Patent Publication Number: US-2023138270-A1

Title: Air conditioning controller and air conditioning system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims the benefit of priority from earlier Japanese Patent Application No. 2021-179047 filed Nov. 1, 2021, the description of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     Technical Field of the Invention 
     The present disclosure relates to an air conditioning controller and an air conditioning system. 
     Background Art 
     An air conditioning system installed in a building such as a house may include an air conditioning controller that allows a user to set an operation mode (e.g., air conditioning, heating, dehumidification, ventilation) and an air conditioner that achieves air conditioning in accordance with control signals (i.e., commands) sent through relays installed in the air conditioning controller. For example, Patent Literature (JP 2017-3193 A) describes a thermostat (corresponding to an air conditioning controller) including multiple relays such as a ventilation relay, an air conditioning relay, and a heating relay. The multiple relays close their contacts if the air conditioner is controlled; otherwise, the relays open the contacts. 
     A relay including a stationary terminal, a movable terminal, and a drive coil for moving the movable terminal is also provided. The contacts correspond to the point of contact between the stationary terminal and the movable terminal. The relay energizes the drive coil to move the movable terminal, bringing the movable terminal and the stationary terminal into contact with each other (i.e., closing the contacts) and sending a signal. 
     SUMMARY 
     A conventional relay switches between the open contact state and the closed contact state in accordance with control of the air conditioner as described in the above Patent Literature. For the above relay including the movable terminal, whether the open contact state and the closed contact state should be switched may be different depending on the state of the air conditioning controller. 
     The present disclosure has been made in view of the above, and a main object of the disclosure is to provide an air conditioning controller capable of efficiently controlling the contact between the movable terminal and the stationary terminal in accordance with the state of the air conditioning controller. 
     An air conditioning controller according to an embodiment of the present disclosure comprises: a mechanical relay including a movable terminal, a stationary terminal, and a drive coil configured to move the movable terminal to a position in contact with the stationary terminal and a position out of contact with the stationary terminal; a memory; and a processor configured to execute a program stored in the memory. The air conditioning controller sends a control signal through the mechanical relay to an air conditioner. the processor performs boot processing for the air conditioning controller when the air conditioning controller satisfies a boot condition or a reboot condition, and the processor energizes the drive coil to move the movable terminal to a predetermined position. The predetermined position is the position in contact with the stationary terminal or the position out of contact with the stationary terminal and the predetermined position corresponds to transmission of a shutoff control signal for shutting off the air conditioner. The mechanical relay holds the movable terminal at the predetermined position after energization of the drive coil ends. At the boot processing, the processor moves the movable terminal to the predetermined position when a switch avoidance condition is not satisfied, whereas at the boot processing, the processor does not move the movable terminal to the predetermined position when the switch avoidance condition is satisfied. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG.  1    is a schematic diagram showing a building and an air conditioning system according to an embodiment. 
         FIG.  2    is a block diagram showing the electrical structure of the air conditioning system. 
         FIG.  3    is a schematic diagram showing a relay structure. 
         FIG.  4    is a schematic diagram showing the relationship between relay states and operation modes. 
         FIG.  5    is a schematic diagram illustrating a relocation of an air conditioning controller. 
         FIG.  6 A  is a flowchart showing a preparation process for power-off duration monitoring. 
         FIG.  6 B  is a flowchart showing a relay related process. 
         FIG.  7 A  is an example timing chart for a relocation of the air conditioning controller. 
         FIG.  7 B  is an example timing chart for an automatic update performed in the air conditioning controller. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of the present disclosure will now be described with reference to the drawings. In the present embodiment, the disclosure is embodied in an air conditioning system installed in a building. 
     As shown in  FIG.  1   , an air conditioning system  30  installed in a building  10  includes an air conditioner  40  placed in an interior equipment room  24 , an exterior unit  41  placed outside, a heat exchange pipe  44  connecting the air conditioner  40  and the exterior unit  41 , intake ducts  45  to  47  that take air used for air conditioning into the air conditioner  40 , supply ducts  48  and  49  that feed air conditioned to spaces such as living rooms  21  and  22  in the building  10 , and an exhaust duct that discharges air out of the building. 
     The building  10  has multiple living rooms in its inside (interior space IS) with each living room provided with the inlet port of the corresponding intake duct and the outlet port of the corresponding supply duct. For example, the living room  21  is provided with an inlet port  45   a  fitted to the intake duct  45  and an outlet port  48   a  fitted to the supply duct  48 . The living room  22  is provided with an inlet port  46   a  fitted to the intake duct  46  and an outlet port  49   a  fitted to the supply duct  49 . The building  10  in the present embodiment is a highly airtight and insulated house, and the air conditioning system  30  (the air conditioner  40 ) provides air conditioning in the whole building (i.e., central air conditioning). 
     The air conditioning system  30  also includes an air conditioning controller  50  installed on a wall of the living room  21 . The air conditioning controller  50  allows a user to set an operation mode (air conditioning, heating, dehumidification, ventilation). The air conditioner  40  and the exterior unit  41  operate in accordance with the set operation mode. 
     As shown in  FIG.  2   , the air conditioning controller  50  includes a processor (e.g., a CPU  61 ) that performs various types of control as to air conditioning, and memory (a ROM  62 , a RAM  63 ) that stores various programs and data for the control. The air conditioning controller  50  is connected to an external power supply (commercial power supply), and the CPU  61  operates by electric power supplied from the external power supply. 
     The air conditioning controller  50  according to the present embodiment is connected to a cloud server over the internet. The cloud server allows the latest program and data for air conditioning to be downloaded from it. In other words, the air conditioning programs and data stored in the air conditioning controller  50  can be updated even after the shipment of the product. Such updates (online updates) are broadly classified into manual updates each performed based on an update operation by a user, and automatic updates each performed when the air conditioning controller  50  checks for an update as appropriate and confirms the distribution of an update program. Regardless of which of a manual update and an automatic update is performed, the air conditioning controller  50  is rebooted upon the completion of the download and installation of the program. 
     The memory stores a program for performing update processing, a self-diagnosing program for examining the air conditioning controller  50  for an abnormality such as freezing, and a program for troubleshooting the abnormality determined as a result of the diagnosis. In the present embodiment, when the air conditioning controller  50  is booted or rebooted, boot processing described later is performed. The boot processing involves the deletion of the information stored in the CPU  61  and the temporary storage area of the memory. The troubleshooting program reboots the air conditioning controller  50  forcibly and deletes the information stored in the temporary storage area, or specifically, the information that may be the cause of the abnormality. This can eliminate the abnormality. 
     The air conditioning controller  50  also includes a real-time clock (hereinafter referred to as an RTC  64 ) and an internal power supply for the RTC  64 . The RTC  64  operates by electric power supplied from the internal power supply and is operable even under conditions in which the air conditioning controller  50  is not connected to the external power supply, or in other words, the air conditioning controller  50  is powered off. As detailed later, the CPU  61  reads out the current time from the RTC  64  and stores the readout current time into a time storage area in the memory. The time storage area is provided in the non-volatile memory and capable of holding stored information even under conditions in which the external power supply is supplying no electric power to the air conditioning controller  50 . Note that the time storage area is not subjected to the deletion of information in the boot processing. 
