EP1789731A1

EP1789731A1 - Ventilator with fresh air capability together with heating and/or cooling capability and methods for operating such ventilator

Info

Publication number: EP1789731A1
Application number: EP04744801A
Authority: EP
Inventors: Henning Stougaard
Original assignee: Ribe Jernindustri AS
Current assignee: Ribe Jernindustri AS
Priority date: 2004-08-18
Filing date: 2004-08-18
Publication date: 2007-05-30
Also published as: WO2006018675A1

Abstract

A ventilator (2) capable of supplying fresh air in combination with heating and/or cooling for a ventilated room is provided. The ventilator comprises at least two blowers (6), a heat exchanger (8), a motorised damper (4) and a microprocessor (12) for cross-flow controlling the ventilator. A method for controlling a ventilator by adjusting the rotational speed of the cross-flow blowers, the opening of the damper and optionally the opening of a motorised valve controlling the flow rate of heat transfer medium is also provided. In preferred embodiments, the method further comprises thermal protection to prevent frost damage and boost of temperature or fresh air.

Description

VENTILATOR WITH FRESH AIR CAPABILITY TOGETHER WITH HEATING AND/OR COOLING CAPABILITY AND METHODS FOR OPERATING SUCH VENTILATOR

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a ventilator with at least two cross-flow blowers, and in particularly, the invention relates to a ventilator which during use may provide fresh air together with heating and/or cooling. Furthermore, the invention relates to a method for operating such a ventilator.

BACKGROUND OF THE INVENTION

The air of quality within a room deteriorates over time, particularly when persons occupy the room. For example, the CO₂-leveI may increase or the temperature may increase or decrease to an unacceptable level..

WO 02/04871 discloses a ventilating device, capable of heating or cooling the air in a room while circulating air within the room. The ventilating device consists of one unit with one motor and at least two impellers. However, WO 02/04871 is completely silent on introduction of fresh air into the room.

OBJECTS OF THE INVENTION

It is an object of the invention to provide an improved ventilator which allows for improved comfort in the ventilated room.

It is another object of the invention to provide a method of operating a ventilator according to the first aspect of the invention.

DISCLOSURE OF THE INVENTION

The above and other objects of the invention are realised by a ventilator according to claim 1 and the method of operating a ventilator according to claim 13. Further embodiments of the invention are disclosed in the dependent claims and in the following detailed description.

A ventilator according to the invention has two or more cross-flow blowers arranged to suck fresh air and/or air from the room to be ventilated over a substantial part of the length of the cross-flow blowers and force the air via a heat exchanger to the room to be ventilated. A motorised damper controls the ratio between fresh air and air from the room to be ventilated in the air that is sucked into interaction with the heat exchanger via the cross-flow blowers. A microprocessor is arranged to control the motorised damper and the rotational speed of the cross-flow blowers such that the ventilator may provide fresh air as well as heating and/or cooling of the ventilated room.

One or more ventilators may be combined with a central control unit to form a system for ventilating one or more rooms. The central control unit, which should be in communication with at least one ventilator, may provide control input, such as set temperature for the ventilator(s) and/or co-ordinate operation of ventilators.

In a broad embodiment of the method of operating, a ventilator comprises the steps of receiving an input set temperature and optionally further input temperatures when these are used for establishing the output parameters for control of a motorised damper and rotational speed of at least two cross-flow blowers. The output parameters may e.g. be optimised to maximise the fresh air input without compromising the room temperature, to minimise the cost of heating/cooling the room or to keep the room temperature steady while keeping a high air quality.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained more fully below with reference to exemplary embodiments as well as the drawings, in which

Fig. 1 shows top view of ventilators according to the invention,

Fig. 2 shows cross sectional view of ventilators according to the invention, and

Fig. 3 shows system for ventilating at least one room in a building. All the figures are highly schematic and not necessarily to scale, and they show only parts which are necessary in order to elucidate the invention, other parts being omitted or merely suggested.

