System and method for controlling the temperature of a sauna room

Abstract

The invention relates to a system for controlling the temperature of a sauna room (8), the system including a sauna stove (10) arranged in the sauna room (8) for heating the sauna room (8) to a temperature of 60-120 °C, a temperature sensor (40) for measuring the temperature of the sauna room (8), control means for controlling the temperature of the sauna room (8) based on measurement data of the temperature sensor (40), wherein in the system the sauna stove (10) includes a frame (12), a stone space (14) including a thermal mass capable of being heated to a temperature of 200-700 °C and of evaporating water dispensed into the stone space (14), a flow channel (20) in which a flowing fluid can flow by natural convection and in which said fluid can be heated by the heat produced in the stone space (14), and a valve (30) configured to control the flow of the fluid in the flow channel (20). The system includes thermostat means by means of which the system is configured to control the temperature of the sauna room (8) by controlling the opening state of said valve (30) based on the measurement data (40) of the temperature sensor (40) that measures the temperature of the sauna room (8). The invention also relates to a corresponding method.

Description

[0001] SYSTEM AND METHOD FOR CONTROLLING THE TEMPERATURE OF A SAUNA ROOM

[0002] The invention relates to a system for controlling the temperature of a sauna room, the system including

[0003] - a sauna stove arranged in the sauna room for heating the sauna room to a temperature of 60-120 °C,

[0004] - a temperature sensor for measuring the temperature of the sauna room,

[0005] - control means for controlling the temperature of the sauna room based on measurement data of the temperature sensor, wherein in the system the sauna stove includes

[0006] - a frame,

[0007] - a stone space including a thermal mass capable of being heated to a temperature of 200-700 °C and of evaporating water dispensed into the stone space,

[0008] - a flow channel in which a flowing fluid can flow by natural convection and in which said fluid can be heated by the heat produced in the stone space, and

[0009] - a valve configured to control the flow of the fluid in the flow channel .

[0010] The invention also relates to a corresponding method.

[0011] A sauna stove in what is known as a Finnish sauna includes a stone space that is filled with heat-retaining stones or some other heat-retaining mass, such as ceramic material. The mass in the stone space is typically heated to a temperature of around 200-700 °C in operation. The water dispensed into the stone space of the sauna stove in operation thus evaporates quickly and forms vapour, or steam, which mainly rises upwards out of the stone space and spreads into the room. The hot stone space of the sauna stove simultaneously also contributes to the heating of the air in the sauna room, the air typically being heated to a temperature of around 60-120 °C, mainly by natural convection .

[0012] A problem with sauna stoves according to the prior art is that, when the sauna room reaches the target temperature, it is necessary to limit the heating power of the sauna stove in order to prevent the temperature of the sauna room from becoming uncomfortably high, whereby the mass in the stone space cools down. Frequently, the temperature of the sauna room is the only factor used to control the heating or more specifically the heating power of the sauna stove. Moreover, a continued dispensing of water into the stone space of the sauna stove during the sauna session can cool the sauna-stove stones, and the power of the sauna stove is insufficient to maintain an adequate temperature in the stone space when the temperature of the sauna room is at the target temperature. Once the temperature of the sauna room has stabilized and most of the structures in the sauna are at the target temperature, a heating power is no longer needed. The mass in the stone space is thus not heated or is heated minimally, although the users still throw water onto the stones. This results in the experience of the user that the sauna stove does not produce enough water vapour, i.e. steam.

[0013] Typically, the structure of a sauna stove is designed so as to allow air to be conducted through the stone space. Nevertheless, the air flow through the stone space is poor in sauna stoves based on natural convection.

[0014] Furthermore, when the sauna stove is used both to heat the air in the room and to form a hot stone space used for the production of steam, there is hardly any way to control the intensity of the steam, as the temperature of the stone space directly affects both the intensity of the steam and the temperature in the room. There is thus no way of controlling the intensity of the steam without affecting the temperature of the room at the same time.

[0015] Typically, for example, in an electric sauna stove heated by resistance, the electric current supplied to the resistors is controlled by thermostat means based on measurement data of the temperature sensor measuring the temperature of the sauna room. As a result, if the temperature of the sauna room is above a selected limit value and a large amount of water is thrown into the stone space, the temperature in the stone space can drop and become too low to produce steam, while the temperature of the sauna room does not decrease significantly. If there is no decrease in the temperature of the sauna room, the thermostat means will not command the sauna stove to provide additional heating power.

