WO2009091310A2

WO2009091310A2 - A ventilating arrangement and a heat exchanging assembly

Info

Publication number: WO2009091310A2
Application number: PCT/SE2008/051277
Authority: WO
Inventors: Per Eriksson; Mats Eriksson; Magnus Isaksson
Original assignee: Per Eriksson; Mats Eriksson; Magnus Isaksson
Priority date: 2008-01-14
Filing date: 2008-11-07
Publication date: 2009-07-23
Also published as: WO2009091310A3; SE1050783A1

Abstract

A ventilating arrangement for ventilating spaces (4) in a building has at least one heat exchanging assembly for heat exchange between exhaust air from the building and outdoor air supplied to the building. An outdoor air channel (14) conducts through an opening (12) in the external wall of the building outdoor air to the heat exchanging assembly. Exhaust air is conducted through exhaust air members (7) to the heat exchanging assembly. The flow of air to the spaces from the exterior of the building through supply air members (11) connected to the heat exchanging assembly only takes place through the negative air pressure generated in the spaces of the building through a flow of exhaust air leaving the spaces through said exhaust air members.

Description

A ventilating arrangement and a heat exchanging assembly

TECHNICAL FIELD OF THE INVENTION AND PRIOR ART

The present invention relates to an arrangement for ventilating spaces in a building, which comprises at least one exhaust air member connected to said spaces, at least one exhaust air channel connecting said exhaust air member to means for generating an exhaust air flow from said spaces in the channel and discharging thereof to the exterior of the building, at least one supply air member for supplying outdoor air from the exterior of the building to said spaces, and at least one assembly for heat exchange between said exhaust air and said outdoor air, as well as a heat exchanging assembly for use in such a ventilating ar- rangement.

Such arrangements may be intended for ventilating spaces in all types of buildings, such as for examples schools, industrial premises and dwelling-houses, in one as well as multiple dwell- ing-houses. For illuminating and better explaining the present invention the application of ventilating spaces in dwelling-houses, i.e. flats, will hereinafter mainly be described without for that sake restricting the invention to that use.

The arrangement may also in multiple dwelling-houses be intended for ventilating one single flat, but it may also be designed to take care of ventilation of several flats, which may then have one or more said heat exchanging assemblies each but a said common means for generating an exhaust air flow, such as an exhaust air fan located close to a chimney of the building. Considerable savings of energy may be achieved particularly in colder regions if the sometimes very cold outdoor air surrounding the building may be preheated by the considerably warmer exhaust air from the building before the former is supplied to the flat through supply air members located therein. A number of different ventilation arrangements of the type defined in the introduction having at least one assembly for heat exchange between the exhaust air and the outdoor air have been manu- factured for obtaining this. Such an arrangement is described in EP 0 343 938 A1/ Such ventilating arrangements already known are in spite of the fact that they may be comparatively efficient with respect to the heat recovery capacity be associated with a number of problems. The heat exchanging assembly is often constituted by a rotary heat exchanger or another comparatively costly heat exchanger requiring a number of electrically actuated control members and one or more extra fan members for the function thereof. This results in a comparatively high manufacturing cost of the ventilating arrangement, but also the re- quirement of maintenance of the ventilating arrangement and by that costs therefor are sometimes unmotivatedly high. Furthermore, the installation of such previously known ventilating arrangements in already existing buildings already having a ventilating system is costly, since it requires considerable recon- struction work. Some of the ventilating arrangements of this type already known also generate annoying noises in operation thereof, especially emanating from the heat exchanging assembly.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an arrangement of the type defined in the introduction, which makes it possible to reduce at least some of the disadvantages mentioned above of such arrangements already known. This object is according to the invention obtained by providing such an arrangement also with at least one outdoor air channel, which through an opening in the external wall of the building directly connects the exterior of the building to a first inlet in said heat exchanging assembly for conducting outdoor air to this and out of this through a first outlet thereof connected to said supply air member, the heat exchanging assembly has a second inlet connected to said exhaust air member downstream thereof and a second outlet connected to said exhaust air channel and the arrangement is configured to create said flow of air to the spaces from the /exterior of the building through said supply air member only through the negative air pressure generated in said spaces through the flow of exhaust air leaving said spaces through said exhaust air member.