DESCRIPTION OF THE DRAWINGS

A ventilator according to the invention is shown in Fig. 1. The shown ventilator 2 has two cross-flow blowers 6. It is highly advantageous to have more than one cross-flow blower 6, such as two, three, four, five, six or more, in the ventilator as this allows for a long, slim unit with a correspondingly extended ventilator air outlet to the room whereby a low linear air velocity may be realised even when large volumes of air are treated. The cross-flow blowers are typically arranged in a line.

It is preferred to have the cross-flow blowers 6 arranged end to end and close to neighbouring cross-flow blowers 6. However, in another embodiment, at least two neighbouring cross-flow blowers 6, while still arranged end to end, are separated by a substantial distance, such as more than 0.5 m or even more than 1 m. Such an arrangement may be advantageous if the heat exchange requirements in a room is limited or if the cross-flow blowers are arranged such that not all cross-flow blowers are used for the same main purpose, such as one or more cross-flow blower(s) for heating, one or more cross-flow blower(s) for cooling and/or one or more cross-flow blower(s) for fresh air. In such cases and when the ventilator is oriented vertically, it is preferred to arrange cross-flow blowers associated with heating in the lower part and cross-flow blowers associated with cooling in the upper part.

One or more motors 20, which drive the cross-flow blowers 6, are capable of operating at different rotational speed. It is preferred that the rotational speed may be varied continuously, but step-wise variation may also be used according to the invention. The rotational force may be transferred between adjacent cross-flow blowers, e.g. via a shaft of via a gear.

It is preferred to have an arrangement of driving mechanisms for the cross-flow blowers which allow for the rotational speed of the cross-flow blowers to be individually controllable. This allows for various parts of the ventilator being used for different purposes. For example, a vertically arranged ventilator may advantageously mainly use the lower part of the ventilator for heating purposes and the upper part of the ventilator for cooling and/or fresh air purposes. Thereby a better mixing of air within the room may be realised. Furthermore, the ventilator may be operated such that the parts of the ventilator near zones of the room where people stay often have a particularly lower linear velocity of the ventilator exit air 46 to prevent draught.

This may easily be realised by having at least two motors in the ventilator. In a preferred embodiment each cross-flow blower is operable by a separate motor 20, whereby it is particularly simple to arrange for variation of rotational speed, and complex structures for transferring of rotational speed between neighbouring cross- flow ventilators 6 are dispensed with Such a multiplicity of motors 20 may be operated at the same or at different rotational speed(s).

The ventilator 2 is equipped with a motorised damper 4 for controlling the input ratio to the ventilator 2 of fresh air 42 to recycled room air 44, for example as shown in Fig. 2. The fresh air intake may comprise an extended slit in a substantial length along the length of the ventilator 2 and/or it may comprise one or more smaller slits or holes distributed along the length of the ventilator 2 through the wall 40. The damper 4 may consist of one piece extending along most of the length of the ventilator 2 or the damper 4 may comprise two or more, such as two, three, four or more, co-operated or separately operated dampers 4. If several dampers 4 are used, the dampers 4 may be interconnected and operated by one motor, or several independent motors may drive the dampers 4 independently or co-ordinated. In a preferred embodiment, the damper 4 only control the flow of the fresh air, whereas the damper does not block the recycled room air directly. This allows for a damper which only needs a relatively small movement whereby the opening of the fresh air may be adjusted more precisely. In another embodiment, several dampers are used of which at least one is dedicated for controlling the opening of the fresh air intake and at least one is dedicated to controlling the opening of the recycled room air intake. Thereby a very precise control of the air flow ratio is realised.

A microprocessor 12 is used for controlling the ventilator 2. It is preferred that the microprocessor 12 is integrated into the ventilator 2, but a centralised microprocessor 12 may control more than one ventilator 2 at the same time. The microprocessor 12 is used for controlling the motorised damper 4 and the rotational speed of the cross-flow blowers 6 based on input parameters, which may be set parameters, such as set temperature for the room, or e.g. result from temperature sensors 32, such as room temperature, ventilator exit temperature and/or fresh air temperature. Other categories of sensor input are air quality measurements, such as humidity and/or CO₂- concentration, and presence of persons in the ventilated room by a movement sensor, such as an infrared sensor.

