WO2006038109A2

WO2006038109A2 - Accumulator water heater, flange for accumulator water heater and control method for water heater scaling

Info

Publication number: WO2006038109A2
Application number: PCT/IB2005/003011
Authority: WO
Inventors: Roberto Sampaolesi; Angelo Mancini
Original assignee: Merloni Termosanitari S.P.A.
Priority date: 2004-10-01
Filing date: 2005-09-16
Publication date: 2006-04-13
Also published as: WO2006038109A3; EP1794496A2; ITAN20040046A1; RU2007113010A; CN101069038B; CN101069038A; RU2419028C2

Abstract

The present invention relates to a water heater (1), preferably of the accumulator type, comprising a water heating means (4) and a sheath (5) containing one or more sensors, conceived to measure the temperature of the water in proximity to said water heating means (4), characterised in that it comprises means (6) for reading the presence of lime scaling on said water heating means (4), said reading means (6) using the temperature information of said sensor/s (5) during the heating stage of said means (4); also included in the description is a flange (3) for a water heater and a method for controlling the forming of lime scaling.

Description

ACCUMULATOR WATER HEATER, FLANGE FOR ACCUMULATOR WATER HEATER AND CONTROL METHOD FOR WATER HEATER SCALING

DESCRIPTION

The present invention relates to a water heater, preferably of the electric accumulator type, a flange for said water heater, and a control method for lime scaling on the water heating means in a water heater, and the use of temperature sensors to reveal the presence of lime scaling on the water heating means of a water heater. The present invention is also applied to a gas fired accumulator water heater, or at least, to those models wherein the water is heated by means of a smoke flue positioned inside the same accumulator tank.

Hereafter in the following description for easier comprehension, reference will be made only to electric water heaters, keeping in mind that all aspects that refer to the electric resistance also apply in the same manner to the smoke flue, at least according to the description above.

Currently known electric water heaters generally comprise a tank and a removable flange mounted -with one or more resistances, a sheath containing one or more thermostat sensors and an anti-corrosion device. Among the most common thermostats currently on the market, the most widely used is the so-called "rod type" followed by the so-called "bulb type", both with electromechanical action, but electronic thermostats are also used, where the sensor is generally an NTC. Even though electronic sensors are more expensive, they have the advantage of being able to control the temperature with very high precision, and with only a small extra cost and appropriate electronic logic, they can perform other supplementary functions such as a timing or water temperature signal transmission.

In the case where the electronic thermostat is equipped with at least two sensors positioned at a sufficient distance from each other along the vertical line, it is also possible to obtain information concerning the contents of the heated water in an accumulator water heater, as is common knowledge because of products distributed on the market in recent years.

Currently known water heaters on the market present reliability problems over a certain period of time. In particular, the lime that deposits progressively on the heating resistances gradually touches and encases the sheath of the thermostat sensor(s), reducing the effect of the thermal contact between the sensors and the heated water, and creating a thermal bridge between the heating resistance and the sheath.

This provokes errors in measuring the water temperature. In fact the thermal bridge permits the temperature sensor to heat more rapidly in comparison to the volume of water in the tank thus providing a water temperature reading higher than the actual temperature.

Moreover, when lime builds up around the resistance, this causes excessive heating, the noise effects typical of surface water boiling, and leads to rapid deterioration. Current state of the art does not include any devices able to signal excessive lime scaling on the electric resistances.

In order to control the lime scaling on electric resistance, regular control checks must be made, disassembling the flange on the water heater.

These regular control operations lead to a considerable increase in the cost of running and maintenance of the said water heaters.

The task of the present patent is to eliminate at least part of the problems involved currently present on water heaters, and in particular those problems described above.

In particular, the task of the present patent is to identify means and methods able to rapidly signal the forming of lime scaling. Said task is achieved by means of the water heater according to the description provided in claim 1, a water heater flange according to the description provided in claim 11 , and a method for controlling the forming of lime scaling according to the description provided in claims 19, 23 and 27.