The present inventors have in a very surprising way understood and recognized that a ventilating arrangement with this construction being advantageous in a number of respects may in fact be realized. By taking the outdoor air to the spaces of the building directly into the heat exchanging assembly it has turned out that it is possible to manage without any fan as complement to said means for generating an exhaust air flow from the building for operation of a ventilating arrangement of the type defined in the introduction by designing the heat exchanging assembly with a sufficiently low air flow resistance.

This means a considerably reduced manufacturing cost for the ventilating arrangement and especially for the heat exchanging assembly thereof with surrounding equipment. By this it will also be possible to design the heat exchanging assembly without any requirement of energy supply whatsoever, i.e. totally non-electrified, and this possibility is also valid for the entire ventilating arrangement except for possibly an energy supply to said means generating an exhaust air flow in the case that this is constituted by an exhaust air fan. This means of course a minimum requirement of maintenance of the ventilating arrangement and by this very low costs for this. Another advantage of the ventilating arrangement according to the invention is that it may be installed and connected to existing ventilating systems to a low cost.

A further advantage is that it will in the spaces in the building in question not deliver any noticeable noise, but it may be experienced as silent by the persons present in these spaces and not in any way disturbing these persons.

According to an , embodiment of the invention the arrangement comprises a plurality of said heat exchanging assemblies connected to a said outdoor air channel each and at least one exhaust air member each, and these heat exchanging assemblies are connected to a said common exhaust air flow generating means. The arrangement according to the invention may in this way recover heat from the exhaust air at several different locations in the building and in spite of that manage with one said common exhaust air flow generating means.

According to another embodiment of the invention said exhaust air member may comprise a stove hood in a kitchen of the building and/or be arranged in a sanitary room, such as a bathroom, of the building. By the simple design of the heat ex- changing assembly of the arrangement and the way in which this is connected to the outdoor air channel and exhaust air channel a ventilating arrangement of this type may have a plurality of said heat exchanging assemblies also in one single flat, such as one in the kitchen and one in the bathroom, and the manufac- turing and installation cost for the arrangement may still stay on such a level that the investment in a short time will be profitable.

According to another embodiment of the invention said exhaust air flow generating means is formed by an exhaust air fan ar- ranged in said exhaust air channel close to a chimney of the building, and such an exhaust air fan is normally already ar- ranged in an existing building lacking possibility to heat recovery from the exhaust air through a heat exchanging assembly. However, it is also possible that the arrangement according to the invention has an exhaust air flow generating means formed by a chimney designed to connect said exhaust air channel to the exterior of the building, which is a subject of another embodiment of the invention. Thus, when the chimney and the exhaust air channel connected thereto are suitably designed the ventilating arrangement according to the present invention may in some cases manage totally without fan members.

According to another embodiment of the invention each of said at least one heat exchanging assembly is associated on one hand with an air conducting portion designed to form a by-pass conduit for outdoor air from said outdoor channel by-passing the heat exchanging assembly to said supply air member and on the other with a throttle, and the arrangement comprises a device configured to adjust said throttle between a closed position, in which it closes said by-passing air conducting portion and forces the outdoor air to pass through the heat exchanging assembly, and an opened position, in which it allows the outdoor air to flow in said air conducting portion while by-passing the heat exchanging assembly. It is then possible that the throttle may stop in different positions between the closed position and the totally opened position, i.e. the open position comprises a number of different positions of the throttle.

Thanks to these features of the arrangement it gets through adjustment of the throttle possible to entirely or partially refrain from heat exchange between the outdoor air and the exhaust air before the former reaches said supply air members if desired, and that may be a great advantage under certain circumstances, which will be explained more in detail further below.

According to another embodiment of the invention said device is configured to adjust said throttle through a purely mechanical control, so that in spite of the existence of said adjusting function no energy supply to the heat exchanging assembly is required and by that costs for manufacture and maintenance may be kept low at the same time as a high reliability of the control function of the throttle is obtained.