The sensors may be arranged separated from the ventilator but in communication with the ventilator. However, it is preferred that at least one of the sensors, such as a temperature sensor 32, a COrsensor 34 or a movement sensor 36, preferably a temperature sensor 32, is integrated with the ventilator, as shown in Fig. 1B and Fig. 2, to realise a simple design by limiting the number of non-integrated parts.

The ventilator according to the invention is also equipped with a heat exchanger 8. Many types of heat exchangers may be utilised within the scope of the invention. Examples of usable heat exchangers are a pipe, a pipe with convector plates, a convector, a plate convector or a radiator. A heat exchange medium is transported through the heat exchanger. The heat exchanger may have two separate systems, i.e. one for heating purposes and one for cooling purposes, however, in many applications only heating or cooling is needed at one time, leading to only one heat exchange medium distribution system. Such a single system may preferably be used for heating during wintertime and cooling during summertime by switching heat transfer medium or treatment of the heat exchange medium. The heat exchange medium is typically supplied to the ventilator by pipes 9 from a central heating or cooling facility which may be arranged in the same or another building.

In a preferred embodiment, e.g. as the one shown in Fig. 1 B, a pipe for heat exchange medium to or from the heat exchanger 8 of the ventilator 2 is equipped with a motorised valve 10 which is also controlled by the microprocessor 12 of the ventilator 2, whereby further freedom in operating the ventilator is introduced. This may e.g. allow for stopping of the heat exchange medium while the room is not in use or if a boost of fresh air is desired and hence increase the energy efficiency of the ventilator. The motorised valve may be chosen from a wide range of electrically controllable valves, but it is preferred to use a valve, which allow for continuous variation of the flow even though on/off or stepwise control may also be applied for a ventilator according to the invention. The ventilator may be assembled directly on the site of application, such as in a floor, or in/on a wall e.g. with holding members, however, it is preferred to assemble the ventilator on a member for supporting the elements of the ventilator, such as a frame. This greatly facilitates installation at the site of application and may also facilitate transportation of the ventilator from the site of manufacture to the site of application.

In a preferred embodiment, the ventilator is equipped with a removable cover member 22 for preventing the user from accidentally accessing the moving parts, e.g. cross- flow blowers. The cover member 22 may extend substantially the full length of the ventilator as shown in Fig. 1C, or it may comprise numerous separate or connected parts. The cover 22 should preferably communicate with a safety lock, i.e. a means for preventing the cover 22 from being removed unless the cross-flow blowers are at rest, and/or a safety switch, i.e. a means for actuating a complete stop of the rotation of the cross-flow blowers if attempting to remove the cover 22. This would greatly increase the safety of the user as accidents are thereby prevented.

The ventilator is typically installed either vertically or horizontally on a wall, on the ceiling or in the floor. The preferred type of installation depends on the shape and use of the room to be ventilated.

The rest position for the motorised damper, i.e. the position, which would result from a power failure, may advantageously by the zero fresh air position. For the motorised valve, the preferred rest position depends on the ventilated room. If the room may be subjected to frost damage, the preferred rest position may be partially or fully open, whereas for rooms which are not subject to frost damage the rest position should be close, i.e. no flow of heat exchange medium.

Many types of ventilated rooms may advantageously have a ventilator according to the present invention installed. Particularly, rooms of limited size or frequented by many people would gain from such ventilators. Some examples are: • Housings, particularly

- Living rooms, where heating/cooling without noise or draught is important;

- Bedrooms, where low noise emission and a low CO₂-level are desired;

- Bathrooms, where the ventilator may advantageously be equipped with a humidity sensor; - Kitchens, where space may be limited and the ventilator may advantageously be equipped with a humidity or fume detector; • Commercial buildings, such as

- Offices; - Schools, e.g. classrooms and auditoriums, where the air quality may drop dramatically during use;

- Hotels, corresponding to housings;

- Shops of limited size.

However, ventilators and the methods of operating ventilators according to the invention may also be used in other types of structures.

