Patent Publication Number: US-7714713-B2

Title: Relay apparatus

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a relay apparatus which relays communication between a water heater main body and a radio remote control unit, and more particularly, to a relay apparatus which establishes wire communication with the water heater main body and which establishes radio communication with the radio remote control unit. 
   2. Description of the Related Art 
   As a conventional water heater, since an indoor wiring operation of a remote control unit is unnecessary and installation is easy, and besides a remote control unit can easily be provided for an already installed water heater, there is a water heater in which a relay apparatus (master set) is connected to an outdoor water heater main body by a wire, and the water heater main body is remote-operated by radio communication of a radio remote control unit (slave set) through the relay apparatus from a room (e.g., Japanese Patent Application Laid-open No. 2005-328295). 
   A plurality of radio remote control units can be installed in a bathroom, a kitchen and the like, wherein a master set ID of the relay apparatus is registered in each radio remote control unit, and a slave set ID of each radio remote control unit is registered in the relay apparatus. With this configuration, radio communication between the radio remote control units and the relay apparatus is performed without causing interference with other devices. 
   The radio remote control unit is usually used for operating the water heater. In addition to this, the radio remote control unit can also display maintenance information of the water heater main body on a display section by specifying and operating a switch at the time of maintenance operation of the water heater main body (e.g., Japanese Patent Application Laid-open No. HEI09-280557). Such a radio remote control unit can freely be taken outside. Therefore, an operator of the maintenance operation takes the radio remote control unit outside, displays the maintenance information at an outside installation place of the water heater main body, and the operator can carry out a predetermined maintenance operation while seeing the maintenance information. 
   However, if none of the radio remote control units is registered in the relay apparatus, the maintenance information of the water heater main body is not displayed. In a case where the water heater main body is set outside of a house, the relay apparatus is connected to the water heater main body, but none of the radio remote control units is ID-registered, the maintenance information of the water heater main body cannot be seen for e.g. inspection on setting condition of the water heater main body. 
   Even if at least one of the radio remote control units is registered in the relay apparatus, the maintenance information of the water heater main body cannot be seen when no one stays in the house or the radio remote control unit is out of order or the battery is dead. If the operator cannot see the maintenance information of the water heater main body, he or she cannot carry out the maintenance operation of the water heater main body. 
   Thus, in preparation for such cases, another radio remote control unit can be separately prepared for maintenance operation. This radio remote control unit is ID-registered in the relay apparatus, and maintenance information of the water heater main body is obtained by operating this radio remote control unit. However, it is very troublesome to prepare another radio remote control unit only for the maintenance operation and to ID-register the radio remote control prepared for the maintenance operation. Further, it is necessary to delete the ID registration of the radio remote control in the relay apparatus after the maintenance operation is completed. Furthermore, where the operator doesn&#39;t know whether or not a radio remote control unit is used during the maintenance operation is carried out, it is uneconomical to separately prepare the radio remote control unit for the maintenance operation, which leads to an increase in the maintenance cost. Even when the radio remote control unit is separately prepared, if the full registrable number of radio remote control units are all registered in the relay apparatus, another radio remote control unit cannot be further ID-registered. Therefore, the operator cannot see the maintenance information in this case. 
   SUMMARY OF THE INVENTION 
   The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a relay apparatus capable of easily obtaining maintenance information from a water heater main body without using a radio remote control unit. 
   According to a first aspect of the invention, there is provided a relay apparatus for relaying communication between a water heater main body and a radio remote control unit, comprising: 
   a switch section for setting an address of the radio remote control unit; 
   a control section for establishing communication with the water heater main body and commanding and controlling to read out maintenance information stored in the water heater main body, assuming that input information at the switch section is a request from the radio remote control unit having an address which was set by operation of the switch section; and 
   a display section for displaying the maintenance information received from the water heater main body. 
   Other objects, features and advantages of the present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram showing a structure of a radio communication system including a relay apparatus according to an embodiment of the present invention; 
       FIGS. 2A and 2B  are plan views showing outward appearance of the relay apparatus and a radio remote control unit according to the embodiment, wherein  FIG. 2A  shows the radio remote control unit and  FIG. 2B  shows the relay apparatus; and 
       FIG. 3  is a flowchart showing operation procedure when maintenance information is displayed on the relay apparatus according to the embodiment. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   As shown in  FIG. 1 , a relay apparatus  1  according to an embodiment of the present invention is used for a radio communication system in a water heater. The relay apparatus  1  performs wire communication with a water heater main body  3  outside the house and performs radio communication with radio remote control unit  5  in the house as well, and relays the radio communication of the radio remote control unit  5  which remotely operates the water heater main body  3 . 
