Heat exchange ventilator

Abstract

This heat exchange ventilator comprises: an air-supplying blower; an exhaust blower; a casing; a heat exchanger; a drain pan; a supplied airflow temperature sensor; a supplied airflow humidity sensor;

Description

Heat exchange ventilation system

[0001] The present disclosure relates to a heat exchange ventilation device that performs ventilation while exchanging heat between an intake airflow and an exhaust airflow.

[0002] Patent Document 1 discloses a heat exchange ventilation device that can switch between heat exchange ventilation operation and non-heat exchange ventilation operation. The heat exchange ventilation operation is an operation in which supply air, which supplies outdoor air into a room, and exhaust air, which exhausts indoor air to the outside, are passed through a heat exchanger, and indoor ventilation is performed while heat is exchanged between the supply air and the exhaust air. The non-heat exchange ventilation operation is an operation in which outdoor air is passed through a bypass passage without passing through the heat exchanger, and heat exchange between the supply air and the exhaust air is not performed. The heat exchange ventilation device described in Patent Document 1 switches to non-heat exchange ventilation operation during heat exchange ventilation operation when the humidity of the outdoor air is higher than a predetermined value.

[0003] JP 2011-220561 A

[0004] The heat exchanger ventilator described in Patent Document 1 switches from heat exchange ventilation operation to non-heat exchange ventilation operation when it determines that the outdoor air humidity is high enough to cause the heat exchanger to become wet. Therefore, while ventilation can continue, the switch to non-heat exchange ventilation operation results in poor energy conservation during non-heat exchange ventilation operation. Furthermore, the heat exchanger ventilator described in Patent Document 1 determines operating conditions based solely on air conditions. Therefore, the heat exchanger ventilator described in Patent Document 1 also has the problem of poor energy conservation in that it activates control to protect the product earlier than the conditions the product could withstand. For example, if the technology described in Patent Document 1 is applied to a heat exchanger ventilator equipped with a drain pan to store condensation water generated in the heat exchanger, operation is controlled solely by the outdoor air humidity, regardless of the amount of condensation water accumulated in the drain pan. Therefore, even though heat exchange ventilation operation is possible until the water in the drain pan reaches a predetermined level, non-heat exchange ventilation operation is executed before that time, resulting in poor energy conservation.

[0005] The present disclosure has been made in consideration of the above, and aims to provide a heat exchange ventilation device that can ventilate without water overflowing from the drain pan, while achieving greater energy savings than conventional devices, in situations where condensation water is constantly generated from the heat exchanger.

[0006] In order to solve the above-mentioned problems and achieve the object, the heat exchange ventilator of the present disclosure includes an intake air blower, an exhaust air blower, a casing, a heat exchanger, a drain pan, an intake airflow temperature sensor, an intake airflow humidity sensor, an exhaust airflow temperature sensor, an exhaust airflow humidity sensor, and a control unit. The casing has an intake air duct formed by the intake air blower through which an intake airflow traveling from outdoors to indoors passes, and an exhaust air duct formed by the exhaust air blower through which an exhaust airflow traveling from indoors to outdoors passes. The heat exchanger is installed between the intake air duct and the exhaust air duct and exchanges heat between the intake airflow and the exhaust airflow. The drain pan retains and drains water generated by condensation in the heat exchanger. The intake airflow temperature sensor detects the temperature of the intake airflow. The intake airflow humidity sensor detects the humidity of the intake airflow. The exhaust airflow temperature sensor detects the temperature of the exhaust airflow. The exhaust airflow humidity sensor detects the humidity of the exhaust airflow. The control unit controls at least one of the intake air blower and the exhaust air blower based on the total amount of water that occurs in the drain pan due to condensation in the heat exchanger, which is calculated based on the temperature and humidity of the intake air flow and the temperature and humidity of the exhaust air flow.

[0007] The heat exchange ventilation device disclosed herein has the advantage of being able to ventilate without water overflowing from the drain pan, while achieving greater energy savings than conventional devices, in situations where condensation water is constantly generated from the heat exchanger.

[0008] FIG. 1 is a perspective side view schematically showing an example of the configuration of a heat exchanger according to embodiment 1; FIG. 2 is a perspective view showing an example of the configuration of a heat exchanger; FIG. 3 is a diagram showing a case where the air-channel switching damper of the heat exchanger ventilator according to embodiment 1 is in an open state; FIG. 4 is a control block diagram showing an example of control of the heat exchanger ventilator according to embodiment 1; FIG. 5 is a diagram showing an example of a state where condensation water is generated in the heat exchanger ventilator according to embodiment 1;

[0009] Hereinafter, a heat exchange ventilation device according to an embodiment of the present disclosure will be described in detail with reference to the drawings.

[0010] 1 is a perspective side view schematically illustrating an example of the configuration of a heat exchange ventilator according to Embodiment 1. The heat exchange ventilator 1 includes a main body casing 11, an exhaust fan 12E, an intake fan 12S, a heat exchanger 13, an outdoor air (OA) temperature sensor 14, an OA humidity sensor 15, a return air (RA) temperature sensor 16, an RA humidity sensor 17, a drain pan 18, an air path switching damper 19, a remote controller 20, and a control circuit unit 30. Hereinafter, the remote controller 20 will be referred to as a remote control 20.

[0011] The main body casing 11 has a box-like structure that forms the outer shell of the heat exchange ventilator 1. In one example, the main body casing 11 has a rectangular parallelepiped shape. The main body casing 11 corresponds to a casing. The main body casing 11 has an outside air intake port 111 and an exhaust air discharge port 112 provided on one end face 11a of the main body casing 11 in the longitudinal direction. The main body casing 11 has an intake air discharge port 113 and an indoor air intake port 114 provided on the other end face 11b of the main body casing 11 that faces the one end face 11a in the longitudinal direction.