The ventilator is typically but not necessarily part of a system for ventilating at least one room in a building. In Fig. 3 an example of such a system is shown. Such a system comprises central control unit 30, where a set temperature for the ventilator may be introduced. The set temperature is typically introduced by user input means 48 or from an external system. The central control unit 30 may act to measure input data for the ventilator unit, such as movement, air quality etc. In another embodiment, the central control unit 30 acts to monitor the operation of one or more ventilators. Such monitoring may involve normal operation and/or collection of error messages and could include forwarding such data to an external unit. In a further embodiment, the central control unit 30 co-ordinates the operation of numerous ventilators within one room, numerous ventilators in several rooms within one building or in several rooms in more than one building. Thereby an easy overview and/or distance control of a large number of ventilators may be realised, thus saving time for transport.

A central control unit 30 may be integrated with the ventilator which may be particularly advantageous for simple systems with one or only a few ventilators, such as e.g. one or two. In many cases, however, it is advantageous to have a central control unit 30 arranged in a more frequently used part of the same room which may be away from the ventilator. For larger systems, a central control unit 30 may advantageously be arranged In another room or building, whereby monitoring may be facilitated. In Fig. 3 a system with several ventilators 2 and one centralised control unit 30 is shown schematically.

In general, units in communication as indicated herein may communicate via wired connections, via wireless connections or by a combination of wired and wireless connections. Wired connections are advantageous in the communication being easy to control, whereas wireless connections are advantageous due to rapid installation.

The cross-flow blowers force air to interact with the heat exchanger, and the higher the air velocity at the heat exchanger, the more energy is transferred between the heat exchanger and the air. It is therefore advantageous to increase the rotational speed of the cross-flow blowers when the difference between the temperature of the ventilated room and the set temperature is above a threshold value. Experimental work has shown that it is advantageous to increase the rotational speed of the cross-flow blowers when the difference is larger than about 0.5⁰C. In a preferred embodiment, the initiation of increase of rotational speed is initiated when the difference is between about 1 to 3⁰C. At this difference, it is preferred to increase the rotational speed of the cross-flow blowers. The increase is preferably at least 25% of maximum rotational speed, more preferably at least 50%, but in some applications the increase may be up to about 100%. In another embodiment, the rotational speed is increased continuously or in a number of steps as the difference between set temperature and temperature of the ventilated room is increased. The person skilled in the art would understand that the increase in rotational speed accounts for increase in airflow via a heating heat exchanger when the room temperature is below the set temperature and via a cooling heat exchanger when room temperature is above the set temperature. In a preferred embodiment, it may be advantageous to reduce or stop the rotation of the cross-flow blower(s) at a heating heat exchanger when the room temperature is above the set temperature and equivalents to reduce or stop the rotation of the cross-flow blower(s) at a cooling heat exchanger when room temperature is below the set temperature.

In a method according to the invention, the position of the motorised damper 4 is preferably restricted according to the fresh air temperature, such that the higher the fresh air temperature, the larger the maximum fraction of fresh air. In other words, if the fresh air temperature falls below a certain threshold temperature, then the damper is restricted from allowing too much fresh air to enter into the ventilator. This prevents too great heat loss during cold periods. This method step may advantageously be combined with a CCVsensor control step or equivalent, whereby the fresh air is restricted to a necessary minimum to keep a good air quality while restricting the heat loss. The motorised damper may be adjustable in steps, such as 2, 3, 4, 5, or more steps from zero to 100% fresh air, or the variation may be continuous or on/off-type controlled. In a method according to the invention, the motorised valve 10 is preferably adjusted according to the difference between the temperature of the ventilated room and the set temperature. In a preferred embodiment, the opening of the valve 10 is linearly dependent on the temperature difference. In other words, for heating purposes, the valve for heating heat exchange medium may be 100 % open when the set temperature is more than e.g. about 1.5 to 3⁰C above the temperature of the ventilated room, whereas if the set temperature is the same or below the temperature of the ventilated room, the valve should be nearly closed, such as less than 10% open, preferably about 0% open. The skilled person would from this deduce a similar - but opposite - control step for cooling heat exchange medium, i.e. the opening of the valve is increased the more the set temperature is below the temperature of the ventilated room.

