NZ737372A - Regulating method for an electric heater and the associated heater - Google Patents

Abstract

The present invention relates to a control method for regulating a heating apparatus (10), comprising: an envelope (14, 16); an electric heating element (12, 22); an inertial element (14) and a temperature sensor (42); wherein the control method comprises a first and a second mode of operation which are respectively associated with a first temperature (T1) and a second temperature (Tc). The heater further comprises a device for blowing an air flow (21) towards the electric heating element and/or towards the inertial element. The method comprises the following steps: - command (100) to change from the first to the second mode of operation; then - increasing (102) the heating and starting (104) the blowing; then - stopping (106) the blowing if the outside temperature (T) reaches a predetermined value equal to T1 + α(Tc - T1), such that 0 < α ≤ 1. are respectively associated with a first temperature (T1) and a second temperature (Tc). The heater further comprises a device for blowing an air flow (21) towards the electric heating element and/or towards the inertial element. The method comprises the following steps: - command (100) to change from the first to the second mode of operation; then - increasing (102) the heating and starting (104) the blowing; then - stopping (106) the blowing if the outside temperature (T) reaches a predetermined value equal to T1 + α(Tc - T1), such that 0 < α ≤ 1.

Description

Regulating method for an electric heater and the associated heater The present invention relates to a method of regulating a heater of the type comprising: an envelope defining an interior space and a space outside the apparatus; an electric heating element designed to convert electrical energy into heat and located in the interior space; an inertial element made of a material with thermal inertia, able to store the heat emitted by the electric heating element and to restore the heat to air outside the apparatus; a sensor of a temperature of the outside air; wherein the control method comprises a first mode of operation of the apparatus for maintaining the outside air at a first temperature T , and a second mode of operation of the apparatus for maintaining the outside air at a second temperature T that is higher than the first temperature.

In such a heating apparatus, referred to as a thermal inertia apparatus, the heat of the heating element is transferred to the outside air by the inertial element. Thus, the outside temperature variations are attenuated compared to direct transfer, and which thus improves the comfort of the users.

The regulation methods of electric heaters generally provide for an "economy mode" and a "comfort mode", each aimed at keeping the outside air at a different temperature. The economy mode, which corresponds to the lowest temperature, is generally adopted in the absence of users. When switching to comfort mode, the heating element is supplied with electricity to raise the temperature of the room.

In such a case, the presence of an inertial element slows the rise in temperature compared with direct heat transfer between the heating element and the air.

One solution to accelerate the temperature rise is to increase the maximum heating power of the apparatus. This solution is nevertheless expensive in energy.

The present invention aims to provide a heater offering a rapid rise in temperature without significantly increasing the energy cost.

To this end, the object of the invention is a method of the aforementioned type, wherein: the heating apparatus further comprises a blowing device, capable of directing a flow of air towards the electric heating element and/or towards the inertial element, wherein the air flow is in communication with the outside air; and wherein the method comprises the following steps: with the apparatus in the first mode of operation and the blowing device stopped, reception of a command to change to the second mode of operation; then increasing the electrical energy supplied to the heating element, and starting the blowing device; followed by stopping the blowing device if the temperature of the outside air reaches a first predetermined value equal to T + α (T - T ), such that 0 < α ≤1. 1 c 1 According to other advantageous aspects of the invention, the method comprises one or more of the following characteristics, taken separately or in any technically feasible combination: - α lies between 70% and 99%, more preferably between 80% and 95%; - when switching on the blowing device, the device operates according to a first air flow rate d ; then, when the outside air temperature reaches a second predetermined value equal to T + β(Tc - T ), where 0 < β < α, the blowing device operates according to a second air flow rate d such that 0 < d < d ; 2 2 1 - the first air flow is substantially constant while the second air flow decreases over time; - a first period is measured between a first instant of start-up of the blowing device and a second instant when the temperature of the outside air reaches the second predetermined value; then, from the second instant, an air flow of the blower device varies according to a predetermined model form that is designed to decrease the air flow between the values d and 0 over a second period calculated as a function of the first period; - β lies between 50% and 90%, more preferably between 60% and 70%; - when the electrical energy supplied to the heating element increases, electric power is supplied to the heating element; then, if the temperature of the outside air reaches a third predetermined value equal to T + γ (T - T ), where 0 < γ < α, 1 c 1 the supplied electric power decreases; - the heater further comprises a presence detector near the apparatus; wherein the method further comprises: a step of stopping the blowing device (20) when a presence is detected; and a step of restarting the blowing device when no presence is detected, and if the temperature of the outside air is lower than the first predetermined value.