[0012] The main casing 11 has an intake airflow 115 and an exhaust airflow 116 therein. The intake airflow 115 connects the outdoor air inlet 111 and the intake airflow outlet 113 and is a passage through which an intake airflow SF, which is a flow of air from the outdoors to the indoors and is formed by the intake air blower 12S, passes. The exhaust airflow 116 connects the indoor air inlet 114 and the exhaust airflow outlet 112 and is a passage through which an exhaust airflow EF, which is a flow of air from the indoors to the outdoors and is formed by the exhaust air blower 12E, passes. The heat exchanger 13 is disposed between the intake airflow 115 and the exhaust airflow 116 so as to straddle the intake airflow 115 and the exhaust airflow 116. Hereinafter, the portion of the intake airflow 115 upwind of the heat exchanger 13 will be referred to as the upwind-side intake airflow 115a, and the portion downwind of the heat exchanger 13 will be referred to as the downwind-side intake airflow 115b. The portion of exhaust air duct 116 that is on the windward side of heat exchanger 13 is called windward-side exhaust air duct 116a, and the portion on the leeward side is called downwind-side exhaust air duct 116b. In addition to the air duct that passes through heat exchanger 13, exhaust air duct 116 also has a bypass air duct 116c that does not pass through heat exchanger 13.

[0013] The intake fan 12S is disposed in the intake airflow duct 115 and generates an intake airflow SF. The exhaust fan 12E is disposed in the exhaust airflow duct 116 and generates an exhaust airflow EF. The intake fan 12S and the exhaust fan 12E can change their airflow volumes in multiple stages. In the example shown in FIG. 1 , the intake fan 12S is disposed in the downwind intake airflow duct 115b, and the exhaust fan 12E is disposed in the downwind exhaust airflow duct 116b. The airflow volumes of the intake fan 12S and the exhaust fan 12E can be changed as desired based on the settings and control content from the remote control 20. Hereinafter, the intake fan 12S and the exhaust fan 12E will be referred to as fans 12 when they are not individually distinguished.

[0014] Heat exchanger 13 is installed between supply air duct 115 and exhaust air duct 116, and performs continuous heat exchange between supply airflow SF and exhaust airflow EF. Heat exchanger 13 may be a sensible heat exchanger that exchanges sensible heat, i.e., temperature, between supply airflow SF and exhaust airflow EF, or may be a total heat exchanger that exchanges sensible heat and latent heat, i.e., temperature and humidity, between supply airflow SF and exhaust airflow EF. Here, a case where heat exchanger 13 is a sensible heat exchanger will be taken as an example.

[0015] Fig. 2 is a perspective view showing an example of the configuration of a heat exchanger. Fig. 2 illustrates a cross-flow type heat exchanger 13 in which the traveling direction of the exhaust air flow EF and the traveling direction of the intake air flow SF passing through the heat exchanger 13 are perpendicular to each other. The heat exchanger 13 includes a plurality of sheet materials 131 arranged at intervals from each other and a spacing member 132 that maintains the spacing between the plurality of sheet materials 131. The heat exchanger 13 is a laminate obtained by stacking the sheet materials 131 and the spacing members 132. The sheet material 131 is a flat, plate-like member. The spacing member 132 is a sheet-like member with a corrugated texture. The sheet material 131 and the spacing member 132 are bonded to each other.

[0016] The spacing member 132 includes spacing member 132a and spacing member 132b, which are oriented in different directions so that the directions of the corrugated folds are perpendicular to each other. The space formed between the spacing member 132a and the sheet material 131 is a primary-side air passage 133a through which the exhaust air flow EF passes. The space formed between the spacing member 132b and the sheet material 131 is a secondary-side air passage 133b through which the supply air flow SF passes. The heat exchanger 13 is formed with a plurality of primary-side air passages 133a and a plurality of secondary-side air passages 133b. The sheet material 131, the spacing member 132a, which is a component of the primary-side air passage 133a, and the spacing member 132b, which is a component of the secondary-side air passage 133b, are stacked in the thickness direction of the sheet material 131.

[0017] When the heat exchanger 13 is a sensible heat exchanger, the spacing member 132 is made of a material that is gas-blocking but not moisture-permeable. In this case, the sheet material 131 exchanges only heat between the exhaust air flow EF passing through the primary air passage 133a and the intake air flow SF passing through the secondary air passage 133b, i.e., sensible heat, without mixing the exhaust air flow EF and the intake air flow SF, thereby enabling heat exchange ventilation. At this time, if the treated air exceeds the dew point temperature, condensation water will be generated from the heat exchanger 13.

[0018] The air flowing through the supply air duct 115 and the exhaust air duct 116 is classified into the following four types depending on whether it is before or after the heat exchanger 13. The air flowing through the upwind supply air duct 115a is called outside air OA, the air flowing through the downwind supply air duct 115b is called supply air SA, the air flowing through the upwind exhaust air duct 116a is called return air RA, and the air flowing through the downwind exhaust air duct 116b is called exhaust air EA. The supply air flow SF is the flow of outside air OA before the heat exchanger 13, and the flow of supply air SA after the heat exchanger 13. The exhaust air flow EF is the flow of return air RA before the heat exchanger 13, and the flow of exhaust air EA after the heat exchanger 13.

[0019] Returning to FIG. 1 , OA temperature sensor 14 and OA humidity sensor 15 are disposed on the windward side of heat exchanger 13 in supply air duct 115, i.e., in windward-side supply air duct 115a, and are connected to control circuit 30 via wiring. OA temperature sensor 14 detects the temperature of outside air OA and transmits the detection results to control circuit 30 at predetermined time intervals. OA humidity sensor 15 detects the humidity of outside air OA and transmits the detection results to control circuit 30 at predetermined time intervals. OA humidity sensor 15 detects relative humidity. OA temperature sensor 14 corresponds to an supply airflow temperature sensor that detects the temperature of supply airflow SF, and OA humidity sensor 15 corresponds to an supply airflow humidity sensor that detects the humidity of supply airflow SF.

[0020] The RA temperature sensor 16 and the RA humidity sensor 17 are disposed on the windward side of the heat exchanger 13 in the exhaust air duct 116, i.e., in the windward-side exhaust air duct 116a, and are connected to the control circuit unit 30 via wiring. The RA temperature sensor 16 detects the temperature of the return air RA and transmits the detection result to the control circuit unit 30 at predetermined time intervals. The RA humidity sensor 17 detects the humidity of the return air RA and transmits the detection result to the control circuit unit 30 at predetermined time intervals. The RA humidity sensor 17 detects the relative humidity. The RA temperature sensor 16 corresponds to an exhaust air flow temperature sensor that detects the temperature of the exhaust air flow EF, and the RA humidity sensor 17 corresponds to an exhaust air flow humidity sensor that detects the humidity of the exhaust air flow EF.