Other mathematical relationships than linear may equivalently be used between the temperature difference and the opening of the valve without departing from the inventive concept of the present invention. For example, the valve may be operated according to parable relationship, a stepwise function or an on/off function.

Near equilibrium operation

The ventilator may advantageously be designed such that when the ventilator is operating near equilibrium conditions, i.e. when the temperature of the ventilated room and the set temperature are the same or nearly the same, the temperature of the ventilated room is kept constant by operating the ventilator with i) no rotation of the cross-flow blower, ii) no or a small amount of fresh air introduced by the damper and iii) the motorised valve opened to a low level, preferably less than 25%, more preferably less than 20%, such as about 3 to 15% opened. The opening of the valve should be adjusted according to the flow of fresh air. Thereby a very silent, highly energy efficient and yet highly flexible operation may be realised for the ventilator.

Draught-preventing steps

The feeling of draught is an interplay between a number of parameters of which the air temperature, the relative air temperature and linear air velocity are important parameters. In a preferred embodiment, the method according to the invention of operating a ventilator comprises draught-preventing steps. In a first embodiment, the draught-preventing steps are such that when the ventilator exit temperature is below a threshold temperature, then the maximum rotational speed of the cross-flow blowers is reduced.. By maximum rotational speed is meant the maximum allowable rotational speed that the microprocessor may provide as an output when establishing the optimum operating parameters for the cross-flow blowers and the other elements of the ventilator. The threshold temperature depends to a large extent on the linear air velocity and is typically in the range of 15 to 20°C, but higher as well as lower threshold temperatures may be relevant in some applications.

In a second embodiment, the draught-preventing steps are such that when the difference between the temperature of the ventilated room and the ventilator exit temperature is greater than a threshold temperature difference, then the maximum rotational speed of the cross-flow blowers is reduced. The threshold temperature difference should in general be higher when the ventilator exit temperature is higher than the temperature of the ventilated room than when the ventilator exit temperature is lower than the temperature of the ventilated room as a moving warmer air is more acceptable. The threshold temperature difference depends to a large extent on the linear air velocity and is typically between 1 to 8⁰C, preferred values being 1.5 to 5⁰C.

Draught may, if desired and a motorised valve 4 is included with the ventilator, be further reduced by increasing the flow of heating heat exchange medium or decreasing the flow of cooling heat exchange medium by adjusting the opening of the motorised valve 4.

Thermal protection

In a method according to the invention, steps for thermal protection may also be added. Thermal protection may e.g. by introduced to prevent frost or condensation damage, which may arise if the temperature of the ventilated room is reduced considerably below room temperature, e.g. to about or below the dew point or the freezing point. Such a situation could arise, for example if the fresh air temperature becomes very low so that the heat exchanger does not have sufficient capacity to heat up the fresh air. Another example is if the heat exchange medium is not warm on entry into the heat exchanger, or if the heat exchange medium distribution system has been blocked. A first embodiment of a thermal protection procedure is triggered below a first threshold ventilator exit temperature, whereby a maximum allowable fresh air fraction at the damper 4 is restricted and/or the maximum rotational speed of the cross-flow blowers is restricted. In a preferred embodiment of this thermal protection procedure, the fresh air fraction of the damper is adjusted to about zero fresh air and the maximum rotational speed is restricted to about 50% of full speed or less, such as below about 33%.

A second embodiment of a thermal protection procedure is triggered below a second threshold ventilator exit temperature, whereby the damper is adjusted to zero fresh air and the rotational speed of the cross-flow blowers is set to about zero and/or the motorised valve for heating heat exchange medium is opened to about 100%. It is preferred that the dampers are adjusted to zero AND the rotational speed of the cross- flow blowers is set to about zero AND the motorised valve is opened to about 100%, whereby the risk of frost damage would typically be minimised.

In a preferred embodiment of a thermal protection procedure, the first and the second embodiment of thermal protection procedures are combined such that the first threshold ventilator exit temperature is higher than the second threshold ventilator exit temperature. It is preferred that the first threshold temperature is below 14°C, more preferably below 12"C₁ such as about 11 - 8°C, and that the second threshold temperature is below 10⁰C, preferably between 9 - 3°C, more preferably between 8 - 4°C.