[0016] Sauna stoves are known in the prior art that include an adjustable flow channel in which air is conveyed through the sauna stove so as to momentarily increase the transmission of heat into the sauna room. For example, the patent publication FI101261B discloses a so-called steam-ready sauna stove which includes a closing mechanism, which is configured in connection with a cover, for closing a vent that regulates a flow through the stone space, wherein opening the closing mechanism causes a rapid passage of air through the hot stones into the surrounding sauna space. This is mainly intended to accelerate the heating of the sauna room in the initial stages of heating. With the sauna stoves according to the prior art, there is no way, however, of controlling the temperature of the sauna room and of the stone space in a desired manner, so that there is also no way to improve or control the sauna steam experience of the user. The solutions according to the prior art, such as FI101261B, additionally use a fan to produce a forced convection, which accelerates the air flow through the stone space. A forced convection produced by a fan complicates the design of the sauna stove.

[0017] The object of the invention is to provide an improved system and method for controlling the temperature of a sauna room which allow a more versatile control of the temperatures of a stone space and of a sauna room than before and thereby permit an enhanced sauna experience. The characteristic features of a sauna stove according to the invention are set out in claim 1, while the characteristic features of a method according to the invention are set out in claim 13.

[0018] A system according to the invention for controlling the temperature of a sauna room includes a sauna stove arranged in the sauna room for heating the sauna room to a temperature of 60-120°C, a temperature sensor for measuring the temperature of the sauna room, control means for controlling the temperature of the sauna room based on measurement data of the temperature sensor, wherein in the system the sauna stove includes a frame, a stone space including a thermal mass capable of being heated to a temperature of 200-700 °C and of evaporating water dispensed into the stone space, a flow channel in which a flowing fluid can flow by natural convection and in which said fluid can be heated by the heat produced in the stone space, and a valve configured to control the flow of the fluid in the flow channel. The system includes thermostat means by means of which the system is configured to control the temperature of the sauna room by controlling an opening state of said valve based on measurement data of the temperature sensor that measures the temperature of the sauna room. In other words, the system according to the invention controls the temperature of the sauna room by controlling the amount of fluid heated by the heat of the stone space that flows through the flow channel so as to control the amount of power transferred from the stone space to the sauna room. The intended function of the sauna stove is to keep the sauna-stove stones in a steam-ready state throughout a sauna session, i.e. to maintain the temperature of the stone space at a selected level. The temperature of the sauna room is measured by the temperature sensor, which can be arranged anywhere in the sauna room, or which can be attached to the sauna stove. It is not essential to measure the absolute temperature of the sauna room, but rather the temperature sensor measures any temperature that is a function of the temperature of the sauna room and / or that indicates the temperature of the sauna room. It is thus possible to control the temperature of the sauna room by controlling the position of the valve with the thermostat means. When additional heat is needed in the sauna room, the flow channel running through the sauna stove, which flow channel can be formed by the stone space or by a separate pipe that runs through the stone space or next to it, is opened, so that heat is transferred from the stone space into the sauna room. When the sauna room is warm enough, the flow channel is closed, so that it is possible to control the temperature of the stone space better and maintain a selected temperature level in the stone space. In other words, the valve is configured to open and close the flow channel. The temperature of the sauna room is maintained by the control means at a selected level during the sauna session. It thus becomes possible to control the temperature of the stone space better than before and, in particular, to keep the temperature of the stone space at a sufficiently high level even when the temperature of the sauna room is at its target level. The system is configured to measure the temperature of the sauna room during a sauna session with the temperature sensor and to control the opening state of the valve during the sauna session with the thermostat means based on measurement data of the temperature sensor. Preferably, the system is configured to open and close the flow channel repeatedly during a sauna session, so as to achieve a precise control of the temperature over the sauna session.

[0019] This enables a control of the temperatures of a sauna that is more versatile than before in terms of the temperatures of both the sauna room and the stone space. In particular, the stone space can be kept at a selected temperature over a sauna session in order to produce a potent sauna steam effect.

[0020] The valve referred to here does not have to be completely airtight, but rather the valve limits the flow of the fluid by at least 90% in the closed position compared to the open position. The valve can be controlled between a closed and an open position, or a fine control can additionally be provided in the form of one or more partially open positions. The valve can be located in any part of the flow channel. The fluid can be air or water vapour or a mixture of the two.