   The water heater main body  3  includes a burner  31 , a heat exchanger  32 , an air supply fan  33 , an electronic control unit  2  and the like. The burner  31  is provided with an igniter  71  for ignition, and a flame rod  72  for detecting the ignition. The burner  31  has a gas supply passage G, and the gas supply passage G is provided with a gas amount adjusting valve  73  for adjusting the amount of gas to be supplied, and an interruption valve  74  for opening and closing the gas supply passage G. A water supply passage W 1  for tap water is connected to an upstream side of the heat exchanger  32 , and a hot water supply passage W 2  is connected to a downstream side of the heat exchanger  32 . The water supply passage W 1  is provided with a water amount sensor S 1  for detecting an outgoing hot water amount, and a hot water temperature sensor S 2  for detecting hot water temperature. The hot water supply passage W 2  is provided with an outgoing hot water temperature sensor S 3  for detecting outgoing hot water temperature, and a flow rate adjusting valve  75  for adjusting an outgoing hot water amount. A faucet  34  for switching between the opening and closing of the valve is connected to a terminal end of the hot water supply passage W 2 . 
   The electronic control unit  2  which controls various operations of the water heater main body  3  is connected with the igniter  71 , the flame rod  72 , the gas amount adjusting valve  73 , the interruption valve  74 , the water amount sensor S 1 , the hot water temperature sensor S 2 , the outgoing hot water temperature sensor S 3 , the flow rate adjusting valve  75  and the air supply fan  33 . A storing unit M is connected to the electronic control unit  2 . Maintenance information including setting conditions of the water heater main body  3  and operational history are stored in the storing unit M. The storing unit M contains an EEPROM or the like, and the maintenance information is read and rewritten by control of the electronic control unit  2 . Examples of the maintenance information are setting conditions such as model type, kinds of gas to be applied, hot water supply ability, set hot water supply temperature, set number of rotation of fan, and set flow rate, and combustion time, hot water temperature, outgoing hot water temperature, operational history such as trouble history. The electronic control unit  2  is provided with a communication circuit (not shown) and is connected to the relay apparatus  1  through a wire communication line  6 , and delivers various information to and from the relay apparatus  1  through wire communication. 
   The radio remote control unit  5  includes a remote control unit radio communication circuit  50  which performs radio communication with the relay apparatus  1 , a remote control unit switch section  51  which remotely operates the water heater main body  3 , a remote control unit display section  52  which displays information such as operational information at the remote control unit switch section  51  and driving information of the water heater main body  3 , a remote control unit control section  53  which controls various operations of the radio remote control unit  5 , and a remote control unit memory  54  for storing a slave set ID of its own and a master set ID of the relay apparatus  1 . 
   As an outward appearance structure of the radio remote control unit  5 , as shown in  FIG. 2A , the radio remote control unit  5  includes a driving switch  55  with respect to the water heater main body  3 , an UP switch  56  and a DOWN switch  57  for setting the hot water supply temperature, a priority switch  58  which has precedence over other radio remote control units  5  for setting the hot water supply temperature, and a liquid crystal panel  59  for displaying the hot water supply temperature and the driving state of the water heater main body  3 . The driving switch  55 , the UP switch  56 , the DOWN switch  57 , the priority switch  58  and the like constitute the remote control unit switch section  51 . The liquid crystal panel  59  constitutes the remote control unit display section  52 . During the maintenance operation, the remote control unit switch section  51  of the radio remote control unit  5  functions as a special switch, and the maintenance information of the water heater main body  3  is displayed on the remote control unit display section  52 . 
   The relay apparatus  1  can perform data communication with the maximum four radio remote control units  5 . The relay apparatus  1  includes a wire communication circuit  10  which performs wire communication with the water heater main body  3 , a radio communication circuit  11  which performs radio communication with the radio remote control unit  5 , a switch section  12  for registering the radio remote control unit  5 , a display section  13  for displaying the registration state of the radio remote control unit  5  and maintenance information, a control section  14  for controlling various operations of the relay apparatus  1 , and a memory  15  for storing a master set ID of its own and a slave set ID of the radio remote control unit  5 . 