Timer

A preferred embodiment of the method according to the invention further comprises a timer procedure, whereby e.g. set temperatures, threshold temperatures etc. may be adjusted automatically based on a 24 hour basis, such as e.g. according to variation of ventilation needs according to day/night variation, on a 7 day basis, such as e.g. according to variation of ventilation needs according to weekday/weekend variation, or on an annular basis, such as e.g. according to variation of needs according to summer/winter variation and/or daylight saving. A timer may also be used for controlling the extent of a boost period as discussed below. Boost

In a number of situations it is advantageous to be able to overrule the normal operation of a ventilator to provide a boost of heating, cooling or fresh air without taking into account possible side effects, such as draught, overheating and/or overcooling.

The boost may be activated manually, e.g. via a central control unit, by a timer function, e.g. at fixed intervals, e.g. for 1 minute every 15 minutes or 3 minutes every hour, and/or in the morning/evening and/or by a sensor, such as an air quality sensor, like a humidity sensor or a CO₂-sensor, or a movement sensor, which may e.g. activate a boost of fresh air or heating when a room is entered after a longer period without persons in the room. The boost may be deactivated manually, by a timer after a specified period of time, such as 1 , 2, 3, 4, 5 or 10 minutes, or by an acceptable sensor value. However, the boost may also be deactivated by an overruling method step, such as e.g. a thermal protection step.

A fresh air boost is often highly desired in meeting rooms during brakes. In a preferred embodiment, the method according to the invention further comprises the steps of increasing the rotational speed of the cross-flow blowers to near maximum and adjusting the damper to about 100% fresh air. Heating or cooling may advantageously be disabled during such a fresh air boost to prevent unnecessary energy waste, as the air may be exchanged several times during a fresh air boost.

A preferred embodiment of the method according to the invention incorporates a heating boost, whereby upon activation the rotational speed of the cross-flow blowers is maximised, the motorised valve for heat exchange fluid for heating purposes is opened near 100% and the damper is adjusted according to the fresh air temperature such that for fresh air temperatures above the temperature of the ventilated room the damper is put to near 100% fresh air, whereas for fresh air temperatures below the temperature of the ventilated room the damper is put to near zero fresh air.

Correspondingly, a cooling boost may be incorporated into the method according to the invention. Air quality enhancing

The quality of air amongst others depends on the humidity content and presence of particles or molecules. The relevant types of air quality problems depend on the actual application. The method according to the invention for operating a ventilator may further comprise air-quality-enhancing steps, which is preferably initiated by the measurement of an air quality value above a threshold value by an air quality sensor. This triggers the rotational speed of the cross-flow blowers to be increased, preferably to about maximum, and the minimum fresh air fraction to be increased, preferably the damper is adjusted to about 100 % fresh air.

In some cases, the fastest increase in air quality may be achieved by circulating the air within the room via an air filter, such as an active coal filter or a particle filter. In such situations, the preferred air-quality-enhancing steps are to increase the rotational speed of the cross-flow blowers, preferably to about maximum, and to adjust the damper to about zero fresh air.

Physically feasible combinations of features

An individual feature or combination of features from an embodiment of the invention described herein, as well as obvious variations thereof, is combinable with or exchangeable for features of the other embodiments described herein, unless the person skilled in the art would immediately realise that the resulting embodiment is not physically feasible.

TABLE FOR IDENTIFICATION

2 Ventilator

4 Motorised damper

6 Cross-flow blower

8 Heat exchanger

9 Pipe for heat exchange medium

10 Motorised valve

12 Microprocessor

20 Motor for cross-flow blower

22 Cover

30 Central control unit

32 Temperature sensor

34 Air quality sensor

36 Movement sensor

40 Wall

42 Fresh air

44 Recycled room air

46 Ventilated air exit

48 User input means

Claims

1. A ventilator (2) with fresh air capability together with heating and/or cooling capability comprising - at least two cross-flow blowers (6), a rnotorised damper (4) for controlling the input ratio of fresh air to recycled room air to the ventilator,

- a heat exchanger (8),

- a microprocessor (12) for controlling said motorised damper (4) and said cross- flow blowers (6).