     The air conditioning controller  50  includes an input/output (I/O) unit  65  connected to the air conditioner  40  via a harness. Specifically, the I/O unit  65  includes a relay unit  71  having multiple (in the present embodiment, eight) relays R1 to R8 such as a heating relay, an air conditioning relay, a dehumidifying relay, a ventilating relay, an airflow amount setting relay, and an airflow direction setting relay. The wires forming the harness are attached to the relays R1 to R8. The relays R1 to R4 are relays for operation mode switching, whereas the relays R5 to R8 are relays for control of, for example, the amount of airflow. The air conditioner  40  operates based on control signals (control commands) sent via the relays R1 to R8 and the harness. Referring now to  FIG.  3   , the structure of the relays R1 to R8 will be described. Each of the relays R1 to R8 is a double-winding latching mechanical relay and has the same main structure. 
     The relays R1 to R8 each include a signal line  72  connected to the corresponding wire of the harness, a contact unit  75  including a pair of stationary terminals  73  provided at the ends of the divided signal line  72  and a movable terminal  74  forming a part of the signal transmission path together with the pair of stationary terminals  73 , and a drive coil that drives the movable terminal  74 . The signal line  72  of each of the relays R1 to R8 leads to the external power supply through a converter circuit included in the air conditioning controller  50 . When the air conditioning controller  50  is booted, the converter circuit applies a voltage to each signal line  72 . 
     The drive coil includes a set coil  76  and a reset coil  77 . The set coil  76  and the reset coil  77  face each other across the contact unit  75  (more specifically, the movable terminal  74 ). The set coil  76  and the reset coil  77  can be switched individually by the CPU  61  between an energized state and a de-energized state. 
     When the set coil  76  enters into the energized state and the reset coil  77  enters into the de-energized state, the set coil  76  generates an attractive force that draws the movable terminal  74  toward it. The movable terminal  74  drawn by the attractive force comes into contact with the stationary terminals  73  and can no longer move further toward the set coil  76 , forming the signal transmission path together with the stationary terminals  73  (see the left part of  FIG.  3    and the central part of  FIG.  3   ). Hereinafter, this state is referred to as the closed state. In the closed state, the movable terminal  74  and the stationary terminals  73  are in contact with each other. 
     The stationary terminals  73  are provided with a magnetic force that attracts the movable terminal  74 , and the movable terminal  74  that has moved to the position in contact with the stationary terminals  73  stays at this contact position even after the set coil  76  is de-energized (see the central part of  FIG.  3   ). In other words, the relay remains in the closed state. Under conditions in which the relay is in the closed state, the passage of an electric current from the relay to the air conditioner  40  inputs an ON signal (HI level signal) to the air conditioner  40 . 
     Under conditions in which the relay in the closed state, when the reset coil  77  is energized, the set coil  76  enters into the de-energized state, and the reset coil  77  enters into the energized state, the reset coil  77  generates an attractive force that draws the movable terminal  74  toward it. The movable terminal  74  is drawn toward the reset coil  77  against the magnetic force of the stationary terminals  73 , and the movable terminal  74  leaves the stationary terminals  73 . The movable terminal  74  that has left the stationary terminals  73  comes into contact with a stopper  78  adjacent to the contact unit  75 . This contact prevents the movable terminal  74  from moving further toward the reset coil  77  (see the central part of  FIG.  3    and the right part of  FIG.  3   ). 
     The stopper  78  is also provided with a magnetic force that attracts the movable terminal  74 , and the movable terminal  74  stays at the position in contact with the stopper  78  even after the reset coil  77  is de-energized. With the stationary terminals  73  and the movable terminal  74  spaced apart from each other, the relay outputs an OFF signal (LOW level signal) to the air conditioner  40 . Hereinafter, this state is referred to as the open state. In the open state, the movable terminal  74  and the stationary terminals  73  are out of contact with each other. 
     Referring now to  FIG.  4   , the relationship between the operation modes of the air conditioner  40  and control commands will be described. 
     While all the relays R1 to R4 are in the open state, all signals input from the relays R1 to R4 to the air conditioner  40  are OFF signals. The air conditioner  40  stops operating when receiving this control command during operation, and remains off when receiving this control command during a stopped state. Hereinafter, the state of the relay unit  71  with the relays R1 to R4 in the open state is referred to as the initial state (or the predetermined state). The position of the movable terminal  74  in the initial state is also referred to as the initial position (or the predetermined position). 
     While the relay R1 is in the closed state and the relays R2 to R4 are in the open state, the relay R1 inputs an ON signal to the air conditioner  40 , and the relays R2 to R4 input OFF signals to the air conditioner  40 . The air conditioner  40  switches the operation mode to the heating mode when receiving this control command during operation, and starts operating in the heating mode when receiving this control command during a stopped state. 
     While the relays R1, R3 to R4 are in the open state and the relay R2 is in the closed state, the relays R1, R3 to R4 input OFF signals to the air conditioner  40 , and the relay R2 inputs an ON signal to the air conditioner  40 . The air conditioner  40  switches the operation mode to the air conditioning mode when receiving this control command during operation, and starts operating in the air conditioning mode when receiving this control command during a stopped state. 
     While the relays R1 to R2, R4 are in the open state and the relay R3 is in the closed state, the relays R1 to R2, R4 input OFF signals to the air conditioner  40 , and the relay R3 inputs an ON signal to the air conditioner  40 . The air conditioner  40  switches the operation mode to the dehumidifying mode when receiving this control command during operation, and starts operating in the dehumidifying mode when receiving this control command during a stopped state. 
     While the relays R1 to R3 are in the open state and the relay R4 is in the closed state, the relays R1 to R3 input OFF signals to the air conditioner  40 , and the relay R4 inputs an ON signal to the air conditioner  40 . The air conditioner  40  switches the operation mode to the ventilating mode when receiving this control command during operation, and starts operating in the ventilating mode when receiving this control command during a stopped state. 
     As detailed above, the state of the relay unit  71  with all the relays R1 to R4 in the open state (i.e., the initial state) corresponds to the output of a control command not to operate. The state of the relay unit  71  with any one of the relays R1 to R4 in the closed state corresponds to the output of a control command to operate. 
     Referring now to  FIG.  5   , the installation of the air conditioning controller  50  will be additionally described.  FIG.  5    illustrates an example in which the air conditioning controller  50  installed in a living room A is relocated to a living room B. 
     The living room A has a wall  31 A in which the above-described harness is embedded to connect the air conditioning controller  50  to the external power supply, the air conditioner  40 , and a router for the internet. The harness has a connector  32 A fixed to a bracket provided on the wall  31 A. The bracket allows the air conditioning controller  50  to be installed on the wall  31 A. The air conditioning controller  50  is fixed to the bracket in such a way that a display screen  51  for displaying various information items as to air conditioning faces inside the room. With the air conditioning controller  50  fixed to the bracket, the connector  32 A is connected with a connector  52  provided on the rear surface of the air conditioning controller  50 . The connection between the connector  52  and the connector  32 A forms a power supply path (power line) from the external power supply to the air conditioning controller  50 , a signal transmission path from the air conditioning controller  50  to the air conditioner  40 , and a communication path to the cloud server. 