[0021] The adjustable valve according to the invention also makes it possible to insulate the stone space better than to date without adversely affecting the steam production of the sauna stove. In other words, as the flow of air is actively controlled by the valve, it is possible to insulate the stone space better and thus store heat in the stone space better than to date. When the valve is closed, the flow of air through the stone space of the sauna stove is reduced, so that heat is stored better in the mass in the stone space. Preferably, the system includes a temperature sensor that measures the temperature of the stone space in the sauna stove, and the system is configured to control the temperature of the stone space, using the thermostat means, based on measurement data of the temperature sensor that measures the temperature of the stone space. The temperature of the stone space is thus measured by the temperature sensor, and it can be controlled by the thermostat means. The temperature of the stone space can consequently be maintained at a selected level during a sauna session with greater precision than to date. The temperature of the stone space can also be controlled with greater precision than before in a manner desired by the user, whereby it is possible to influence the steam intensity. For example, the user can enter a desired temperature of the stone space into the control means, so that the temperature of the stone space is maintained at that desired temperature within a selected tolerance. If the temperature sensor that measures the temperature of the stone space detects a cooling of the stone space below a selected limit value during the sauna session, the control means can be configured to order, based on the reading of the temperature sensor that measures the temperature of the stone space, additional heating power to heat the mass in the stone space.

[0022] Thermostat means is broadly defined here as any device that automatically controls the temperature, for example a device that controls the opening state of the valve or that controls the heating power of the stone space. The system can include a plurality of thermostat means, for example in such a manner that a first thermostat means is configured to control the temperature of the sauna room by controlling the opening state of the valve and a second thermostat means is configured to control the temperature of the stone space by controlling the heating power, such as a wattage of electric current supplied to the resistors.

[0023] Similarly, control means is broadly defined here as any device that can be used to control the temperature of the sauna room by means of which a control command generated based on the reading of the temperature sensor is transmitted to the thermostat means. The control means can include electronic and / or mechanical components. The control means can consist, for example, of an electronic control unit of the sauna and software belonging to the same, wherein the electronic control unit is configured to read one or more temperature sensors and to control, using the thermostat means, the opening state of the valve and / or the heating power supplied to the sauna stove. The control means can also be, for example, a mechanical component which transmits a control command based on a reading of the temperature sensor to the thermostat means that controls the valve, or which controls a supply of combustible material in the sauna stove based on a reading of the temperature sensor.

[0024] The stone space of the sauna stove can be partially enclosed in such a manner that the frame of the sauna stove can cover at least 50%, preferably at least 80%, of the stone space. In other words, at most 50 %, preferably at most 20 %, of the surface area of the edges of the stone space is thus visible from outside the sauna stove. This makes it easier to maintain a desired temperature in the stone space.

[0025] The sauna stove can additionally include a cover over the stone space in which an opening of a selected size is arranged for the dispensing of water. This makes it possible to store heat in the stone space during operation better than to date, which enables an improved control of the temperature of the stone space. The stone space can also be thermally insulated and include a cover that is closed when the sauna is not in use to keep the heat in the stone space.

[0026] In one embodiment, the stone space of the sauna stove is configured to be heated by resistors, and the thermostat means is configured to control the power of the electric current supplied to the resistors. It is thus possible to use electrical energy to produce a desired temperature in the stone space. The resistors can be arranged in the stone space or outside the stone space.

[0027] In another embodiment, the stone space of the sauna stove is configured to be heated by burning wood or gas or a combustible liquid, such as oil, or by the friction generated by an electrically operated turbine. It is alternatively possible to produce a desired temperature in the stone space by burning organic matter.

[0028] In other words, in the system according to the invention, any heat-producing means and any energy source according to the prior art can be used to heat the sauna room and the stone space .

[0029] The sauna stove can thus include a firebox, and the system can include means for controlling the flow of air into the firebox. It is thereby possible to control the combustive power and thus the temperature of the stone space.

[0030] The sauna stove can also include means for controlling the supply of a gaseous or liquid combustible material. It is thereby possible to control the heating power of the sauna stove in an alternative manner. The sauna stove can thus include a flue and a flue-gas temperature sensor, and the system includes an adjustable damper in the flue for controlling the combustive power by narrowing the flue based on measurement data of the flue-gas temperature sensor. It is thereby possible to control the combustive power and thus the temperature of the stone space in an alternative manner.

[0031] The throttling of the air into the firebox and / or the narrowing of the flue can be employed in one embodiment or in different embodiments .

[0032] In one embodiment, the system includes an electronic actuator, such as a solenoid or servomotor, for controlling the opening state of the valve. It is thus possible to use electrical energy to control the opening state of the valve with precision.

