An electric sauna heater and a method of heating a sauna sweat room

Abstract

An electric sauna heater for heating a sauna sweat room comprising an inner housing comprising an upper layer of stones on a water permeable base on top of the inner housing, a lower layer of stones at a distance from at least 50 mm below the water permeable base, a set of heating elements at least partially in contact with the lower layer of stones, one or more inner housing openings above the lower layer of stones; an outer housing surrounding the inner housing; a ventilator chamber below the inner housing, the ventilator chamber comprising one or more ventilator chamber inlets, one or more ventilator chamber outlets, one or more ventilation fans; an air gap formed between the inner housing and the outer housing, the air gap arranged to receive air from the one or more inner housing openings and direct the received air towards the one or more ventilator chamber inlets. Disclosed is also a method of heating a sauna sweat room.

Description

[0001] AN ELECTRIC SAUNA HEATER AND A METHOD OF HEATING A SAUNA

[0002] SWEAT ROOM

[0003] TECHNICAL FIELD

[0004] The present disclosure relates generally to the field of sauna heaters for heating sauna sweat rooms in traditional Finnish saunas. The present disclosure discloses an electric sauna heater and a method of heating a sauna sweat room.

[0005] BACKGROUND

[0006] A sauna is a small room or enclosed space that is configured to create dry or wet heat. When using the sauna, the skin temperature of a person rises roughly to 40 °C leading to heavy sweating, which can help cleanse the skin, promote relaxation, and provide a sense of well-being. Saunas are often used for relaxation and stress relief, as the heat and sweating can help soothe muscles, stress management, reduce tension, and additionally improve blood circulation, cardiovascular function, metabolism, weight loss and sleep.

[0007] The sauna comprises a sauna sweat room, where the heat is generated by the sauna heater comprising heating elements and stones. The heating elements of the sauna heater are heating the stones, which accumulate the heat and constantly release the heat into the sauna sweat room. Generally, the sauna heater may be a wood, a gas or an electric sauna heater. Electrical heaters are widely used in modern sauna sweat rooms, as these are easy to install and use. The sauna sweat room can be either dry or humid. The humid sauna sweat room also comprises a hot steam besides the heat, caused by pouring water over heated stones or coals, which produces steam and raises the humidity level. The dry sauna sweat room is used by heating only the stones without generating any hot steam. The typical sauna heaters used in the sauna sweat rooms have stones arranged as a pile or a layer above the heating elements. In electric sauna heaters, the stones are heated with electrical heating elements, like electric coils, and the heat provided by the electrical heating elements accumulates in the stones, and followingly the heat is constantly provided into the sauna sweat room by the stones. To create a steam, a water is poured over the stones and the steam is generated by the heated stones. However, a thermal shock occurs on the stones, as the water temperature is normally very low compared to the temperature of the heated stones. Furthermore, some of the poured water reaches directly the electrical heating elements, which generates also thermal shock on the electrical heating elements leading to damages, which eventually reduce lifetime of the electrical heating elements and the sauna heater itself. Furthermore, it is difficult to control, that the water is poured on the stones evenly. As the temperature above the stones is very high or even burning, the water is normally just thrown from a distance and the water will reach only specific area of the stones.

[0008] Another problem with typical sauna heaters is that the hot air from the heated stones reaches directly the sauna sweat room. This means that all the hot air is accumulated in the upper sections of the sauna sweat room while the lower sections are cooler and therefore the heat in the sauna sweat room is not uniform, causing an uncomfortable experience for the user. Some sauna heaters comprise a collecting unit, which collects the hot air either from the upper sections of the sauna sweat room or above the sauna heater and directs the hot air to lower sections of the sauna sweat room. However, it is a challenge to collect the hot air above the sauna heater or from the upper sections of the sauna sweat room, as hot air rises quite fast. It is even a bigger challenge to collect the hot steam provided by pouring the water over the heated stones. While the water is poured on the stones the water converts into hot air almost immediately and is also dissipating fast. Hence, the hot air cannot be effectively collected from the stones and significant amount of hot air still reaches the upper section of the sauna sweat room. This will result a temperature difference between the lower section and the lower section of the sauna sweat room and such a temperature difference between the level of the feet and the head is not healthy, is tiring and heavy for the heart, as the heart must start pumping extra blood to cool down the head and body goes under stress because of uneven temperature.

[0009] Therefore, in light of the foregoing discussion, there exists a need to overcome the aforementioned drawbacks associated with sauna heaters and methods of heating sauna sweat rooms.