[0021] Drain pan 18 is provided inside main casing 11 so as to include at least an area below where heat exchanger 13 is installed. Drain pan 18 holds and drains water generated by condensation in heat exchanger 13. Drain pan 18 is provided with a drain outlet 181 that drains water stored in drain pan 18 to the outside.

[0022] The airflow path switching damper 19 is provided on the upwind side of the exhaust airflow duct 116, i.e., in the upwind-side exhaust airflow duct 116a, and switches between passing the exhaust airflow EF to the heat exchanger 13 or passing the exhaust airflow EF through the bypass airflow 116c and directly to the exhaust fan 12E without passing through the heat exchanger 13. Here, when the airflow path switching damper 19 is in a closed state blocking the bypass airflow 116c so that the exhaust airflow EF passes through the heat exchanger 13, the exhaust airflow EF passes through the heat exchanger 13 and continuously exchanges heat with the supply airflow SF. When the airflow path switching damper 19 is in an open state blocking the airflow path to the heat exchanger 13 so that the exhaust airflow EF passes through the bypass airflow 116c, the exhaust airflow EF is discharged to the outdoors via the exhaust fan 12E as non-heat-exchange ventilation.

[0023] In one example, the opening and closing of the air-channel switching damper 19 is performed manually through a setting on the remote control 20. Alternatively, the opening and closing of the air-channel switching damper 19 may be performed by a command from the control circuit unit 30 when it is determined that the temperature of the outdoor air OA is lower than the room temperature, such as in outdoor air cooling, based on the temperatures detected by the OA temperature sensor 14 and the RA temperature sensor 16. FIG. 1 shows the air-channel switching damper 19 in a closed state. In FIG. 1, return air RA drawn in through the indoor air intake port 114 passes through the main body casing 11, the upwind exhaust air duct 116a, the heat exchanger 13, and the downwind exhaust air duct 116b, and is then exhausted to the outdoors as exhaust air EA from the exhaust outlet 112. Meanwhile, the outdoor air OA always passes through the heat exchanger 13, so the return air RA exchanges heat with the outdoor air OA in the heat exchanger 13.

[0024] 3 is a schematic diagram illustrating the heat exchange ventilator according to Embodiment 1 when the air-path switching damper 19 is in an open state. When the air-path switching damper 19 is in an open state, the air-path switching damper 19 closes the air path from the indoor air inlet 114 to the heat exchanger 13. Therefore, the return air RA drawn in through the indoor air inlet 114 passes through the upwind exhaust air duct 116a, the bypass air duct 116c, and the downwind exhaust air duct 116b inside the main casing 11, and is then exhausted to the outdoors as exhaust air EA from the exhaust outlet 112. Therefore, the return air RA does not exchange heat with the outside air OA that always passes through the heat exchanger 13, and non-heat-exchange ventilation is performed.

[0025] 1 , the remote control 20 instructs the control circuit unit 30 on settings made by a user (not shown) regarding ventilation of the room in which the heat exchange ventilator 1 is installed. The remote control 20 is connected to the control circuit unit 30 by wire or wirelessly.

[0026] The control circuit unit 30 controls the operation of the heat exchange ventilator 1 in accordance with user instructions determined by the user operating the remote control 20. The control circuit unit 30 corresponds to the control unit. FIG. 4 is a control block diagram showing an example of a heat exchange ventilator according to the first embodiment. As shown in FIG. 4, the control circuit unit 30 is connected via wiring to the exhaust fan 12E, the intake fan 12S, the OA temperature sensor 14, the OA humidity sensor 15, the RA temperature sensor 16, the RA humidity sensor 17, the air path switching damper 19, and the remote control 20. The wiring may be wired or wireless.

[0027] In the first embodiment, the control circuit unit 30 controls the operation of the blower 12 and the air-path switching damper 19 based on user instructions from the remote control 20 and the temperature and humidity detected by the OA temperature sensor 14, the OA humidity sensor 15, the RA temperature sensor 16, and the RA humidity sensor 17. Specifically, the control circuit unit 30 calculates the amount of condensation water generated in the heat exchanger 13 based on the temperature and humidity of the supply airflow SF detected by the OA temperature sensor 14 and the OA humidity sensor 15 and the temperature and humidity of the exhaust airflow EF detected by the RA temperature sensor 16 and the RA humidity sensor 17. The control circuit unit 30 further calculates the total amount of water generated by condensation stored in the drain pan 18 from the start of operation to the calculation time point using the amount of condensation water discharged from the drain pan 18. The control circuit unit 30 then controls the airflow rate of the blower 12 based on the total amount of water generated by condensation to prevent water from overflowing from the drain pan 18. In addition, when water generated by condensation is about to overflow from the drain pan 18, the control circuit unit 30 switches the air path switching damper 19 to an open state so that the return air RA does not pass through the heat exchanger 13 but passes through the bypass air path 116c.

[0028] In the first embodiment, the operation of a sensible heat exchanger that exchanges only temperature will be described. In winter, the outdoor air OA receives only sensible heat recovery through the heat exchanger 13, resulting in an increase in the temperature of the supply air SA but no change in absolute humidity. Meanwhile, the return air RA, which is indoor air, passes through the heat exchanger 13, decreasing only its temperature without changing its absolute humidity. This may cause the exhaust air EA to exceed its dew point temperature. In this case, condensation occurs in the heat exchanger 13. FIG. 5 is a schematic diagram illustrating an example of a state in which condensation occurs in the heat exchange ventilator according to the first embodiment. Components identical to those in FIGS. 1 and 3 are designated by the same reference numerals and will not be described again. The condensation 60 drips into the drain pan 18. The condensation 60 is collected in a drain outlet 181 provided in the drain pan 18 and drained to the outside of the heat exchanger 13.

[0029] Next, a control algorithm for performing heat exchange ventilation while saving energy compared to conventional methods and preventing condensation water from overflowing from the drain pan 18 by the control circuit 30 will be described. Figures 6 and 7 are flowcharts showing an example of a procedure for control processing of the heat exchange ventilation device according to the first embodiment.

[0030] First, the control circuit unit 30 pre-stores values ​​set for the operating airflow rate, the sensible heat exchange efficiency of the heat exchanger 13, the capacity and drainage volume of the drain pan 18, and the calculation target time (step S11). The calculation target time, for example, is the time between the acquisition of the previous sensor detection result and the acquisition of the current sensor detection result. The calculation target time can be determined based on the communication status of the installed sensor and the temperature and humidity changes in the room that is the target of ventilation or air conditioning. For example, the calculation target time may be the time between sensor measurement timings, or, if the sensor measurement frequency is high, may be an arbitrarily determined time at regular intervals. For example, the calculation target time may be approximately one minute.