[0033] In another embodiment, the system includes a thermomechanical actuator, such as a capillary thermostat or a bimetal thermostat, for controlling the opening state of the valve. It is thereby possible to control the opening state of the valve without electricity, whereby the system can be designed without any electrical components.

[0034] In one embodiment, the flow channel of the sauna stove consists of an opening in a lower part of the frame of the sauna stove, in which opening the valve is arranged, and the stone space. The flow channel in which the flowing fluid can be heated by the heat produced in the stone space can thus be provided in the sauna stove in a simple manner.

[0035] In a second embodiment, the flow channel of the sauna stove is a closed pipe with a first opening for an air inlet and a second opening for an air outlet, and the first opening is arranged in a lower part of the sauna stove, and the second opening lies outside the stone space and above the stone space in a height direction. It is thereby possible to control the flow of fluid flowing through the sauna stove with precision, and the fluid discharged from the flow channel can be delivered to a desired location .

[0036] A closed pipe here means that the pipe has a first opening and a second opening between which the pipe is essentially closed. Thus, when the valve is closed, there is essentially no or very little air flow in the pipe compared to a situation in which the valve is open.

[0037] Alternatively, the second opening of the pipe can also lie inside the stone space.

[0038] In a third embodiment, the flow channel of the sauna stove is a closed pipe with a first opening for an air inlet and a second opening for an air outlet, and the first opening is arranged in a lower part of the sauna stove, and the second opening lies outside the stone space and below the centreline of the stone space in a height direction. It is thereby possible to produce warm air in the lower part of the sauna room, whereby it is possible to even out temperature differences in the sauna room, in which the air in the upper part is typically significantly warmer than the air in the lower part during operation.

[0039] In the third embodiment just described, the pipe preferably runs between the first opening and the second opening above the stone space. This produces a natural convection, whereby air is made to flow through the pipe.

[0040] The pipe described in the foregoing can also be used without the valve described in the foregoing. In this case, the pipe can be used to guide the flow of warm fluid flowing out of the sauna stove to a desired location in the sauna room.

[0041] Preferably, a radiation shield is provided between the part of the pipe located outside the stone space and the stone space. It is thereby possible to prevent heat from the sauna stove from radiating into the pipe, so that the flow of air in the pipe is not disturbed. The radiation shield can be a separate component or part of the frame of the sauna stove.

[0042] In a method according to the invention for controlling the temperature of a sauna room, a sauna stove is used to heat the sauna room, which sauna stove includes a frame, a stone space, which includes a thermal mass and into which water is dispensed in order to be evaporated, a flow channel, in which fluid flowing by natural convection is heated by the heat produced in the stone space, and a valve, which valve controls the flow of the fluid in the flow channel, wherein the sauna room is heated to a temperature of 60-120 °C, the stone space is heated to a temperature of 200-700 °C, the temperature of the sauna room is measured by a temperature sensor, and the temperature of the sauna room is controlled based on measurement data of the temperature sensor. In the method, the temperature of the sauna room is controlled by thermostat means which control the opening state of the valve based on measurement data of the temperature sensor that measures the temperature of the sauna room .

[0043] This enables a control of the temperatures of the sauna that is more versatile than before in terms of the temperatures of both the sauna room and the stone space. In particular, the stone space can be kept at a selected temperature over a sauna session in order to produce a potent sauna steam effect. Preferably, the temperature of the stone space is measured by a temperature sensor and the heating of the stone space is controlled by the thermostat means based on measurement data of the temperature sensor that measures the temperature of the stone space. This also allows the temperature of the stone space to be controlled with greater precision than before in a manner desired by the user, whereby it is possible to influence the steam intensity.

[0044] Preferably, in the method, a first limit value and a second limit value are set for the temperature of the sauna room, wherein the first limit value is lower than the second limit value, and, when the temperature of the sauna room is below the selected first limit value, the stone space is heated and the valve is opened, and, when the temperature of the sauna room is above the first selected limit value and below the second selected limit value, the stone space is heated and the valve is closed, and, when the temperature of the sauna room is above the second selected limit value, the heating of the stone space is limited and the valve is closed. This makes it possible to increase the transfer of the heat produced in the stone space into the air of the sauna room in a selected first phase and to then reduce the transfer of the heat produced in the stone space into the air of the sauna room in a selected second phase, so that the heat can be retained in the stone space in order to produce a potent sauna steam effect while still maintaining the temperature of the air in the sauna room at a level that is agreeable to the user.