[0010] SUMMARY

[0011] An aim of the present disclosure is to provide an electric sauna heater for heating a sauna sweat room. Another object of the present disclosure is to provide a solution that overcomes at least partially the problems encountered in the prior art. Advantageous features are set out in the appended dependent claims.

[0012] Embodiments of the present disclosure enable a uniform dissipation of hot air in the sauna sweat room and the longer lifetime of the electric sauna heater.

[0013] Additional aspects, advantages, features, and objects of the present disclosure will be made apparent from the drawings and the detailed description of the illustrative embodiments construed in conjunction with the appended claims that follow.

[0014] It will be appreciated that features of the present disclosure are susceptible to being combined in various combinations without departing from the scope of the present disclosure as defined by the appended claims.

[0015] BRIEF DESCRIPTION OF DRAWINGS

[0016] The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. Embodiments of the present disclosure will now be described, by way of example only, with references to the following diagrams wherein:

[0017] FIG. 1 shows a schematic illustration of an electric sauna heater.

[0018] FIG. 2 illustrates an electric sauna heater with stones between the heating elements and levelling chamber.

[0019] FIG. 3 illustrates a method of heating a lower stones when the ventilator fan is not working.

[0020] FIG. 4 illustrates a method further comprising pouring water onto the upper layer of stones.

[0021] FIG. 5 illustrates a method of heating the sauna sweat room.

[0022] FIG. 6a illustrates a ventilator chamber with ventilator chamber outlet guide.

[0023] FIG. 6b illustrates a front view of a ventilator chamber with ventilator chamber outlet guide.

[0024] FIG. 6c illustrates a top view at the cross section of a ventilator chamber with ventilator chamber outlet guide.

[0025] DETAILED DESCRIPTION OF EMBODIMENTS

[0026] The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognize that other embodiments for carrying out or practicing the present disclosure are also possible. Furthermore, what has been described for the apparatus also corresponds to the method of the present disclosure.

[0027] In a first aspect, an embodiment of the present disclosure provides an electric sauna heater for heating a sauna sweat room comprising an inner housing comprising an upper layer of stones on a water permeable base on top of the inner housing, a lower layer of stones at a distance from at least 50 mm below the water permeable base, a set of heating elements at least partially in contact with the lower layer of stones, one or more inner housing openings above the lower layer of stones; an outer housing surrounding the inner housing; a ventilator chamber below the inner housing, the ventilator chamber comprising one or more ventilator chamber inlets, one or more ventilator chamber outlets, one or more ventilators; an air gap formed between the inner housing and the outer housing, the air gap arranged to receive air from the one or more inner housing openings and direct the received air towards the one or more ventilator chamber inlets.

[0028] In an another aspect, an embodiment of the present disclosure provides a method of heating a sauna sweat room, the method comprising heating a lower layer of stones by a set of heating elements, providing heated air above the lower layer of stones, heating an upper layer of stones by at least part of the heated air, wherein the lower layer of stones is at a distance from at least 50 mm below the upper layer of stones, guiding at least part of the heated air from between the lower layer of stones and the upper layer of stones towards a lower section of the sauna sweat room.

[0029] The term "sauna" in the present application is a Finnish or other such type of sauna (e.g., Estonian sauna, Russian sauna) comprising a sauna sweat room, wherein air of the sauna sweat room is heated up by an electric stove (e.g. „electric sauna heater") with stones on top and around the electric heating elements. The electric heating elements are heating the stones. The heated stones function as a heat accumulator. The heated hot air in the sauna sweat room is normally from 60 °C up to 120 °C. A person starts to sweat in the sauna sweat room because of the raised skin temperature caused by heating. At lower temperatures than 60 ° it takes too much time to raise the skin temperature and temperatures above 120 °C are not easy to bear. The sauna sweat room can be divided into two sections, the upper section e.g. the ceiling area and the lower section e.g. the floor area. With just a normal electric sauna heater, the temperature difference between the upper and lower sections normally can be between 25 °C-50 °C, but may even reach up to 90 °C.

[0030] The electric sauna heater in the present disclosure comprises an inner housing, an outer housing, a ventilator chamber and an air gap.

[0031] The term „inner housing" as used herein refers to an inner section of the electric sauna heater that accommodates at least two layers of stones, namely an upper layer of stones and a lower layer of stones, set of heating elements, one or more inner housing openings and an air gap.