[0031] Next, the control circuit unit 30 receives from the remote control 20 an operation command including an operation mode indicating the operating state of the heat exchange ventilator 1 (step S12). That is, the operation command is a command to start the operation of the heat exchange ventilator 1 including a ventilation mode indicating the air volume and type of ventilation. The ventilation mode is heat exchange ventilation operation or non-heat exchange ventilation operation. The control circuit unit 30 then starts operation in the operation mode included in the operation command (step S13). That is, the control circuit unit 30 starts operation of the exhaust fan 12E and the intake fan 12S based on the air volume included in the operation command from the remote control 20, and controls the opening and closing of the bypass air passage 116c, i.e., the operation of the air passage switching damper 19, based on the ventilation mode included in the operation command from the remote control 20.

[0032] Here, the control circuit unit 30 starts operation in the operation mode included in the operation command by receiving the operation command from the remote control 20, but the start of operation in the operation mode is not limited to being initiated by the remote control 20. In one example, if the control circuit unit 30 is equipped with a timer, the control circuit unit 30 may be configured to automatically start the operation mode included in the operation command at a time preset by the remote control 20.

[0033] After operation starts, OA temperature sensor 14 and RA temperature sensor 16 each measure temperature, and OA humidity sensor 15 and RA humidity sensor 17 each measure humidity. Control circuit 30 receives temperature information, which is the detection result, from OA temperature sensor 14 and RA temperature sensor 16, and humidity information, which is the detection result, from OA humidity sensor 15 and RA humidity sensor 17, at predetermined time intervals (step S14). Because OA humidity sensor 15 and RA humidity sensor 17 generally measure relative humidity, control circuit 30 converts the relative humidity to absolute humidity. Hereinafter, the temperature measured by OA temperature sensor 14 will be referred to as the "OA temperature measurement value," the humidity measured by OA humidity sensor 15 will be referred to as the "OA humidity measurement value," the temperature measured by RA temperature sensor 16 will be referred to as the "RA temperature measurement value," and the humidity measured by RA humidity sensor 17 will be referred to as the "RA humidity measurement value." The OA temperature measurement corresponds to the temperature of the supply airflow SF, and the OA humidity measurement corresponds to the humidity of the supply airflow SF. The RA temperature measurement corresponds to the temperature of the exhaust airflow EF, and the RA humidity measurement corresponds to the humidity of the exhaust airflow EF.

[0034] Thereafter, the control circuit 30 calculates the temperature and absolute humidity of the exhaust air EA from the OA temperature measurement value, the OA humidity measurement value, the RA temperature measurement value, and the RA humidity measurement value received in step S14 (step S15). The control circuit 30 calculates the temperature T EA On the other hand, since the heat exchanger 13 does not recover humidity, the absolute humidity AH of the exhaust gas EA is calculated. EA is the absolute humidity AH of RA RA is calculated to be the same as

[0035] Next, the control circuit unit 30 calculates the temperature T EA is the dew point temperature when the absolute humidity AH DEA (Step S16). The dew point temperature is calculated as the value when the relative humidity is 100%. In the following, the temperature T of the exhaust gas EA is calculated as EA is the dew point temperature, the temperature T of the exhaust gas EA EA is EA (Exhaust Air) dew point temperature T EA It is called.

[0036] Furthermore, the control circuit unit 30 calculates the amount of condensed water M per unit time generated by heat exchange. W (Step S17). The amount of condensed water per unit time M W is the absolute humidity AH of the exhaust gas EA calculated as shown in the following equation (1). EA and EA dew point temperature T EA Absolute humidity AH DEA is calculated by multiplying the difference between the air density ρ and the exhaust air volume Q.

[0037] M W =ρ×Q×(AH EA -AH DEA ) ... (1)

[0038] Here, the amount of condensed water per unit time M W >0 indicates that condensation water actually occurs from the exhaust air EA, and the amount of condensation water per unit time M W ≦0 indicates that no condensation occurs.

[0039] Next, the control circuit 30 calculates the amount of condensed water per unit time M W From this, the generated water volume M in (Step S18). in is the amount of condensed water per unit time M W is calculated by multiplying the calculated water volume M by the calculation target time t. As described above, the calculation target time t is determined depending on the communication status of the OA temperature sensor 14, OA humidity sensor 15, RA temperature sensor 16, and RA humidity sensor 17, and the temperature or humidity change in the room used for ventilation or air conditioning. in is the amount of water generated last time, M in The amount of condensed water M at the calculation target time t from the time of calculation W corresponds to the change in

[0040] M in = M W × t ... (2)

[0041] Thereafter, the control circuit unit 30 calculates the amount of water M actually remaining in the drain pan 18 at the calculation target time t (step S19). The amount of water M remaining in the drain pan 18 at the calculation target time t is calculated by the following equation (3): in and the amount of water discharged from the drain pan 18 M out It is calculated by the difference between

[0042] M=M in -M out ...(3)

[0043] Here, when M>0, it means that water is accumulating in the drain pan 18, and conversely, when M≦0, it means that the amount of water discharged is greater than the amount of water accumulated in the drain pan 18. out is the amount of drainage at the calculation target time t, and is a value that can be calculated based on the diameter and number of drain ports 181. Normally, this is stored in the memory of the control circuit unit 30 as a product-specific value.

[0044] When the OA temperature measurement value TOA is 0°C or higher, i.e., TOA≧0, the water generated in the heat exchanger 13 and the water being drained do not freeze, so the amount of water M that actually remains in the drain pan 18 can be calculated using equation (3). However, when the OA temperature measurement value TOA is below freezing, i.e., TOA<0, the water generated in the heat exchanger 13 and the water being drained will freeze, and there is a possibility that water will not drip into the drain pan 18 or that water will freeze on the drain pan 18 and will not be drained from the drain pan 18. When TOA<0, the control circuit unit 30 calculates the amount of water generated M in All of these are accumulated, and M = M in Let's say.

