Systems and methods for integrating a water heating unit and a heat pump

An integrated heat pump-water heater system, comprising:

• a heat pump operable in multiple operating modes for conditioning an indoor space, the heat pump comprising a refrigerant loop, and an indoor heat exchanger and an outdoor heat exchanger each on the refrigerant loop;
• a water heater comprising a water loop and a water-refrigerant heat exchanger (WRHX) that thermally connects water in the water loop and refrigerant in the refrigerant loop;
• and
• a controller connected to the heat pump and the water heater, wherein the controller is configured to:
• when the heat pump is operating in a space heating mode, control the heat pump to reject heat from the refrigerant in the indoor heat exchanger into an inlet air stream;
• when the heat pump is operating in a space cooling mode, control the heat pump to absorb heat into the refrigerant in the indoor heat exchanger from the inlet air stream;
• in each of the space heating mode and the space cooling mode, determine that a condition of the water heater indicates a need for water heating and that a condition of the heat pump indicates an availability of the refrigerant in the refrigerant loop to heat the water in the water loop and, in response, control supply of the water to the WRHX and control the heat pump to direct the refrigerant through the WRHX for heating the water;
• and
• in the space heating mode, determine that the condition of the heat pump indicates that the refrigerant in the refrigerant loop is not available to heat the water in the water loop and, in response and irrespective of the need for water heating in the water heater, limit supply of the water to the WRHX.

A method for operating an integrated heat pump-water heater system to condition an indoor space and heat water, the method comprising:

• circulating a refrigerant through a refrigerant loop using a heat pump operable in multiple operating modes, wherein the heat pump includes a compressor, an indoor air-refrigerant heat exchanger (ARHX), and an outdoor ARHX each positioned on the refrigerant loop;
• positioning a reversing valve on the refrigerant loop, the reversing valve being connected to the compressor, to direct a flow of the refrigerant between the indoor ARHX and the outdoor ARHX based on a selected operating mode of the heat pump;
• circulating water through a water loop of a water heater, wherein the water loop is thermally connected to the refrigerant loop via a water-refrigerant heat exchanger (WRHX);
• positioning a network of valves on the refrigerant loop, the network of valves being connected to the reversing valve, the indoor ARHX, and the outdoor ARHX;
• directing, by the network of valves, the flow of the refrigerant through the WRHX in each operating mode of the heat pump;
• and
• transferring heat from the refrigerant to the water via the WRHX to heat the water, wherein the steps of circulating the refrigerant, positioning the reversing valve, circulating the water, positioning the network of valves, directing the flow, and transferring heat are performed in an interconnected sequence to enable simultaneous conditioning of the indoor space and heating of the water across the multiple operating modes.