     When the air conditioning controller  50  is relocated from the living room A to the living room B because of, for example, remodeling, the air conditioning controller  50  is operated to stop the operation of the air conditioner  40 . This stop operation switches the relay unit  71  to the above-described initial state. Then, the air conditioning controller  50  is removed from the bracket, and thus the connector  32 A and the connector  52  are separated from each other, cutting off the power supplied from the external power supply to the air conditioning controller  50 . As a result, a control command corresponding to a stopped state is input to the air conditioner  40 . 
     The air conditioning controller  50  according to the present embodiment does not include a power button (power supply operation unit) that allows the air conditioning controller  50  to be turned on or off. When the supply of power is cut off, the air conditioning controller  50  is turned off. The removed air conditioning controller  50  is carried to the living room B. 
     The living room B also has a wall  31 B in which the above-described harness is embedded to connect the air conditioning controller  50  to the external power supply, the air conditioner  40 , and the router for the internet. The harness has a connector  32 B fixed to a bracket provided on the wall  31 B. When the air conditioning controller  50  carried to the living room B is fixed to the bracket, the connector  52  of the air conditioning controller  50  is connected to the connector  32 B on the bracket. The connection between the connector  52  and the connector  32 B forms a power supply path from the external power supply to the air conditioning controller  50 , a signal transmission path from the air conditioning controller  50  to the air conditioner  40 , and a communication path to the cloud server. Then, the external power supply restarts supplying the power to the air conditioning controller  50 , turning on the air conditioning controller  50 . 
     The air conditioning controller  50  according to the present embodiment has a latching function. Thus, even after the energization of the drive coil ends, the movable terminal  74  is held at the position to which it has moved. However, the air conditioning controller  50  may undergo vibration or other external forces during work such as installation or relocation (in particular, carrying), and the external forces can move the movable terminal  74 . In a case where such a movement switches the relay unit  71  to a state for outputting a control command corresponding to any one of heating, air conditioning, dehumidification, and ventilation, the air conditioner  40  may start operating unexpectedly when the air conditioning controller  50  is booted. In the example shown in  FIG.  5   , while the air conditioning controller  50  is being carried, the movable terminal  74  of the relay R2 is moved by an external force, and the relay R2 is switched from the open state to the closed state. That is, the relay unit  71  has switched from the initial state corresponding to a stopped state to the state corresponding to the air conditioning operation. If the air conditioning controller  50  in this state is installed in the living room B, and the air conditioning controller  50  is booted, then the air conditioner  40  will start operating unexpectedly during work. Such an event is unfavorable because it may interfere with the work and lower the reliability of the air conditioning system  30 . 
     In the present embodiment, a way to avoid such an event is devised as described below. Specifically, when the CPU  61  of the air conditioning controller  50  performs the processing of booting the air conditioning controller  50 , the relay unit  71  can be forcibly switched to the initial state. This prevents the air conditioner  40  from unexpectedly starting operating. 
     However, the air conditioning controller  50  satisfies a reboot condition at the time of updating or at an attempt to eliminate an abnormal state, and then the boot processing is performed. Thus, when the function of forcibly switching the relay unit  71  to the initial state coexists with the function of rebooting the air conditioning controller  50  using an update as a trigger, the performing the boot processing for the air conditioning controller  50  causes a new concern as described below. Specifically, when the boot processing is performed in response to rebooting triggered by an update, and the state of the relay unit  71  is switched, the movement of the movable terminal  74  may produce a snapping sound (e.g., a click). The air conditioning controller  50  is often installed in a room for ease of user operations. For this reason, the emission of the above snapping sound in such an environment can easily sound unpleasant for the user. In particular, under conditions in which the user is paying no attention to the air conditioning controller  50 , the emission of such a snapping sound may easily discomfort the user. This is likely to lower the degree of user satisfaction and thus unfavorable. 
     In the present embodiment, a way to solve the problem is further devised as described below. Specifically, the air conditioning controller  50  avoids the above-described forced switching when the trigger for booting or rebooting is an update or the elimination of an abnormal state. An example basis for the determination is a power-off duration for which the air conditioning controller  50  stays off. Details of the devised way, or more specifically, various types of processing performed by the CPU  61  will now be described with reference to the flowcharts of  FIG.  6   . 
     When the air conditioning controller  50  satisfies a boot condition or a reboot condition, the CPU  61  performs the boot processing so as to boot the air conditioning controller  50 . After the completion of the boot processing, a preparation process for monitoring the power-off duration (also referred to as a preparation process for power-off duration monitoring) is run as a regular process. 
     In the preparation process for power-off duration monitoring as shown in  FIG.  6 A , it is determined first in step S 101  whether a preset time interval (in the present embodiment, one minute) has elapsed since the previous time acquisition. If the time interval has not elapsed, the preparation process ends. If the time interval has elapsed, current time acquisition processing is performed in steps S 102  to S 103  before the preparation process ends. Specifically, the current time is read out from the RTC  64  in step S 102 , and then the time read out in step S 102  is stored in the time storage area of the non-volatile memory in step S 103  (by overwriting the area). In this manner, the current time stored in the time storage area is updated per minute. The time stored in the time storage area is held without deletion even after the air conditioning controller  50  is turned off. 
     The CPU  61  of the air conditioning controller  50  performs the boot processing (1) if the external power supply starts supplying power to the air conditioning controller  50  or (2) if the reboot condition is satisfied in response to an update or an abnormality diagnosis serving as a trigger. This boot processing includes a relay related process for switching the state of the relay unit  71 . 
     In the relay related process as shown in  FIG.  6 B , the past time is first read out in step S 201 . Specifically, the time stored in the time storage area is read out. Then, in step S 202 , the current time is read out from the RTC  64 . In step S 203 , the current time is compared with the past time to calculate the power-off duration for which the air conditioning controller  50  is estimated to have been powered off. 
     Next, the power-off duration calculated in step S 203  is compared with a preset reference time (in the present embodiment, three minutes). In the present embodiment, regarding the case in which the reboot condition is satisfied in response to an update or an abnormality diagnosis serving as a trigger, the period from the power-off time to the power-on time (rebooting period) is set to be equal to or shorter than the reference time. Specifically, the rebooting period is set at a few seconds. That is, usually, when the reboot condition is satisfied in response to an update or an abnormality diagnosis serving as a trigger, the power-off duration is equal to or shorter than the reference time. In contrast, when the air conditioning controller  50  after shipment is installed in the building  10  or the installed air conditioning controller  50  is relocated, the air conditioning controller  50  is removed, carried, and installed. For this reason, the power-off duration is usually longer than the reference time. In other words, the reference time is set to be shorter than the time taken to perform work such as relocation. 
     If the calculated power-off duration is longer than the reference time, the processing proceeds to step S 205 , in which the relay unit  71  is switched forcibly to the initial state. As a result, the control command output to the air conditioner  40  after the completion of the boot processing is a control command not to operate. 