[0045] After that, the control circuit unit 30 integrates the amount of water M accumulated in the product, i.e., the heat exchange ventilator 1, after the heat exchange ventilator 1 is operated, and calculates the total amount of water M present in the heat exchange ventilator 1. sum In one example, the total amount of water M sum The amount of water accumulated inside the product, M, is the amount of condensation water, M WAlternatively, the amount of water generated M in By integrating the total amount of water M sum Alternatively, the total amount of water stored in the previous sum The total amount of water M is calculated by adding the amount of water M remaining in the drain pan 18 to the calculation target time t obtained in step S19. sum is required.

[0046] Next, the control circuit unit 30 calculates the total amount of water M sum It is determined whether the total amount of water M is greater than a predetermined threshold value that serves as a reference value for determining the possibility of overflow (step S21). sum is higher than the threshold value (Yes in step S21), there is a possibility that water will overflow from the drain pan 18 if the blower 12 is operated in the current state. Therefore, the control circuit unit 30 determines whether the blower 12 is operating at the minimum air volume (step S22). If the blower 12 is not operating at the minimum air volume (No in step S22), the control circuit unit 30 switches to an operation that suppresses the amount of water generated (step S23). In one example, the control circuit unit 30 suppresses the air volume from the previous air volume state, thereby reducing the amount of condensation water M generated by sensible heat exchange. W In addition, the total amount of water actually collected in the drain pan 18 M sum Since the airflow is controlled by the temperature, the operating time is expected to be longer than when the airflow is uniformly reduced depending on the air conditions. The extended operating time is expected to result in comfort and energy savings due to the continued heat exchange ventilation operation. The threshold for controlling the airflow can be determined based on the capacity of the drain pan 18 installed.

[0047] In step S23, the generated water amount M inIf the only thing you want to suppress is to reduce the airflow rate on the exhaust EA side where water is generated, then you only need to reduce the airflow rate on the exhaust EA side where water is generated. If you want to prioritize the balance of indoor airflow rates through ventilation, then you only need to reduce both the supply airflow rate and the exhaust airflow rate. Furthermore, multiple thresholds for switching airflow rates may be provided. For example, multiple thresholds may be provided, and the control circuit unit 30 may reduce the airflow rate of the blower 12 in stages, or the threshold for reducing the airflow rate may be set to the threshold for stopping the blower 12.

[0048] Thereafter, the control circuit unit 30 determines whether or not an operation command including an instruction to terminate the operation of the heat exchange ventilator 1 has been received from the remote controller 20 (step S27). If an operation command including an instruction to terminate the operation of the heat exchange ventilator 1 has not been received from the remote controller 20 (No in step S27), the process returns to step S14. Thereafter, in step S21, the total amount of water M sum If the state where the airflow rate exceeds the threshold continues, the control circuit 30 reduces the airflow rate of the blower 12. The control circuit 30 can reduce the airflow rate until it reaches the minimum airflow rate.

[0049] If the blower 12 is operating at the minimum air volume in step S22 (Yes in step S22), the control circuit 30 determines whether operation at the minimum air volume has continued for a predetermined period (step S24). If operation at the minimum air volume has not continued for the predetermined period (No in step S24), the process proceeds to step S27.

[0050] On the other hand, if operation at the minimum air volume has continued for a predetermined period (Yes in step S24), the control circuit unit 30 temporarily stops operation of the blower 12, stops the generation of condensation water, and drains water from the drain pan 18 (step S25). After draining of water from the drain pan 18 is completed, the control circuit unit 30 resumes operation of the blower 12 (step S26). Note that, although FIG. 7 illustrates a case in which operation of the blower 12 is temporarily stopped when operation at the minimum air volume has continued for a predetermined period, the control circuit unit 30 may also be configured to temporarily stop operation of the blower 12 when the total amount of water M is reached, rather than when the blower 12 is at the minimum air volume. sum If the state where the temperature exceeds the threshold continues, the operation of the blower 12 may be temporarily stopped.

[0051] The stop time is determined by the amount of water M discharged from the drain pan 18. out The drain time can be determined from the drainage time calculated from the capacity of the drain pan 18 and the temperature of the building. A shorter stop time minimizes the deterioration of comfort due to ventilation stoppage, so a stop time of approximately 5 minutes is appropriate. Furthermore, of the blowers 12 stopped in step S25, only the exhaust blower 12E, which can suppress the generation of condensation water, may be stopped. However, to maintain the balance between the supply air SA and the exhaust air EA of the building, both the exhaust blower 12E and the supply air blower 12S may be stopped simultaneously. The process then proceeds to step S27.

[0052] On the other hand, in step S21, the total amount of water M sum If the threshold value is equal to or less than the threshold value (No in step S21), the control circuit unit 30 increases the air volume of the blower 12 from the previous air volume state (step S28). If multiple threshold values ​​for switching the air volume are provided, the control circuit unit 30 may increase the air volume in stages. Alternatively, a threshold value may be provided separately for returning the air volume to the state before the protective operation, which is an operation for suppressing the amount of water generated. Then, the process returns to step S14.

[0053] Furthermore, in step S27, if an operation command including an instruction to end the operation of the heat exchange ventilator 1 is received from the remote controller 20 (Yes in step S27), the process ends.

[0054] The above explanation has been about a method for suppressing condensation water in winter, but in summer when condensation water is generated on the supply air SA side, heat exchange ventilation can be performed while saving more energy than conventional methods without causing condensation water to overflow from the drain pan 18. In this case, the control circuit unit 30 calculates the absolute humidity at the SA (Supply Air) dew point temperature from the absolute humidity and dew point temperature of the supply air SA. The control circuit unit 30 also calculates the amount of condensation water M per unit time generated by heat exchange from the absolute humidity of the supply air SA, the absolute humidity at the SA dew point temperature, and the supply air flow rate of the supply air blower 12S. W , and the amount of condensation water per unit time M W Generated water volume M inThen, in the same manner as in the processing procedure shown in Fig. 6, the air volume of the intake air blower 12S may be changed or temporarily stopped to drain the water from the drain pan 18.

[0055] The above description has been directed to a method for controlling the air volume of the blower 12 when the heat exchanger 13 is a sensible heat exchanger. However, even when the heat exchanger 13 is a total heat exchanger, this method is useful when used under air conditions that may cause condensation. When the heat exchanger 13 is a total heat exchanger, the spacing member 132 is made of a material that is gas-shielding and moisture-permeable. In this case, the sheet material 131 exchanges sensible heat and latent heat between the exhaust air flow EF passing through the primary air passage 133a and the supply air flow SF passing through the secondary air passage 133b without mixing the exhaust air flow EF and the supply air flow SF.

