EP1503151B1 - Air treatment and heating system - Google Patents

Abstract

The air-conditioning and heating installation has a feed-in channel (16) with an inlet (10) preferably to a permanent room in a building and comprises a ventilation unit (11), a connecting piece (12) and a heating unit (15). The ventilation unit contains a control unit and is positioned between the inlet and feed-in channel. The connecting piece is in the feed-in channel. The connecting piece further has a first check valve (120) between the branches for the supply apertures (13) and the feed-in aperture (14). The heating unit has, in series with each other, a further check valve (150), a fan (152) and a combustion unit (154).

Description

The invention relates to an air treatment and heating system, to a heating unit for use in such a system and to a ventilation unit for use in such a system.

For heating and ventilation of rooms in buildings, it is known to provide the buildings with supply and discharge ducts for air for ventilation and with supply and discharge ducts for air for combustion in a heating unit. Both for generating an air flow for ventilation and for combustion, fans are generally included in the building, for example a first fan between the rooms in the building and the discharge duct for ventilation and a second fan between the combustion air supply duct and the combustion chamber.

Out DE 100 34 485 it is known to couple the supply opening of the heating unit to the discharge duct of the ventilation. It is also known to couple the discharge opening of the heating unit to the discharge channel of the ventilation. In this way, a part of the discharged ventilation air can be used for combustion in the heating unit. This has the advantage that in the building less space needs to be reserved for supply and discharge channels. In contrast, additional provisions are necessary to prevent combustion gases from flowing back from the heating unit to lounges in the building, for example when the fan between the lounges and the discharge channel for the ventilation fails.

It is known, therefore, to include a check valve in the discharge channel of the ventilation, between the common rooms on the one hand and the supply and discharge channels of the heating unit on the other. This check valve is arranged to close when the lounges do not have sufficient overpressure relative to the discharge channel. When the fan fails in the discharge channel, the check valve closes. This cuts off the supply of air to the heating unit, causing the heating unit to fail within a short time. As an additional precaution, the check valve is probably also provided with a fuse that turns off the heating unit when it is detected that the check valve is not working well.

The check valve is particularly important if the common discharge channel is divided by a number of ventilation units. In this case, if one of the heating units discharges flue gas to the discharge channel, a defect in an arbitrary ventilation unit may give rise to a dangerous situation.

In case of failure of such a system, the heating unit falls off almost immediately, which can bring the necessary complaints with it.

It is inter alia an object of the invention to provide a combination of a ventilation unit and a heating unit which is coupled to the discharge duct of the ventilation unit and in which the combination can remain at least partially functional in the event that items become defective.

It is inter alia another purpose of the invention to provide a combination of a ventilation unit and a heating unit which, together with other heating units, can be connected to a common discharge duct and which can still function in the event of defects.

• einem Abfuhrkanal;
• einer Ventilationseinheit für Abfuhr von Luft zum Abfuhrkanal aus einem Raum in einem Gebäude;
• einer Heizungseinheit, versehen mit einer Zufuhröffnung für Luft und einer Abfuhröffnung für Rauchgase, wobei die Zu- und Abfuhröffnungen an den Abfuhrkanal gekuppelt sind, die Abfuhröffnung stromabwärts der Zufuhröffnung, welche Heizungseinheit versehen ist mit einer Verbrennungseinheit und einem Ventilator in Serie miteinander zwischen der Zufuhröffnung und der Abfuhröffnung;
• einem Rückschlagventil im Abfuhrkanal zwischen der Zufuhröffnung und der Abfuhröffnung, versehen mit einem Sensor zur Kontrolle einer Wirkung des Rückschlagventils;
• einer Steuereinheit für die Heizungseinheit, gekoppelt an den Sensor und eingerichtet zum Erzeugen eines Alarmsignals, wenn ein Signal des Sensors angibt, dass das Rückschlagventil einen Defekt aufweist, wodurch das Rückschlagventil nicht oder ungenügend schließen wird in Abwesenheit eines Ventilationsluftstroms durch den Abfuhrkanal aus der Ventilationseinheit. Da die Heizungseinheit ihre Luft von vor dem Rückschlagventil zuführt, wird die Möglichkeit geschaffen, die Heizungseinheit mindestens teilweise weiterarbeiten zu lassen, wenn das Rückschlagventil oder die Ventilationseinheit in nicht-gefährlicher Weise defekt ist, zum Beispiel wenn das Ventil permanent geschlossen ist oder die Ventilationseinheit ausfällt. Andererseits wird ein Alarmsignal erzeugt im Falle, dass das Rückschlagventil ein potentiell gefährliches Defekt aufweist.