The invention further relates to a heater comprising: an envelope defining an interior space and a space outside the apparatus; an electric heating element adapted to convert electrical energy into heat and located in the interior space; an inertial element formed of a material with thermal inertia and able to store the heat emitted by the electric heating element and to restore the heat to air outside the apparatus; a sensor of the temperature of the outside air; and a blowing device that is designed to direct a flow of air towards the electric heating element and/or the inertial element, wherein the air flow is in communication with the outside air; and wherein the heater is provided with means for implementing a control method as described above.

According to other advantageous aspects of the invention, the heating apparatus comprises one or more of the following characteristics, taken separately or in any technically feasible combination: - the inertial element forms a front panel included in the envelope of the apparatus, wherein the front panel has an internal face facing towards the interior of the apparatus, and wherein the electric heating element is in contact with the internal face; - the inertial element is formed of a material capable of emitting infrared radiation under the effect of an increase in its temperature; - the blowing device comprises at least one fan, preferably at least two fans, located in the interior space.

The invention will be better understood on reading the description which follows and that is given solely by way of a non-limiting example with reference to the drawings, wherein: Fig. 1 shows a schematic sectional view of a heater according to one embodiment of the invention; Fig. 2 shows a schematic view of a device for regulating the heater of Fig. 1; Fig. 3 shows a method according to one embodiment of the invention in the form of a flow chart; and Fig. 4 graphically represents temperature and power variations as a function of time for the heating apparatus of Fig. 1.

Fig. 1 shows schematically and in section, a heating apparatus 10 according to one embodiment of the invention. Preferably, the apparatus 10 is a domestic heater or radiator. In the following description, the heating apparatus 10 is considered to be installed in a room of a residential building.

The heating apparatus 10 comprises, in particular, a main electric heating element 12 and an inertial element 14 forming a front panel of the heating apparatus 10. The heating apparatus 10 further comprises a rear bodywork 16, assembled with the front panel 14 to form an envelope of the heating apparatus 10. The envelope defines an interior space 17 and an outer space 18 of the apparatus.

In the rest of the description, the terms "interior" and "exterior" refer respectively to the interior space 17 and exterior space 18 of the apparatus 10. The outer space 18 is considered to be limited to the room in which the device 10 is installed.

The apparatus 10 further comprises a blowing device 20. In the embodiment of Fig. 1, the apparatus 10 further comprises a secondary electric heating element 22. The blowing device 20 and the secondary heating electric element 22 are arranged in the interior space The apparatus 10 also comprises an electronic device 23 for regulating the electrical supply of the heating elements 12, 22 and the blowing device 20.

The front panel 14 is able to store the heat emitted by the heating elements 12, 22 and to restore the heat to air outside the apparatus 10. The front panel 14 is preferably made of a thermal inertia material, particularly of the glass, stone or metal type, such as cast iron.

Preferably, the material of the front panel 14 is also emissive, i.e. able to emit infrared radiation under the effect of an increase in temperature.

In the embodiment of Fig. 1, the front panel 14 has a substantially planar shape, arranged vertically in an operating position of the apparatus 10. According to the variant, the front panel 14 has a curved or angular shape.

The front panel 14 comprises a front face 25 and a rear face 26, respectively oriented towards the outside and towards the inside of the apparatus 10.

The main electric heating element 12 is an electrical resistance, in thermal contact with the rear face 26 of the front panel 14. In the embodiment of Fig. 1, the electrical resistance 12 is screen-printed on a plastic film 28, while the plastic film is stuck on the rear face 26 of the front panel. According to an alternative embodiment (not shown), the electrical resistance is formed by a heating cable applied to the rear face 26 of the front panel.

The rear bodywork 16 is, for example, made of metal and comprises means (not shown) for attachment to a vertical wall. The rear bodywork 16 further comprises lower openings 30 and upper openings 31 for a substantially vertical air flow in the interior space 17.