2.. Ventilator (2) according to claim 1 further comprising a motorised valve (10) for controlling a flow of heat exchange medium to the heat exchanger (8); said motorised valve (10) being controllable by said microprocessor (12).

3. Ventilator (2) according to claim 1 or 2, wherein the rotational speed of the cross- flow blowers (6) is individually controllable.

4. Ventilator (2) according to claim 3, wherein the cross-flow blowers (6) are operable by at least two motors (20), preferably each of the cross-flow blowers (6) is operable by a separate motor (20).

5. Ventilator (2) according to any one of the claims 1 to 4, wherein said microprocessor (12) is in communication with at least one temperature sensor (32), preferably at least 3 temperature sensors (32), such as a room temperature sensor, a ventilator exit temperature sensor and a fresh air temperature sensor.

6. Ventilator (2) according to claim 5, wherein at least one sensor (32) is integrated with the ventilator.

7. Ventilator (2) according to any one of the claims 1 to 6, wherein said microprocessor (12) is in communication with an air quality sensor (34), preferably a C0₂-sensor and/or a humidity sensor.

8. Ventilator (2) according to any one of the claims 1 to 7, wherein said microprocessor (12) is in communication with a movement sensor (36), preferably an infrared movement sensor.

9. Ventilator (2) according to any one of the claims 1 to 8, further comprising a member for supporting elements of the ventilator (2) and for facilitating installation of the ventilator.

10. Ventilator (2) according to any one of the claims 1 to 9, further comprising a removable cover member (22) for preventing user access to the moving parts of the ventilator, preferably said cover member (22) is in communication with a safety lock and/or a safety switch.

11. System for ventilating at least one room in a building comprising at least one ventilator (2) according to any one of the claims 1 to 10 and a central control unit

(30) for providing control input, such as set temperature, and/or monitoring and/or co-ordinating the operation of ventilators; said central control unit (30) is in communication with at least one ventilator.

12. System according to claim 11, wherein the central control unit (30) is integrated with the ventilator, arranged away from the ventilator, preferably in another part of the same room, in another room of the same building or in a different building.

13. Method of operating a ventilator (2) comprising the steps of: - receiving an input set temperature,

- optionally receiving further input temperatures, such as temperature of the ventilated room, ventilator exit temperature and/or fresh air temperature,

- adjusting output parameters according to input parameters, said output parameters including position of motorised damper (4) and rotational speed of at least two cross-flow blowers.

14. Method according to claim 13, wherein the rotational speed of the cross-flow blowers (6) is increased when the difference between the temperature of the ventilated room and the set temperature is larger than about 1"C₁ preferably when the difference is between 1.5 to 3°C.

15. Method according to claim 13 or 14, further comprising the step of adjusting the opening of a motorised valve (10) for controlling a flow of heat exchange medium to the heat exchanger (8), wherein the motorised valve (10) is adjusted according to the difference between the temperature of the ventilated room and the set temperature, such that the larger the difference, the more open the valve (10), preferably the valve (10) is adjusted continuously.

16. Method according to any one of the claims 13 to 15 further comprising draught- preventing steps, whereby the maximum rotational speed of the cross-flow blowers (6) depends on the ventilator exit temperature such that when the ventilator exit temperature is below a threshold temperature, then the maximum rotational speed of the cross-flow blowers (6) is reduced, optionally the motorised valve (10) being adjusted to increase the flow of heating heat exchange medium and/or decrease the flow of cooling heat exchange medium.

17. Method according to any one of the claims 13 to 16 further comprising draught- preventing steps, whereby the maximum rotational speed of the cross-flow blowers (6) depends on the difference between the temperature of the ventilated room and the ventilator exit temperature such that when the difference between the temperature of the ventilated room and the ventilator exit temperature is greater than a threshold temperature, then the maximum rotational speed of the cross-flow blowers (6) is reduced, optionally the motorised valve (10) being adjusted to increase the flow of heating heat exchange medium and/or decrease the flow of cooling heat exchange medium.