Further advantages can also be obtained by means of the supplementary characteristics described in the subordinate claims.

A possible embodiment of the invention according to the claims of the patent is described below with reference to the appended drawings wherein:

Figure 1 shows a front view of a cross section of an electric water heater;

Figure 2 shows a partial front view of a cross section of a flange for a water heater according to a first embodiment;

Figure 3 shows a partial front view of a cross section of a flange for a water heater according to a second embodiment;

Figure 4 shows the layout diagram of an algorithm for calculating the temperature gradient; - Figure 5 shows a graph of the temperature progression, in absence of lime and after 27 days' use, respectively, according to a first embodiment;

Figure 6 shows a graph of the temperature progression, in absence of lime according to a second embodiment;

Figure 7 shows a graph of the temperature progression, after 130 days of water heater use, according to a second embodiment

In the appended drawings, the numeral 1 refers throughout to a water heater, preferably of the electric accumulator type, comprising a tank 2 and a flange 3 that is mounted with one or more electric resistances 4, a sheath 5 containing one or more sensors 6.1 or 6.2 and 6.3 conceived to read the temperature of the water in the tank, and to transmit signals to a means 6 (typically an electronic device), and lastly preferably a means against corrosion 7.

According to the present invention, the presence of lime scaling on the electric resistance 4 during the heating stage is read by using the temperature information tό.l, or t6.2 and t6.3 from the said sensors 6.1 or 6.2 and 6.3, respectively. Advantageously, said sensors 6.1 or 6.2 and 6.3 are the same as those used by the water heater thermostat, which must be electronic in this case; even more advantageously, a single electronic device can be foreseen which, as well as performing known functions such as thermostatation and/or calculating the amount of hot water and/or signalling the temperature of the water, is also able to signal the forming of lime scaling, according to the invention.

According to a first embodiment, shown in figure 2 and in the layout diagram in figure 4, a single temperature sensor 6.1 is foreseen, positioned in proximity to the resistance 4. It must be noted that the term "in proximity" must be understood as being that the distance of the temperature sensor 6.1 from the resistance 4 is such that it is covered by the lime scaling that has begun to form, before it has reached a thickness that will provoke irreversible damage, according to the judgement of the technicians expert in this sector. As an example, in water heaters for domestic use, said distance is less than 60 mm, and more preferably, less than 50 mm and, even more preferably, less than 40 mm. Preferably the sensor 6.1 is positioned at a height less than the maximum height of the electric resistance 4; however, it can also be positioned at a height above the resistance 4, on condition that it can be reached by the lime scaling as it is formed, before it provokes irreversible damage. As will be explained in more detail further on, the temperature information t6.1 read by sensor 6.1 can be compared in relation to the thickness of the lime scaling which forms on the electric resistance 4.

For this purpose, the means 6 comprise a calculating means 6.4 (analog or digital) conceived to determine the speed of the heating of the water GI_f in proximity to the resistance 4, and to compare said heating speed with a reference value.

Preferably said reference value is based in relation to the reference heating speed Gl₀ which corresponds with the heating speed that can be observed in the absence of lime or with very low lime scaling levels. The reference heating speed Gl₀ depends on the type of water heater, and in particular, on the installed power and on the geometry. Each time the heating speed GI_f exceeds the reference speed Gl₀ by a certain threshold ΔG, the lime scaling is considered as being strong enough to require maintenance operations.

The faster the measured speed, the greater the difference between the temperature value t6.1 measured by the temperature sensor 6.1 located in proximity to the electric resistance 4, and the actual temperature of the water in the water heater.

The increase in lime scaling is therefore calculated by measuring the actual heating speed GI_f in proximity to the resistance 4 during the first minutes of heating and comparing this value with the reference value Gl₀, which corresponds with the heating speed that is observed in the absence of lime or when the lime scaling is very slight.