   As an outward appearance structure of the relay apparatus  1 , as shown in  FIG. 2B , the relay apparatus  1  includes a lid  4  which is pivotally supported by an upper portion of the relay apparatus  1  for opening and closing a front surface of the relay apparatus  1 , a registration switch  16  for registering the radio remote control units  5 , registration clear switches  17   a  to  17   d  for deleting the registration of the radio remote control units  5  one by one, registration LEDs  18   a  to  18   d  for indicating a registration state of the radio remote control unit  5 , and a display panel  19  for displaying the maintenance information. The registration switch  16  and the registration clear switches  17   a  to  17   d  constitute the switch section  12 . The registration LEDs  18   a  to  18   d  and the display panel  19  constitute the display section  13 . 
   In the relay apparatus  1  also, during the maintenance operation, the switch section  12  functions as a special switch, and the maintenance information of the water heater main body  3  is displayed on the display section  13  (display panel  19 ). For example, the registration clear switches  17   a  to  17   d  individually delete the registration of the slave set ID of each of the radio remote control units  5 , but during the maintenance operation, the registration clear switches  17   a  to  17   d  also function as special switches for displaying the maintenance information of the water heater main body  3  on the display section  13  by performing specifying operation. 
   As pairing processing for mutually registering IDs between the relay apparatus  1  and the radio remote control unit  5 , for example, an installation operator of the water heater main body  3  operates the registration switch  16  of the relay apparatus  1 , operates the driving switch  55  of an unregistered radio remote control unit  5 . With this, a master set ID and a slave set ID are transmitted and received between the relay apparatus  1  and the radio remote control unit  5 . Then, the relay apparatus  1  and the radio remote control unit  5  recognize their mutual communication partners, the master set ID of the relay apparatus  1  is registered in the radio remote control unit  5 , and the slave set ID of the radio remote control unit  5  as the communication partner is registered in the relay apparatus  1 . Hence, the ID registration between the radio remote control unit  5  and the relay apparatus  1  is completed, and thereafter, radio communication can be established between them as the communication partners, and the radio remote control unit  5  can remotely operate the water heater main body  3  through the relay apparatus  1 . Also, various information of the water heater main body  3  can be displayed on the radio remote control unit  5 . 
   If the radio remote control unit  5  turns the driving switch  55  ON, a currently set hot water supply temperature or the like in the water heater main body  3  is displayed on the liquid crystal panel  59  by data communication including the slave set ID through the relay apparatus  1 , and the set hot water supply temperature of the water heater main body  3  can be changed to a desired temperature by turning the priority switch  58  ON and by switching operation of the UP switch  56  and the DOWN switch  57 . When the faucet  34  is opened, hot water at the hot water supply temperature, which has been set by the radio remote control unit  5 , flows from the outgoing hot water opening by the operational control of the water heater main body  3 . 
   Not only is the radio remote control unit  5  used for normal use of the hot water supply operation, but also the maintenance information of the water heater main body  3  is displayed on the liquid crystal panel  59  thereof by radio data communication including the slave set ID through the relay apparatus  1  during the maintenance operation. For example, in the ON state of the driving switch  55 , if specifying operation in which the UP switch  56  and the DOWN switch  57  are pressed simultaneously is performed, an indication of the liquid crystal panel  59  (remote control unit display section  52 ) is switched to a maintenance mode, the maintenance information is transmitted from the water heater main body  3  to the radio remote control unit  5  by the radio data communication including the slave set ID through the relay apparatus  1 , and the maintenance information is displayed on the liquid crystal panel  59 . In this state, by appropriately operating the UP switch  56  and the DOWN switch  57 , various maintenance information are successively displayed on the liquid crystal panel  59 . 
   Next, a case in which the maintenance information is displayed by the relay apparatus  1  will be described. 
   The relay apparatus  1  relays communication between the radio remote control unit  5  and the water heater main body  3 , and registers the radio remote control unit  5  and deletes the registration. The relay apparatus  1  also has a function to display the maintenance information of the water heater main body  3  like the radio remote control unit  5 . 
   As shown in  FIG. 3 , to display the maintenance information of the water heater main body  3  using the relay apparatus  1 , a specifying operation of the relay apparatus  1  is first performed (S 1 ) to switch the relay apparatus  1  from its normal mode to a maintenance display mode. For example, if the specifying operation in which any two of the registration clear switches  17   a  to  17   d  are pressed simultaneously is performed, the normal mode is switched to the maintenance display mode in the relay apparatus  1 . Then, the registration clear switches  17   a  to  17   d  become the special switches (a selecting button  17   a , a determining button  17   b , an advancing button  17   c  and a returning button  17   d ) for displaying the maintenance information, and display of the display panel  19  is activated. 