The invention provides an air treatment and heating system, provided with

• a discharge channel;
• a ventilation unit for removing air to the discharge duct from a room in a building;
• a heating unit provided with a supply port for air and a discharge port for flue gases, the supply and discharge ports are coupled to the discharge channel, the discharge port downstream of the supply port, which heating unit is provided with a combustion unit and a fan in series with each other between the supply port and the discharge opening;
• a check valve in the discharge passage between the supply port and the discharge port provided with a sensor for controlling an action of the check valve;
• a heater control unit coupled to the sensor and configured to generate an alarm signal when a signal from the sensor indicates that the check valve is defective, whereby the check valve will not or insufficiently close in the absence of a ventilation air flow through the discharge duct from the ventilation unit. Since the heating unit supplies its air from in front of the check valve, it is possible to at least partially continue to operate the heating unit when the check valve or the ventilation unit is non-dangerously defective, for example when the valve is permanently closed or the ventilation unit fails , On the other hand, an alarm signal is generated in the event that the check valve has a potentially dangerous defect.

Preferably, the heating unit is provided with a further non-return valve in order to prevent flue gases from flowing to the supply opening in the ventilation channel in the event of a defect in the combustion unit. This increases the safety, since in this way, in the event of a defect in the heating unit, no flue gases can flow back to the supply opening. Other measures are also taken to prevent the backflow of flue gases in such a defect, such as For example, electronic detection of the dangerous situation and then switching off the combustion unit, but a check valve offers the simplest solution. When this is closed, the combustion unit automatically fails in the absence of air supply.

Preferably, the air treatment and heating system is applied in a building with several rooms, which have the discharge channel at least partially in common. Each of the rooms is provided with its own part of the discharge channel, which opens onto the common part of the discharge channel, and each of the rooms is provided with its own ventilation unit, heating unit, check valve and control unit connected to its own part of the discharge channel as described in the claim 1. In this way, each of the rooms is protected from defects.

In one embodiment of the air treatment and heating system, the control unit is set up to have the defective check valve, and the potentially dangerous situation has not yet occurred, but could occur to make combustion impossible. This also happens when there is still a flow of air. The impossibility can be instantaneous or if the defect has not disappeared within a certain time (for example 24 hours) after the alarm signal has been generated. This increases safety and provides a stronger warning to the user to remedy the defect.

In another embodiment of the air treatment and heating system, the control unit is configured to turn on the fan of the heating unit upon detection of absence of air flow through the discharge duct of the air treatment system. In this way, the fan in this case assumes the function of the ventilation unit at least partially.

In another embodiment, the control unit is configured to control the action of the check valve during a test in which the ventilation unit is at a low ventilation level wherein there is a substantial difference between a first and a second value of the pressure drop with each check valve being properly responsive and being non-return open, which controller generates an alarm signal if, during the test, the pressure drop remains below a threshold between the first and second pressure drop values ,

• Fig. 1 zeigt eine Luftbehandlungs- und Heizungsanlage;
• Fig. 2 zeigt ein Flow-Chart;
• Fig. 3 zeigt Druckfall-Strömungstärke-Diagramme eines Ventils;
• Fig. 4 zeigt den Druckfall als Funktion der Zeit beim Testen;
• Fig. 5 zeigt eine Anlage mit einer Vielzahl von Heizungseinheiten.

These and other purposes and advantageous aspects of the air treatment and heating system according to the invention will be described in more detail with reference to the following drawings.

• Fig. 1 shows an air treatment and heating system;
• Fig. 2 shows a flow chart;
• Fig. 3 shows pressure drop flow strength diagrams of a valve;
• Fig. 4 shows the pressure drop as a function of time during testing;
• Fig. 5 shows a system with a large number of heating units.