     In contrast, if the power-off duration is equal to or shorter than the reference time, the relay related process ends. That is, the forced switching is avoided, and the state of the relay unit  71  remains the same as before the reboot. 
     Referring now to  FIGS.  7 A and  7 B , changes in the signal in the air conditioning controller  50  will be described.  FIG.  7 A  is a timing chart for a relocation of the air conditioning controller  50 .  FIG.  7 B  is a timing chart for an automatic update performed in the air conditioning controller  50 . 
     In the example shown in  FIG.  7 A , the air conditioning controller  50  is removed from the above-described bracket at a time ta. This removal turns off the air conditioning controller  50 . Although the worker should have shut off the air conditioner  40  before removing the air conditioning controller  50 , the worker in the example shown in  FIG.  7 A  has removed the air conditioning controller  50  without a shutoff operation. However, due to the removal, the control command input to the air conditioner  40  is switched from the control command corresponding to the air conditioning operation to the control command corresponding to the stopped state. The operation of the air conditioner  40  is also stopped at the time ta. In the state with the air conditioning controller  50  removed, the relay unit  71  can still output the control command corresponding to the air conditioning operation. That is, only the relay R2 is in the closed state. The air conditioning controller  50  in this state is carried to another room. 
     At a time tb, about 45 minutes after the time ta, the air conditioning controller  50  is fixed to a bracket prepared in the other room. This causes the external power supply to start supplying power to the air conditioning controller  50 , and also causes the CPU  61  of the air conditioning controller  50  to start the boot processing. In the boot processing, the power-off duration of the air conditioning controller  50  is calculated. In the example in  FIG.  7 A , the power-off duration is longer than the reference time (e.g., three minutes), and thus the relay unit  71  is switched forcibly to the initial state during the boot processing. Specifically, each reset coil  77  is energized to bring all the relays R1 to R8 into the open state. As a result, the boot of the air conditioning controller  50  is complete at a time tc, at which the control command input to the air conditioner  40  is the control command corresponding to the stopped state. That is, the air conditioner  40  remains off and avoids an unexpected start of the operation. Also for the first installation of the air conditioning controller  50  in the building  10 , if the power-off duration is longer than the reference time, then the relays R1 to R8 are switched forcibly to the open state as in the example shown in  FIG.  7 A . 
     In the example shown in  FIG.  7 B , the air conditioning controller  50  starts an automatic update at a time td during an air conditioning operation. At a time te after the start of the automatic update, the download and installation of a newly released program are complete, and the air conditioning controller  50  satisfies the reboot condition. At the time te, the CPU  61  performs shutoff processing, turning off the air conditioning controller  50 . At a time tf immediately after the power shutoff, or specifically, when the rebooting period (e.g., a few seconds) has elapsed from the power shutoff, the air conditioning controller  50  is turned on, starting the boot processing of the air conditioning controller  50 . 
     When the air conditioning controller  50  is turned on from the off state using an update as a trigger, the power-off duration is equal to or shorter than the reference time. Accordingly, the forced switching of the relay unit  71  is avoided, and the state of the relay unit  71  remains the same as before the turn-on. The boot of the air conditioning controller  50  is complete at a time tg, restarting the output of a control command to the air conditioner  40 . This control command is the same as before the reboot, or specifically, the control command corresponding to the air conditioning operation. Also for a manual update, the power-off duration is usually equal to or shorter than the reference time, and thus the forced switching of the relay unit  71  is avoided as in the example shown in  FIG.  7 B . 
     The embodiment described in detail above can achieve the following advantageous effects. 
     During work such as the installation or relocation of the air conditioning controller  50 , an unexpected start of the operation of the air conditioner  40  is unfavorable because such a start may interfere with the work and lower the reliability of the air conditioning system  30 . In the present embodiment, when the CPU  61  of the air conditioning controller  50  performs the boot processing of the air conditioning controller  50 , the relay unit  71  is switched forcibly to the initial state to prevent the air conditioner  40  from unexpectedly starting the operation. 
     In contrast, when the boot processing is performed in response to rebooting triggered by an update, the relay unit  71  avoids being switched forcibly to the initial state. This prevents the emission of a snapping sound caused by the movement of the movable terminal  74 . The prevention of the emission of a snapping sound that can easily sound unpleasant for the user can reduce the likelihood that the user will be discomforted, and accordingly the snapping sound is prevented from lowering the degree of user satisfaction. 
     A latching mechanical relay is favorable to, for example, reduce the power consumption of the air conditioning controller  50 . However, the structure cannot eliminate the likelihood that when the air conditioning controller  50  undergoes vibration or other external forces, the external forces will move the movable terminal  74 . Although the effects of external forces could be reduced by carrying the air conditioning controller  50  carefully, such a restriction during the carrying may lower the working efficiency. 
     At the boot of the air conditioning controller  50 , when the power-off duration of the air conditioning controller  50  is longer than the reference time, the boot has likely been triggered by the installation or relocation of the air conditioning controller  50 . Thus, in the present embodiment, when the air conditioning controller  50  is booted, the relay unit  71  is switched to the initial state to suitably prevent the air conditioner  40  from unexpectedly starting the operation. This can suitably eliminate the above-described concern. 
     The forced switching to the initial state is avoided when the power-off duration at the boot of the air conditioning controller  50  is equal to or shorter than the reference time. In other words, the forced switching has an exclusion condition (i.e., a switch avoidance condition). If the condition is satisfied, the state of the relay unit  71  remains the same as before the boot. For example, when the air conditioning controller  50  is rebooted using an update or an attempt to eliminate an abnormal state as a trigger, the above mechanism can suitably prevent the emission of a snapping sound caused by the movement of the movable terminal  74 . A snapping sound can easily sound unpleasant for the user, and thus the prevention of the emission of a snapping sound definitely has technical significance. 
     In the case where the air conditioning controller  50  after shipment is carried to a site of work, or the air conditioning controller  50  is relocated because of, for example, remodeling, the air conditioning controller  50  is booted using the start of the supply of power as a trigger. In contrast, for an update or an attempt to eliminate an abnormal state of the air conditioning controller  50  (in other words, automatic resumption), the air conditioning controller  50  is booted or rebooted without stopping the supply of power. The power-off duration in the former case is longer than the power-off duration in the latter case. Thus, as indicated in the present embodiment, the power-off duration can be compared with the reference time to determine, by the trigger for the boot processing, whether to perform forced switching to the initial state. As a result, improvements in the reliability of the air conditioner (in other words, the safety of the air conditioner) are compatible with the prevention of reductions in user convenience. 
     As indicated in the present embodiment, the current time is stored periodically, enabling the air conditioning controller  50  to roughly calculate the power-off duration without storing the time in response to a power shutoff. This is favorable to simplify the processing at a power shutoff. 
     Other Embodiments 
     It should be noted that the air conditioning controller according to an embodiment of the present disclosure is not limited to the description of the above embodiment. For example, one of the modifications listed below may be made to the above embodiment, and a combination of some or all of the modifications may also be made to the above embodiment.