An example of the temperature progression read by a probe in proximity to the electric resistance in the absence of lime scaling and after 27 days' water heater use is shown in figure 5. After the water heater has been used, and consequently, once the lime has deposited on the electric resistance, the heating speed is subject to increase.

Preferably other means are also foreseen to memorise and/or adjust the reference speed Gl₀ permitting the user to pre-set or modify said speed.

The reference speed Gl₀ can also be self-taught, by providing for means that permit the memorising of the reference signal GIo during initial installation.

The value of the threshold ΔG depends on the model of the water heater used, it can be pre-set or modified during use, and for the more common models, it has a value of between 3 and 5 °C/minute.

According to a preferred operating mode, the heating speed is measured in a predetermined interval of time that does not exceed 5 minutes, or until the water temperature has reached 30 °C.

In fact the main differences between the heating curves with and without the presence of lime stratification read up to temperatures of about 30°C, which are generally reached within a period under 5 minutes. Visual and/or acoustic signals are also foreseen to warn when the heating speed GIf in proximity to the resistance exceeds by a certain threshold ΔG the pre-established reference speed Gl₀, or, in other words, when the lime scaling is great enough to require maintenance operations.

According to a second alternative embodiment, as shown in figure 3 and in the layout diagram in figure 4, the water heater is equipped with a first sensor 6.2, located in proximity to the resistance 4, and a second temperature sensor 6.3, positioned at a certain distance from resistance 4.

The first sensor 6.2, conceived to measure the temperature T₁, is positioned inside the heating zone, or inside the zone slightly above said heating area, under the same conditions as those described for the first embodiment.

The second sensor 6.3 is positioned at a certain distance from the electric resistance in a position to be able to measure the actual temperature T₂ of the volume of the heated water even in the presence of lime.

For this purpose, the second sensor 6.3 is positioned generally at least 100 mm, and preferably at least 150mm from the resistance 4.

The temperature gradient Ti-T₂ read by the pair of sensors 6.2 and 6.3 can be compared in relation to the thickness of the lime scaling.

Figures 5 and 6 show examples of the temperature progression read by the two temperature probes and the temperature gradient progression T₁-T₂, respectively, when the resistor is in new condition, and after 130 days use.

After the water heater has been in use, and consequently also as a result of the accumulated lime scaling on the resistance, the temperature gradient Tj-T₂ will be subject to an increase.

For this purpose, the means 6 comprise calculation means 6.4 (analog or digital) conceived to measure the temperature gradient Ti-T₂ of the water, in proximity to the two sensors at exactly the same time and to compare this with a reference gradient

ΔT₀.

The reference gradient ΔT₀ depends on the type of water heater, and in particular on the installed power and on the geometry, and is defined in relation to a condition where no or very little lime is present. For more common models the reference gradient ΔT₀ ranges between 20 and 30 °C.

Preferably means are also provided for memorising and/or adjusting the reference gradient ΔTo that permits the user to pre-set and/or modify said gradient.

The reference gradient ΔT₀ can also be self-taught, providing for means that permit memorising the reference during the initial installation.

Each time the measured temperature gradient Tj-T₂ exceeds the pre-established reference value ΔT_0; the lime scaling is considered as great enough to reduce the efficiency of the water heater and therefore the water heater requires maintenance operations. Preferably the temperature gradient is measured during the whole heating period, and even more preferably, within a heating time no greater than 5 minutes, or within a time that corresponds with a temperature, at the resistance 6.2, that is not higher than

30 ⁰C.

If the value of the reference gradient ΔT₀ is exceeded, the presence of excessive lime scaling is signalled by means of visual and/or acoustic signals.

Indicators can be provided to show how the heating speed or the heating gradient varies in time, to permit the user to control the presence of lime scaling on the electric resistance.

As well as the visual and/or acoustic signal warnings, the water heater can also be provided with a system to turn to switch-off.

