Water heating apparatus and water heating system

Abstract

In an immediate hot water supply operation mode in which a circulation pump is activated while a hot water supply faucet is closed, a water heating apparatus forms an immediate hot water supply circulation path by an inner path and an outer path as being combined, the inner path including a heating mechanism including a combustion mechanism and a heat exchanger, the outer path bypassing the hot water supply faucet outside the water heating apparatus. The outer path includes a crossover valve. In the immediate hot water supply operation mode, a controller introduces intermittent combustion to control a detection temperature detected by the temperature sensor to a set temperature. In intermittent combustion, a minimum combustion state and a combustion stop state are alternately provided. In the minimum combustion state, a quantity of heat output from the combustion mechanism is reduced to a minimum value.

What is claimed is: 
     
         1 . A water heating apparatus that outputs hot water to a hot water supply faucet, the water heating apparatus comprising:
 a heating mechanism including a combustion mechanism;   an inner path,
 in an immediate hot water supply operation mode in which a circulation pump arranged inside or outside of the water heating apparatus is activated while the hot water supply faucet is closed, the inner path forming an immediate hot water supply circulation path through which fluid passes through the heating mechanism, as being combined with an outer path, the outer path bypassing the hot water supply faucet on outside of the water heating apparatus; 
   a first temperature detector that detects a fluid temperature upstream from the heating mechanism in the immediate hot water supply circulation path;   a second temperature detector that detects a fluid temperature downstream from the heating mechanism in the immediate hot water supply circulation path;   a flow rate detector that detects a circulation flow rate in the immediate hot water supply circulation path; and   a controller that controls the heating mechanism and the circulation pump, wherein   the outer path includes a thermal water stop bypass valve including a path that is closed when a temperature increases,   the controller includes
 a heat quantity controller that sets, in the immediate hot water supply operation mode, an output heat quantity command value for the combustion mechanism for controlling a temperature detection value detected by the second temperature detector to a set temperature in the immediate hot water supply operation mode, and 
 a combustion controller that controls the combustion mechanism in accordance with the output heat quantity command value, 
   the output heat quantity command value is set as being restricted within a range from a minimum heat quantity value to a maximum heat quantity value in a combustion state of the combustion mechanism, and   the combustion controller controls the combustion mechanism in the immediate hot water supply operation mode so as to alternately provide a minimum combustion state and a combustion stop state when the output heat quantity command value is set to the minimum heat quantity value and when the temperature detection value detected by the second temperature detector increases to a control upper limit temperature set to be higher than the set temperature,   in the minimum combustion state, the combustion mechanism operates in accordance with the minimum heat quantity value.   
     
     
         2 . The water heating apparatus according to  claim 1 , wherein
 at least in the immediate hot water supply operation mode, when the temperature detection value detected by the second temperature detector exceeds the control upper limit temperature, the combustion controller controls the combustion mechanism to be in the combustion stop state, and when the temperature detection value detected by the second temperature detector lowers to a control lower limit temperature set to be lower than the set temperature in the combustion stop state of the combustion mechanism, the combustion controller controls the combustion mechanism to be in the combustion state in accordance with the output heat quantity command value.   
     
     
         3 . The water heating apparatus according to  claim 1 , wherein
 in the immediate hot water supply operation mode, when the circulation flow rate becomes lower than a predetermined first flow rate value or when a detection temperature detected by the first temperature detector increases to a predetermined first criterion temperature, the controller deactivates the immediate hot water supply operation mode and starts a stand-by mode in which the circulation pump and the combustion mechanism are deactivated.   
     
     
         4 . The water heating apparatus according to  claim 3 , wherein
 in the stand-by mode, when the detection temperature detected by the first or second temperature detector lowers to a predetermined second criterion temperature, the controller activates the circulation pump, and when the circulation flow rate increases to a predetermined second flow rate value while the circulation pump is active, the controller quits the stand-by mode and resumes the immediate hot water supply operation mode.   
     
     
         5 . The water heating apparatus according to  claim 4 , wherein
 the controller does not activate the circulation pump until a duration of the stand-by mode reaches a predetermined first time period.   
     
     
         6 . The water heating apparatus according to  claim 2 , wherein
 in the immediate hot water supply operation mode, when the circulation flow rate becomes lower than a predetermined first flow rate value or when a detection temperature detected by the first temperature detector increases to a predetermined first criterion temperature, the controller deactivates the immediate hot water supply operation mode and starts a stand-by mode in which the circulation pump and the combustion mechanism are deactivated.   
     
     
         7 . The water heating apparatus according to  claim 6 , wherein
 in the stand-by mode, when the detection temperature detected by the first or second temperature detector lowers to a predetermined second criterion temperature, the controller activates the circulation pump, and when the circulation flow rate increases to a predetermined second flow rate value while the circulation pump is active, the controller quits the stand-by mode and resumes the immediate hot water supply operation mode.   
     