         In the above embodiment, when the boot processing of the air conditioning controller  50  is performed, the power-off duration of the air conditioning controller  50  is calculated, and the calculated power-off duration is compared with the reference time. Based on the comparison, the air conditioning controller  50  determines whether to switch the relay unit  71  to the initial state. During work such as the installation or relocation of the air conditioning controller  50 , the power supply path from the external power supply to the air conditioning controller  50  is disconnected. In contrast, at an update or automatic recovery from an abnormal state, the power supply path is not disconnected. In view of the above, the components related to the forced switching of the relay unit  71  may be modified as described below.       

     Specifically, the air conditioning controller  50  may include a monitoring circuit that monitors the status of the supply of power from the external power supply. When the supply of power has been shut off before a boot, the relay unit  71  may be switched to the initial state at the boot. In contrast, when the supply of power has not been shut off before a boot, the relay unit  71  may be kept in the same state as before the boot. That is, the relay unit  71  is not switched to the initial state. 
     The power supply monitoring function of the monitoring circuit may be used in combination with the function of calculating the power-off duration. For example, when the power-off duration is longer than the reference time and the supply of power is determined to have been shut off before a boot, the relay unit  71  may be switched to the initial state at the boot. In contrast, when the power-off duration is equal to or shorter than the reference time and the supply of power is determined not to have been shut off before a boot, the relay unit  71  may be kept in the same state as before the boot. That is, the relay unit  71  is not switched to the initial state. Note that for the purpose of reducing the forced switching, when the power-off duration is equal to or shorter than the reference time and the supply of power is determined to have been shut off before a boot or when the power-off duration is longer than the reference time and the supply of power is determined not to have been shut off before a boot, the relay unit  71  may also be kept in the same state as before the boot. Alternatively, for the purpose of enhancing the safety of the air conditioner, when the power-off duration is equal to or shorter than the reference time and the supply of power is determined to have been shut off before a boot or when the power-off duration is longer than the reference time and the supply of power is determined not to have been shut off before a boot, the relay unit  71  may be switched to the initial state at the boot.
         When the air conditioning controller  50  is updated, an update flag indicating the performance of the update (in other words, update information) may be stored into the retaining area of the RAM  63 . The retaining area is an area in which information is held without deletion at booting. When the boot processing performed, the air conditioning controller  50  may determine whether to switch the relay unit  71  to the initial state based on the presence or absence of the update flag. Specifically, with no update flag stored at booting, the relay unit  71  is switched to the initial state. In contrast, with an update flag stored at booting, the relay unit  71  may be kept in the same state as before the boot. Note that the update flag may be deleted when the boot processing is complete.       

     The function of identifying the presence or absence of an update based on an update flag may be used together with the function of calculating the power-off duration. For example, when the power-off duration is longer than the reference time and no update flag is stored, the relay unit  71  may be switched to the initial state at the boot. In contrast, when the power-off duration is equal to or shorter than the reference time and an update flag is stored, the relay unit  71  may be kept in the same state as before the boot. That is, the relay unit  71  is not switched to the initial state. Note that for the purpose of reducing the forced switching, when the power-off duration is equal to or shorter than the reference time and no update flag is stored or when the power-off duration is longer than the reference time and an update flag is stored, the relay unit  71  may also be kept in the same state as before the boot. Alternatively, for the purpose of enhancing the safety of the air conditioner, when the power-off duration is equal to or shorter than the reference time and no update flag is stored or when the power-off duration is longer than the reference time and an update flag is stored, the relay unit  71  may be switched to the initial state at the boot.
         In the above embodiment, although the CPU  61  of the air conditioning controller  50  obtains the current time from the RTC  64 , this is not restrictive. For example, the current time may be obtained from the internet.   The power-off duration indicated in the above embodiment may be measured by any method. For example, the power-off duration may be measured with a timer counter.   In the example described in the above embodiment, the air conditioning controller  50  is rebooted at an update of a program (in other words, software) installed in the air conditioning controller  50  or at automatic recovery from an abnormal state of the air conditioning controller  50 . However, the air conditioning controller  50  may have only one of the update function and the function of automatic recovery from an abnormal state.   In the above embodiment, the air conditioning controller  50  determines the necessity to update a program and performs the update automatically. However, alternatively or additionally, the update may be performed based on an update operation by a user. In the above embodiment, the air conditioning controller  50  determines the presence or absence of an abnormality and recovers automatically. However, alternatively or additionally, the recovery may be performed based on a recovery operation (e.g., a reset operation) by a user.   In the above embodiment, when all the relays R1 to R8 are in the open state, the air conditioner  40  stops operating, or in other words, in the predetermined state, any one of the relays R1 to R8 is in the open state. That is, the predetermined position is a position of the movable terminal  74  out of contact with the stationary terminals  73 . However, the predetermined state and the predetermined position corresponding to the stopped state of the air conditioner  40  are not limited to those in the embodiment. For example, in the predetermined state, all the relays R1 to R8 may be in the closed state. That is, the predetermined position is a position of the movable terminal  74  in contact with the stationary terminals  73 .   The relays R1 to R8 may be any mechanical relays having the latching function. For example, the relays R1 to R8 may be mechanical ratchet relays.   In the above embodiment, after the boot processing is complete, the time is obtained periodically from the RTC  64  and stored. However, the time may be obtained in a different manner as described below. Specifically, the air conditioning controller  50  may include a capacitor unit such as a power capacitor, and when the supply of power from the external power supply is cut off, the capacitor unit may supply power to the CPU  61  for performing shutoff processing. At the time of the shutoff processing, the time may be obtained from the RTC  64 .   The air conditioning controller  50  illustrated in the above embodiment may include a power button that allows the air conditioning controller  50  to be turned on or off. In this case, boot processing triggered by the touch of the power button and automatic boot processing triggered by an event other than the touch of the power button may give different processing results as to whether to perform the forced switching of the relay unit  71  to the initial state. Specifically, when the trigger is the touch of the power button, the relay unit  71  may be switched to the initial state. In contrast, when the trigger is not the touch of the power button, the relay unit  71  may be kept in the same state as before the boot.   The air conditioning controller  50  illustrated in the above embodiment may be used in another air conditioning system such as a room air conditioner or an air cleaner, instead of central air conditioning. The air conditioning controller  50  may not only be used in an air conditioning system for a building, but also may be used in an air conditioning system installed in means of transportation such as a vehicle, a train, and an airplane.
 
&lt;Features Extracted from Above-Described Embodiments&gt;
       

     Features extracted from the above embodiments will now be described in connection with their advantageous effects indicated as appropriate. Hereinafter, although corresponding components in the embodiments are represented within parentheses for ease of understanding, the features are not limited to the specific components in the parentheses. 