[0032] The term „upper layer of stones" as used herein refers to a layer of stones on an upper part of the inner housing. The upper layer of stones are supported by a water permeable base. The water permeable base serves as a support for the upper layer of stones, keeping it at a certain distance from a lower layer of stones. The water permeable base enables a water, that is poured on the stones, to fall through. Furthermore, the water permeable base enables to at least partially collect and divide water more evenly before falling through. The water falls on the lower layer of stones more evenly, there will be more effective production of hot steam. Optionally, the amount of the upper layer of stones is between 5-15 kg.

[0033] The term „lower layer of stones" as used herein refers to a layer of stones inside the inner housing at a certain distance below the water permeable base. Herein, a distance between the water permeable base and the lower layer of stones is at least 50 mm. The distance generates an empty space between the upper layer of stones and the lower layer of stones enabling free movement of the heated air between the mentioned layers of stones. Furthermore, if the distance would be less than 50 mm, the previously mentioned separate layers of stones would be not formed.

[0034] The inner housing further comprises a set of heating elements that at least partially are in contact with the lower layer of stones. The heating elements are electrical heating elements comprising coils. Heating elements are used to heat the electric sauna heater, including the lower layer of stones. The heating elements are at least partially in contact with the lower layer of stones thereby enabling better heat transfer for heating the lower layer of stones.

[0035] Furthermore, the inner housing comprises one or more inner housing openings above the lower layer of stones. The one or more inner housing openings are collecting the heated air rising from the lower layer of stones from the empty space between the upper layer of stones and the lower layer of stones.

[0036] The term "outer housing" as used herein refers to an outer section of the electric sauna heater that surrounds the inner housing. The term „air gap" as used herein refers to an area that is formed between the inner housing and the outer housing and is arranged to receive air from the one or more inner housing openings and direct the received air towards the one or more ventilator chamber inlets.

[0037] The term „ventilator chamber" as used herein refers to a chamber below the inner housing that comprises one or more ventilator chamber inlets, one or more ventilator chamber outlets and one or more ventilation fans. The purpose of the ventilator chamber is to help the hot air and / or steam to move inside the electric sauna heater. The hot air and / or steam will be directed through the one or more ventilator chamber inlets and then guided out of the ventilator chamber through the one or more ventilator chamber outlets. The ventilator chamber is needed to guide the hot air and / or steam towards the lower section of the electric sauna heater and furthermore into the lower section of the sauna sweat room. Without the ventilator chamber, the hot air and / or steam coming from the upper layer of stones would move upwards.

[0038] According to an embodiment of the present disclosure, the set of heating elements are providing heat to the lower layer of stones. The heat accumulates in the lower layer of stones and is also thereby constantly released as a hot air to the empty space between the upper layer of stones and the lower layer of stones. The hot air travels from the empty space towards the upper layer of stones thereby heating up also the upper layer of stones. The upper layer of stones also serves as an obstacle for the hot air, decreasing the speed it enters the sauna sweat room. When water is poured onto the upper layer of stones, the water is preheated by the upper layer of stones. The preheated water will drip through the upper layer of stones and the water permeable base reaching the lower layer of stones, which temperature is higher than the upper layer of stones due to direct contact with the heating elements. A hot air and / or steam is generated, when the preheated water reaches the lower layer of stones. The hot air and / or steam will raise into the empty space between the upper layer of stones and the lower layer of stones, where the water permeable base and the lower layer of stones serve as an obstacle preventing the steam escaping directly into the sauna sweat room.

[0039] When the lower layer of stones and the upper layer of stones are heated by the set of heating elements to a high temperature and for the firsttime water is poured to the upper layer of stones, some steam will be generated by the upper layer of stones. However, after the water has been poured for few times consecutively, the upper layer of stones will start to cool down and the temperature of the stones is not high enough to produce the steam and instead the heated water will be guided through the upper layer of stones and the water permeable base to the lower layer of stones. Since the lower layer of stones have not previously received any water, they will be hot and when the water falling through the upper layer of stones reaches the lower layer of stones, it will generate steam. The upper layer of stones will block the steam coming from the lower layer of stones and therefore the steam will be guided through the one or more inner housing openings into an air gap between the inner housing and the outer housing. Since the steam is blocked by the upper layer of stones, it will not be guided directly to the sauna sweat room causing an uneven temperature in the sauna sweat room. In addition, the upper layer of stones will provide more uniform flow of the hot water as the water will be cascading through the stones and when it falls to the lower layer of stones, it will produce more uniform steam. Moreover, since the water falling on the lower layer of stones is heated, it will not cause a thermal shock to the lower layer of stones and the set of heating elements. Since thermal shock can lead to various effects such as cracking, fracturing, or other structural damage due to the differential expansion and contraction of the materials involved, avoiding this will lengthen the lifetime of the lower layer of stones and the set of heating elements. Furthermore, since the steam is generated between the upper layer of stones and the lower layer of stones, it will not directly hit the sauna sweat room, causing less discomfort for the people in the sauna sweat room.

