As a circulation pump is activated while a hot water supply faucet is closed, an immediate hot water supply circulation path is formed to bypass the hot water supply faucet on the outside of a water heating apparatus and to pass through a heat exchanger in the inside of the water heating apparatus. A controller determines in a test mode, whether or not the immediate hot water supply circulation path has been formed by connection of a thermal water stop bypass valve, based on whether or not a temperature detector senses increase in temperature to a predetermined criterion temperature while the circulation pump and a heat source apparatus are active.

A system and a method for controlling twinned heating appliances are described. The system includes a first heating appliance and a second heating appliance. The first heating appliance includes a first blower and a first wireless communication unit. Further, the second heating appliance is operatively coupled with the first heating appliance as a twinned unit. The second heating appliance includes a second blower and a second wireless communication unit. The system also includes a primary control unit configured to receive speed data indicative of a speed of the first blower and speed data indicative of a speed of the second blower. The primary control unit is further configured to output a blower speed control signal to at least one of the first blower and the second blower to synchronize the first blower and the second blower.

The disclosed technology includes systems and methods for operating a fluid heating device comprising an electric heating element and a gas burner. The disclosed technology can include a system and method that can receive flow data from a flow sensor that is indicative of a flow rate of a fluid in a fluid heating system, determine if the flow rate is less than or equal to a threshold flow rate, and output a control signal to heat the fluid with the electric heating element, the gas burner, or both based on the flow rate data.

A water heater including a cabinet having an inlet, an outlet, and a flow path disposed between the inlet and the outlet and having a plurality of upper and lower junctions to redirect the flow path. Each lower junction includes a drain port. A flow rate sensor measures the flow rate of the fluid through the flow path, an inlet temperature sensor measures an inlet temperature, an and outlet temperature sensor measures the outlet temperature. Heating elements are disposed along the flow path between the inlet and outlet temperature sensors, and intermediate temperature sensors are disposed adjacent respective heating elements to measure an intermediate temperature within the flow path. A controller operates the heating elements to heat a fluid within the flow path to a predetermined set point temperature based on the measurements of the flow rate sensor and temperature sensors.

An aircraft water supply system supplies water to a water discharge port in an aircraft. A cold water flow path supplies cold water to the water discharge port. A hot water flow path supplies hot water to the water discharge port. A first control valve adjusts the flow rate of cold water flowing through the cold water flow path. A second control valve adjusts the flow rate of hot water flowing through the hot water flow path. A flow sensor detects the flow rate of water at any point up to the water discharge port. A flow control unit controls the opening/closing state of the first control valve and the second control valve based on the water temperature detected by the flow sensor so that the amount of the water discharged from the water discharge port reaches a predetermined target flow rate.

A hot water returning system according to the present disclosure includes a hot water generator that generates hot water, a hot water line that supplies the hot water to a source of demand, a water returning line that returns the hot water to the hot water generator for preheating the hot water in the hot water line, a pump which pumps the hot water for returning of the hot water, and a processor electrically connected to the pump, and the processor is configured to determine a need for preheating corresponding to whether it is necessary to preheat the hot water and a status for use of hot water corresponding to whether the hot water is supplied to a source of demand, and control the pump based on the need for preheating and the status for use of hot water.

A water heating apparatus is provided. The water heating apparatus includes a pump and is configured to be able to set a hot-water circulation route to circulate hot water discharged from a heat exchanger to be re-entered into the heat exchanger by operation of the pump. When a state of a hot-water supply operation in which a burner drives combustion is changed to an end state, hot water in the heat exchanger is circulated in the hot-water circulation route to suppress deposition of scale.

When a hot water supply operation is started, a single mode is used in which hot water is output only from a second hot water supply circuit of a water heater, by cut-off of a flow path in a first hot water supply circuit of a space-heating water heater by a cut-off mechanism. When a load imposed by hot water supply by the second hot water supply circuit increases during the hot water supply operation in the single mode, the cut-off mechanism is opened to start hot water output from the first hot water supply circuit and a hot water supply operation in a parallel mode is performed in which hot water is output from both of the first hot water supply circuit and the second hot water supply circuit.

The disclosed technology includes an on-demand water heater which uses a heat pump to heat the fluid. The on-demand heat pump water heater can have a low fluid capacity heating chamber which has an inlet and an outlet, a heat pump for heating the fluid, and a controller to control the heat pump and maintain the temperature of the fluid at a predetermined temperature. The on-demand heat pump water heater can include one or more temperature sensors, flow sensors, fluid mixing valves, or supplemental heat sources.

The present invention provides a method of operating a gas heater for water including the steps of: restricting a water flow to the gas heater; determining a first rate of a first gas heating for the restricted water flow; adjusting the gas heating to the restricted water flow; repeating the previous steps until a heated water has a temperature above a temperature threshold; removing the restriction to the water flow to increase the water flow; and determining a second rate of a second gas heating for the increased water flow. The present invention also provides a gas water heater which utilises such a method.