Water Heating Apparatus and Water Heating System

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 of the water heating apparatus;
• a high-temperature water pipe that connects the hot water output port of the water heating apparatus 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,
• a water entry path formed between the water entry port and the heating mechanism,
• a hot water output path formed between the heating mechanism and the hot water output port,
• in an immediate hot water supply operation mode in which the circulation pump is activated while the hot water supply faucet is closed, the water heating apparatus being configured to form an immediate hot water supply circulation path through which fluid passes through the heating mechanism by an inner path and an outer path as being combined, the inner path including at least a part of the water entry path, the heating mechanism, and the hot water output path, the outer path bypassing the hot water supply faucet on outside of the water heating apparatus,
• a flow rate detector that detects a flow rate in the immediate hot water supply circulation path, and
• a controller that gives an instruction to activate and deactivate the heating mechanism and the circulation pump, wherein
• the controller stores as an actual flow rate value for each immediate hot water supply operation mode, a flow rate detection value obtained by the flow rate detector at predetermined timing in the immediate hot water supply operation mode, and calculates a flow rate learning value based on a plurality of stored actual flow rate values, and
• when the flow rate detection value becomes larger than a criterion value set in accordance with the flow rate learning value in the immediate hot water supply operation mode, the controller detects use of the hot water supply faucet and deactivates the circulation pump.