According to another embodiment of the invention said throttle is in said open position configured to close said first inlet for outdoor air to the heat exchanging assembly. A high degree of sim- plicity and reliability may be obtained by this double function, i.e. one and the same throttle regulates the flow in the by-passing air conducting portion as well as the opening degree of the first inlet to the heat exchanging assembly.

According to another embodiment of the invention the device comprises elements designed to be influenced by pressure differences between the air in the region of said first inlet and the air in the region of said second inlet to the heat exchanging assembly, and the device is configured to adjust the throttle in dependence of such air pressure differences detected by said elements. In the case that an undesired resistance in the exhaust air flow through the heat exchanging assembly results, especially in the case of very cold outdoor air, the heat exchange of which with the warmer moisture containing exhaust air in the heat exchanging assembly causes formation of ice in the exhaust air part thereof, results by this a possibility to ensure that the throttle is adjusted so that the outdoor air bypasses the heat exchanging assembly and by that the warm exhaust air may melt the ice away, which may be removed through a suitable drainage. When the air pressure differences then allows this the throttle may be adjusted so that heat recovery from the exhaust air is made possible again.

According to a further development of this embodiment of the invention said elements are configured to detect the air pressure of the exhaust air in the region of said second inlet to the heat exchanging assembly, and the device is, upon detection of an air pressure in the region last mentioned having a value above a determined level, configured to influence the throttle to open said by-passing air conducting portion so as to allow the outdoor air to be conducted to by-pass the heat exchanging assembly. The problems mentioned above of ice formation when the outdoor air is very cold may in this way be solved through a totally autonomous control.

According to another further development of this embodiment said elements comprises a bellow-like element arranged in connection with said second inlet to the heat exchanging assembly and configured to expand upon pressure increase of the air entering the second inlet, and the bellow-like element is mechani- cally connected to the throttle for adjustment thereof through movement of the bellow-like element caused by air pressure changes. This constitutes a very simple and reliable mechanical solution of the task to make the adjustment of the throttle dependent upon air pressure changes.

According to another embodiment of the invention the device comprises elements designed to detect the temperature of the outdoor air arriving to the region of the first inlet to the heat exchanging assembly, and the device is configured to adjust the throttle in dependence of said temperature detected. It gets by this possible to control the heat exchange in the heat exchanging assembly in dependence of the temperature of the outdoor air and by that refrain from such heat exchange when this is not desired. This may for example be the case when the tempera- ture of the outdoor air is below a determined level, in which this determined level is between -5⁰C and -30⁰C, preferably between -5°C and -20⁰C. The reason for this may be that in accordance with experiences the problems mentioned above of ice formation in the heat exchanging assembly get too great at a temperature below this level. However, it is also possible that the throttle is transferred to open the by-passing air conducting portion at a temperature of the outdoor air above a determined level, in which this determined level is between +15°C and +30⁰C, preferably between +18°C and +25°C, and most preferred at about +20⁰C. An unwanted high temperature in the exhaust air would namely at a very warm weather and heat exchange between the outdoor air and the exhaust air be transferred to the outdoor air and result in an undesiredly warm supply air.

According to another embodiment of the invention said tem- perature detecting element comprises a bimetallic element, which is mechanrcally connected to the throttle so as to adjust the position of the throttle through a state of the bimetallic element influenced by temperature changes. This constitutes a very simple, purely mechanical adjustability of the throttle in depend- ence of the temperature of the outdoor air.

It is pointed out that it is well possible that the device for adjusting said throttle has temperature detecting elements as well as air pressure detecting elements or elements of only one of these two types.

According to another embodiment of the invention the arrangement comprises for each said heat exchanging assembly a casing enclosing the assembly and having different connecting members for outdoor air, supply air, exhaust air and used air. Such an arrangement of the heat exchanging assembly makes it possible to easily mount it in a suitable place and connect it to the air paths of the rest of the ventilating arrangement.