In Fig. 1 schematically shown a discharge channel 16 with an inlet 10, for example, to a common room in a building (not shown). The air treatment and heating system includes a ventilation unit 11, a connection piece 12 and a heating unit 15. The ventilation unit 11 contains a control unit 110. The ventilation unit 11 is arranged between the inlet 10 and the discharge channel 16. The connecting piece 12 is arranged in the discharge channel 16. The connector 12 includes branches of the discharge channel 16 to a supply port 13 and a discharge port 14 of the heating unit 15. The connector 12 further includes a first check valve 120 between the branches for the supply port 13 and the discharge port 14th

The heating unit 15 includes, in series with each other, another check valve 150, a fan 152 and a combustion unit 154. The heating unit 15 further includes a control unit 156 coupled to the fan 152, the combustion unit 154 and the check valve 120 of the fitting 12. The combustion unit has further connections for the transport of heat generated, for example to radiators of a central heating and / or connections for tap water.

In normal operation, the ventilation unit 11 sucks air through the inlet 10 from a common room of a building. For this, the ventilation unit preferably includes a fan between the inlet 10 and the discharge channel 16, if desired, the ventilation unit further includes a heat exchanger (not shown) for heating with the sucked air another air flow flowing to a space to be heated. The ventilation unit 11 discharges the sucked air through the discharge channel 16, which communicates with the outside world outside the building. The ventilation unit 11 normally continuously aspirates air, for example, an amount of 90 to 320 m ³ per hour, depending on a set ventilation intensity. The discharged air flows through the connector 12, the air passes through the check valve 120, which is normally open when the pressure in the discharge channel upstream, in the direction of the ventilation unit 11, is higher than downstream in the other direction from the check valve 120th

The heating unit 15 is normally activated intermittently, for example whenever hot water is needed. When the heating unit 15 is active, the control unit 156 turns on the fan 152 to supply combustion air. Further, the control unit turns on the fuel supply (for example, natural gas supply) to the combustion unit 154. The combustion unit 154 burns the supplied fuel. The heating unit 15 uses, for example, an air flow with a flow rate between 3 and 55 m ^{3 of} air per hour. With a minimum discharge of 90 m ³ per hour from the ventilation unit 11, there is still at least one flow with a thickness of 35 m ³ per hour through the check valve 120 from the ventilation unit 11.

The flue gases produced during combustion pass combustion unit 154 through discharge opening 14 to discharge channel 16, downstream of check valve 120. As long as ventilation unit 11 works well, the flue gases are directed through discharge channel 16 in the normal air flow direction (indicated by arrows) dissipated. As described above, the air flow through the check valve is equal to the air flow from the ventilation unit 11, possibly reduced by the (smaller) air flow through the heater unit 15. Under normal conditions, therefore, the air flow through the check valve 120 will have a minimum flow rate in one direction the ventilation unit 11.

The check valve 120 comes into operation in the event of a defect in the ventilation unit 11, whereby the air flow through the discharge channel is eliminated. In this case, upon activation of the combustion unit 154, the pressure across the check valve 120 on the side of the discharge port 14 becomes higher than that on the side of the supply port 13. The check valve 120 then closes and prevents flue gases from flowing back through the discharge channel 16 into the common room.

The check valve 120 may also be defective. The following table describes a number of possible situations with a desired reaction of the plant. Ventilation on Ventilation off Check valve 120 permanently open Potential danger , if not resolved within 24 hours, must be burned out Danger of backflow of flue gases from the neighbors up and down Check valve 120 good (open / closed) No danger
Normal operation Check the valve once every 24 hours No danger
Within 24 hours the ventilation must be on to allow the boiler to control the valve, otherwise the combustion will be blocked later Check valve 120 permanently closed No danger
the burning can not work well No danger
Burning can work well. Ventilation must be activated within 24 hours to allow the heating unit to control the check valve, otherwise the combustion will be blocked later (The aforementioned 24 hours are cited as an example at a time period that keeps a potentially more dangerous situation so short that the risk of accidents remains small, while the user of the facility gets the opportunity to respond before the end of that time period, in practice Of course, the invention is not limited to 24 hours, 12 hours, 48 hours, one week, or periods in between are also contemplated.)

A potential hazard occurs when the flow rate falls below a threshold when the check valve 120 is stuck, such that flow remains possible. The flow direction can even reverse if the ventilation unit 11 has failed or does not work well and the check valve 120 nevertheless remains permanently open.