     
         8 . The water heating apparatus according to  claim 7 , wherein
 the controller does not activate the circulation pump until a duration of the stand-by mode reaches a predetermined first time period.   
     
     
         9 . The water heating apparatus according to  claim 1 , wherein
 in a mode on period during which execution of the immediate hot water supply operation mode is permitted, when the hot water supply faucet is closed and a detection temperature detected by the second temperature detector lowers to a predetermined mode reference temperature, the controller executes the immediate hot water supply operation mode,   when a time period elapsed since stop of previous combustion by the combustion mechanism is longer than a predetermined second time period, the controller conducts diagnosis as to an abnormal condition of the immediate hot water supply circulation path, and   in the diagnosis as to the abnormal condition, when the circulation flow rate does not increase to a predetermined diagnosis reference flow rate while the circulation pump is active, the abnormal condition of the immediate hot water supply circulation path is detected.   
     
     
         10 . The water heating apparatus according to  claim 9 , wherein
 when a phenomenon that the circulation flow rate does not increase to the diagnosis reference flow rate while the circulation pump is active is observed in each of a predetermined plurality of times of the diagnosis as to the abnormal condition, the controller detects the abnormal condition of the immediate hot water supply circulation path.   
     
     
         11 . A water heating system comprising:
 a water heating apparatus including a water entry port and a hot water output port;   a low-temperature water pipe that introduces low-temperature water to the water entry port;   a high-temperature water pipe that connects the hot water output port and a hot water supply faucet to each other; and   a circulation pump arranged inside or outside the water heating apparatus,   the water heating apparatus including
 a heating mechanism including a combustion mechanism, 
 an inner path,
 in an immediate hot water supply operation mode in which the circulation pump is activated while the hot water supply faucet is closed, the inner path forming an immediate hot water supply circulation path through which fluid passes through the heating mechanism, as being combined with an outer path, the outer path bypassing the hot water supply faucet on outside of the water heating apparatus, 
 
 a first temperature detector that detects a fluid temperature upstream from the heating mechanism in the immediate hot water supply circulation path, 
 a second temperature detector that detects a fluid temperature downstream from the heating mechanism in the immediate hot water supply circulation path; 
 a flow rate detector that detects a circulation flow rate in the immediate hot water supply circulation path, and 
 a controller that controls the heating mechanism and the circulation pump, wherein 
   the outer path includes a thermal water stop bypass valve including a path that is closed when a temperature increases,   the controller includes
 a heat quantity controller that sets, in the immediate hot water supply operation mode, an output heat quantity command value for the combustion mechanism for controlling a temperature detection value detected by the second temperature detector to a set temperature in the immediate hot water supply operation mode, and 
 a combustion controller that controls the combustion mechanism in accordance with the output heat quantity command value, 
   the output heat quantity command value is set as being restricted within a range from a minimum heat quantity value to a maximum heat quantity value in a combustion state of the combustion mechanism, and   the combustion controller controls the combustion mechanism in the immediate hot water supply operation mode so as to alternately provide a minimum combustion state and a combustion stop state when the output heat quantity command value is set to the minimum heat quantity value and when the temperature detection value detected by the second temperature detector increases to a control upper limit temperature set to be higher than the set temperature,   in the minimum combustion state, the combustion mechanism operates in accordance with the minimum heat quantity value.   
     
     
         12 . The water heating system according to  claim 11 , wherein
 at least in the immediate hot water supply operation mode, when the temperature detection value detected by the second temperature detector exceeds the control upper limit temperature, the combustion controller controls the combustion mechanism to be in the combustion stop state, and when the temperature detection value detected by the second temperature detector lowers to a control lower limit temperature set to be lower than the set temperature in the combustion stop state of the combustion mechanism, the combustion controller controls the combustion mechanism to be in the combustion state in accordance with the output heat quantity command value.   
     
     
         13 . The water heating system according to  claim 11 , wherein
 in the immediate hot water supply operation mode, when the circulation flow rate becomes lower than a predetermined first flow rate value or when a detection temperature detected by the first temperature detector increases to a predetermined first criterion temperature, the controller deactivates the immediate hot water supply operation mode and starts a stand-by mode in which the circulation pump and the combustion mechanism are deactivated.   
     
     
         14 . The water heating system according to  claim 12 , wherein
 in the immediate hot water supply operation mode, when the circulation flow rate becomes lower than a predetermined first flow rate value or when a detection temperature detected by the first temperature detector increases to a predetermined first criterion temperature, the controller deactivates the immediate hot water supply operation mode and starts a stand-by mode in which the circulation pump and the combustion mechanism are deactivated.