According to a further development of this embodiment of the invention said casing accommodates said by-passing air conducting portion arranged therein between said connecting members for outdoor air and supply air, and the casing also contains said throttle and device for adjustment thereon, which consti- tutes a very simple way of realizing the advantageous embodiments mentioned above of the arrangement. Parts of the inner walls of the casing may then advantageously be utilized for forming walls of the by-passing air conducting portion.

The invention also relates to a heat exchanging assembly for use in a ventilating arrangement of the type according to the invention according to the appended independent claim for such a heat exchanging assembly. The function and advantages thereof appear as clear as desired from the above description of the ventilating arrangement according to the invention and the dif- ferent embodiments thereof.

Further advantages as well as advantageous features of the invention appear from the following description of embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, below follows a description of embodiments of the invention cited as examples.

In the drawings:

Fig 1 a is a very simplified view from above of two adjacent flats in a multiple dwelling-house provided with a ven- tilating arrangement according to an embodiment of the invention,

Fig 1 b is a very simplified perspective view of a multiple dwelling-house provided with a ventilating arrange- ment according to the invention and for which parts are broken away so as to very schematically illustrate a part of the ventilating arrangement,

Fig 2 is a schematic view illustrating a part of a ventilating arrangement according to the invention with a heat exchanging assembly arranged in connection to a kitchen,

Fig 3 is a view corresponding to Fig 2 with a heat exchang- ing assembly of the ventilating arrangement disposed in connection to a bathroom,

Fig 4 is a very simplified lateral view illustrating the inner construction of a heat exchanging assembly and air connections thereto in a ventilating arrangement according to the invention, in which a throttle is arranged to close a said by-passing air conducting portion,

Fig 5 is a view corresponding to Fig 4 but with said throttle in an open position, in which it allows outdoor air to flow in the air conducting portion while by-passing the heat exchanging assembly directly to the supply air members without heat exchange with the exhaust air, and

Fig 6 is a schematic perspective view of a casing accommodating a heat exchanging assembly in a ventilating arrangement according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE I NVENTION

Two flats 1 , 2 in a multiple dwelling-house 3, which are provided with a ventilating arrangement according to the invention, are very schematically shown from above in Fig 1 a. It is here very schematically shown how the ventilating arrangement may be arranged in one of the flats 1 , and when describing this reference is now also made to Figs 2 and 3, from which more details appear. However, the other flat has also a similar ventilating arrangement. The arrangement has exhaust air members, which in the case of location in a kitchen, such as in Fig 2, may comprise a stove hood 5, or be designed in every other conceivable conventional way, which is very schematically indicated in Fig 3 in a bathroom 6. These exhaust air members are designed by 7. The arrangement has also an exhaust air channel 8 schematically indicated in Figs 1 a and 1 b and connecting the exhaust air members with means for generating an exhaust air flow from the spaces in question in the channel and discharging thereof to the exterior of the building. These means are here constituted by an exhaust air fan 10 arranged close to a chimney 9 of the building and which may be in common for several flats.

The device has also supply air members 1 1 (see also Figs 2 and 3) arranged in suitable locations for supply of outdoor air from the exterior of the building to the rooms. Openings 12 are made, for example drilled by a circular saw, through the external wall 13 of the building for conducting outdoor air in towards said supply air members 1 1 . These openings 12 are through an outdoor air channel 14 connected to a connecting member 15 for outdoor air of a substantially parallelepiped casing or box 16, which contains a heat exchanging assembly 17 schematically shown in Figs 4 and 5.

The exhaust air members 7 are also connected to the casing 16, namely to an exhaust air connecting member 18 thereof. The heat exchanging assembly 17 is designed for heat exchange between said exhaust air and the outdoor air in a way which may be explained through reference to Fig 4. The heat exchanging assembly has a first inlet 19 connected to the outdoor air channel 14 through the connecting member 15 for entering of outdoor air into the heat exchanging assembly, and a first outlet 20 for this air for conducting this in the form of supply air through a connecting member 21 for supply air for distribution to different parts of the flat through supply air channels not shown and supply air members 1 1. Casings 16 are advantageously arranged above top cabinets in kitchens and in the ceiling hip in bath/toilet rooms.