[0040] In an embodiment, in the electric sauna heater the lower layer of stones is at a distance from at least 50 mm up to 500 mm below the water permeable base. The distance generates an empty space between the upper layer of stones and the lower layer of stones enabling free movement of the heated air between the mentioned layers of stones. The distance of the lower layer of stones from the water permeable base may be for example from 50, 75, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 375, 400, 425, 450 or 475 mm up to 75, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 375, 400, 425, 450, 475 mm or 500 mm. If the distance of the lower layer of stones from the water permeable base is larger than 500 mm, the heat coming from the heating elements would not effectively heat the upper layer of stones .

[0041] In an embodiment, the electric sauna heater further comprises stones between the set of heating elements. When there are stones between the set of heating elements all the way through, this will allow the electric sauna heater to obtain the desired temperature faster e.g. the lower layer of stones will heat up faster. Both the initial heating will be faster as well as heating between the episodes when the water is poured on the upper layer of stones. This means that the sauna experience can be obtained faster, and temperature of the sauna sweat room kept at constant temperature more easily. With only few stones from the lower layer of stones partially between the set of heating elements, the changing of the heating elements will be easier as only few stones need to be removed before the replacement can be carried out instead all the stones if these were to be between the heating elements. Moreover, if the stones need to be changed, the changing of stones will be easier and faster with fewer stones between the heating elements.

[0042] In an embodiment, the electric sauna heater further comprises a levelling chamber between the air gap and the ventilator chamber, wherein the levelling chamber comprises a levelling chamber guide arranged to guide the air from the air gap towards the one or more ventilator chamber inlets. Levelling chamber is needed so that the hot air can be more efficiently guided towards the ventilation fans. It comprises a levelling chamber guide that is needed to control the flow of the hot air that is directed towards the ventilator chamber. Levelling chamber reduces the speed of the hot air, which will reduce turbulence. Consequently, the ventilation fan will work more smoothly and quietly. With the help of the levelling chamber and the levelling chamber guide, the air is moved from the upper layer of stones, through the one or more inner housing openings into an air gap between the inner housing and the outer housing and then guided directly to the ventilation fan. Without the levelling chamber guide, the air flow would not be uniform and there is a possibility of turbulence. Optionally, the levelling chamber is located below the inner housing and above the ventilator chamber. This is the section in the electric sauna heater where the flow of hot air can be controlled after it leaves the inner housing and before it reaches the ventilator chamber. The hot air is drawn together by the levelling chamber guide right before the ventilator chamber so that it would reach the ventilator chamber without dissipating which would allow better control of the flow of the hot air.

[0043] Optionally, the levelling chamber guide is formed of two internal walls inclining towards each other, wherein the inclined two internal walls are pointing to a centre of the ventilator chamber. Levelling chamber guide improves flow of the hot air by providing a smooth and controlled path for air movement. The two inclining walls are effective in reducing turbulence, enhancing hot air distribution, and directing airflow in the desired direction towards the ventilation fan or ventilation fans. The two inclining walls can create a focused and concentrated flow pattern of the hot air, which is beneficial for targeted ventilation or directed flow of the hot air.

[0044] Optionally, the levelling chamber guide formed of two internal walls inclining towards each other have an angle between that is 25° up to 90° degrees; the degrees can be for example from 25, 35, 45, 55, 65, 75 or 85° up to 30, 40, 50, 60, 70, 80 or 90°. The angle between the two internal walls have various effects on the flow of hot air, primarily influencing the flow pattern of the hot air, velocity, and turbulence. By varying the angles, the flow of the hot air can be guided differently, e.g. with the narrower angles, for example up to 30°, better guidance of the flow of the hot air can be achieved while wider angles up to 90° can provide a broader and more dispersed flow pattern of the hot air and allows the flow of the hot air to spread out over a larger area, leading to a more even distribution of air. Moreover, the wider angles allow to minimize turbulence and maintain efficient flow of the hot air. If the angle is above 90°, there will be no additional effect of the levelling chamber guide.