[0045] The invention is described in detail in the following with reference to the attached drawings illustrating embodiments of the invention, wherein

[0046] Figure 1 shows a system according to an invention Figure 2 shows a sauna stove of a system according to the invention in a situation in which the valve is closed,

[0047] Figure 3 shows a sauna stove according to the invention in a situation in which the valve has been opened,

[0048] Figure 4 shows a second sauna stove of a system according to the invention,

[0049] Figure 5 shows a third sauna stove of a system according to the invention,

[0050] Figure 6 shows a method according to the invention for controlling the temperature of a sauna room.

[0051] Figure 1 shows a system according to the invention for controlling the temperature of a sauna room 8, which system includes a sauna stove 10 arranged in the sauna room 8 for heating the sauna room 8 to a temperature of 60-120°C, a temperature sensor 40 for measuring the temperature of the sauna room 8, control means for controlling the temperature of the sauna room 8 based on measurement data of the temperature sensor 40, wherein in the system the sauna stove 10 includes a frame 12, a stone space 14 including a thermal mass capable of being heated to a temperature of 200-700°C and of evaporating water dispensed into the stone space 14, a flow channel 20 in which a flowing fluid can flow by natural convection and in which said fluid can be heated by the heat produced in the stone space 14, and a valve 30 configured to control the flow of the fluid in the flow channel 20. The system includes thermostat means by means of which the system is configured to control the temperature of the sauna room 8 by controlling an opening state of the valve 30 based on measurement data of the temperature sensor 40 that measures the temperature of the sauna room 8. The stone space 14 here is configured to be heated by resistors 16. The stone space 14 here is partially enclosed in such a manner that the frame 12 of the sauna stove 10 covers more than 50% of the stone space 14. The stone space 14 here includes stones 15 as the heat-retaining mass. The cross section of the sauna stove 10 shown in the figures is illustrative and the frame 12 does not have to be continuous around the stone space 14, but rather the frame 12 can include, in addition to the flow channel 20, other openings via which air can flow through the stone space 14. The sauna stove 10 can also be what is known as a caged sauna stove, in which the frame of the sauna stove consists at least partially of a metal mesh.

[0052] The operation of the sauna stove 10 is based on natural convection here. Air from outside the frame 12 can flow in the flow channel by natural convection. In other words, the sauna stove 10 does not include a fan for producing a forced convection .

[0053] The flow channel 20 is designed here so that all fluid flowing through the flow channel 20 flows through the stone space 14, so that fluid conducted through the flow channel 20 has been heated thoroughly by the heat produced by the stone space 14 when it leaves the flow channel 20.

[0054] The position of the valve 30 is controlled by a motor 34, which acts here as the thermostat means. A motor 34 is used here as a general designation for any electronic or mechanical actuator that can modify the opening state of the valve 30. The motor 34 can be, for example, an electric motor, such as a servo motor, or it is possible to use a solenoid valve. The motor 34 and the valve 30 are connected to the control means of the system. Alternatively, the motor 34 can be a thermo-mechanical component, which will be discussed in more detail later on. The sauna stove 10 of the system shown in Figure 1 is shown in more detail in Figures 2 and 3, with reference to which the operation of the system is explained in more detail.

[0055] The temperature of the sauna room 8 is monitored by a temperature sensor 40, which is arranged on an upper part of a wall of the sauna room 8. Alternatively, the temperature sensor 40 can also be arranged on the ceiling of the sauna room 8 or, for example, integrated in the sauna stove 10. The measurement data of the temperature sensor 40 is transmitted to the control means, which is arranged in a control unit 60 of the system here. The control means here is an electronic component which controls the opening state of the valve 30 of the sauna stove 10 based on the measurement data of the temperature sensor 40. For example, when the temperature of the sauna room 8 is below a selected first limit value, the valve 30 is opened fully, while, when the temperature of the sauna room 8 is above the selected first limit value, the valve 30 is closed fully. It is also possible to use, between the fully opened and the fully closed positions, a fine control in which the valve 30 is partially open.

[0056] The temperature of the stone space 14 is monitored here by a separate temperature sensor 18. The measurement data of the temperature sensor 18 is transmitted to the control means, which controls, based on the measurement data of the temperature sensor 18, the heating of the stone space 14, i.e. here the power of the electric current supplied to the resistors 16. For example, when the temperature of the stone space 14 is below a selected threshold value, 100% of the power capacity of the system is supplied to the resistors 16, and, when the temperature of the stone space 14 is above the selected threshold value, 0% of the power capacity of the system is supplied to the resistors 16. Instead of 100% and 0% power supplies, it is also possible to use a fine control in which the supplied power in a selected situation is between 0% and 100% .