In order to warn in this case, the check valve includes a sensor which generates a signal from which the control unit 156 can deduce whether the check valve 120 is working well or is undesirably open or closed under certain conditions. For example, a flow meter that measures the amount of air flow through the check valve 120 or a pressure differential meter for measuring the pressure difference between both sides of the check valve 120 is used for this sensor.

When the control unit 156 detects that the check valve 120 is permanently or at least excessively open based on the signal from the sensor in the check valve 120, the control unit 156 generates an alarm signal for a potentially dangerous fault on the check valve 120. Further, the control unit 156 preferably switches the combustion unit 154 from, for example, by switching off the supply of fuel to the fan 152, also a part of the functions of the heating unit, such as space heating only or tap heater only, can be switched off. This may only take some time, for example 24 hours, to give the user the chance to respond to warnings about the defect. The shutdown happens in any case, if the control unit 156 in this case, no air flow from the ventilation unit 11 by the check valve 120 measures.

When the control unit 156 detects from the sensor in the check valve 120 that the check valve 120 is permanently or at least too closed, then the control unit 156 permanently turns on the fan 152, for example, not only when the control unit 156 receives fuel Burn combustion unit 154 can supply. Besides, the control unit 156 generates in this case preferably a warning signal that warns the user and / or initiates an intervention in the action of the system. For example, in this case, the control unit 156 flashes a warning light (not shown) in the lounge, or warns it of a service over an Internet connection or alerts it in some other way.

In this way, the control unit 156 thus has a number of possible modes: a normal mode in which the fan 152 is turned on together with combustion in the combustion unit 154, a safety mode in which the fan is permanently turned on when the check valve 120 is closed , and an alarm mode in which the combustion unit 154 is turned off. In the safety mode, the fan of the heating unit 15 modestly assumes the ventilation function when the ventilation unit 11 does not work or does not work well and / or when the check valve 120 is permanently closed. In addition, it remains possible in this mode to continue to perform some of the heating functions or all heating functions in safety mode.

The control unit 156 is preferably configured to execute a test program in cooperation with the ventilation unit 11 for detecting defects on the check valve 120. One embodiment of this test program uses a pressure sensor that measures a pressure difference across the check valve 120.

Fig. 3 shows the pressure drop (entered vertically) via the check valve 120 as a function of the air flow (registered horizontally) through the check valve 120, both for a good-acting check valve 120 (curve 30) and for a permanently open check valve (curve 32). In a well-acting check valve, the pressure drop is more or less constant over a certain range of flow strengths or at least greater than a fully open valve, because the pressure drop against the force of the to be pressed Check valve 120 acts. Of course, with a permanently closed check valve, there is no flow (or high pressure with little flow). Next to it is in Fig. 3 a detection level is shown which the control unit 156 uses to detect faults in the check valve 120.

In the embodiment with the pressure sensor, the control unit 110 preferably periodically executes a program in which the ventilation unit 11 is switched off only during a first time interval (for example 2 minutes), then for a second time interval (for example 2 minutes) on a minimum ventilating one Position is switched on and finally during a third time interval (for example, 2 minutes) is switched to a maximum ventilating position.

With arrows 36, 38 is in Fig. 3 indicates what airflow will occur through the check valve 120 approximately in the second and third time intervals. Note that the pressure across the check valve 120 in the maximum ventilating position (arrow 38) is approximately the same for a good acting check valve 120 and a permanently open check valve 120. At minimum ventilation (arrow 36) there is a difference.

Fig. 4 shows the pressure drop across the check valve 120 as a function of time during such a test. The first, second, and third time intervals are indicated as 41a-c. A number of pressure gradients 40, 42, 44, 46 are shown, each for a normally acting unit 40, a system with a permanently open check valve 42, with a permanently closed check valve 44 and with a failed ventilation unit 46. Also, the level of the threshold 34.

Although it is in principle possible to provide a communication link with which the control unit 110 and the control unit 156 Synchronize electronically during testing, preferably a test algorithm is used, for which no additional communication is necessary.

Fig. 2 FIG. 12 shows a flow chart of the action of the control unit 156 using the algorithm according to this embodiment. The controller 156 cycles through the flowchart (for example, once per minute). In a first step 21, the control unit 156 checks whether a test has been carried out within a predetermined period. If not, then the control unit 156 performs a second step 22 in which the control unit 156 generates an alarm signal and turns off the combustion unit 154. Otherwise, in a third step 23, the control unit 156 executes a normal control program.

