on wet side 101 of carrier unit 120 providing an easy assemble of the heating system component 100 within a respective household appliance. Since there are no components protruding from the dry side of the carrier unit, the risk of damages during assembly is significantly reduced.

[0114] FIG. 7 schematically shows a further embodiment, in which one or more NTC thermistors 270a, 270b are provided at respective pads 250a, 250b made of a ceramic material. Each pad 250a, 250b is fixed at heat conducting plate 240 via a form-fit connection. Heat conducting plate 240 covers at least parts of an inner circumferential portion 113 of carrier unit 110, such that an NTC thermistor 270a mounted at projecting part 241 of heat conducting plate 240 may measure the temperature of the water circulating at wet side 101 of carrier unit 110. Again, in case a second NTC thermistor 270b shall be provided, second NTC thermistor 270b may either be positioned at another portion of the inner circumferential portion 113 of carrier unit 110 or heat conducting plate 240 may also cover at least portions 244 of groove 112 in which heating unit 120 is embedded such that second NTC thermistor 270b may measure the temperature of heating unit 120 itself in addition to the water temperature. Conducting paths 261 which connect NTC thermistors 270a, 270b with an external processing unit (not shown) are electrically connected with NTC thermistors 270a, 270b, wherein NTC thermistor 270a, 270b and conducting paths 261 are covered with a resin. Conducting paths 261 are preferably guided along heat conducting plate 240, wherein a thin insulating layer 260, preferably a thin foil, is provided between conducting paths 261 and heat conducting plate 240. Thin insulating layer 260 is preferably made of the polyimide Kapton. However, any other suitable polyimide, polyamide or polyester may be used instead. In a preferred embodiment, a single plug 300 can be used to provide electric power to connecting pins 123 of heating unit 120 via respective pins 302 and to provide a connection between conducting paths 261 from the one or more NTC thermistors 270a, 270b and an external processing unit. Preferably, heat conducting plate 240 is grounded by plug assembly 300 via a corresponding connection 301. Again, the compact design provides advantages during assembly of heating system component 100 within a superordinate component into which heating system component 100 is integrated. Having a single plug 300 to connect the heating unit 120 as well as one or more temperature sensors 270a, 270b further decreases the complexity during assembly as well as the required material budget.

[0115] The embodiment schematically illustrated in FIG. 8a also shows a heating system component 100 with a heat conducting plate 340, wherein at least a part 341 of heat conducting plate 340 is in direct contact with dry side 102 of carrier unit 110, and wherein one or more NTC thermistors 370a, 370b as well as conducting paths 361 are provided thereon having an insulating layer 360, preferably in form of a thin foil, between heat conducting plate 340 and NTC thermistors 370a, 370b conducting paths 361. Insulating layer 360, the one or more NTC thermistors 370, and the respective conducting paths 361 are printed or sprayed onto heat conducting plate 340 as thin layers, wherein insulating layer 360, preferably made of a ceramic material, is provided as a first layer, NTC thermistors 370 and respective conducting paths 361 are provided on top of that first layer. Again, heating system component 100 may preferably be provided with a single plug 300 as shown in FIG. 8b which is adapted to provide electric power to connecting pins 123 of heating unit 120 as in the embodiment depicted in FIG. 7. Additionally, plug 300 provides one or more connection pins 302 to be coupled to conducting paths 361, e.g. by soldering. Preferably, heat conducting plate 340 is grounded by plug 300 via a corresponding connection 301 as shown in the embodiment depicted in FIG. 7. Alternatively, the grounding may be achieved by connecting an upper extension 345 of the conducting plate with ground providing a plug 300 with connection pins 302 at the bottom to be connected with conducting paths 361 and a ground connection to the side of plug 300. Again, the compact design provides advantages during assembly of heating system component 100 within a superordinate component into which heating system component 100 is integrated. Having a single plug 301 to connect heating unit 120 as well as the one or more temperature sensors 370 further decreases the complexity during assembly as well as the required material budget.

