Abstract: A hot water supply system includes a hot water supply device which can be connected to an external communication network via a communication repeater, and a server. The server obtains, in pairing processing of associating a mobile terminal device which can remotely control the hot water supply device with the hot water supply device, identification information of a communication repeater to which the mobile terminal device is connected, and stores the identification information along with pairing information. Besides, the server performs control to determine conditions of the remote control based on whether the identification information of the communication repeater stored in association with the hot water supply device being a remote operation destination matches identification information of the communication repeater received from the mobile terminal device in the communication, when the communication of the remote control is received from the mobile terminal device.

Abstract: In a communication system, a management server stores information about a hot water systems for each hot water system on the basis of individual identification information, and stores the individual identification information of a plurality of identification target machines for each hot water system. When the individual identification information of the plurality of identification target machines is received from a relay device, the management server collates the received individual identification information with the stored individual identification information.

Abstract: A hot water supply system includes a hot water supply device which can be connected to an external communication network via a communication repeater, and a server. The server obtains, in pairing processing of associating a mobile terminal device which can remotely control the hot water supply device with the hot water supply device, identification information of a communication repeater to which the mobile terminal device is connected, and stores the identification information along with pairing information. Besides, the server performs control to determine conditions of the remote control based on whether the identification information of the communication repeater stored in association with the hot water supply device being a remote operation destination matches identification information of the communication repeater received from the mobile terminal device in the communication, when the communication of the remote control is received from the mobile terminal device.

Abstract: Provided are a hot water using system and a relay device used therein. The hot water using system includes: a hot water server that is one example of hot water using equipment; a relay device that communicates with the hot water server and communicates with a management server via a communication network, the relay device having a communication setting switch (operation switches) that is placed outdoor and is operated when communication setting for communicating with the communication network is performed; and a switching part that is provided separately from the relay device and switches an operation through the communication setting switch between activation and inactivation.