[0056] As described above, in the heat exchange ventilator 1 according to the first embodiment, the control circuit 30 calculates the total amount of water generated by condensation during operation of the heat exchange ventilator 1 based on the OA temperature measurement value, the OA relative humidity measurement value, the RA temperature measurement value, the RA relative humidity measurement value, the heat exchange efficiency, the operating airflow rate, and threshold information. The control circuit 30 then temporarily reduces the airflow rate of at least the exhaust fan 12E when the total amount of water is greater than a predetermined threshold. This allows for continued ventilation operation while suppressing the generation of condensation water during heat exchange and preventing overflow from the drain pan 18. The timing for reducing the airflow rate can be set to the point when the amount of water generated by condensation reaches a predetermined percentage of the capacity of the drain pan 18, as determined by the threshold information. This point is generally later than the point at which the airflow rate of the fan 12 is reduced under air conditions. Therefore, an extended operating time is expected compared to a uniform reduction in the airflow rate of the fan 12 under air conditions. This extension of the operating time is expected to result in comfort and energy savings due to the continuation of heat exchange ventilation operation. In other words, in a situation where condensation water is constantly generated from the heat exchanger 13, water can be prevented from overflowing from the drain pan 18, and ventilation can be performed while saving energy compared to conventional systems.

[0057] Embodiment 2. FIG. 8 is a diagram schematically illustrating an example of the configuration of a heat exchanger ventilator according to embodiment 2. The heat exchanger ventilator 1 is configured to acquire the detection results of a CO2 sensor 41 disposed in a ventilation space, such as a room, in which the heat exchanger ventilator 1 is installed. In the following example, the ventilation space is an indoor space 50. In this example, the control circuit 30 of the heat exchanger ventilator 1 is connected to the CO2 sensor 41 via a communication line 42. The CO2 sensor 41 is a sensor capable of detecting the CO2 concentration in the indoor space 50. The CO2 sensor 41 transmits the detection results of the CO2 concentration to the control circuit 30 of the heat exchanger ventilator 1 at predetermined time intervals. The heat exchanger ventilator 1 may also be equipped with the CO2 sensor 41. Alternatively, another device such as an air conditioner or air purifier, which is placed in the room 50 where the heat exchanger ventilator 1 is installed and is equipped with a CO sensor 41, may be connected to the control circuit 30 of the heat exchanger ventilator 1 so as to be able to communicate with the control circuit 30, and the other device may transmit the detection result of the CO sensor 41 to the control circuit 30 of the heat exchanger ventilator 1. Note that the CO sensor 41 is connected to the heat exchanger ventilator 1 via a communication line 42, but the communication line 42 may be wired or wireless.

[0058] The heat exchange ventilator 1 has a configuration similar to that described in the first embodiment. However, the control circuit 30 cooperates with the CO2 sensor 41 to control the airflow rate of the blower 12. Generally, the control circuit 30 receives the CO2 concentration in the room 50 from the CO2 sensor 41 and sets the airflow rate of the blower 12 to be high if the CO2 concentration in the room 50 is higher than a predetermined reference value. If the CO2 concentration is lower than the predetermined reference value, the control circuit 30 may set the airflow rate of the blower 12 to be high or low if the CO2 concentration is equal to the predetermined reference value. Furthermore, when the heat exchange ventilator 1 is operating with reduced airflow rate to reduce the total amount of water generated within the heat exchange ventilator 1, the control circuit 30 compares the airflow rate required to reduce the total amount of water with the airflow rate required to reduce the CO2 concentration, and controls the blower 12 according to the condition requiring the lower airflow rate.

[0059] 9 is a diagram showing an example of the relationship between the total amount of water and the required air volume in the heat exchange ventilation apparatus according to embodiment 2. In this diagram, the horizontal axis represents the total amount M of water in the heat exchange ventilation apparatus 1. sum 9, the vertical axis represents the required air volume Q1, which is the air volume required for the blower 12. As shown in FIG. sum When the air volume required is less than a1, the air volume required is Q1, and the total amount of water M sum As the amount of water increases from a1, the required air volume Q1 decreases, and the total amount of water M sum When the temperature difference is equal to or greater than a2, the blower 12 is controlled so that the required air volume Q1 is minimized. The required air volume Q1 corresponds to the first required air volume.

[0060] Fig. 10 is a diagram showing an example of the relationship between the CO2 concentration in a room and the required air volume in a heat exchange ventilation system according to embodiment 2. In this diagram, the horizontal axis represents the CO2 concentration in the room 50, and the vertical axis represents the required air volume Q2, which is the air volume required of the blower 12. As shown in Fig. 10, when the CO2 concentration is b2 or higher, the required air volume Q2 is maximized. As the CO2 concentration decreases below b2, the required air volume Q2 decreases. When the CO2 concentration is b1 or lower, the blower 12 is controlled so that the required air volume Q2 is minimized. The required air volume Q2 corresponds to the second required air volume.

[0061] The control circuit unit 30 calculates the total amount of water M sum After calculating the total amount of water M sum Furthermore, when the control circuit unit 30 acquires the CO2 concentration from the CO2 sensor 41, it calculates the required air volume Q2 for maintaining the CO2 concentration in the room 50 at a predetermined value from the information showing the relationship between the CO2 concentration in the room 50 and the required air volume Q2 shown in Figure 10. sum The required air volume Q1 corresponding to the CO2 concentration in the room 50 is compared in magnitude with the required air volume Q2 corresponding to the CO2 concentration in the room 50.

[0062] Total amount of water M sumWhen the required air volume Q1 corresponding to the CO2 concentration in the room 50 is greater than the required air volume Q2 corresponding to the CO2 concentration in the room 50, reducing the air volume of the blower 12 to Q2 can both suppress the generation of condensation and maintain the CO2 concentration. Therefore, the control circuit 30 sets the air volume of the blower 12 to Q2. In this case, because the air volume is smaller than the required air volume Q1, it is possible to reduce the power consumption of the blower 12 compared to when the CO2 concentration in the room 50 is not taken into consideration.