[0045] The internal walls of the levelling chamber guide can optionally be straight or curved. Optionally, the internal walls are curved towards each other. The curved internal walls provide smoother flow of the hot air by reducing turbulence and minimizing disruptions in the hot air. When the hot air encounters the curved internal walls, it tends to follow the curvature and results in a more unform flow of the hot air. Additionally, the curved walls can aid in directing air in a specific path or direction. The shape of the curved walls can be designed to guide the flow of hot air precisely where it is needed, ensuring the flow of hot air in desired pattern.

[0046] In an embodiment, at least one of selected from the air gap, the levelling chamber, the ventilator chamber further comprises one or more cool air inlets. Through the cool air inlets the ventilation fan will bring in the cool air from the sections surrounding the electrical sauna heater and this will be mixed with the hot air coming from the upper layer of stones. This option will have multiple of benefits. First of all, this option will allow to control the temperature of the air entering through the one or more ventilator chamber outlets. As the hot air or steam is generated by the lower layer of stones into the air gap, it might be desired to control this temperature. In order to lower the temperature of this hot air or steam, it needs to be mixed with cool air from the cooler sections of the sauna sweat room. Additionally, the additional use of the cool air inlets will allow to produce better ventilation and air circulation in the sauna sweat room. This is especially necessary when there are more people in the sauna sweat room and the oxygen levels will start to decrease.

[0047] In an embodiment, in the electric sauna heater a thickness D of the upper layer of stones is from 40 mm up to 100 mm; the thickness may be for example from 40, 45, 50, 55, 60, 65, 70, 75, 85 cm up to 50, 55, 60, 65, 70, 75, 85, 90, 95 or 100 cm. The thickness D of the upper layer of stones needs to be optimal. If the thickness D is too thick, the water will not move through the upper layer of stones to the lower layer of stones as the water will dissipate between the upper layer of stones. Additionally, when the thickness D is too thick, the ventilation fan will not be able to pull the hot air towards the ventilator chamber, and therefore the ventilation fan needs to work faster and will make more noise. When the thickness D is optimal, the air will move freely through the upper layer of stones with ventilation fan working normally. Furthermore, when the thickness D is too thick, the electric sauna heater needs longer heating in order to obtain desired temperature. When the thickness D is too thin, it will be not heating the water moving through the stones enough and when the water falls on the lower layer of stones, there is still a risk of a thermal shock. Additionally, if the thickness D is not enough, the flow of the water will not have enough time to spread out while moving though the upper layer of stones and the water will not be equally distributed and will still fall only on a small section of the lower layer of stones. Moreover, if the thickness D is not thick enough, some of the hot air coming from the lower layer of stones might escape through the upper layer of stones and only a small amount of hot air will be moving through the air gap towards the ventilator chamber. In an embodiment, in the electric sauna heater the set of heating elements comprises from 6 up to 15 heating coils. The amount of heating coils is in direct correlation with the load on the heating coils. With more heating coils, the heating capacity will be increased, and the sauna can be heated faster. Additionally, higher temperatures can be achieved if needed. When more heating coils are used, one coil will have less load. In consequence, the lifetime of the heating coils will be longer. The use of more heating coils will also contribute to improved heat distribution since the heating coils can be distributed in the electric sauna heater to eliminate cold spots and provide a more consistent heating. Furthermore, if one heating coil were to malfunction or fail, the other heating coils will continue to provide heat and the sauna can still be operational with fewer heating coils.

[0048] In an embodiment, in the electric sauna heater, the air gap is formed as at least two ducts, wherein each of the at least two ducts is arranged on an opposite side of the inner housing. The ducts are used to guide the hot air towards the ventilator chamber. With the application of at least two ducts, more hot air can be guided e.g. the process of hot air movement is more efficient and larger amounts of hot air can be guided. Furthermore, how much of the hot air can move through the ducts depends on the dimensions of the duct. The length of the duct will influence the change in temperature of the hot air moving towards the ventilator chamber. The longer the duct, the more the temperature of the hot air will decrease. Optionally, the length of the duct is related to the height of the lower layer of stones. Moreover, the area of the crosssection of the duct will have an effect on how much hot air can move through the duck. The cross-section has to be minimally as such that the ventilation fan can work without resistance.