The heat exchanging assembly has also a second inlet 22 for the exhaust air from the exhaust air members 7 and a second outlet 23 for this connected to a connecting member 24 for used air, which is connected to said exhaust air channel 8. The interior of the heat exchanging assembly may be designed in every conceivable way of heat exchanging assemblies with outdoor air and /exhaust air led on different sides of surface elements for transferring heat therethrough from the warmer thereof to the colder thereof, i.e. in most cases from the exhaust air to the outdoor air so as to in this way raise the temperature of the supply air supplied to the flats.

By supplying supply air to the spaces of the building only through air members connected through the heat exchanging assembly and openings 12 in the external wall of the building to the exterior and ensure that the flats are for the rest substantially sealed with respect to the exterior and adapting the air flow resistance in the heat exchanging assembly 17 to a suitable level it will be possible to obtain the air flows required for the function of the ventilating arrangement only by means of the ex- haust air flow generating means mentioned above, here the exhaust air fan 10.

The very function of a heat exchanging assembly according to the invention will now be explained more in detail with reference to especially Figs 4-6. The heat exchanging assembly is associated on one hand with an air conducting portion 25 designed to form a by-pass conduit of outdoor air from the outdoor air channel 14 to the supply air member 1 1 and on the other with a throttle 26. A device generally designed by 27 is designed to adjust the throttle 26 between a closed position (see Fig 4), in which it closes the by-passing air conducting portion 25 and forces the outdoor air to flow through the heat exchanging assembly, and an open position (Fig 5), in which it allows the outdoor air to flow in the air conducting portion 25 while by-passing the heat exchanging assembly.

In the embodiment shown in Figs 4-5 the air conducting portion for by-passing is arranged inside the casing 16 and is delimited by walls of the casing and an outdoor delimiting wall 28 of the heat exchanging assembly. Thus, in the open position of the throttle the connecting member 15 for outdoor air will be connected directly ttf the connecting member 21 for supply air while allowing air to flow directly between these while by-passing the heat exchanging assembly 17. The device 27 is configured to adjust the throttle 26 through a purely mechanical control, and the throttle is designed to, in the open position according to Fig 5, simultaneously close the first inlet 19 for outdoor air to the heat exchanging assembly, which in certain situations may be advantageous. However, it is pointed out that it would be completely possible that in the position in which the throttle opens the by-passing conducting portion the inlet to the heat exchanging assembly is still totally or partially open, since a major part of the outdoor air will in any case flow in said air conducting portion thanks to a substantially lower air flow resistance in that path than in the path through the heat exchanging assembly.

The adjusting device has a bellow-like member 29 very schematically indicated and arranged in connection with the second inlet 22 for exhaust air to the heat exchanging assembly and configured to expand upon a pressure increase of the air enter- ing into this second inlet. The bellow-like element is mechanically connected to the throttle 26, which is here indicated by a cord 30 and a lever 32 (other connecting elements are conceivable), for adjusting the throttle through movement of the bellow- like element caused by air pressure changes. Problems with ice formation in the exhaust air part of the heat exchanging assembly at very low outdoor air temperatures may by this be solved. This takes place in the following way: when the outdoor air has a very low temperature, such as below for example - 10⁰C or - 15⁰C, the heat exchange between the outdoor air and the warm moisture containing exhaust air in the heat exchanging assem- bly will result in ice formation in the exhaust air part, which means that the air flow resistance therein will increase, so that the air pressure increases in the region of the first inlet and by that the bellow-like element 29 moves and will finally adjust the throttle 26 to open the passage for conducting the outdoor air past the heat exchanging assembly. Continued exhaust air flow through the hea? exchanging assembly will then melt the ice, and water formed thereby will be drained in the bottom of the casing 16 in a way not shown. When the air pressure at the exhaust air inlet to the heat exchanging assembly again sinks the bellow-like element will return and transfer the throttle 26 towards the closed position according to Fig 4 for continued heat exchange between the exhaust air and the outdoor air for heat recovery from the former.