     Feature 1. An air conditioning controller (the air conditioning controller  50 ) comprising a mechanical relay (the relay unit  71 ) including: a contact unit (the contact unit  75 ) provided with a movable terminal (the movable terminal  74 ) and a stationary terminal (the stationary terminals  73 ); and a drive coil (the coils  76 ,  77 ) configured to move the movable terminal between a position in contact with the stationary terminal and a position out of contact therewith, wherein the air conditioning controller sends a control signal through the mechanical relay to an air conditioner (the air conditioner  40 ), 
     the air conditioning controller includes 
     a boot processing performing unit (the function of performing the boot processing by the CPU  61 ) configured to perform the boot processing for the air conditioning controller when the air conditioning controller satisfies a boot condition (the start of the supply of power from the external power supply) or a reboot condition (such as an update or an abnormality), and 
     a switching unit (the function of switching the relay unit  71  by the CPU  61 ) configured to energize the drive coil to switch the contact unit between a plurality of states including a predetermined state (the initial state) corresponding to a shutoff control signal for shutting off the air conditioner, 
     the mechanical relay is capable of, even after the end of the energization, holding the movable terminal moved by the energization of the drive coil at the position to which it has moved, and 
     at the boot processing performed by the boot processing performing unit, the switching unit brings the contact unit into the predetermined state when a switch avoidance condition is not satisfied, whereas at the boot processing performed by the boot processing performing unit, the switching unit keeps the contact unit in the same state as before the boot when the switch avoidance condition is satisfied. 
     In other words, an air conditioning controller comprising: a mechanical relay including a movable terminal, a stationary terminal, and a drive coil configured to move the movable terminal between a position in contact with the stationary terminal and a position out of contact with the stationary terminal; a memory; and a processor configured to execute a program stored in the memory, wherein the air conditioning controller sends a control signal through the mechanical relay to an air conditioner, the processor performs boot processing for the air conditioning controller when the air conditioning controller satisfies a boot condition or a reboot condition, the processor energizes the drive coil to move the movable terminal to a predetermined position, the predetermined position being the position in contact with the stationary terminal or the position out of contact with the stationary terminal and the predetermined position corresponding to transmission of a shutoff control signal for shutting off the air conditioner, the mechanical relay holds the movable terminal at the predetermined position after the energization of the drive coil ends, and at the boot processing, the processor moves the movable terminal to the predetermined position when a switch avoidance condition is not satisfied, whereas at the boot processing, the processor does not move the movable terminal to the predetermined position when the switch avoidance condition is satisfied. 
     The above feature enables the contact between the movable terminal and the stationary terminal to be efficiently controlled in accordance with the state of the air conditioning controller. First, when the boot processing for the air conditioning controller is performed with the switch avoidance condition unsatisfied, the mechanical relay (more specifically, the contact unit) included in the air conditioning controller is forcibly switched to the predetermined state (e.g., the initial state) corresponding to the control signal for shutting off the air conditioner. In other words, the movable terminal is moved to the predetermined position (e.g., the initial position) into contact with the stationary terminal. This switching to the predetermined state prevents an unexpected start of the operation of the air conditioner at the boot of the air conditioning controller even if the movable terminal has been moved from the holding position due to vibration or other external forces applied to the air conditioning controller during work such as the installation or the relocation. This is favorable to improve the reliability of the air conditioning system. 
     The above-described forced switching does not take place when the switch avoidance condition is satisfied at the boot of the air conditioning controller. That is, the forced switching has the switch avoidance condition as an exclusion condition, and while this condition is satisfied, the mechanical relay is kept in the same state as before the boot. In other words, the movable terminal is not moved to the predetermined position or brought into contact with the stationary terminal. For example, when a program installed in the air conditioning controller is updated through the internet, and the air conditioning controller reboots using the update as a trigger, the above mechanism enables the mechanical relay to avoid forced switching. That is, the mechanism can prevent the emission of a snapping sound caused by the movement of the movable terminal in response to rebooting triggered by an update. Because the air conditioning controller is often installed in a room (e.g., a wall) for ease of user operations, such a snapping sound can easily sound unpleasant for the user. Thus, the prevention of the emission of a snapping sound definitely has technical significance. For the reasons stated above, the mechanism in this feature improves the reliability of the air conditioning system and prevents an unpleasant snapping sound, contributing to improvements in user satisfaction. 
     Also, constant forced switching may waste power. In an example in which forced switching takes place at rebooting for an update of the program, even when the operating state of the air conditioner (i.e., the control command) is desired to remain the same as before the reboot as shown in  FIG.  7 B , the state is briefly turned to a shutoff by the forced switching and then to the air conditioning operation. However, according to the present feature, the need for forced switching is determined based on the situation, thus preventing unnecessary switching between operating states. That is, the feature can prevent the waste of power caused by unnecessary switching. Additionally, constant forced switching may cause noise due to the drive coil. For example, the described above unnecessary switching may cause noise due to the drive coil. However, according to the present feature, it is possible to prevent unnecessary switching between operating states, thus preventing causing noise. 
     The air conditioning controller may, similarly to rebooting at the update, for example, detect an abnormality by monitoring its own state and reboot when recovering (in other words, resuming) from an abnormal state. If the air conditioning controller reboots by resuming from the abnormal state, the air conditioning controller may avoid forced switching to the predetermined state. Otherwise, the air conditioning controller may perform forced switching to the predetermined state. This can prevent the emission of the above-described snapping sound at rebooting by resuming from the abnormal state. 
     It is noted that the expression “predetermined state” in this feature may be changed to “initial state” and also the expression “at the boot processing performed by the boot processing performing unit, the switching unit brings the contact unit into the predetermined state when a switch avoidance condition is not satisfied, whereas at the boot processing performed by the boot processing performing unit, the switching unit keeps the contact unit in the same state as before the boot when the switch avoidance condition is satisfied” may be changed to the expression “at the boot processing performed by the boot processing performing unit, the switching unit brings the contact unit into the initial state when a resuming condition is satisfied, whereas at the boot processing performed by the boot processing performing unit, the switching unit keeps the contact unit in the same state as before the boot when the resuming condition is not satisfied.” That is, the air conditioning controller detects an abnormal state of the air conditioning controller, and at the boot processing, moves the movable terminal to the predetermined position if resuming from the abnormal state; otherwise, the air conditioning controller does not move the movable terminal to the predetermined position. That is, for resumption from the abnormal state, the mechanical relay is switched to the predetermined state; otherwise, the mechanical relay is not switched to the predetermined state. 
     The air conditioning controller according to this feature may also determine whether the contact unit is in the predetermined state (i.e., the movable terminal is at the predetermined position) in addition to the performance of the boot processing as a condition of determining the switch avoidance condition. 
     Feature 2. The air conditioning controller according to feature 1, in which the boot of the air conditioning controller is complete before the control signal starts being sent through the mechanical relay, and 
     at the boot processing performed by the boot processing performing unit, when the switch avoidance condition is not satisfied, the switching unit switches the contact unit to the predetermined state before the control signal starts being sent, whereas at the boot processing performed by the boot processing performing unit, when the switch avoidance condition is satisfied, the switching unit does not switch the state of the contact unit using the current boot processing as a trigger. 
     According to the above feature, when the switch avoidance condition is not satisfied, the contact unit is switched to the predetermined state before the control signal starts being sent. This switching can appropriately prevent an unexpected start of the operation of the air conditioner even if the movable terminal has been moved from the holding position while the air conditioning controller is powered off. In contrast, when the switch avoidance condition is satisfied, the contact unit is not switched to the predetermined state. This can appropriately prevent the above-described emission of the snapping sound. 