In a fourth step 24, the control unit 156 checks whether the pressure drop across the check valve 120 falls below the threshold that in Fig. 3 at level 35 is indicated. If not, then the ventilation unit 11 acts normally and the control unit 156 ends the flow chart in a fifth step 25, whereupon the flow chart is repeated from the first step 21.

If the pressure drop is below the threshold 34, then the control unit 156 checks in a number of steps 26a-d how long the pressure drop remains below the threshold. This is because in the second time interval, when the ventilation unit 11 is minimally ventilated, there is sufficient pressure drop across the check valve 120, from which it can be deduced that the check valve 120 behaves according to the curve 30 for a good-acting check valve 120 and not according to the curve 32 for the permanently open check valve.

If the pressure drop remains less than a first time period t1 (shorter than the first time interval in which the ventilation unit 11 completely switches off, for example less than 1.5 minutes), then there is talk of a false alarm (for example, as a result of wind influence or opening a window in the lounge) and performs the third step 25.

If the pressure drops again in the second time interval that the ventilation unit 11 is operating at minimum power, then the control unit 156 will respond based on the assumption of a good-acting check valve 120 (curve 30). This is the case if the pressure drop has increased above the threshold before a time t2 which is within the second time interval (for example after 3.5 minutes). In this case, in an eighth step 28, the control unit 156 stores information indicating that a test has been performed at a respective time (so that the second step 22 will not be executed within a predetermined period after the first step 21) and thereafter the fifth step 25 from.

If the pressure drop does not exceed the threshold before time t2, then the control unit 156 checks whether the pressure drop has exceeded the threshold before a next time t3 (for example after four minutes) in the third time interval during which the ventilation unit 11 ventilates to the maximum would. If the pressure drop has not yet risen at this point in time t3, then obviously there is talk of a defect in the ventilation unit 11. If the pressure drop increases, then obviously an open check valve 120 is mentioned.

If the pressure drop has increased prior to time t3, the control unit 156 performs a ninth step 29 in which the control unit 156 both generates the alarm signal and turns off the combustion unit 154. The control unit 156 now acts on the assumption that the check valve 120 is permanently open, so that a dangerous situation could arise during combustion if the ventilation unit 11 were to fail. If desired, the control unit 156 may thereafter repeat the flowchart from the first step, with the Combustion unit 154 remains off until a well-acting check valve 120 is detected.

If the pressure drop has not risen before time t3, the control unit executes a seventh step 27, in which the alarm signal is generated and preferably the combustion unit 154 is not or not permanently switched off. The fan 152 of the heating unit 15 is now permanently switched on to partially take over the function of the ventilation unit 11. If desired, the controller may thereafter repeat the flowchart from the first step with the combustion unit 154 remaining off until sufficient airflow through the check valve 120 is detected.

In the circumscribed test, the pressure drop need only be compared to a threshold value. Therefore, a simple sensor that only indicates whether the pressure drop is above or below the threshold, such as a sensor having a switch that switches from one position to another when the pressure crosses the threshold, is sufficient.

If a communication channel is available between the ventilation unit 11 and the control unit 156, the switching on and off of the ventilation unit and the test by the control unit 156 can be synchronized. In principle, then no special test mode is necessary because the control unit 156 can measure in normal operation, when the ventilation unit 11 indicates that it acts on maximum or minimum ventilation strength. Optionally, the ventilation unit 11 can switch specifically for the test between maximum and minimum ventilation strength.

Turning off the ventilation unit 11 during the test is for synchronization when no other communication is possible between the ventilation unit 11 and the control unit 156. It is not necessary that switching to minimum ventilation and maximum ventilation in the order described happens. As long as this is done in a predetermined time ratio to turn off, before or after, or after a break, the control unit can determine from what time different measurements must be used in the pressure case.

It is highly recommended to also arrange another check valve 150 in the heater unit 15 for the purpose of preventing backflow of flue gases from the collective discharge channel coming from other chambers from other combustion units. If the further check valve 150 remains closed, then the combustion unit 154 will not be able to start due to a lack of air supply. If the further check valve 150 remains open, then the combustion unit 154 will fail to start as a result of a shortage of pre-pressure.