   At the same time, registration information of the radio remote control unit  5  in the memory  15  is recognized, and if no radio remote control unit  5  is registered in the relay apparatus  1  (i.e. No in S 2 ), the display panel  19  displays an input-waiting screen of a vacant address (slave set ID) of the radio remote control unit  5 . The selecting button  17   a  is operated to select a vacant address of the radio remote control unit  5 , the determining button  17   b  is operated for determination to input the vacant address of the radio remote control unit  5 , i.e. an unregistered slave set ID to the relay apparatus  1 . For example, the slave set ID is a five-digit code including numbers, alphabets and symbols, and inherent slave set ID is previously given to each radio remote control unit  5 . In this case, however, since an actual radio remote control unit  5  does not exist, the operator can determine any slave set ID at will. A slave set ID to be inputted as a vacant address of the radio remote control unit  5  is effective only during the maintenance display mode, and the slave set ID serves as an authorization key for accessing the water heater main body  3 . 
   Therefore, if the vacant address of the radio remote control unit  5  is inputted by the determining button  17   b , the control section  14  of the relay apparatus  1  controls such that wire data for displaying the maintenance information is transmitted to the water heater main body  3  while recognizing the information inputted from the determining button  17   b  as a request from a virtual radio remote control unit  5  which is assumed by the vacant address (S 3 ). Then, the water heater main body  3  which received this request reads the maintenance information from the storing unit M by the control of the electronic control unit  2 , and transmits the maintenance information to the relay apparatus  1 . When the relay apparatus  1  receives data of the maintenance information from the water heater main body  3  (S 5 ), the relay apparatus  1  displays the maintenance information on the display panel  19  of the relay apparatus  1  (S 6 ). At this time, in the relay apparatus  1 , the advancing button  17   c  and the returning button  17   d  which now functions as the special switches are operated, the maintenance information is appropriately displayed on the display panel  19 . The maintenance information displayed on the display panel  19  may also be provided as Japanese or English character information in addition to the numbers, symbols and codes. 
   As described above, when a radio remote control unit  5  is not registered in the relay apparatus  1 , a vacant address of the radio remote control unit  5  (slave set ID of an unregistered radio remote control unit  5 ) is inputted to the relay apparatus  1  to have the radio remote control unit  5  assumed to be ID-registered in the relay apparatus  1 . With this, the maintenance information of the water heater main body  3  is displayed on the display panel  19  of the relay apparatus  1  as a request from the virtual radio remote control unit  5 . By this operation, even if individual information such as an address of a single radio remote control unit  5  has not been registered in the relay apparatus  1 , the maintenance information of the water heater main body  3  can be displayed and seen in the relay apparatus  1 . Thus, the operator can easily and swiftly see the maintenance information as compared with a case in which a separately prepared radio remote control unit  5  is ID-registered in the relay apparatus  1  to obtain the maintenance information of the water heater main body  3 . 
   When at least one radio remote control unit  5  is registered in the relay apparatus  1  (i.e. Yes in S 2 ), if the specifying operation for displaying the maintenance information is performed, the display panel  19  displays an input-waiting screen for registered address of the registered radio remote control unit  5 . At this time, a slave set ID registered in the memory  15  may be displayed on the display panel  19  as a registered address. A registered address of the registered radio remote control unit  5  is selected by operating the selecting button  17   a , and the registered address of a specific radio remote control unit  5 , i.e., the registered slave set ID is inputted by operating the determining button  17   b . The registered slave set ID of the radio remote control unit  5  to be inputted is effective only during the maintenance display mode, and the registered slave set ID serves as an authorization key for accessing the water heater main body  3 . 
   When a registered address of a specific radio remote control unit  5  is inputted by the determining button  17   b , the control section  14  of the relay apparatus  1  performs control such that wire data for displaying the maintenance information is transmitted to the water heater main body  3  while recognizing the information inputted from the determining button  17   b  as a request from the radio remote control unit  5  of the registered address (S 4 ). The water heater main body  3  which receives this request reads maintenance information from the storing unit M by the control of the electronic control unit  2 , and transmits the maintenance information to the relay apparatus  1 . Then, when the relay apparatus  1  receives the maintenance information from the water heater main body  3 , the relay apparatus  1  displays the maintenance information on the display panel  19  of the relay apparatus  1  (S 6 ). At this time, in the relay apparatus  1 , desired maintenance information is appropriately displayed on the display panel  19  by operating the advancing button  17   c  and the returning button  17   d  which now function as the special switches. 