[0049] In an embodiment, in the electric sauna heater, the ventilator chamber further comprises at least one ventilator chamber outlet guide arranged to guide the air from the ventilator chamber through one or more ventilator chamber outlets to the lower section of the sauna sweat room. The at least one ventilator chamber outlet guide can be used to give the hot air desired direction when going through the at least one ventilator chamber outlets. This will allow to spread the hot air into the sections of the sauna sweat room most effective for the best sauna experience independently where an electric sauna heater is situated in the sauna sweat room. For example, it is necessary to guide the hot air when the electric sauna heater is not situated in the middle of the sauna sweat room but in the corner. Optionally, the at least one ventilator chamber outlet guide can be adjusted by the user to guide the hot air in the desired direction by changing the location of the at least one ventilator chamber outlet guide or the angle of the hot air.

[0050] In an embodiment, the method of heating a sauna sweat room comprises heating a lower layer of stones by a set of heating elements; providing heated air above the lower layer of stones; heating an upper layer of stones by at least part of the heated air, wherein the lower layer of stones is at a distance from at least 50 mm below the upper layer of stones; guiding at least part of the heated air from between the lower layer of stones and the upper layer of stones towards a lower section of the sauna sweat room. The continuous circulation of the air inside the sauna sweat room allows for a more comprehensive and constant heat transfer to the body, promoting relaxation, increased circulation and potential health benefits. Moreover, the uniform temperature without hotspots or colder areas in the sauna sweat room will provide healthier and more comfortable sensation for the user. Additionally, a uniform temperature will help to prevent localized areas of extreme heat that especially arise when water is poured on the hot stones that are in one layer and could potentially lead to discomfort and burns. In an embodiment, the method of heating a sauna sweat room further comprises providing water onto the upper layer of stones to heat the water, providing the heated water onto the lower layer of stones to generate hot steam, directing the hot steam towards the lower section of the sauna sweat room. Generally, the water is poured on the upper layer of stones using a sauna scoop. However, the electric sauna heater may further comprise a water adding unit, which is configured to add a predefined amount of water during predefined time periods. The water may also be sprayed on the upper layer of stones by a sprayer or sprinkled by a sprinkler. The water may be directed onto the upper layer of stones based on the feedback from a humidity sensor. The water adding unit may start directing the water onto the upper layer of stones only when temperature of at least 50 °C is achieved, as otherwise the upper layer of stones is not hot enough to generate the hot steam. A steam sauna can be generated by directing water onto the upper layer of stones and directing the hot air stream comprising the hot steam towards the sauna sweat room.

[0051] Optionally, the method further comprises mixing the hot air and / or hot steam with a cool air. The at least part of the mixed air stream is directed towards the lower section of the sauna sweat room to evenly heat up the sauna sweat room. Releasing the mixed air stream comprising the hot air mixed with the cool air enables to evenly heat up the sauna sweat room and provide pleasant sauna conditions. Additionally, the mixing of hot air and / or hot steam with a cool air will allow to control the temperature of the sauna sweat room.

[0052] Optionally, in the method the cool air is received from the lower section of a sauna sweat room and / or, outside of a sauna sweat room. The cool air may be collected from the lower section or the floor area, as generally, temperature in the lower section and in the floor area of the sauna sweat room is lower than in the upper section. The cool air may have a temperature from 15 °C up to 70 °C. The cool air may have a temperature from 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, or 71 °C up tol6, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 70 or 72 °C. In the embodiments, wherein the cool air is obtained from the external ventilation unit, the temperature of the cool air is less than the temperature of the air received from the electric sauna heater. In some embodiments, wherein the cool air is obtained from outside the sauna, the temperature of the cool air may be less than 15 °C or below 0 °C when the cool air is led into the sweat room from outside the sauna during winter time. The cool air collected from outside of the sauna sweat room comprises more oxygen and therefore, the air quality in the sauna sweat room can be raised. The cool air can be collected from multiple locations at same or different time periods.

[0053] According to the embodiments of the present disclosure the better ventilation further enables to save energy for heating the sauna sweat room. In the typical prior art sauna sweat rooms when more fresh air is needed then the door or window of the sauna sweat room has to be opened, which leads the hot air out from the sauna sweat room and more energy is needed to heat up the sauna sweat room again.

[0054] In an embodiment, in the method the upper layer of stones is heated from 80 °C up to 260 °C; the temperature can be for example from 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200 or 210°C up to 90, 100, 110, 120, 130, 140 ,150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250 or 260°C. If the upper layer of stones is heated, the water falling on the lower layer of stones is further heated and it will not cause a thermal shock to the lower layer of stones and the set of heating elements. Since thermal shock can lead to various effects such as cracking, fracturing, or other structural damage due to the differential expansion and contraction of the materials involved, avoiding this will lengthen the lifetime of the lower layer of stones and the set of heating elements.