The device 27 for adjusting the throttle 26 also comprises a temperature detecting element in the form of a bimetallic element 31 , which is configured to detect the temperature of outdoor air arriving to the region of the first inlet 19 to the heat exchanging assembly and change the state upon changes of this temperature. The bimetallic element 31 is mechanically connected to the throttle, through a "rope" designed so that it through said state change transfers the throttle to open said bypassing air conducting portion 25 at a temperature exceeding a determined level, for example +20°C, so that at warm weather the outdoor air is not heated by an exhaust air, which may have a relatively high temperature, before it will become supply air.

It would also be possible to design such a temperature detecting element so that this is mechanically connected to the throttle and creates a transfer thereof to said open position when the temperature of the outdoor air falls below a determined level, such as for example -15⁰C, so as to refrain from heat exchange when the risk of ice formation in the heat exchanging assembly is too high.

Through a very simple and cost attractive ventilating arrangement of the type according to the invention the heat in the exhaust air from the flats of a building may in a country with a climate as in Sweden be supplied to the supply air through said heat exchanging assembly so that about 70% of the energy of the ventilating need in a year may be recovered.

It is sufficient to have two openings through the external wall per flat for the supply air instead of one opening per window as is normally required.

The invention is of course not in any way restricted to the embodiments described above, but many possibilities to modifications thereof will be apparent to a person with skill in the art without departing from the scope of the invention as defined in the appended claims.

The different connecting members of the casing accommodating the heat exchanging assembly could for example very well be arranged in another way than shown, for example two per oppo- site sides of the casing.

It is also pointed out that the casing with the heat exchanging assembly may be arranged in different ways and in different locations than schematically indicated in Figs 2 and 3.

A filter not shown is advantageously arranged to filter the outdoor air, and this is advantageously arranged in the casing for the heat exchanging assembly in the path of the air flow before this. Even if it is advantageous that the heat exchanging assembly with surrounding equipment is non-electrified a post-heating battery could be arranged in the supply air path between said assembly and the supply air members so as to raise the temperature of the outdoor air further if required, for example to +18⁰C.

Claims

1 . An arrangement for ventilating spaces in a building , which comprises:

• at least one exhaust air member (7) connected to said spaces,

• at least one exhaust air channel (8) connecting said exhaust air member to means (10) for generating an exhaust air flow from said spaces in the channel and discharging thereof to the exterior of/the building,

• at least one supply air member (1 1 ) for supplying outdoor air from the exterior of the building to said spaces, and

• at least one assembly (17) for heat exchange between said exhaust air and said outdoor air, characterized in that it further comprises at least one supply air channel (14), which through an opening (12) in the external wall (13) of the building directly connects the exterior of the building to a first inlet (19) in said heat exchanging assembly for con- ducting outdoor air to this and out of this through a first outlet (20) thereof connected to said supply air member (11 ), that the heat exchanging assembly has a second inlet (22) connected to said exhaust air member downstream thereof and a second outlet (23) connected to said exhaust air channel (8) and that the arrangement is configured to create said flow of air to the spaces from the exterior of the building through said supply air member (1 1 ) only through the negative air pressure generated in said spaces through the flow of exhaust air leaving said spaces through said exhaust air member (7).

2. An arrangement according to claim 1 , characterized in that it comprises a plurality of said heat exchanging assemblies (17) connected to a said outdoor air channel (14) each and at least one exhaust air member (17) each, and that these heat ex- changing assemblies are connected to a said common exhaust air flow generating means (10).

3. An arrangement according to claim 1 or 2, characterized in that said exhaust air member (17) comprises a stove hood (5) in a kitchen (4) of the building and/or is arranged in a sanitary room (6), such as a bathroom, of the building.

4. An arrangement according to any of the preceding claims, characterized in that said exhaust air flow generating means is formed by an exhaust air fan (10) arranged in said exhaust air channel (8) close to a chimney (9) of the building.

5. An arrangement according to any of claims 1-3, characterized in that said exhaust air flow generating means is formed by a chimney designed to connect said exhaust air channel to the exterior of the building.