[0063] Total amount of water M sum If the required air volume Q1 corresponding to the CO2 concentration in the room 50 is smaller than the required air volume Q2 corresponding to the CO2 concentration in the room 50, the control circuit unit 30 sets the air volume of the blower 12 to Q1 and continues operation in order to suppress the occurrence of overflow of the drain pan 18 due to condensation water rather than the CO2 concentration.

[0064] The total amount of water M sum When the required air volume Q1 corresponding to the CO2 concentration in the room 50 is equal to the required air volume Q2 corresponding to the CO2 concentration in the room 50, the control circuit unit 30 sets the air volume of the blower 12 to Q1, i.e., Q2.

[0065] Next, a control algorithm for heat exchange ventilation that reduces the CO2 concentration in the room 50 without causing condensation water to overflow from the drain pan 18 by the control circuit unit 30 will be described. Fig. 11 is a flowchart showing an example of the control process procedure for the heat exchange ventilation device according to embodiment 2. Note that steps S11 to S20 are the same as those shown in Fig. 6 of embodiment 1, and therefore drawings and descriptions thereof will be omitted.

[0066] In step S20 of FIG. 6, the total amount of water M sum After calculating and storing the total amount of water M sumThe control circuit 30 calculates the required air volume Q1 for suppressing condensation, which is obtained by the above equation (step S51). Next, the control circuit 30 acquires the CO2 concentration in the room 50 from the CO2 sensor 41 (step S52). The control circuit 30 calculates the required air volume Q2 for maintaining a comfortable CO2 concentration in the room 50 from the acquired CO2 concentration (step S53). Thereafter, the control circuit 30 compares the required air volume Q1 for suppressing condensation with the required air volume Q2 for maintaining a comfortable CO2 concentration in the room 50, and determines whether the required air volume Q1 is greater than the required air volume Q2 (step S54).

[0067] If the required airflow Q1 is greater than the required airflow Q2 (Yes in step S54), reducing the airflow to the required airflow Q2 can both suppress condensation and maintain the CO2 concentration, so the heat exchange ventilator 1 can reduce the airflow to Q2. Therefore, the control circuit 30 controls the airflow of the blower 12 to Q2 (step S55). Then, the process returns to step S14.

[0068] If the required airflow Q1 is equal to or less than the required airflow Q2 (No in step S54), the control circuit 30 determines whether the blower 12 is operating at the minimum airflow (step S56). If the blower 12 is not operating at the minimum airflow (No in step S56), the control circuit 30 controls the airflow of the blower 12 to Q1 (step S57) to prioritize preventing overflow of the drain pan 18 due to condensation over CO2 concentration. Note that if the total amount of water due to condensation in the heat exchange ventilator 1 decreases, the required airflow Q1 increases. If the required airflow Q1 becomes greater than the required airflow Q2, the system can return to energy-saving operation prioritizing CO2 concentration.

[0069] Then, the process proceeds to step S27 described in FIG. 7 of the first embodiment. That is, the control circuit unit 30 determines whether an operation command including an instruction to terminate operation of the heat exchanger ventilator 1 has been received from the remote control 20. If an operation command including an instruction to terminate operation of the heat exchanger ventilator 1 has not been received from the remote control 20, the process returns to step S14. After this, if the required airflow Q1 remains equal to or less than the required airflow Q2 in step S53 and the required airflow Q1 is decreasing, the control circuit unit 30 decreases the airflow of the blower 12 in step S57. The airflow can then be decreased until the required airflow Q1 becomes the minimum airflow.

[0070] If blower 12 is operating at the minimum air volume in step S56 (if Yes in step S56), that is, if required air volume Q1 is the minimum air volume of blower 12, control circuit 30 proceeds to step S24 described in Fig. 7 of embodiment 1. The processes from step S24 onwards are the same as those described in embodiment 1, and therefore will not be described again.

[0071] Although the above description describes a method for controlling the air volume using the CO2 concentration in the room 50 measured using the CO2 sensor 41, the air volume may also be controlled using the results of measuring the air quality, which is the property of the air in the room 50. Air quality can be measured not only for CO2 but also for dust, odorous substances, chemical substances emitted from buildings, etc. Odorous substances are substances emitted by the human body, and examples include ammonia, hydrogen sulfide, and methyl mercaptan. In this case, an air quality detection unit capable of detecting the target substance to be exhausted from the room 50 is provided instead of the CO2 sensor 41 in FIG. 8. Then, in step S53 of FIG. 11, a required air volume Q2 is calculated so that the concentration of the target substance detected by the air quality detection unit becomes a concentration sufficient to keep the room 50 comfortable.

[0072] In the heat exchange ventilator 1 according to the second embodiment, the control circuit 30 calculates a required airflow Q1 to suppress condensation from the total amount of water calculated from the OA temperature measurement value, the OA relative humidity measurement value, the RA temperature measurement value, the RA relative humidity measurement value, the heat exchange efficiency, the operating airflow, and threshold information. The control circuit 30 then calculates a required airflow Q2 to reduce the concentration of the air quality in the room 50 below a predetermined reference value based on the air quality measurement results. If the required airflow Q2 is smaller than the required airflow Q1, the control circuit 30 controls the airflow of the blower 12 to Q2. This allows for both suppression of condensation and maintenance of air quality. Furthermore, since the airflow is smaller than the required airflow Q1, the power consumption of the blower 12 can be reduced compared to the first embodiment, in which the air quality in the room 50 is not considered. Furthermore, if the required airflow Q1 is smaller than the required airflow Q2, the control circuit 30 controls the airflow of the blower 12 to Q1. This makes it possible to suppress overflow of the drain pan 18 due to condensed water rather than CO2 concentration.

[0073] In the above description, the RA temperature sensor 16 and the RA humidity sensor 17 are disposed on the windward side of the heat exchanger 13 in the exhaust air duct 116, i.e., in the windward-side exhaust air duct 116a. However, they may be disposed in any position capable of detecting the temperature and humidity of the exhaust air flow EF. For example, the RA temperature sensor 16 and the RA humidity sensor 17 may be disposed on the leeward side of the heat exchanger 13 in the exhaust air duct 116, i.e., in the leeward-side exhaust air duct 116b. Furthermore, the OA temperature sensor 14 and the OA humidity sensor 15 are disposed on the windward side of the heat exchanger 13 in the supply air duct 115, i.e., in the windward-side supply air duct 115a. However, they may be disposed in any position capable of detecting the temperature and humidity of the supply air flow SF. For example, the OA temperature sensor 14 and the OA humidity sensor 15 may be disposed on the leeward side of the heat exchanger 13 in the supply air duct 115, i.e., in the leeward-side supply air duct 115b.