The blowing device 20 is preferably located in the lower part of the apparatus 10, in particular near the lower openings 30 of the rear bodywork 16. The blowing device 20 preferably comprises at least one fan, and more preferably two fans, arranged, for example on either side of a vertical median plane of the apparatus 10. The blowing device 20 is designed to direct an air flow 21 towards the electrical resistance 12 and to the front panel 14.

The flow of air is, for example, oriented obliquely, from the bottom to the top.

The secondary heating element 22 is preferably a convection heating element. The secondary heating element 22 comprises, for example, an electrical resistance embedded in a cast iron, ceramic or aluminum heater. The heating body is, for example, fixed to the rear bodywork 16.

One considers a ratio between the maximum powers P and P of the power max1 max2 supply of the electric heating elements, respectively the main element 12 and the secondary element 22. Preferably, the ratio lies between 1 and 4.

The electronic control device 23 is shown schematically in Fig. 2. The electronic control device 23 comprises, in particular, a control unit 32 situated at the upper part of the apparatus 10. The control unit 32 comprises, for example, a microprocessor 33, a program memory 34 and at least one communication bus 36.

The control unit 32 also comprises a man/machine interface 40, of the screen/keyboard type, enabling a user to select parameters of the control method, such as a set temperature T of the apparatus 10.

The electronic control device 23 also comprises a temperature sensor 42 located in the lower part of the apparatus 10 and connected to the control box 32. The sensor 42 makes it possible to measure a temperature T of the air outside the apparatus 10.

Optionally, the electronic control device 23 further comprises a presence detector 43 that is able to detect a presence in the vicinity of the apparatus 10. This is, for example, an optical detector, especially an infrared, or an acoustic detector.

The electronic control device 23 is able to supply electrically the electrical resistances of the heating elements 12, 22, as well as the blowing device 20.

More specifically, the program memory 34 contains a program 44 controlling the power supply of the heating elements 12, 22, as a function of the outside temperature T measured by the sensor 42, and with the set temperature T set at the interface 40.

In the case where the apparatus 10 includes a secondary heating element 22, the main heating element 12 is preferably a priority in the program 44. In other words, as long as the power supply of the resistance 12 is lower than the maximum power P , the resistance max1 of the secondary heating element 22 is not supplied with electricity.

Moreover, the program 44 provides a first mode of operation of the apparatus 10, the economy mode. The economy mode is intended to maintain the outside temperature T at a first value T . Preferably, T is equal to T - ∆T, wherein T is the setpoint temperature 1 1 c c adjustable at the interface 40, while ∆T is a predefined interval in the program memory 34.

The program 44 further provides a second mode of operation of the apparatus 10, the comfort mode. The comfort mode is intended to maintain the outside temperature T at a second value T that is greater than the first value T . In the remainder of the description, T is 2 1 2 considered to be equal to the set temperature T .

Preferably, in the economic mode as in the comfort mode, the blowing device 20 is by default at a standstill. In other words, the operation of the apparatus 10 is primarily based on radiation, i.e. the infrared emission by the front panel 14, and on the natural convection, or the heat transfer of the heating elements 12, 22 to the air without blowing.

When switching from the economy mode to the comfort mode, the program 44 executes the steps of a method according to one embodiment of the invention, as described below. The method is represented by a logic diagram in Fig. 3.

Since the apparatus 10 is in economy mode, a first step of the method is the reception 100 by the program 44 of a comfort mode command. This command is, for example, generated by time programming the apparatus 10. Alternatively, the command to change to comfort mode is generated by the detection of a presence by the detector 43.

The command to pass to comfort mode leads to the supply 102 of power to the heating elements 12, 22, or to an increase in the power supplied compared to the economy mode. Preferably, upon reception of the command to pass to comfort mode, each of the heating elements is supplied its maximum power, respectively P and P . max1 max2 In a substantially simultaneous manner, the program 44 triggers the operation of the blowing device 20, or the fans, corresponding to a first air flow d . Preferably, d is equal to or close to a maximum air flow rate of the blowing device.

The blowing device 20 thus directs an air flow 21 towards the resistance 12 and to the front panel 14, wherein the air flow is directed from the bottom upwards. In other words, outside air enters the interior space 17 through the lower openings 30 of the rear bodywork 16. The air is heated by contact with the resistance 12 and/or the front panel 14 and then comes out in the outer space 18 through the upper openings 31.

