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.

A water heater includes a heat exchanger, a heat pump, a first valve in fluid communication with the heat exchanger and the heat pump, and a controller configured to control the first valve. The first valve can be configured to direct water flow toward at least one of the gas heater or the electric heat pump. A second valve in fluid communication with the first valve and the heat pump can be provided, and the controller can be further configured to control the second valve. A water heater inlet and a water heater outlet can be included and in fluid communication with the first valve, and the controller can be configured to monitor a temperature of water entering the water heater inlet and control the first valve dependent upon the monitored temperature.

A heater tank for a heat pump system having a structure in which a capacity of a storage space may be changed as hot fluid is discharged. For example, the heater tank may include a main body having an internal space and one open side, and a capacity changing member that forms a storage space, in which a hot fluid, such as water may be stored, by closing the one open side in the internal space of the main body, and being moved so that a capacity of the storage space may be changed as the hot fluid is discharged.

The present disclosure provides hot water heating systems and methods for heating the atmosphere within a predefined area. The systems include a hybrid water heating and storage apparatus configured to heat and store water including a heat pump and an electric heating tank. The systems include a recirculating pump configured to selectively draw a hot output flow of heated water from the electric heating tank, pass the heated water through a heat exchange fixture to heat the atmosphere within a predefined area, and direct the water back to the electric heating tank from the heat exchange fixture as a cold input flow. The systems further include thermostat electrically coupled to the recirculating pump and positioned within the predefined area configured to sense the temperature of the atmosphere within the first predefined area and selective operate of the recirculating pump based on a sensed temperature and a user selected temperature.

A water heater is provided that heats water in a storage tank and discharges the heated water. The water heater includes a storage tank configured to store water, at least one first temperature sensor configured to sense a temperature of the water stored in the storage tank, a second temperature sensor configured to sense a temperature related to an outside of the water heater, a first heat exchanger comprising at least one heating element configured to heat the water, a second heat exchanger comprising a heat pump system and configured to heat the water, and a controller configured to control at least one of the first heat exchanger and the second heat exchanger based on a temperature sensed by the second temperature sensor and a set water temperature.

A flame sensor for a furnace of a heating, ventilation, and air conditioning (HVAC) system includes a sensor body and an electrically conductive member of the sensor body. The electrically conductive member is configured to be disposed within a flame region of a burner of the furnace and configured to receive electrical current from a controller of the furnace. The flame sensor also includes an anti-oxidation coating disposed on an outer surface of the electrically conductive member and configured to transmit the electrical current from the electrically conductive member. The anti-oxidation coating is configured to contact a flame produced by the burner and expose the electrical current to the flame.

A method for constructing a water circulation device including a water circulation circuit that circulates water heat-exchanged with a refrigerant heated by a heat pump includes: installing a heater in the water circulation device in contact with the water; depositing scale from the water on the heater by heating the heater while circulating the water in the water circulation circuit; and removing the heater from the water circulation device after the depositing.

A water heater may operate according to different modes. The water heater may include a storage tank configured to store water, at least one sensor configured to sense a temperature of the water and a temperature related to an outside of the water heater, a first heater assembly (comprising a heating element) configured to heat the water, a first controller configured to control the first heater assembly, a second heater assembly (comprising a heat pump system) configured to heat the water, an inverter connected with the heat pump system, and a second controller configured to control the heat pump system by adjusting an output frequency of the inverter.

A heat pump may include a compressor configured to compress a refrigerant, a first temperature sensor configured to detect an outdoor temperature, a second temperature sensor provided in heating pipes connected to a heating device that performs indoor heating and configured to detect a temperature of fluid flowing through the heating pipes, an outdoor heat exchanger configured to perform heat exchange between outdoor air and a refrigerant, a third temperature sensor configured to detect a temperature of the outdoor heat exchanger, and a controller. The controller may be configured to: control power to a boiler and/or to the compressor based on sensing values of the first, second, and third temperature sensors, calculate an expected efficiency of the heat pump based on the sensing value of the first temperature sensor and an initial target temperature, and control power to the boiler based on the expected efficiency.

The disclosed technology includes an on-demand water heater which uses an electric heat source to heat the water. The on-demand water heater can have a low fluid capacity heating chamber which has an inlet and an outlet, an electric heat source for heating the water, and a controller to control the electric heat source and maintain the temperature of the water at a predetermined temperature setting. The on-demand water heater can be powered by a direct current power source. The on-demand water heater can also utilize a solar thermal system to provide additional heat to the water.