In both embodiments it is possible to perform a specific control operation to check the amount of lime scaling.

This operation foresees the heating of the electric resistance for a sufficient period of time in order to calculate the heating speed or the temperature gradient, and to compare it with the reference values.

Preferably the heating time will be less than 5 minutes.

Advantageously, the water heater can also be equipped with remote control transmission means to send a signal for lime scaling readings.

It must be remembered that for water heaters which are already equipped with a thermostat/electronic device with the additional functions described in the introduction (timer, hot water volume reading, etc), the invention basically applies without any extra cost, apart the upgrading of the calculation capacity and the signal/activation means output.

Claims

C L AI MS

Claim 1. Water heater (1), preferably the accumulator type, comprising a water heating means (4) and a sheath (5) containing one or more sensors, conceived to measure the water temperature in proximity of said water heating means (4), characterised in that it comprises a means (6) for reading the presence of lime scaling on said water heating means (4), said reading means (6) using the temperature information of said sensor/s during the heating stage of said means (4).

Claim 2. Water heater (1), according to claim 1, characterised in that said water heating means (4) comprise at least one electric resistance.

Claim 3. Water heater (1), according to claim 1, characterised in that said water heating means (4) comprise at least one smoke flue.

Claim 4. Water heater (1), according to claim 1 or 2 or 3, characterised in that said means (6) comprise a temperature sensor (6.1) positioned in proximity to said water heating means (4) and calculating means (6.4) conceived to measure the heating speed of the water (GI_f) in proximity to the water heating means (4) and to compare said heating speed (GI_f) with a reference value.

Claim 5. Water heater (1), according to claim 4, characterised in that it comprises means for memorising and/or adjusting said reference value.

Claim 6. Water heater (1), according to claim 4 or 5, characterised in that said reference value is equal to the sum of a reference speed (Gl₀), that corresponds with the heating speed when no lime scaling is present, plus a threshold value (ΔG).

Claim 7. Water heater (1), according to claim 6, characterised in that said threshold value (ΔG) ranges between 3 and 20 °C/minute.

Claim 8. Water heater (1), according to claim 1 or 2 or 3, characterised in that said means (6) comprise a first sensor (6.2) positioned in proximity to said water heating means (4), a second temperature sensor, positioned at a certain distance from said water heating means (4) and calculating means (6.4) conceived to measure the temperature gradient (Ti-T₂) inside the tank between said point in proximity to the water heating means (4) and said point at a certain distance from said water heating means (4) and to compare said gradient (T₁-T₂) with a reference value.(ΔT₀).

Claim 9. Water heater (1), according to claim 8, characterised in that it comprises means for memorising and/or adjusting said reference gradient (ΔTo).

Claim 10. Water heater (1), according to claim 8 or 9, characterised in that said reference gradient (ΔT₀) ranges between 20 and 30 °C.

Claim 11. Flange (3) for a water heater comprising at least one electric resistance (4) and a sheath (5) containing one or more sensors, conceived to measure the temperature of the water in proximity to said resistance (4), characterised in that it comprises means (6) for reading the presence of lime scaling on said electric resistance (4), said reading means (6) using the temperature information of said sensor/s during the heating stage of said resistance (4).

Claim 12. Flange (3) for a water heater, according to claim 11, characterised in that said means (6) comprise a temperature sensor (6.1) positioned in proximity to said electric resistance (4) and calculating means (6.4) conceived to measure the heating speed of the water (GI_f) in proximity to the resistance (4) and to compare said heating speed to a reference value.

Claim 13. Flange (3) for a water heater, according to claim 12, characterised in that it comprises means for memorising and/or adjusting said reference value.

Claim 14. Flange (3) for a water heater, according to claim 12 or 13, characterised in that said reference value is equal to the sum of a reference speed (GIo), that corresponds to the heating speed when no lime scaling is present, plus a threshold value (ΔG).