Preferably, the interior space 17 is small enough for the air flow 21 to be heated also by the secondary heating element 22.

The outside air is thus heated by forced convection within the apparatus 10, which accelerates the rise of the temperature T with respect to a radiation/natural convection operation.

The blowing device 20 is then stopped 106 when the temperature T of the outside air, measured by the sensor 42, reaches a third value T defined as a function of the set temperature T . T is, for example, calculated according to a predefined formula in the program memory 34, such that T = T + α(∆T), where 0 < α ≤ 1. In other words, the blowing device 20 stops when the temperature of the outside air has reached, or is at least sufficiently close to, the set temperature T .

Preferably, the value α lies between 70% and 99%, more preferably between 80% and 95%.

According to a first variant of the method, represented by the arrow 108 in Fig. 3, the air flow of the blowing device 20 remains substantially constant until the step of stopping 106.

The graph of Fig. 4 shows the variation of the outside temperature T as a function of time, for a heater 10 as described above, during a process according to the first variant above. The curve 50 represents a first so-called "dynamic" case, corresponding to a value α equal to 95%. The curve 52 represents a second case corresponding to a value α equal to 65%.

The curve 54 represents a third reference case, called "static". In the "static" case, the blowing device 20 is not used, while the other steps of the above method are retained.

The origin of the time axis corresponds to the command to change from economy mode to comfort mode. In the example shown in Figure 4, T = 19 °C; ∆T = 3.5 °C; while the total electrical power of the apparatus 10, corresponding to P + P , is 1000 W. max1 max2 It is found that in the "dynamic" case, the temperature of 18.8 °C (i.e. T - 5% ∆T) is reached after 35 minutes, compared with 48 minutes in the "static" case. The time saving 56 with respect to the rise in temperature, related to the use of a blowing device, is therefore about 27%.

In the case of the curve 52, from the stopping of the blowing device 20, it is found that the rise in temperature slows down sharply. In fact, the inertial material of the front panel 14, previously cooled by the air flow 21, absorbs most of the heat emitted by the resistance 12. From the stopping of the blowing device 20, the curve 52 thus approximates the curve 54 ("static" case).

In order to optimize both the heating comfort and the noise nuisance associated with the blowing device 20, a second variant of the method provides for a gradual decrease in the air flow rate until the blowing device is stopped.

According to this second variant, represented by the arrow 110 in Fig. 3, the step 104 corresponds to a first operating phase of the blowing device 20 according to the first airflow d . The temperature T increases until a fourth value T defined as a function of the set temperature T is reached. T is, for example, calculated according to a predefined formula in the program memory 34, such that T = T + β(∆T), where 0 < β < α. Preferentially, the β value lies between 50% and 90%, more preferably between 60% and 70%.

The program 44 then passes to a second phase 112 of operation of the blowing device 20 in a second air flow d where 0 < d < d . The temperature T continues to increase 2 2 1 until it reaches the value T , which leads to the total stoppage of the blowing device 20.

The reduction of the air flow makes it possible to limit the noise of the blowing device 20 when a certain level of heating comfort is already ensured in the room.

According to a first embodiment, the second air flow rate d is constant over the period of the second phase 112, wherein, for example, d /d = 30%.

According to a second embodiment, d decreases during the second phase 112, up to the step of stopping 106 the blowing device 20. The decrease of d during the second phase 112 is effected according to a predetermined model form, stored in the program memory 34. It is, for example, an incremental decrease, or a continuous decrease, in particular linear.

According to a first alternative of the second embodiment, a period τ of decrease at the rate d between the values d and 0 is predefined in the program memory 34, based on experimental data.

It is, however, difficult to set the period τ before the installation of the apparatus 10, because the rate of rise in temperature depends on several parameters external to the apparatus. Such parameters include, in particular, the size of the installation piece, as well as the thermal characteristics of the building.

Thus, if the period τ is chosen too short, the blowing device 20 stops before the temperature T has reached the third value T . If the period τ2 is chosen too long, the noise nuisance related to the operation of the blowing device 20 is not optimized.

In addition, according to a second alternative of the second embodiment, the period τ of decrease at the rate d between the values d and 0 is calculated as a function of a 2 2 1 period τ of the first phase 104.