     Feature 3. The air conditioning controller according to feature 1 or 2, in which the air conditioning controller includes a duration determination unit (the function of calculating the power-off duration by the CPU  61 ) configured to, when the boot processing is performed by the boot processing performing unit, determine the power-off duration for which the air conditioning controller has been powered off, and 
     at the boot processing performed by the boot processing performing unit, when the power-off duration determined by the duration determination unit is longer than a preset reference time, the switching unit determines the switch avoidance condition to have been satisfied and brings the contact unit into the predetermined state, whereas at the boot processing performed by the boot processing performing unit, when the power-off duration determined by the duration determination unit is equal to or shorter than or the reference time, the switching unit determines the switch avoidance condition to have been unsatisfied and keeps the contact unit in the same state as before the boot. 
     In other words, the air conditioning controller according to feature 1, wherein when the boot processing is performed, the processor determines a power-off duration for which the air conditioning controller has been powered off, and the switch avoidance condition includes the determined power-off duration being equal to or shorter than a preset reference time. 
     The period of time for which the conditioning controller is powered off varies greatly depending on the situation. For example, in the case where the air conditioning controller after shipment is carried to a site of work, or the air conditioning controller is relocated because of, for example, remodeling, the power-off duration is longer than the power-off duration for an update of the air conditioning controller or automatic resumption from an abnormal state. Thus, as indicated in this feature, the power-off duration can be compared with the reference time to determine, by the trigger for the boot processing, whether to forcibly switch the mechanical relay to the predetermined state. As a result, improvements in the reliability of the air conditioner are compatible with the prevention of reductions in user convenience. 
     Feature 5. The air conditioning controller according to feature 3, in which the power-off duration for the boot processing performed in response to the reboot condition being satisfied is set to be equal to or shorter than the reference time. 
     The above feature allows the switch avoidance condition to be satisfied at rebooting. 
     Feature 6. The air conditioning controller according to any one of feature 3 and feature 5, in which the duration determination unit determines the power-off duration based on a time storage unit (the retaining area of the RAM  63 ) configured to store the current time periodically after the performance of the boot processing, a time obtaining unit (the function of obtaining the time of a boot by the CPU  61 ) configured to obtain the current time at the performance of the boot processing, the time stored in the time storage unit, and the time obtained by the time obtaining unit. 
     As indicated this feature, the current time is stored periodically, enabling the air conditioning controller to roughly calculate the power-off duration without storing the time in response to a power shutoff. This is favorable to simplify the processing at a power shutoff. In addition, this feature eliminates the need for a capacitor unit such as a capacitor used to obtain the time in response to a power shutoff. This is favorable to simplify the electrical structure of the air conditioning controller. 
     The time storage unit may store the current time periodically. The period may be shorter than the reference time. 
     Feature 7. The air conditioning controller according to feature 3, 5, or 6, in which the air conditioning controller includes a monitoring unit (a power line monitoring circuit) configured to monitor the supply of power from the external power supply to the air conditioning controller, and 
     at the boot processing performed by the boot processing performing unit, when the power-off duration determined by the duration determination unit is longer than the reference time and the monitoring unit determines the supply of power to have been shut off before the boot processing, the switching unit determines the switch avoidance condition to have been unsatisfied and brings the contact unit into the predetermined state, whereas at the boot processing performed by the boot processing performing unit, when the power-off duration determined by the duration determination unit is equal to or shorter than the reference time and the monitoring unit determines the supply of power not to have been shut off before the boot processing, the switching unit determines the switch avoidance condition to have been satisfied and keeps the contact unit in the same state as before the boot. 
     In other words, the air conditioning controller according to feature 3, in which the processor monitors supply of power from an external power supply to the air conditioning controller, and the switch avoidance condition includes the determined power-off duration being equal to or shorter than the preset reference time and the supply of power being determined not to have been shut off before the boot processing. 
     Work such as the installation or relocation of the air conditioning controller is likely to increase the power-off duration and expected to briefly shut off the supply of power from the external power supply. Thus, when these two conditions are satisfied, the contact unit may be switched to the predetermined state to appropriately achieve the effect of avoiding an unexpected start of the operation by the air conditioner. When the air conditioning controller is rebooted using an update or recovery from an abnormal state as a trigger, the power-off duration is equal to or near zero and the supply of power is not shut off. Thus, when these two conditions are satisfied, the state of the contact unit may be kept to appropriately achieve the effect of preventing the emission of the above-described snapping sound. 
     Feature 8. An air conditioning controller (the air conditioning controller  50 ) comprising a mechanical relay (the relay unit  71 ) including: a contact unit (the contact unit  75 ) provided with a movable terminal (the movable terminal  74 ) and a stationary terminal (the stationary terminals  73 ); and a drive coil (the coils  76 ,  77 ) configured to move the movable terminal between a position in contact with the stationary terminal and a position out of contact therewith, in which the air conditioning controller sends a control signal through the mechanical relay to an air conditioner (the air conditioner  40 ), 
     the air conditioning controller includes 
     a boot processing performing unit (the function of performing the boot processing by the CPU  61 ) configured to perform the boot processing for the air conditioning controller when the air conditioning controller satisfies a boot condition (the start of the supply of power from the external power supply) or a reboot condition (such as an update or an abnormality), and 
     a switching unit (the function of switching the relay unit  71  by the CPU  61 ) configured to energize the drive coil to switch the contact unit between a plurality of states including a predetermined state (the initial state) corresponding to a shutoff control signal for shutting off the air conditioner, 
     the mechanical relay is capable of, even after the end of the energization, holding the movable terminal moved by the energization of the drive coil at the position to which it has moved, 
     the air conditioning controller includes a monitoring unit (a power line monitoring circuit) configured to monitor the supply of power from the external power supply to the air conditioning controller, and 
     at the boot processing performed by the boot processing performing unit, the switching unit brings the contact unit into the predetermined state when the monitoring unit determines the supply of power to have been shut off before the boot processing, whereas at the boot processing performed by the boot processing performing unit, the switching unit keeps the contact unit in the same state as before the boot when the monitoring unit determines the supply of power not to have been shut off before the boot processing. 
     In other words, an air conditioning controller comprising: a mechanical relay including a movable terminal, a stationary terminal, and a drive coil configured to move the movable terminal between a position in contact with the stationary terminal and a position out of contact with the stationary terminal; a memory; and a processor configured to execute a program stored in the memory, in which the air conditioning controller sends a control signal through the mechanical relay to an air conditioner, the processor performs boot processing for the air conditioning controller when the air conditioning controller satisfies a boot condition or a reboot condition, the processor energizes the drive coil to move the movable terminal to a predetermined position, the predetermined position being the position in contact with the stationary terminal or the position out of contact with the stationary terminal and the predetermined position corresponding to transmission of a shutoff control signal for shutting off the air conditioner, the mechanical relay holds the movable terminal at the predetermined position after energization of the drive coil ends, the processor monitors supply of power from an external power supply to the air conditioning controller, and at the boot processing, the processor moves the movable terminal to the predetermined position when the supply of power is determined to have been shut off before the boot processing, whereas at the boot processing, the processor does not move the movable terminal to the predetermined position when the supply of power is determined not to have been shut off before the boot processing. 