The fitting 12 is preferably supplied as a standard part for connection to a discharge duct 16 and a heating unit 15, but it may also be part of the heating unit. The connecting piece 12 contains channel connections for the discharge channel 16, for example with a diameter of 150 mm (from the inside) and supply and discharge openings for the heating unit 15 with, for example, a diameter of 80 mm (from the inside). Further, the connector 12 includes the check valve 120, which is provided with a sensor for the air flow and direction through the check valve 120, with a sensor signal output for coupling to the control unit 156. The connector 12 is carried out at the discharge opening of the heating unit 15 condensate discharging, preferably such that condensed water flows back to the combustion unit 154.

As described, the ventilation and heating system on the one hand protects against the consequences of defects in the system and on the other hand, the possibility of maintaining a certain degree of functioning in the case of defects that are not directly serious.

Instead of a pressure decay sensor at the check valve 120 and a flow sensor can be used. In this case, the flow sensor is positioned to the check valve 120, for example, such that the air flow through a portion of the discharge channel is selectively measured where a greater flow velocity occurs when the check valve 120 is partially open at a low pressure drop. In this way, the difference between a well-functioning check valve 120 and a non-functioning check valve 120 can be determined based on the strength of the air flow in the time interval t1 to t2. Of course, an accurate flow meter can of course be used to detect a dangerous backflow in normal use and then generate an alarm message.

Fig. 5 shows an air treatment and heating system with a plurality of independently ventilated spaces 50. Each room has its own part 59a, b of the discharge channel, which is connected to a common part 58 of the discharge channel. In the own part 59a, b of the discharge channel, a ventilation unit 52 and a check valve 54 are respectively received. Furthermore, a heating unit 56 is received in each case with an inlet and outlet, which are respectively coupled in front of and behind the check valve 54 to the own part 59a, b of the discharge channel, the supply to a first part 59a between the ventilation unit 52 and the check valve 54 and the discharge to a second own part 59b between the check valve 54 and the common part 58 of the discharge channel. If desired, the discharge of the heating unit can also be coupled to the common part 59b of the discharge channel.

In operation, each of the heating units 56 acts as described in the system of Fig. 1 , A defect on a check valve 54 Such a system leads to a potential danger due to flue gases, which can in principle come from each of the heating units 56. This risk is contested by the fact that the action of the check valve is periodically checked with its own ventilation unit 52 and an alarm signal is given upon detection of a fault, for example by switching off its own heating unit 56.

Claims (17)

1. Air treatment and heating system, provided with

   - a discharge channel (16);

   - a ventilation unit (11) for discharging air to the discharge channel from a room in a building;

   - a heating unit (15) provided with a supply opening (13) for air and a discharge opening (14) for flue gases, the supply and discharge opening being coupled to the discharge channel (16), which discharge opening lies downstream of the supply opening, the heating unit provided with a combustion unit (154) and with a fan (152) switched in series between the supply opening and the discharge opening, characterised by

   - a non-return valve (150) in the discharge channel between the supply opening and the discharge opening, provided with a sensor for monitoring the effect of the non-return valve and;