An example is considered where β = 63% and α = 95%. The period τ of the first phase 104 is measured between an instant t of operating the blowing device and a time t when the temperature T reaches the fourth value T . Then, starting from said instant t , defining the beginning of the second phase 112, the air flow d of the blowing device decreases according to a predetermined model form, for example linear. The model is configured to change the airflow from d to 0 over a period τ calculated as a function of the time τ1 previously measured.

The program 44 provides, for example, that τ = τ . Other ratios may be defined between the periods τ and τ , according to the values of α and β.

If the temperature T reaches the third value T before the end of the period τ , the blower 20 is stopped (step 106). Thus, in this example, the second phase 112 is designed to have a maximum period equal to the period τ of the first phase 104.

The example described above is illustrated in Fig. 4 by the curve 58, representing the temperature variation T. This curve 58 is very close to the curve 50 of the "dynamic" case.

The example described above thus provides a heating comfort comparable to the "dynamic" case, while reducing the noise nuisance of the blowing device 20 if it is in the room.

According to a third alternative of the second embodiment, the program 44 provides for a determination of τ through self-learning of the apparatus 10. In other words, the period τ is calculated on the basis of an average of the periods τ measured in previous phases of the change from economy mode to comfort mode.

In parallel with the operation of the blowing device 20, it is possible to vary the power supply of the heating elements 12, 22 as a function of time, in order to prevent the apparatus 10 from overheating.

For example, program 44 provides that step 102 corresponds to a first phase of operation of the heating elements 12, 22, at a first electrical power. Preferably, upon receipt of the command to pass to comfort mode, each of the heating elements is supplied at its maximum power, respectively P and P . max1 max2 The temperature T increases until it reaches a fifth value T defined as a function of the set temperature T . For example, T is calculated according to a predefined formula in the program memory 34, such that T = T + γ(∆T), where 0 < γ < α. Preferably, the value γ lies between 50% and 90%, more preferably between 60% and 70%.

The program 44 then passes to a second phase 114 of operation of the heating elements 12, 22. During this second phase, the total power supplied to the heating elements 12, 22 decreases gradually.

Preferably, the power supplied to the main heating element 12 is substantially maintained at P as long as the set temperature T , or even the third value T , is not max1 c 3 reached. During the second phase 114, it is, therefore, the power supplied to the secondary heating element 22 which gradually decreases.

The curves 60 and 62 of Fig. 4 respectively represent the variations of the electric power supplied as a function of time, respectively in the "dynamic" and "static" cases as described above. The electric power supplied is expressed as a percentage of the total power of the apparatus 10.

It may be seen that the use of blowing allows curve 60 of the "dynamic" case to decrease earlier than in the "static" case. A space 64 between the curves 60 and 62 illustrates an energy saving for the rise in temperature, linked to the use of a blowing device.

This saving of energy is of the order of 6%. Such an energy gain largely offsets the energy consumed by the fans of the blowing device 20.

In the "dynamic" case described above, the blowing is maintained at the first rate d until the third value T of the temperature T is obtained. According to a variant, the blowing device 20 is synchronized with the heating elements . More specifically, the program 44 corresponds to the second variant described above, represented by the arrow 110 in Fig. 3, where T = T . Thus, from the moment T reaches the fourth value T , the flow rate of the 4 4 blower 20 and the power supplied to the secondary heating element 22 decrease together.

Preferably, the electronic control device 23 offers the possibility to the user of disabling the execution of the program 44. Thus, the user may overcome the noise associated with the blowing device 20 if he is present in the room.

According to one embodiment, in the case where the command to change to comfort mode is not related to the presence detector 43, the program 44 causes the blowing device 20 to stop as the detector 43 detects a presence close to the apparatus 10. Thus, the blowing only works when the room is unoccupied, in order to reduce noise.

The method as described above allows faster temperature rise than in the case of devices without a blowing device. Consequently, it is possible to configure an interval ∆T between the temperatures of the economy and comfort modes, greater than for radiators of the prior art.

Preferably, ∆T is greater than 3.0 °C and more preferably between 3.5 °C and 5.0 °C. Such a method thus allows energy savings in economy mode, without degrading the heating comfort in comfort mode.