[0116] FIG. 9a schematically shows a further embodiment, in which one or more temperature sensors 470 are provided at an inner circumferential portion of carrier unit 110, wherein carrier unit 110 comprises an undercut portion 400 which is filled with a thermoplastic layer 500 by injection-molding to form bases of a so-called molded interconnect device (MID). In a first step, the undercut portion 400 is provided with a microstructure by a thin laser beam. The thermoplastic is provided on top of the microstructured surface of the metal layer. The metal layer is heated up by a further laser beam while the thermoplastic is pressed onto the microstructure at surface in order to provide a hybrid metal-plastic connection. Thermoplastic layer 500 is doped with a metal-plastic additive that can be activated by exposure to a laser beam. This process is commonly referred to as metallization, wherein two different sections are metalized, one for the temperature sensors 470, e.g. NTC thermistors, and the other for conducting paths 461. The NTC thermistors 470 and respective conducting paths 461 are cut free with a laser. Also in this embodiment, a form-fit plug 600 is provided having connection pins 602 to connect to the respective conducting paths 461. The housing of plug 600 is preferably made of a transparent plastic material which can be laser-welded to thermoplastic layer 500 which should therefore preferably be made of thermoplastic material absorbing the energy of a laser beam which previously passes the transparent plug 600 housing without depositing significant amounts of energy in the plastic material and thus deforming it. The form-fit design provided by this embodiment eases the assembly of heating system component 100 into a superordinate system as well as reduces the size and material budget required to implement a temperature sensor 470 for heating system component 100.

[0117] FIG. 10 schematically shows a further embodiment, in which one or more temperature sensors, in particular NTC thermistors 770 as well as conductor paths 761 between the one or more NTC thermistors 770 and an external plug are formed at a thin layer 760, preferably a thin polymer foil, before the foil is attached to carrier unit 110. NTC thermistors 770 as well as conductor paths 761 may either be formed by printing, vapor deposition or metallization. Preferably, the sensor foil is pre-assembled with a suitable plug 600 providing conductor pins to the conductor paths as well as preferably also power connections for the heating unit and as well as a pin to ground the carrier unit. Plug 600 may then be mounted at carrier unit 710 by welding, in particular spot welding power connections 302 and a ground connection 301 to heating unit 120 and carrier unit 710, respectively. Thin foil 760 is then attached to carrier unit 710 by gluing at least a portion of the lower side of foil 760 to the dry side of carrier unit 110 using a heat resistant gluing material. The NTC thermistors are preferably positioned at a portion of the dry side of carrier unit 110 whose wet side is in contact with the fluid circulating at the wet side. The embodiment allows a particularly flexible way of arranging the temperature sensors at a desired position of the carrier unit. Furthermore, the embodiment provides a very compact design without any protrusions or cables which require space and caution during assembly.

[0118] FIGS. 11a to 11c show a further embodiment of heating system component 100, which again comprises a carrier unit 110 and a heating unit 120 attached thereto. In the overall drawing of FIG. 11a, it can be seen that heating system component 100 is attached to a pump housing 800, which can be assembled within an appliance. Heating system component 100 comprises a main connector board 802 comprising two male connectors 804 for heating unit 120 and one male connector 806 for the temperature sensor 480, which will be described in more detail with respect to FIGS. 11b, 11c. Male connectors 804, 806 are connectable to a first female connector 808 for heating unit 120 and a second female connector 810 for temperature sensor 480. In this embodiment, heating system component 100 only comprises one single temperature sensor 480.

[0119] The two main connectors 408 for heating unit 120 are basically formed at a heating unit connector frame 812, which is shown in FIG. 11b. This frame 812 comprises the two male connectors 804 and furthermore, a first and second heating unit contact 814a, 814b, which extend from frame 812 and contact the two respective end contacts 816a, 816b of heating unit 120 (see FIG. 11a). Frame 812 is attached to carrier unit 110 by means of a clip housing 820, which comprises a holding down clip 822, whose function will be described below.

[0120] Moreover, male contact 806 for temperature sensor 480 is attached to a basically Z-shaped lash element 824, which comprises a holding arm 826. At the free distal end of holding arm 826, temperature sensor 480 is arranged. At a little portion, there is provided a foil, in particular a Kapton-foil, which is electrically insulating and heat conductive, as particularly described in the European patent application 17188041.2.

[0121] On the left-hand side of FIG. 11b, lash element 824 is shown mounted to the frame 812, and on the right-hand side of FIG. 11b, lash element 824 is shown separately.

[0122] When clip housing 812 is mounted over frame 812 and lash element 824, holding down clip 822 will contact temperature sensor 480 and hold and push it towards heating unit 120, as basically shown in FIG. 11a. Holding down clip 822 may also be attached to temperature sensor 480 for holding it in place.

[0123] To improve the contact properties, a contact paste 850 (e.g. silver paste) with good thermal properties can optionally be used.

[0124] Also, an elastic element 860 can optionally be used to compensate the mounting tolerances (e.g. heat resistant rubber or similar).