   In this manner, even when the radio remote control unit  5  is registered in the relay apparatus  1 , the registered address of the registered radio remote control unit  5  (slave set ID of the registered radio remote control unit  5 ) is inputted to the relay apparatus  1 , and the maintenance information of the water heater main body  3  is displayed on the display panel  19  of the relay apparatus  1  as a request from the registered radio remote control unit  5 . Hence, even when no one stays in the house or the radio remote control unit  5  is out of order or the battery is dead and thus the indoor radio remote control unit  5  cannot be used, maintenance information of the water heater main body  3  can be displayed in the relay apparatus  1  and can be seen. Thus, the operator can easily and swiftly see the maintenance information as compared with a case in which a separately prepared radio remote control unit  5  is ID-registered in the relay apparatus  1  to obtain the maintenance information of the water heater main body  3 . Thus, the maintenance operation is not hindered. 
   According to the above embodiment, in the relay apparatus  1  which relays the communication between the radio remote control unit  5  and the water heater main body  3 , maintenance information of the water heater main body  3  is displayed. With this configuration, when none of the radio remote control unit  5  has been registered in the relay apparatus  1  or when the indoor radio remote control unit  5  cannot be used for any reason, an operator of a maintenance operation can easily see the maintenance information in relay apparatus  1  without depending upon the radio remote control unit  5 . Thus, the maintenance operation is not hindered. 
   Since the relay apparatus  1  is installed near the water heater main body  3 , the operator can see the maintenance information of the water heater main body  3  near the water heater main body  3 . Thus, the maintenance operation can be carried out efficiently. 
   Therefore, the operator can reliably see the maintenance information in the relay apparatus  1  irrespective of presence or absence of the radio remote control unit  5  and as a result, inspection of the setting conditions of the water heater main body  3  installed outdoor and inspection at the time of the maintenance operation of the water heater main body  3  can reliably and smoothly be carried out. 
   Other Embodiments 
   1) In the above embodiment, when no radio remote control unit  5  is ID-registered in the relay apparatus  1 , a vacant address of an unregistered radio remote control unit  5  is inputted. Alternatively, the control section may be performed such that when at least one vacancy for an unregistered radio remote control unit exists in the relay apparatus  1 , a vacant address of the unregistered radio remote control unit  5  is inputted to the relay apparatus  1  and maintenance information is displayed on the display panel  19  of the relay apparatus  1 . 
   That is, the control section may be performed such that when radio remote control units  5  are ID-registered in the relay apparatus  1  but not all the registrable number of radio remote control units  5  are registered in the relay apparatus  1 , maintenance information is displayed on the display panel  19  of the relay apparatus  1  by inputting a vacant address of an unregistered radio remote control unit  5  or by inputting a registered address of the registered radio remote control unit  5 . 
   2) The control section may be performed such that only when at least one vacancy for an unregistered radio remote control unit  5  exists in the relay apparatus  1 , a vacant address of the unregistered radio remote control unit  5  is inputted to the relay apparatus  1  and maintenance information is displayed on the display panel  19  of the relay apparatus  1 . 
   3) The control section may be performed such that only when at least one radio remote control unit  5  is ID-registered in the relay apparatus  1 , an address of the registered radio remote control unit  5  is inputted to the relay apparatus  1  and the maintenance information is displayed on the display panel  19  of the relay apparatus  1 . 
   4) The registration clear switches  17   a  to  17   d  of the relay apparatus  1  function as special switches by a specifying operation for displaying the maintenance information, but the switches used exclusively for displaying the maintenance information may be provided on the relay apparatus  1 . 
   5) The display panel  19  of the relay apparatus  1  displays maintenance information, but the display panel  19  may also display information such as operation information of the radio remote control unit  5  and operational information of the water heater main body  3  obtained by relay of communication between the radio remote control unit  5  and the water heater main body  3 , and various information (e.g., maintenance manual information) obtained by connecting the relay apparatus  1  to an external line (e.g., telephone line or the Internet line). 