[0074] The control circuit unit 30 is realized as a processing circuit. The processing circuit may be dedicated hardware, an integrated circuit, or a circuit including a processor. FIG. 12 is a block diagram showing an example of the hardware configuration of the control unit of the heat exchange ventilator according to the first and second embodiments. The control circuit unit 30 includes a processor 501 and a memory 502. The processor 501 may be a CPU (Central Processing Unit, also referred to as a central processing unit, processing device, arithmetic unit, microprocessor, microcomputer, or DSP (Digital Signal Processor)), a system LSI (Large Scale Integration), or the like. The memory 502 may be a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), a magnetic disk, a flexible disk, an optical disk, a compact disk, a minidisk, or a DVD (Digital Versatile Disc), or the like. The processor 501 and the memory 502 are connected via a bus line 503 .

[0075] The control circuit unit 30 is realized by the processor 501 reading from the memory 502 a program describing the procedures for controlling the airflow rates of the intake air blower 12S and the exhaust air blower 12E based on the detection results of the OA temperature sensor 14, the OA humidity sensor 15, the RA temperature sensor 16, and the RA humidity sensor 17, or based on the detection results of these sensors and the air quality detection unit. The program read from the memory 502 and executed by the processor 501. The above functions may also be realized by multiple processors and multiple memories working together. Alternatively, some of the functions of the control circuit unit 30 may be implemented as dedicated hardware electronic circuits, and other functions may be realized using the processor 501 and the memory 502. In one example, the control circuit unit 30 controls the operation of the intake air blower 12S and the exhaust air blower 12E using electrical signals.

[0076] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0077] 1 Heat exchange ventilation device, 11 Main body casing, 12 Fan, 12E Exhaust fan, 12S Intake fan, 13 Heat exchanger, 14 OA temperature sensor, 15 OA humidity sensor, 16 RA temperature sensor, 17 RA humidity sensor, 18 Drain pan, 19 Air path switching damper, 20 Remote control, 30 Control circuit unit, 41 CO2 sensor, 42 Communication line, 50 Indoor, 60 Condensed water, 111 Outside air intake port, 112 Exhaust outlet port, 113 Intake air outlet port, 114 Indoor air intake port, 115 Intake air duct, 115a Upwind side intake air duct, 115b Downwind side intake air duct, 116 Exhaust air duct, 116a Upwind side exhaust air duct, 116b Downwind side exhaust air duct, 116c Bypass air duct, 131 sheet material, 132 spacing member, 132a spacing member, 132b spacing member, 133a primary side air duct, 133b secondary side air duct, 181 drain outlet, EA exhaust, EF exhaust flow, OA outside air, Q1 required air volume, Q2 required air volume, RA return air, SA supply air, SF supply air flow.

Claims

1. A casing having an intake fan; an exhaust fan; an intake air duct formed by the intake fan and through which an intake air flow from the outdoors to the indoors passes, and an exhaust air duct formed by the exhaust fan and through which an exhaust air flow from the indoors to the outdoors passes; a heat exchanger installed between the intake air duct and the exhaust air duct and performing heat exchange between the intake air flow and the exhaust air flow; a drain pan for retaining and discharging water generated by condensation in the heat exchanger; an intake air flow temperature sensor for detecting the temperature of the intake air flow; an intake air flow humidity sensor for detecting the humidity of the intake air flow; an exhaust air flow temperature sensor for detecting the temperature of the exhaust air flow; an exhaust air flow humidity sensor for detecting the humidity of the exhaust air flow; and a control unit for controlling at least one of the intake air fan and the exhaust air fan based on the total amount of water generated by condensation in the heat exchanger and present in the drain pan, calculated based on the temperature and humidity of the intake air flow and the temperature and humidity of the exhaust air flow. A heat exchange ventilation device comprising:

2. The heat exchange ventilation device described in claim 1, characterized in that the control unit reduces the air volume of at least one of the exhaust fan and the intake fan when the calculated total amount of water is higher than a predetermined threshold.

3. A heat exchange ventilation device as described in claim 1 or 2, characterized in that the control unit increases the air volume of the intake air blower and the exhaust air blower when the calculated total amount of water is lower than a predetermined threshold value.

4. A heat exchange ventilation device as described in any one of claims 1 to 3, characterized in that the control unit stops at least one of the intake air blower and the exhaust air blower when the calculated total amount of water remains higher than a predetermined threshold for a predetermined period of time.

5. A heat exchange ventilation device as described in any one of claims 1 to 4, characterized in that the control unit calculates the total amount of water using the difference between the amount of water generated by the condensation calculated using the temperature of the intake air flow detected by the intake air flow temperature sensor, the humidity of the intake air flow detected by the intake air flow humidity sensor, the temperature of the exhaust air flow detected by the exhaust air flow temperature sensor, and the humidity of the exhaust air flow detected by the exhaust air flow humidity sensor, and the amount of water drained from the drain pan.

6. A heat exchange ventilation device described in any one of claims 1 to 5, characterized in that the control unit receives the detection results of the air quality of the space in which the heat exchange ventilation device is placed, compares a first required air volume, which is the air volume required to suppress condensation from the total amount of water calculated from the temperature and humidity of the intake air flow and the temperature and humidity of the exhaust air flow, with a second required air volume, which is the air volume required to reduce the air quality to a predetermined standard value based on the detection results of the air quality, and switches at least one of the intake air blower and the exhaust air blower to the smaller required air volume.

7. The heat exchange ventilation device according to claim 6, wherein the air quality is any one of CO2, dust, odorous substances, and chemical substances emitted from buildings.

8. A heat exchange ventilation device as described in any one of claims 1 to 7, characterized in that the intake air temperature sensor and the intake air humidity sensor are provided on the upwind side of the heat exchanger in the intake air duct.

9. A heat exchange ventilation device as described in any one of claims 1 to 8, wherein the exhaust air temperature sensor and the exhaust air humidity sensor are provided on the upwind side of the heat exchanger in the exhaust air duct.

10. A heat exchange ventilation device as described in any one of claims 1 to 8, characterized in that the exhaust flow temperature sensor and the exhaust flow humidity sensor are provided on the downwind side of the heat exchanger in the exhaust air duct.

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