6. An arrangement according to any of the preceding claims, characterized in that each of said at least one heat exchanging assembly (1 7) is associated on one hand with an air conducting portion (25) designed to form a by-pass conduit for outdoor air from said outdoor channel (14) by-passing the heat exchanging assembly to said supply air member (1 1 ) and on the other with a throttle (26), and that the arrangement comprises a device (27) configured to adjust said throttle between a closed position, in which it closes said by-passing air conducting portion and forces the outdoor air to pass through the heat exchanging assembly, and an opened position, in which it allows the outdoor air to flow in said air conducting portion while by-passing the heat exchanging assembly.

7. An arrangement according to claim 6, characterized in that said device (27) is configured to adjust said throttle (26) through a purely mechanical control.

8. An arrangement according to claim 6 or 7, characterized in that said throttle (26) is configured to close said first inlet (19) for the outdoor air to the heat exchanging assembly (17) in said open position.

9. An arrangement according to any of claims 6-8, charac- terized in that said device (27) comprises elements (26) designed to be influenced by pressure differences between the air in the region of said first inlet (19) and the air in the region of said second inlet (22) to the heat exchanging assembly (17), and that the device is configured to adjust the throttle (26) in dependence of such air pressure differences detected by said elements.

10. An arrangement according to claim 9, characterized in that said elements (29) are designed to detect the air pressure of the exhaust air in the region of said second inlet (22) to the heat exchanging assembly (17), and that the device (27) is, upon detection of an air pressure in the region last mentioned having a value above a determined level, configured to influence the throttle (26) to open said by-passing air conducting portion (25) so as to allow the outdoor air to be conducted to by-pass the heat exchanging assembly.

1 1 . An arrangement according to claim 10, characterized in that said elements comprise a bellow-like element (29) arranged in connection to said second inlet (22) to the heat exchanging assembly (17) and configured to expand upon a pressure increase of the air entering said second inlet, and that the bellow-like element is mechanically connected to the throttle (26) for adjustment thereof through movement of the bellow-like element caused by air pressure changes.

12. An arrangement according to any of claims 6-1 1 , characterized in that said device (27) comprises elements (31 ) designed to detect the temperature of outdoor air arriving to the region of said first inlet (19) through the heat exchanging as- sembly (17), and that the device is configured to adjust said throttle (26) in dependence of said detected temperature.

13. An arrangement according to claim 12, characterized in that the device (27) is configured to transfer said throttle (26) to open said by-passing air conducting portion and a said temperature detected below a determined level , in which this determined level is between -5⁰C and -3O⁰C, preferably between -5⁰C and -2O⁰C.

14. An arrangement according to claim 12 or 13, characterized in that the device (27) is designed to transfer said throttle (26) to open said by-passing air conducting portion (25) at a detected said temperature above a determined level, in which this deter- mined level is between +15⁰C and +30⁰C, preferably between + 18°C and +25⁰C and most preferred at about +2O⁰C.

15. An arrangement according to any of claims 12-14, characterized in that said temperature detecting element comprises a bimetallic element (31 ) mechanically connected to said throttle (26) so as to adjust the position of the throttle through the state of the bimetallic element influenced by temperature changes.

16. An arrangement according to any of the preceding claims, characterized in that it for each said heat exchanging assembly

(17) comprises a casing (16) enclosing the assembly with different connecting members (15, 21 , 18, 24) for outdoor air, supply air, exhaust air and used air.

17. An arrangement according to claim 6 and 16, characterized in that the casing (16) accommodates said by-passing air conducting portion arranged therein between said connecting members (15, 21 ) for outdoor air and supply air, and that the casing further contains said throttle (26) and the device (27) for ad- justing the throttle.

18. A heat exchanging assembly for use in a ventilating arrangement according to any of claims 1 -17, characterized in that it comprises a first inlet (19) for outdoor air, a first outlet (20) for conducting outdoor air entering through the inlet out to supply air members, a second inlet (22) for exhaust air and a second outlet (23) for conducting exhaust air entering through said second inlet out.