[0055] DETAILED DESCRIPTION OF DRAWINGS

[0056] FIG. 1, there is shown a schematic illustration of an electric sauna heater 100 comprising an inner housing 114, an outer housing 124, a ventilator chamber 110 and an air gap 118. The air gap 118 is formed as at least two ducts comprising a first duct 118a and a second duct 118b, wherein each of the first duct 118a and the second duct 118b is arranged on an opposite side of the inner housing 114. An inner housing 100 comprises an upper layer of stones 102 on a water permeable base 106 top of the inner housing; a lower layer of stones 104 at a distance from at least 50 mm below the water permeable base; a set of heating elements 108 at least partially in contact with the lower layer of stones; and one or more inner housing openings 120 above the lower layer of stones. The upper layer of stones have a thickness D. A ventilator chamber 110 comprises one or more ventilator chamber inlets 122, one or more ventilator chamber outlets 116, and one or more ventilation fans 112.

[0057] FIG. 2, illustrates an embodiment of an electric sauna heater of FIG. 1 further comprising stones 130 between the set of heating elements 108 and / or an electric sauna heater where the set of heating elements 108 comprises from heating coils 134. In the exemplary embodiment, an electric sauna heater 100 further comprises a levelling chamber 126 between the air gap 118 and the ventilator chamber 110, wherein the levelling chamber comprises a levelling chamber guide arranged to guide the air from the air gap 118 towards the one or more ventilator chamber inlets 122. A ventilator chamber 110 comprises one or more ventilator chamber inlets 122, one or more ventilator chamber outlets 116, and one or more ventilation fans 112. The air gap 118 is formed as at least two ducts comprising a first duct 118a and a second duct 118b, wherein each of the first duct 118a and the second duct 118b is arranged on an opposite side of the inner housing 114. Levelling chamber guide 132 is formed of a first internal wall 133a and a second internal wall 133b inclining towards each other, wherein the inclined two internal walls are pointing to a centre of the ventilator chamber 110. An angle a between the inclined a first internal wall 133a and a second internal wall 133b is from 25° up to 90° degrees.

[0058] Further, in the exemplary embodiment an electric sauna heater 100 comprises one or more cool air inlets 128.

[0059] FIG. 3 illustrates a method of heating a lower layer of stones 104 by a set of heating elements 108, providing heated air above the lower layer of stones and heating an upper layer of stones 102 by at least part of the heated air in an electric sauna heater 100. The hot air is going though the water permeable base 106. In this embodiment, the ventilation fan is not working 112a.

[0060] FIG. 4 illustrates a method of FIG. 3 using electric sauna heater 100 further comprising pouring water 404 with the bucket 402 onto the upper layer of stones 102 to heat the water and providing the heated water through the water permeable base 106 onto the lower layer of stones 104 generating hot steam. In this embodiment, the ventilation fan is not working 112a.

[0061] FIG. 5 illustrates a method of FIG. 3 using electric sauna heater 100 where hot air and / or hot steam above the lower layer of stones 104 is at least partly guided from between the lower layer of stones 104 and the upper layer of stones 102 through the inner housing openings 120 and through the air gap 118 and the ventilator chamber inlets 122. The air gap 118 is formed as at least two ducts comprising a first duct 118a and a second duct 118b, wherein each of the first duct 118a and the second duct 118b is arranged on an opposite side of the inner housing 114. Hot air and / or hot steam is further mixed with a cool air received from the lower section of a sauna sweat room and / or outside of a sauna sweat room through cool air inlets 128. Levelling chamber guide 132 is used to guide the hot air and / or steam in the levelling chamber. In the exemplary embodiment, mixing can take place in the levelling chamber 126 and / or the ventilator chamber 110 using the ventilation fan 112b. After mixing the ventilator chamber outlets 116 are used to send the air mixture into a lower section of the sauna sweat room.

[0062] FIG. 6a illustrates a ventilator chamber 110 (ventilation fan not shown on the scheme) with ventilator chamber outlet guide 602 arranged to guide the air towards ventilator chamber outlets 116 and the air enters the sauna sweat room through the ventilator chamber outlets 116.

[0063] FIG. 6b illustrates a front view of the a ventilator chamber 110 (ventilation fan not shown on the scheme) with ventilator chamber outlet guide 602 inside the ventilator chamber 110 and ventilator chamber outlets 116.

