Hot-water supply system

A hot-water supply system comprising:

• a hot-water tank,
• a hot-water supply pipe connected to the hot-water tank,
• a water supply pipe connected to the hot-water tank and the hot-water supply pipe,
• a heating unit configured to heat the water in the hot-water tank,
• a water current sensor configured to detect a water current in the water supply pipe,
• a hot-water flow regulation valve disposed between a joint location of the hot-water supply pipe to the hot-water tank and a joint location of the hot-water supply pipe to the water supply pipe for regulating an opening degree of the hot-water supply pipe,
• a water flow regulation valve disposed between a joint location of the water supply pipe to the hot-water tank and a joint location of the water supply pipe to the hot-water supply pipe for regulating an opening degree of the water supply pipe,
• a hot-water storage temperature sensor configured to detect a temperature of the water in the hot-water tank,
• a hot-water supply apparatus disposed in the midway of the hot-water supply pipe at a downstream side of the joint location between the hot-water supply pipe and the water supply pipe for heating the water flowing through the hot-water supply pipe,
• a hot-water supply temperature setting unit configured to set a desired hot-water supply temperature, and
• a temperature regulation control unit configured to perform a temperature regulation control via mixing by prohibiting the heating by the hot-water supply apparatus and regulating a mixing ratio of the hot-water supplied from the hot-water tank to the hot-water supply pipe and the water supplied from the water supply pipe to the hot-water supply pipe by the hot-water flow regulation valve and the water flow regulation valve so as to supply the hot-water having the desired hot-water supply temperature from the hot-water supply pipe when the water current is detected by the water current sensor and the detection temperature by the hot-water storage temperature sensor is higher than a hot-water shortage determination temperature set according to the desired hot-water supply temperature, and to perform a temperature regulation control via heating by permitting the heating by the hot-water supply apparatus so as to supply the hot-water having the desired hot-water supply temperature from the hot-water supply pipe when the water current is detected by the water current sensor and the detection temperature by the hot-water storage temperature sensor is equal to or lower than the hot-water shortage determination temperature,
• wherein the hot-water supply system further comprises a sterilization processing unit configured to perform a sterilization process by heating the hot-water in the hot-water tank equal to or higher than a sterilization temperature set according to an assumption that bacteria in the hot-water tank will be sterilized under such temperature by the heating unit when the detection temperature by the hot-water storage temperature sensor has been equal to or lower than a re-heating determination temperature set according to an assumption that the reproduction of bacteria in the hot-water tank will progress under such temperature over at least a predefined re-heating determination time,
• when the detection temperature by the hot-water storage temperature sensor has been equal to or lower than a determination temperature for prohibiting the use of hot-water in the hot-water tank which is set lower than the re-heating determination temperature over at least a determination time for prohibiting the use of hot-water in the hot-water tank set equal to or longer than the re-heating determination time, the temperature regulation control unit performs only the temperature regulation control via heating while maintaining the hot-water flow regulation valve in a closed state regardless of the detection temperature by the hot-water storage temperature sensor.