18. Method according to any one of the claims 13 to 17, wherein the maximum allowable damper opening is adjusted according to the fresh air temperature, such that the higher the fresh air temperature, the larger the maximum fraction of fresh air, preferably the maximum allowed damper opening is adjusted in steps, such as 2, 3, 4, 5 or more steps from zero to 100% fresh air.

19. Method according to claim 18, wherein the rest position of the damper (4) is zero fresh air.

20. Method according to any one of the claims 13 to 19, further comprising thermal protection procedures for preventing frost or condensation damage of goods or building whereby

- below a first threshold ventilator exit temperature, the maximum allowable fresh air opening of the damper (4) is restricted and/or the maximum rotational speed of the cross-flow blowers (6) is restricted, preferably the fresh air opening of the damper (4) is adjusted to provide about zero fresh air and the maximum rotational speed of the cross-flow blowers (6) is restricted to about 50 % of full speed or less.

21. Method according to any one of the claims 13 to 20, further comprising thermal protection procedures for preventing frost or condensation damage of goods or building whereby

- below a second threshold ventilator exit temperature, the damper (4) is adjusted to provide about zero fresh air and a) the rotational speed of the cross-flow blowers (6) is adjusted to about zero, and/or b) the motorised valve (10) is opened about 100 %.

22. Method according to any one of the claims 13 to 21, further comprising the step of receiving at least one further input parameter, such as CO₂-level in the room to be ventilated, presence of persons, time-variation data and/or boost instruction.

23. Method according to claim 22, further comprising a timer procedure for adjusting the operation based on a 24 hour basis, on a 7 day basis and/or on an annular basis to take into account expected use of the ventilated room, such as day/night variation and/or weekday/weekend variation.

24. Method according to any one of the claims 22 to 23, further comprising a boost procedure for fast renewal of the air in the room, whereby upon activation

- the rotational speed of the cross-flow blowers (6) is adjusted to about maximum, and

- the damper (4) is adjusted to about 100 % fresh air, preferably the boost is initiated manually, by a timer function and/or by a sensor, such as a temperature sensor (32), an air quality sensor (34) or a movement sensor (36).

25. Method according to any one of the claims 22 to 24, further comprising a boost procedure for fast increase of the room temperature, whereby upon activation

- the rotational speed of the cross-flow blowers (6) is adjusted to about maximum,

- the motorised valve (10) for heat exchange medium for heating purposes is opened about 100%, and

- the damper (4) is adjusted according to the outside air temperature such that a) as long as the outside air temperature is below the temperature of the room, to about zero fresh air, or b) as long as the outside air temperature is above the temperature of the room, to about 100 % fresh air, preferably the boost is initiated manually, by a timer function and/or by a sensor, such as a temperature sensor (32), an air quality sensor (34) or a movement sensor (36).

26. Method according to any one of the claims 22 to 25, further comprising a boost procedure for fast decrease of the room temperature, whereby upon activation

- the motorised valve (10) for heat exchange medium for cooling purposes is opened about 100%, and

- the damper (4) is adjusted according to the outside air temperature such that c) as long as the outside air temperature is below the temperature of the room, to about 100 % fresh air, or d) as long as the outside air temperature is above the temperature of the room, to about zero fresh air, preferably the boost is initiated manually, by a timer function and/or by a sensor, such as a temperature sensor (32), an air quality sensor (34) or a movement sensor (36).

27. Method according to any one of the claims 22 to 26, further comprising an air quality procedure for preventing unacceptable levels of undesired airborne particles or molecules, whereby upon activation - the damper (4) is adjusted such that the minimum fresh air fraction is increased, preferably the procedure is initiated by an air quality sensor value above a first threshold value.

28. Method according to any one of the claims 22 to 27, further comprising an air quality procedure for preventing unacceptable levels of undesired airborne particles or molecules, whereby upon activation

- the damper (4) is adjusted to about 100 % fresh air, preferably the procedure is initiated by an air quality sensor value above a second threshold value.