   6) The relay apparatus  1  may be constituted such that if the switch section  12  is operated for displaying the maintenance information (e.g., specifying operations of the registration clear switches  17   a  to  17   d ), a slave set ID to be an address of the radio remote control unit  5  is automatically set, and the relay apparatus  1  establishes data communication with the water heater main body  3 . 
   In this case, as a slave set ID to be used, a slave set ID to be a vacant address of a virtual radio remote control unit  5  may always be set automatically, or a slave set ID may be set in order of desired priority. For example, the control section  14  may be constituted such that when a radio remote control unit  5  for kitchen and a radio remote control unit  5  for bath are registered in the relay apparatus  1 , a slave set ID (address) of the radio remote control unit  5  for kitchen is automatically set by priority, and when no radio remote control unit  5  is registered in the relay apparatus  1 , a slave set ID to be a vacant address of a virtual radio remote control unit  5  is automatically set. The vacant address of the virtual radio remote control unit  5  may be set at random in the control section  14  of the relay apparatus  1 , or may previously be registered in the memory  15 . 
   With this configuration, an operator need not bother inputting directly an address of the radio remote control unit  5 , and maintenance information can easily and swiftly be displayed on the relay apparatus  1 . 
   As described in detail above, according to a first aspect of the invention, there is provided a relay apparatus for relaying communication between a water heater main body and a radio remote control unit, comprising: 
   a switch section for setting an address of the radio remote control unit; 
   a control section for communicating with the water heater main body and commanding and controlling to read out maintenance information stored in the water heater main body, assuming that input information at the switch section is a request from the radio remote control unit having an address which was set by operation of the switch section; and 
   a display section for displaying the maintenance information received from the water heater main body. 
   In the configuration above, the address of the radio remote control unit may be automatically set by operating the switch section, may be manually set by operating the switch section, or may be set by selecting an address of a registered radio remote control unit displayed by operating the switch section. 
   According to the above configuration, by using the address of the radio remote control unit, the relay apparatus which relays the communication between the radio remote control unit and the water heater main body acquires maintenance information stored in the water heater main body, and maintenance information of the water heater main body is displayed on the display of the relay apparatus. Therefore, an operator of a maintenance operation can easily see the maintenance information in relay apparatus  1  without depending upon the radio remote control unit. Thus, the maintenance operation is not hindered. 
   Since the relay apparatus is installed near the water heater main body, the operator can see the maintenance information of the water heater main body near the water heater main body. Thus, the maintenance operation can be carried out efficiently. 
   In the relay apparatus above, when the radio remote control unit is not registered in the relay apparatus, the address of the radio remote control unit which is set by operation of the switch section may be a vacant address of the radio remote control unit. 
   According to the above configuration, even if individual information of even a single radio remote control unit has not been registered in the relay apparatus, the maintenance information of the water heater main body can be displayed and seen in the relay apparatus. Thus, the operator can easily and swiftly see the maintenance information as compared with a case in which a separately prepared radio remote control unit is ID-registered in the relay apparatus to obtain the maintenance information of the water heater main body. Thus, the maintenance operation is not hindered. 
   In the relay apparatus above, when the radio remote control unit is registered in the relay apparatus, the address of the radio remote control unit which is set by operation of the switch section may be a registered address of the radio remote control unit. 
   According to the above configuration, even when no one stays in the house or the radio remote control unit is out of order or the battery is dead and thus the indoor radio remote control unit cannot be used, maintenance information of the water heater main body can be displayed in the relay apparatus and can be seen. Thus, the operator can easily and swiftly see the maintenance information as compared with a case in which a separately prepared radio remote control unit is ID-registered in the relay apparatus to obtain the maintenance information of the water heater main body. Thus, the maintenance operation is not hindered. 
   Therefore, according to the relay apparatus provided by the invention, the operator can reliably see the maintenance information in the relay apparatus irrespective of presence or absence of the radio remote control unit and as a result, inspection of the setting conditions of the water heater main body installed outdoor and inspection at the time of the maintenance operation of the water heater main body can reliably and smoothly be carried out. 
   The present application claims priority based on a Japanese Patent Application No. 2006-164472 filed on Jun. 14, 2006, the content of which is hereby incorporated by reference in its entirely. 
   Although the present invention has been described in detail, the foregoing descriptions are merely exemplary at all aspects, and do not limit the present invention thereto. It should be understood that an enormous number of unillustrated modifications may be assumed without departing from the scope of the present invention.