Similarly, the method described above may be used in the case of a change from a frost-free mode to comfort mode. The frost-free mode is characterized by a lower T temperature than the economy mode. For example T = T - 10 °C. hg c

Claims (12)

1. Method of regulating a heating apparatus (10), wherein the apparatus comprises: - an envelope (14, 16) defining an interior space (17) and an outer space (18) to the 5 apparatus; - an electric heating element (12, 22) adapted to convert electrical energy into heat and located in the interior space; - an inertial element (14) made of a material with thermal inertia, capable of storing the heat emitted by the electric heating element and of returning the heat to air 10 outside the apparatus; - a sensor (42) for a temperature (T) of the outside air; wherein the control method comprises a first mode of operation of the apparatus for maintaining the outside air at a first temperature (T ) and a second mode of operation of the apparatus for maintaining outside air at a second temperature (T ) that is greater than the first 15 temperature; characterized in that the heating apparatus further comprises a blowing device (20), designed to direct an air flow (21) towards the electric heating element and/or the inertial element, wherein the air flow is in communication with the outside air; and wherein the method comprises the following 20 steps: - as the apparatus is in the first mode of operation and the blowing device is at a standstill, reception (100) of a command to change to the second mode of operation; then - increasing (102) the electrical energy supplied to the heating element, and 25 starting (104) of the blowing device; then - stopping (106) of the blowing device if the temperature (T) of the outside air reaches a first predetermined value (T ) equal to T + α(T - T ), such that 0 < α 3 1 c 1 ≤ 1.

2. Method according to claim 1, wherein α lies between 70% and 99%, more 30 preferably between 80% and 95%.

3. Method according to claim 1 or claim 2, wherein: - when the blowing device is switched on (104), the device operates according to a first air flow rate (d ); then - if the outside air temperature reaches a second predetermined value (T ) equal to T + β(T - T ), where 0 < β < α, the blowing device operates (112) at a second air 1 c 1 5 flow rate (d ) such that 0 < d < d . 2 2 1

4. Method according to claim 3, wherein the first air flow (d ) is substantially constant and the second air flow (d ) decreases over time. 10

5. Method according to claim 4, wherein - a first period (τ ) is measured between a first instant (t ) for starting the blowing device and a second instant (t ) when the temperature of the outside air reaches the second predetermined value (T ); then - from the second instant (t ), an air flow of the blowing device varies according to a 15 predetermined model form, and designed to decrease the air flow between the values d and 0 over a second period (τ ) calculated as a function of the first period.

6. Method according to one of the claims 3 to 5, wherein β lies between 50% and 20 90%, more preferably between 60% and 70%.

7. Method according to one of the preceding claims, wherein - during the increase (102) of the electric energy supplied to the heating element, electric power is supplied to the heating element; then 25 - if the outside air temperature reaches a third predetermined value (T ) equal to T + γ(T - T ), where 0 < γ < α, the electric power supplied decreases.

8. Method according to one of the preceding claims, wherein the heater (10) further comprises a presence detector (43) near the apparatus; wherein the method further 30 comprises: - a step of stopping the blowing device (20) when a presence is detected; and - a step of restarting the blowing device when no presence is detected, and if the temperature (T) of the outside air is less than the first predetermined value (T ).

9. Heating apparatus (10) comprises: - an envelope (14, 16) defining an interior space (17) and an outer space (18) to the heater; 5 - an electric heating element (12, 22) designed to convert electrical energy into heat and located in the interior space; - an inertial element (14) made of a material with thermal inertia and capable of storing the heat emitted by the electric heating element and of returning the heat to air outside the apparatus; 10 - a sensor (42) for a temperature (T) of the outside air; - a blowing device (20), designed to direct an air flow towards the electric heating element and/or to the inertial element, and the air flow is in communication with the outside air; wherein the heating apparatus is provided with means (23, 44) for implementing a 15 control method according to one of the preceding claims.

10. Heating apparatus (10) according to claim 9, wherein the inertial element (14) forms a front panel included in the envelope of the apparatus, wherein the front panel has an inner face (26) facing towards the inside of the heating apparatus, and wherein the electric 20 heating element (12) is in contact with the inner face.

11. Heating apparatus according to claim 9 or claim 10, wherein the inertial element (14) is made of a material capable of emitting infrared radiation under the effect of an increase in its temperature.

12. Heating apparatus according to one of the claims 9 to 11, wherein the blowing device (20) comprises at least one fan, preferably at least two fans, located in the interior space (17).