[0125] FIG. 11c now shows a second view of frame 812, lash element 824 as well as clip housing 820. Lash element 824 is preferably formed out of the Kapton-foil as defined above.

[0126] In FIG. 11c, moreover, grounding contact 830 for heating unit 120 is shown.

[0127] FIG. 12 additionally shows three different mounting positions for the temperature sensor. One first mounting position 840 would be directly on heating unit 120. This is the most heated portion and therefore mounting of the temperature sensor could be difficult. A second position 842 is a position between heating unit 120 and carrier unit 110, which is closer to carrier unit 110 and thus would be a preferred mounting place. According to the present embodiment of FIGS. 11a to 11c, a third placement 844 is used, which is easy to assemble and the temperature sensor 480 can be held in place by the clip housing 820.

[0128] An example application of the invention generally relates to situations where a fluid medium needs to be heated in an efficient manner, for example in household appliances such as dishwashers, dryers, and washing machines, small electrical appliances such as coffeemakers, irons, steam generators etc. or in water heaters. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

[0129] In the claims, the word comprising does not exclude other elements or steps, and the indefinite article a or an does not exclude a plurality.

[0130] A single unit or device may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0131] Determinations like measuring a temperature performed by one or several units or devices can be performed by any other number of units or devices. For example, measuring a temperature can be performed by a single temperature sensor or by any other number of different units. The determinations and/or the control of the heating system for heating fluid media can be implemented as program code means of a computer program and/or as dedicated hardware.

[0132] A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the internet or other wired or wireless telecommunication systems. The term software code may also refer to embedded software.

[0133] Any reference signs in the claims should not be construed as limiting the scope.

REFERENCE SIGNS LIST

[0134] 1 method for controlling a heating system [0135] 2 receiving a starting signal [0136] 3 test routine [0137] 4 sending a test signal [0138] 6 powering the heating unit [0139] 8 obtaining a temperature test value [0140] 10 comparing the obtained test value [0141] 12 determining whether test routine is successful [0142] 14 continue starting process [0143] 16 entering safe state [0144] 30 controller [0145] 32 memory [0146] 34 software code [0147] 36 processor [0148] 40, 42, 44, 46 graphs, heating curve [0149] 100 heating system component [0150] 101 wet side [0151] 102 dry side [0152] 110 carrier unit [0153] 111 circular hole [0154] 112 groove [0155] 113 circumferential portion [0156] 120 heating unit [0157] 122 thermally conducting paste [0158] 123 heating unit connecting pins [0159] 140, 240, 340 heat conducting plate [0160] 141, 241, 341 projecting part [0161] 142 detached portion [0162] 143 trenches [0163] 144, 244 non-detached portion [0164] 170, 180, 270, temperature sensor [0165] 370, 470, 480, 770 [0166] 170a, 180a, first temperature sensor [0167] 270a, 370a, 470a [0168] 170b, 180b, second temperature sensor [0169] 270b, 370b, 470b [0170] 181 shielding unit [0171] 182 hollow chamber [0172] 250a first ceramic pad [0173] 250b second ceramic pad [0174] 260, 360, 760 insulating layer [0175] 261, 361, 461, [0176] 300, 600 plug [0177] 301 connection [0178] 302, 602 connection pins [0179] 345 upper extension [0180] 400 undercut portion [0181] 500 thermoplastic layer [0182] 761 conductor paths [0183] 800 pump housing [0184] 802 connector board [0185] 804 first male connectors [0186] 806 second male connector [0187] 808 first female connector [0188] 810 second female connector [0189] 812 frame [0190] 814a, 814b contacts [0191] 816a, 816b contacts of heating unit [0192] 820 clip housing [0193] 822 holding down clip [0194] 826 holding arm [0195] 824 lash element [0196] 828 foil element [0197] 830 grounding contact [0198] 840 first mounting place (hot areaon heating element) [0199] 842 second mounting place (mix areabetween 840 and 844) [0200] 844 third mounting place (area with media temperature) [0201] 850 contact paste [0202] 860 elastic element [0203] S1 starting signal [0204] S2 test signal [0205] S2R test return signal [0206] S3 powering signal for heating unit [0207] S4 temperature test value signal [0208] S5 feedback signal [0209] Td detection time [0210] Te temperature value exceeding threshold [0211] Tf temperature value below threshold [0212] Th heating time [0213] Tt temperature threshold [0214] TO test start time [0215] T1 test end time [0216] T2 duration [0217] Wt test power level [0218] Y slope of heating curve