Claim 15. Flange (3) for a water heater, according to claim 14, characterised in that said threshold value (ΔG) ranges between 3 and 20 °C/minute.

Claim 16. Flange (3) for a water heater, according to claim 11, characterised in that said means (6) comprise a first sensor (6.2) positioned in proximity to said electric resistance (4), a second temperature sensor, positioned at a certain distance from said electric resistance (4) and calculating means (6.4) conceived to measure the temperature gradient (Ti-T₂) between said point in proximity to the resistance (4) and said point at a certain distance from said resistance (4) and to compare said gradient (Ti-T₂) with a reference gradient (ΔT₀).

Claim 17. Flange (3) for a water heater, according to claim 16, characterised in that it comprises means for memorising and/or adjusting said reference gradient (AT₀).

Claim 18. Flange (3), according to claim 16 or 17, characterised in that said reference gradient (ΔT₀) ranges between 20 and 30 ⁰C.

Claim 19. Method for controlling the forming of lime scaling on water heating means (4) for a water heater (1) comprising the following stages:

- feeding the water heating means (4) for a pre-set period of time;

- measuring the heating speed of the water (GI_f), in a zone in proximity to said water heating means, in said pre-set period of time;

- comparing the heating speed measured in this manner (GI_f) with a reference heating speed (GIo);

- sending a warning signal when the measured heating speed (GI_f) exceeds the reference speed (G I₀) by a certain threshold (ΔG) .

Claim 20. Method for controlling the forming of lime scaling, according to claim 19, also comprising the following stages:

- pre-setting, modifying or self-teaching of said reference speed (Gl 0);

- pre-setting or modifying said threshold value (ΔG).

Claim 21. Method for controlling the forming of lime scaling, according to claim 19 or 20, wherein said pre-set time is less than or equal to 5 minutes.

Claim 22. Method for controlling the forming of lime scaling, according to claim 19 or 20 or 21, wherein said threshold value (ΔG) ranges between 3 and 20 °C/minute.

Claim 23. Method for controlling the forming of lime scaling on a water heating means (4) for a water heater (1), comprising the following stages: - heating the water up to a pre-set temperature;

- measuring the heating speed of the water (GI_f), in a zone in proximity to a said water heating means (4), during the heat-up stage;

- comparing the measured heating speed (GI_f) with the reference heating speed (Gl₀);

- sending a warning signal when the measured heating speed (GI_f) exceeds the reference speed (GIo) by a certain threshold (ΔG).

Claim 24. Method for controlling the forming of lime scaling, according to claim 23, also including the following stages: - pre-setting, modifying or self-teaching of said reference speed (Gl o);

- pre-setting or modifying said threshold value (ΔG).

Claim 25. Method for controlling the forming of lime scaling, according to claim 23 or 24, wherein said pre-set temperature is lower than or equal to 30 ⁰C.

Claim 26. Method for controlling the forming of lime scaling, according to claim 23 or 24 or 25, wherein said threshold value (ΔG) ranges between 3 and 20

°C/minute.

Claim 27. Method for controlling the forming of lime scaling on water heating means (4) for a water heater (1) comprising the following stages:

- heating the water for a pre-set period of time; - measuring the temperature gradient T₁-T₂, between a point in proximity to a point at a certain distance from said water heating means (4), after said pre-set time;

- comparing said temperature gradient T₁-T₂ with a reference gradient (ΔT₀); - sending a warning signal when the measured temperature gradient is higher than the reference gradient (ΔT₀).

Claim 28. Method for controlling the forming of lime scaling, according to claim 27, also comprising the stage of pre-setting, modifying or self-teaching said reference gradient (ΔTo).

Claim 29. Control method, according to claim 27 or 28, wherein said pre-set time is less than or equal to 5 minutes.

Claim 30. Control method, according to claim 27 or 28 or 29, wherein said reference gradient (ΔTo) ranges between 20 and 30 ⁰C.