[0064] FIG. 6c illustrates a top view at the cross section of the a ventilator chamber 110 (ventilation fan not shown on the scheme) with ventilator chamber outlet guide 602.

[0065] Modifications to embodiments of the present disclosure described in the foregoing are possible without departing from the scope of the present disclosure as defined by the accompanying claims. Expressions such as "including", "comprising", "incorporating", "have", "is" used to describe and claim the present disclosure are intended to be construed in a nonexclusive manner, namely allowing for items, components or elements not explicitly described also to be present.

Claims

CLAIMS1. An electric sauna heater (100) for heating a sauna sweat room comprising:- an inner housing (114) comprising:- an upper layer of stones (102) on a water permeable base (106) on top of the inner housing,- a lower layer of stones (104) at a distance from at least 50 mm below the water permeable base,- a set of heating elements (108) at least partially in contact with the lower layer of stones,- one or more inner housing openings (120) above the lower layer of stones;- an outer housing (124) surrounding the inner housing;- a ventilator chamber (110) below the inner housing, the ventilator chamber comprising- one or more ventilator chamber inlets (122),- one or more ventilator chamber outlets (116),- one or more ventilation fans (112);- an air gap (118) formed between the inner housing and the outer housing, the air gap arranged to receive air from the one or more inner housing openings and direct the received air towards the one or more ventilator chamber inlets.

2. An electric sauna heater (100) according to claim 1, wherein the lower layer of stones (104) is at a distance from at least 50 mm up to 500 mm below the water permeable base.

3. An electric sauna heater (100) according to claims 1 or 2 further comprising stones (130) between the set of heating elements (108).

4. An electric sauna heater (100) according to any of the preceding claims, further comprising a levelling chamber (126) between the air gap(118) and the ventilator chamber (110), wherein the levelling chamber comprises a levelling chamber guide (132) arranged to guide the air from the air gap (118) towards the one or more ventilator chamber inlets (122).

5. An electric sauna heater (100) according to claim 4, wherein the levelling chamber (126) is located below the inner housing (114) and above the ventilator chamber (110).

6. An electric sauna heater (100) according claims 5 or 6, wherein the levelling chamber guide (132) is formed of two internal walls (133a, 133b) inclining towards each other, wherein the inclined two internal walls are pointing to a centre of the ventilator chamber (110).

7. An electric sauna heater (100) according to claim 6, wherein an angle (oc) between the inclined two internal walls (133a, 133b) is from 25° up to 90° degrees.

8. An electric sauna heater (100) according to any of the claims 4 to 7, wherein at least one of selected from the air gap (118), the levelling chamber (126), the ventilator chamber (110) further comprises one or more cool air inlets (128).

9. An electric sauna heater (100) according to any of the preceding claims, wherein a thickness D of the upper layer of stones is from 40 mm up to 100 mm.

10. An electric sauna heater (100) according to any of the preceding claims, wherein the set of heating elements (108) comprises from 6 up to 15 heating coils (134).

11. An electric sauna heater (100) according to any of the preceding claims, wherein the air gap (118) is formed as at least two ducts (118a,118b), wherein each of the at least two ducts is arranged on an opposite side of the inner housing (114).

12. An electric sauna heater (100) according to any of the preceding claims, wherein the ventilator chamber (110) further comprises at least one ventilator chamber outlet guide (602) arranged to guide the air from the ventilator chamber (119) through one or more ventilator chamber outlets (116) to the lower section of the sauna sweat room.

13. A method of heating a sauna sweat room, the method comprising- heating a lower layer of stones by a set of heating elements,- providing heated air above the lower layer of stones,- heating an upper layer of stones by at least part of the heated air, wherein the lower layer of stones (104) is at a distance from at least 50 mm below the upper layer of stones,- guiding at least part of the heated air from between the lower layer of stones and the upper layer of stones towards a lower section of the sauna sweat room.

14. A method according to claim 13 further comprising- providing water onto the upper layer of stones to heat the water,- providing the heated water onto the lower layer of stones to generate hot steam,- directing the hot steam towards the lower section of the sauna sweat room.

15. A method according to claims 13 or 14 further comprising mixing the hot air and / or hot steam with a cool air.

16. A method according to claim 15, wherein the cool air is received from:- the lower section of a sauna sweat room,- outside of a sauna sweat room.

17. A method according to any of the claims 13 to 16, wherein the upper layer of stones (104) is heated from 80°C up to 260°C.

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