[0057] Using the control means, a user can preferably set the control of the system to automatically maintain a first selected temperature for the air of the sauna room 8 and a second selected temperature for the stone space 14.

[0058] In order to ensure the safety of the sauna, the system can also be programmed to limit the heating of the stone space 14 if the temperature of the air in the sauna room 8 rises above a selected second limit value. In other words, if closing the valve 30 is insufficient to maintain the temperature of the sauna room 8 at the selected level, the heating of the stone space 14 is also interrupted or reduced to a partial power.

[0059] In this embodiment, the flow channel 20 of the sauna stove 10 consists of an opening 25 located in a lower part of the frame 12 of the sauna stove 10, in which opening 25 the valve 30 is arranged, and the stone space 14.

[0060] In the situation shown in Figure 2, the valve 30 is closed and closes the opening 25. The flow of air through the stone space 14 is thus very low and the transfer of heat from the stone space 14 to the air in the sauna room 8 by convection is consequently negligible.

[0061] In the situation shown in Figure 3, the valve 30 and the opening 25 are fully open. The air 42 can thus flow from outside the frame 12 of the sauna stove 10 through the opening 25 into the flow channel 20, into the stone space 14 and through the stone space 14. Heat is transferred from the stone space 14 to the air 42 flowing through the stone space 14, which exits the same via the top of the sauna stove 10. The air 42 flowing through the flow channel 20 thus effectively heats the air of the sauna room 8 by convection.

[0062] Figure 4 shows a second embodiment of a sauna stove 10 of the system, in which the flow channel 20 of the sauna stove 10 is formed by a closed pipe 50 with a first opening 51 for an air inlet and a second opening 52 for an air outlet, and the first opening 51 is arranged in a lower part of the sauna stove 10, and the second opening 52 lies outside the stone space 14 and above the stone space 14 in a height direction. Cool air can thus be drawn from the lower part of the sauna room 8 into the first opening 51 of the pipe 50. The pipe 50 here is configured to run through the stone space 14. Alternatively, the pipe 50 or other alternative flow channel 20 can lie, for example, next to the stone space 14, yet in such a manner that the heat produced in the stone space 14 is transferred to the air flowing in the flow channel 20. As the air 42 passes through the pipe 50, the air 42 is heated, and the heated air is discharged from the second opening 52 of the pipe 50 in a controlled manner to a selected location in the sauna room 8. The fluid flowing in the pipe 50 is thoroughly heated inside the pipe 50, and the heated fluid is discharged from the pipe 50 from the second opening 52.

[0063] Figure 5 shows a third embodiment of a sauna stove 10 of the system, in which the flow channel 20 of the sauna stove 10 is a closed pipe 50 with a first opening 51 for an air inlet and a second opening 52 for an air outlet, and the first opening 51 is arranged in a lower part of the sauna stove 10, and the second opening 52 lies outside the stone space 14 and below the centreline of the stone space 14 in a height direction. In this embodiment, the warm air 42 discharged from the second opening 52 of the flow channel 20 is conveyed to the lower part of the sauna room 8, so that it is possible to even out temperature differences in the height direction of the sauna room 8. In this embodiment, a radiation shield 56, for example a metal plate, is provided between the part of the flow channel 20 located outside the stone space 14 and the stone space 14.

[0064] In a fourth embodiment according to the invention, the stone space 14 of the sauna stove 10 of the system is configured to be heated by burning wood or gas or a combustible liquid, such as oil.

[0065] In this case, the sauna stove 10 includes a firebox, and the system includes means for controlling the flow of air into the firebox. These means can be any means according to the prior art, such as a manual or electrical control device, that can control the cross-sectional surface area of the inlet air channel. In this case, the sauna stove 10 can also include means for controlling the supply of combustible material.

[0066] Alternatively or additionally, the sauna stove 10 includes a flue and a flue-gas temperature sensor, and the system includes an adjustable damper in the flue for controlling the combustive power by narrowing the flue based on measurement data of the flue-gas temperature sensor. The damper can be any damper according to the prior art, such as a manual or electronic control device, that controls the cross-sectional surface area of the flue. In its simplest form, the damper is a metal plate that is configured to be movable in the flue.

[0067] The system does not need to be fully automated, but rather, for example, the means for controlling the flow of air into the firebox and / or the flue damper can be manual components that the user adjusts manually to achieve the desired temperature of the stone space and thereby the desired sauna steam effect. Preferably, however, the heating of the stone space 14 is automated, so that the temperature of the stone space 14 can be maintained at a desired level for the duration of a sauna session without any action on the part of the user.