   - a control unit (156) for the heating unit, coupled to the sensor and designed to produce a warning signal, if a signal of the sensor indicates that the non-return valve has a defect, as a result of which the non-return valve will not close or will close insufficiently in the absence of a ventilation air flow through the discharge channel from the ventilation unit.
2. Air treatment and heating system according to claim 1, for a plurality of rooms to be ventilated independently of one another, wherein each of the rooms has its own part of the discharge channel (16), which leads to a common part of the discharge channel, which system for each of the rooms respectively contains a ventilation unit (11), a heating unit (15), a non-return valve (150) and a control unit (156) within the meaning of claim 1.
3. Air treatment and heating system according to claim 1 or 2, wherein the control unit (156) is designed, to make combustion in the combustion unit (154) impossible in response to detecting the defect.
4. Air treatment and heating system according to claim 3, wherein the control unit (156) is designed, to initially continuously allow combustion in the combustion unit (154) at least during a pre-determined time interval in response to detecting the defect and after the time interval mentioned, to make combustion impossible if the defect continues.
5. Air treatment and heating system according to any one of the preceding claims, wherein the control unit (156) is designed to detect a further defect, as a result of which the non-return valve (150) cannot open or can open insufficiently, whereby the control unit is designed to switch on the fan (152) of the combustion unit in response to detecting the further defect.
6. Air treatment and heating system according to any one of the preceding claims, wherein the control unit (156) is designed to check the effect of the non-return valve (150) during a test, in which the ventilation unit (11) switches back to a low ventilation strength, with which ventilation strength there is a substantial difference between a first and a second value of the pressure drop across the non-return valve, which are expected in each case with the correct non-return effect of the non-return valve and when staying open without non-return effect, which control unit produces a warning signal, if during the test the pressure drop remains below a threshold, which is between the first and the second pressure drop value.
7. Air treatment and heating system according to claim 6, wherein the ventilation unit (11) is designed to switch back periodically to the low ventilation strength and in a pre-determined time relation with the switching back to switch back further to a ventilation strength, at which the pressure drop, neither with correct effect nor when permanently staying open, exceeds the threshold and in which the control unit is designed to synchronise the checking and the switching back by means of detecting further switching back.
8. Air treatment and heating system according to any one of the preceding claims, wherein the control unit (156) is designed to check the effect of the non-return valve during a test, in which the ventilation unit (11) switches back to a low ventilation strength and wherein an air speed is measured, in a position, where the strength of the measured air flow is for correct non-return effect of the non-return valve (120) and staying open of the non-return valve without non-return effect respectively, which control unit produces a warning signal, if during the test the air speed remains below a threshold between the first and second value.
9. Air treatment and heating system according to any one of the preceding claims, wherein the heating unit (15) is provided with a further non-return valve (150) in series with the fan (152) and the combustion unit (154) between the supply opening and the discharge opening.
10. Heating unit (15), provided with

    - a supply opening (13) for air and a discharge opening (14) for flue gases;

    - a combustion unit (154);

    - a fan (152) in series with the combustion unit (154) between the supply opening and the discharge opening;

    - a control unit (156) for the heating unit, provided with a sensor input for receiving a sensor signal which is indicative of a good effect of a non-return valve (150), which stands parallel to the heating unit, which control unit is designed to produce a warning signal, if a signal of the sensor indicates that the non-return valve has a defect, as a result of which the non-return valve (150) will not close or will close insufficiently in the absence of a ventilation air flow through the discharge channel (16) from a ventilation unit.
11. Heating unit according to claim 10, wherein the control unit (156) is designed, to make combustion in the combustion unit (154) impossible in response to detection of the defect.
12. Heating unit according to claim 11, wherein the control unit (156) is designed, to initially continuously allow combustion in the combustion unit (154) at least during a pre-determined time interval in response to detecting the defect, and after the time interval mentioned, to make combustion impossible if the defect continues.
13. Heating unit according to any one of claims 10 to 12, wherein the control unit (156) is designed to detect a further defect, as a result of which the non-return valve (150) cannot open or can open insufficiently, wherein the control unit (156) is designed to switch on the fan (152) of the combustion unit in response to detecting the further defect.
14. Heating unit according to any one of claims 10 to 13, wherein the control unit (156) is designed to check the effect of the non-return valve (150) during a test, in which the ventilation unit (11) switches back to a low ventilation strength, with which ventilation strength there is a substantial difference between a first and a second value of the pressure drop across the non-return valve, which are expected in each case with the correct non-return effect of the non-return valve and when staying open without non-return effect, which control unit produces a warning signal, if during the test the pressure drop remains below a threshold, which is between the first and the second pressure drop value.
15. Heating unit (15) according to claim 14 for use in combinations with a ventilation unit (11), which is designed to switch back periodically to the low ventilation strength and in a pre-determined time relation with the switching back to switch back further to a ventilation strength, at which the pressure drop, neither with correct effect nor when permanently staying open, exceeds the threshold and in which the control unit 156 is designed to synchronise the checking and the switching back by means of detecting further switching back.
16. Heating unit (15) according to claim 10, wherein the control unit (156) is designed to check the effect of the non-return valve (150) during a test, in which the ventilation unit (11) switches back to a low ventilation strength and wherein an air speed is measured, in a position, where the strength of the measured air flow is for correct non-return effect of the non-return valve and staying open of the non-return valve (150) without non-return effect respectively, which control unit produces a warning signal, if during the test the air speed remains below a threshold between the first and the second value.
17. Heating unit according to claim 10, provided with a further non-return valve (150) in series with the fan (11) and the combustion unit (154) between the supply opening (13) and the discharge opening (14).

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