     For work such as the installation or relocation of the air conditioning controller, the supply of power from the external power supply is briefly shut off. Thus, when the supply of power is shut off, the contact unit may be switched to the predetermined state to appropriately achieve the effect of avoiding an unexpected start of the operation by the air conditioner. When the air conditioning controller is rebooted using an update or recovery from an abnormal state as a trigger, the supply of power is not shut off. Thus, when the supply of power is not shut off, the state of the contact unit may be kept to appropriately achieve the effect of preventing the emission of the above-described snapping sound. 
     Feature 9. The air conditioning controller according to feature 3 or feature 5, in which the air conditioning controller includes 
     an update performing unit (the function of performing update processing by the CPU  61 ) configured to update a program stored in the air conditioning controller, and 
     an information storage unit (the retaining area of the RAM  63 ) configured to, when the update performing unit performs the update, store update information (an update flag) indicating the performance of the update, 
     the information storage unit stores the update information before the reboot condition is satisfied at the update and the boot processing performing unit performs the boot processing, and 
     at the boot processing performed by the boot processing performing unit, when the power-off duration determined by the duration determination unit is longer than the reference time and the information storage unit does not store the update information, the switching unit determines the switch avoidance condition to have been unsatisfied and brings the contact unit into the predetermined state, whereas at the boot processing performed by the boot processing performing unit, when the power-off duration determined by the duration determination unit is equal to or shorter than the reference time and the information storage unit stores the update information, the switching unit determines the switch avoidance condition to have been satisfied and keeps the contact unit in the same state as before the boot. 
     In other words, in the air conditioning controller according to feature 3, in which the processor performs an update of the program stored in the memory of the air conditioning controller, when the update is performed, the processor stores update information indicating the performance of the update into the memory before the boot processing is performed in response to the reboot condition being satisfied by the update, and the switch avoidance condition includes the determined power-off duration being equal to or smaller than the preset reference time and the update information being stored in the memory. 
     When the air conditioning controller updates the program, the air conditioning controller is rebooted. At the performance of the update, update information indicating the performance of the update is stored before the boot processing is performed (e.g., before the air conditioning controller is shut down). Only when the power-off duration is longer than the reference time and no update information is stored, the contact unit may be switched to the predetermined state to appropriately achieve the effect of avoiding an unexpected start of the operation by the air conditioner. In contrast, when the power-off duration is equal to or shorter than the reference time and the update information is stored, the state of the contact unit may be kept to appropriately achieve the effect of preventing the emission of the above-described snapping sound. 
     Feature 10. An air conditioning controller (the air conditioning controller  50 ) comprising a mechanical relay (the relay unit  71 ) including: a contact unit (the contact unit  75 ) provided with a movable terminal (the movable terminal  74 ) and a stationary terminal (the stationary terminals  73 ); and a drive coil (the coils  76 ,  77 ) configured to move the movable terminal between a position in contact with the stationary terminal and a position out of contact therewith, in which the air conditioning controller sends a control signal through the mechanical relay to an air conditioner (the air conditioner  40 ), 
     the air conditioning controller includes 
     a boot processing performing unit (the function of performing the boot processing by the CPU  61 ) configured to perform the boot processing for the air conditioning controller when the air conditioning controller satisfies a boot condition (the start of the supply of power from the external power supply) or a reboot condition (such as an update or an abnormality), and 
     a switching unit (the function of switching the relay unit  71  by the CPU  61 ) configured to energize the drive coil to switch the contact unit between a plurality of states including a predetermined state (the initial state) corresponding to a shutoff control signal for shutting off the air conditioner, 
     the mechanical relay is capable of, even after the end of the energization, holding the movable terminal moved by the energization of the drive coil at the position to which it has moved, 
     the air conditioning controller includes 
     an update performing unit (the function of performing update processing by the CPU  61 ) configured to update a program stored in the air conditioning controller, and 
     an information storage unit (the retaining area of the RAM  63 ) configured to, when the update performing unit performs the update, store update information (an update flag) indicating the performance of the update, 
     the information storage unit stores the update information before the reboot condition is satisfied at the update and the boot processing performing unit performs the boot processing, and 
     at the boot processing performed by the boot processing performing unit, the switching unit brings the contact unit into the predetermined state when the information storage unit does not store the update information, whereas at the boot processing performed by the boot processing performing unit, the switching unit keeps the contact unit in the same state as before the boot when the information storage unit stores the update information. 
     In other words, an air conditioning controller comprising: a mechanical relay including a movable terminal, a stationary terminal, and a drive coil configured to move the movable terminal between a position in contact with the stationary terminal and a position out of contact with the stationary terminal; a memory; and a processor configured to execute a program stored in the memory, in which the air conditioning controller sends a control signal through the mechanical relay to an air conditioner, the processor performs boot processing for the air conditioning controller when the air conditioning controller satisfies a boot condition or a reboot condition, the processor energizes the drive coil to move the movable terminal to a predetermined position, the predetermined position being the position in contact with the stationary terminal or the position out of contact with the stationary terminal and the predetermined position corresponding to transmission of a shutoff control signal for shutting off the air conditioner, the mechanical relay holds the movable terminal at the predetermined position after energization of the drive coil ends, the processor performs an update of the program stored in the memory of the air conditioning controller, when the update is performed, the processor stores update information indicating the performance of the update into the memory before the boot processing is performed in response to the reboot condition being satisfied by the update, and at the boot processing, the processor moves the movable terminal to the predetermined position when the update information is not stored in the memory, whereas at the boot processing, the processor does not move the movable terminal to the predetermined position when the update information is stored in the memory. 
     When the air conditioning controller updates the program, the air conditioning controller is rebooted. At the performance of the update, update information indicating the performance of the update is stored before the boot processing is performed (e.g., before the air conditioning controller is shut down). When no update information is stored, the contact unit may be switched to the predetermined state to appropriately achieve the effect of avoiding an unexpected start of the operation by the air conditioner. In contrast, when the update information is stored, the state of the contact unit may be kept to appropriately achieve the effect of preventing the emission of the above-described snapping sound. 
     Feature 11. The air conditioning controller according to any one of features 1 to 10, in which the mechanical relay includes a stopper (the stopper  78 ) configured to come into contact with the movable terminal moved to the out-of-contact position by the energization of the drive coil, and prevent the movable terminal from moving further. 
     With the stopper provided to come into contact with the movable terminal moved to the out-of-contact position, when the movable terminal and the stopper come into contact with each other, a snapping sound may be emitted. The air conditioning controller including the stopper can appropriately reduce the chance of snapping sound emission. Note that the stopper may be a stationary terminal provided at a different signal line from the described above signal line. 
     Feature 12. An air conditioning system comprising the air conditioner and the air conditioning controller according to any one of features 1 to 11. 
     The air conditioning system according to this feature can improve the reliability of the air conditioning system and prevent an unpleasant snapping sound, contributing to improvements in user satisfaction.