[0068] Preferably, the heating of the sauna room 8 is automated, so that the temperature of the sauna room 8 can be maintained at a desired level for the duration of a sauna session without any action on the part of the user. Regardless of how the stone space 14 is heated, it is alternatively possible to use a thermo-mechanical actuator, such as a capillary thermostat or a bimetal thermostat, as the motor 34 for controlling the opening state of the valve 30. In this case, the valve 30 is hinged and the thermomechanical actuator is configured to apply a mechanical force to the valve 30 according to a change in the temperature of the sauna room 8, which controls the opening state of the valve 30. The thermo-mechanical actuator can be, for example, the "solid fuel thermostat" manufactured by Rathgeber GmbH.

[0069] In a method according to the invention for controlling the temperature of a sauna room 8

[0070] - a sauna stove 10 is used to heat the sauna room 8, which sauna stove 10 includes a frame 12, a stone space 14, which includes a thermal mass and into which water is dispensed in order to be evaporated, a flow channel 20, in which fluid flowing by natural convection is heated by the heat produced in the stone space 14, and a valve 30, which valve 30 controls the flow of the fluid in the flow channel 20, wherein

[0071] - the sauna room 8 is heated to a temperature of 60-120 °C,

[0072] - the stone space 14 is heated to a temperature of 200-700 °C,

[0073] - the temperature of the sauna room 8 is measured by a temperature sensor 40 - the temperature of the sauna room 8 is controlled based on measurement data of the temperature sensor 40,

[0074] - the temperature of the sauna room 8 is controlled by thermostat means which control the opening state of said valve 30 based on measurement data of the temperature sensor 40 that measures the temperature of the sauna room 8.

[0075] In Figure 6, which illustrates a method according to the invention, the temperature of the sauna room 8 is shown as a function of time. In the method, a first limit value Tl, for example 75°C, and a second limit value T2, for example 80°C, are set for the temperature of the sauna room 8, so that the first limit value Tl is lower than the second limit value T2, and

[0076] - when the temperature of the sauna room 8 is below the first selected limit value Tl, the stone space 14 is heated and the valve 30 is open,

[0077] - when the temperature of the sauna room 8 is above the first selected limit value Tl and below the second selected limit value T2, the stone space 14 is heated and the valve 30 is closed, and

[0078] - when the temperature of the sauna room 8 is above the selected second limit value T2, the heating of the stone space 14 is limited and the valve 30 is closed.

[0079] The aim is to keep the temperature of the sauna room 8 between the first limit value Tl and the second limit value T2. Preferably, specific limit values between which the temperature of the stone space 14 is to be kept are set for the temperature of the stone space 14.

[0080] Limiting the heating of the stone space 14 can mean that the heating of the stone space 14 is stopped completely or that the heating power is reduced. Figure 6 shows a simplified embodiment. Besides the heating of the stone space 14, it is also possible to use a fine control for the opening state of the valve 30. It is thus possible to set multiple limit values for the temperature of the sauna room 8 in order to implement a fine control of the heating.

[0081] In addition, the temperature of the stone space 14 can be measured by a temperature sensor 18, and the heating of the stone space 14 can be controlled by the thermostat means based on measurement data of the temperature sensor 18 that measures the temperature of the stone space 14.

Claims

CLAIMS1. A system for controlling the temperature of a sauna room (8) , the system including- a sauna stove (10) arranged in the sauna room (8) for heating the sauna room (8) to a temperature of 60-120° C,- a temperature sensor (40) for measuring the temperature of the sauna room (8) ,- control means for controlling the temperature of the sauna room (8) based on measurement data of the temperature sensor (40) , wherein in the system the sauna stove (10) includes- a frame ( 12 ) ,- a stone space (14) including a thermal mass capable of being heated to a temperature of 200-700° C and of evaporating water dispensed into the stone space (14) ,- a flow channel (20) in which a flowing fluid can flow by natural convection and in which said fluid can be heated by the heat produced in the stone space (14) , and- a valve (30) configured to control the flow of the fluid in the flow channel (20) , characterized in that- the system includes thermostat means by means of which the system is configured to control the temperature of the sauna room (8) by controlling the opening state of said valve (30) based on measurement data of the temperature sensor (40) that measures the temperature of the sauna room (8) .

