The water circuit module, which includes the plate heat exchanger, water outlet valve and water inlet valve, is the key component of the water circuit system control in gas wall-hung furnaces. Through the connection with the main heat exchanger, cold water inlet, hot water outlet and external radiator, the water circuit is switched between heating cycle and bathroom heating cycle according to the user's usage. The water circuit module also integrates water pressure protection and monitoring of system pressure, flow rate, temperature, etc.