2. The system according to claim 1, characterized in that the system includes a temperature sensor (18) that measures the temperature of the stone space (14) in the sauna stove (10) , and the system is configured to control the temperature of the stone space (14) , using the thermostat means, based onmeasurement data of the temperature sensor (18) that measures the temperature of the stone space (14) .

3. The system according to claim 1 or 2, characterized in that the stone space (14) of the sauna stove (10) is partially enclosed in such a manner that the frame (12) of the sauna stove (10) covers at least 50%, preferably at least 80%, of the stone space (14) .

4. The system according to any one of claims 1 - 3, characterized in that the stone space (14) of the sauna stove (10) is configured to be heated by resistors (16) , and the thermostat means is configured to control the power of the electric current supplied to the resistors (16) .

5. The system according to any one of claims 1 - 3, characterized in that the stone space (14) of the sauna stove (10) is configured to be heated by burning wood or gas or a combustible liquid, such as oil, or by the friction generated by an electrically operated turbine.

6. The system according to claim 5, characterized in that the sauna stove (10) includes a firebox, and the system includes means for controlling the flow of air into the firebox.

7. The system according to claim 5 or 6, characterized in that the sauna stove (10) includes a flue and a flue-gas temperature sensor, and the system includes an adjustable damper in the flue for controlling the combustive power by narrowing the flue based on measurement data of the flue-gas temperature sensor.

8. The system according to any one of claims 1 - 7, characterized in that the system includes an electronicactuator, such as a solenoid or servomotor, for controlling the opening state of the valve (30) .

9. The system according to any one of claims 1 - 8, characterized in that the system includes a thermomechanical actuator, such as a capillary thermostat or a bimetal thermostat, for controlling the opening state of the valve (30) .

10. The system according to any one of claims 1 - 9, characterized in that the flow channel (20) of the sauna stove (10) consists of an opening in a lower part of the frame (12) of the sauna stove (10) , in which opening the valve (30) is arranged, and the stone space (14) .

11. The system according to any one of claims 1 - 8, characterized in that the flow channel (20) of the sauna stove (10) is a closed pipe (50) with a first opening (51) for an air inlet and a second opening (52) for an air outlet, and the first opening (51) is arranged in a lower part of the sauna stove (10) , and the second opening (52) lies outside the stone space (14) and above the stone space (14) in a height direction.

12. The system according to any one of claims 1 - 8, characterized in that the flow channel (20) of the sauna stove (10) is a closed pipe (50) with a first opening (51) for an air inlet and a second opening (52) for an air outlet, and the first opening (51) is arranged in a lower part of the sauna stove (10) , and the second opening (52) lies outside the stone space (14) and below the centreline of the stone space (14) in a height direction.

13. A method for controlling the temperature of a sauna room (8) , in which method- a sauna stove (10) is used to heat the sauna room (8) , which sauna stove (10) includes a frame (12) , a stone space (14) , which includes a thermal mass and into which water is dispensed in order to be evaporated, a flow channel (20) , in which a fluid flowing by natural convection is heated by the heat produced in the stone space (14) , and a valve (30) , which valve (30) controls the flow of the fluid in the flow channel (20) , wherein- the sauna room (8) is heated to a temperature of 60-120 °C,- the stone space (14) is heated to a temperature of 200-700 °C,- the temperature of the sauna room (8) is measured by a temperature sensor (40) ,- the temperature of the sauna room (8) is controlled based on measurement data of the temperature sensor (40) , characterized in that- the temperature of the sauna room (8) is controlled by thermostat means which control the opening state of said valve (30) based on measurement data of the temperature sensor (40) that measures the temperature of the sauna room (8) .

14. The method according to claim 13, characterized in that the temperature of the stone space (14) is measured by a temperature sensor (18) and the heating of the stone space (14) is controlled with the thermostat means based on measurement data of the temperature sensor (18) that measures the temperature of the stone space (14) .

15. The method according to claim 13 or 14, characterized in that a first limit value (Tl) and a second limit value (T2) are set for the temperature of the sauna room (8) , wherein the first limit value (Tl) is lower than the second limit value (T2 ) , and- when the temperature of the sauna room (8) is below the first selected limit value (Tl) , the stone space (14) is heated and said valve (30) is opened,- when the temperature of the sauna room (8) is above the first selected limit value (Tl) and below the second selected limit value (T2) , the stone space (14) is heated and said valve (30) is closed, and- when the temperature of the sauna room (8) is above the selected second limit value (T2) , the heating of the stone space (14) is limited and said valve (30) is closed.

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