A method of operating a water heater is disclosed. The method includes obtaining a first input corresponding to ambient temperature and a second input corresponding to evaporator temperature. The method includes determining the ambient temperature from the first input and the evaporator temperature from the second input, followed by determining whether the ambient temperature is less than a first threshold temperature. The method includes determining whether the evaporator temperature is less than a second threshold temperature when the ambient temperature is less than the first threshold temperature, where the second threshold temperature is less than the first threshold temperature. The method also includes actuating a heating element coupled to one or more tubes of the evaporator to heat refrigerant present in the one or more tubes, when the evaporator temperature is less than the second threshold temperature.

A method of operating a water heater is disclosed. The method includes obtaining a first input corresponding to ambient temperature and a second input corresponding to evaporator temperature. The method includes determining the ambient temperature from the first input and the evaporator temperature from the second input, followed by determining whether the ambient temperature is less than a first threshold temperature. The method includes determining whether the evaporator temperature is less than a second threshold temperature when the ambient temperature is less than the first threshold temperature, where the second threshold temperature is less than the first threshold temperature. The method also includes actuating a heating element coupled to one or more tubes of the evaporator to heat refrigerant present in the one or more tubes, when the evaporator temperature is less than the second threshold temperature.

A district public water supply pipe network system compatible for ground source heat pump water and reclaimed water comprises a water supply main pipe connected with a reclaimed water outlet side of a sewage treatment system and connected to a plurality of energy stations and a plurality of transmission and distribution station, and a return water main pipe arranged between the adjacent energy stations to connect them. The energy stations are provided with a plurality of shallow geothermal heat exchange system for exchanging heat with shallow geothermal energy in the region. Both the energy stations and the transmission and distribution station are connected with corresponding distribution pipe networks connected with a user terminal water supply system. The system provides the source side water and the reclaimed water to users. It is a district public geothermal pipe network and a reclaimed water pipe network.

A district public water supply pipe network system compatible for ground source heat pump water and reclaimed water comprises a water supply main pipe connected with a reclaimed water outlet side of a sewage treatment system and connected to a plurality of energy stations and a plurality of transmission and distribution station, and a return water main pipe arranged between the adjacent energy stations to connect them. The energy stations are provided with a plurality of shallow geothermal heat exchange system for exchanging heat with shallow geothermal energy in the region. Both the energy stations and the transmission and distribution station are connected with corresponding distribution pipe networks connected with a user terminal water supply system. The system provides the source side water and the reclaimed water to users. It is a district public geothermal pipe network and a reclaimed water pipe network.

A heat pump system adjusts a degree of subcooling of an indoor-side heat exchanger in a heating priority mode, and adjusts any one of a degree of subcooling of a hot-water supply-side heat exchanger (water-side heat exchanger) and a discharge temperature of a compressor in a hot-water supply priority mode.

A heat pump system adjusts a degree of subcooling of an indoor-side heat exchanger in a heating priority mode, and adjusts any one of a degree of subcooling of a hot-water supply-side heat exchanger (water-side heat exchanger) and a discharge temperature of a compressor in a hot-water supply priority mode.

A plate heat exchanger can reduce thermal contact between a second fluid (water and a third fluid (low-temperature, low-pressure two-phase refrigerant) to enhance thermal efficiency. A plate heat exchanger (1b) includes a heat transfer plate group (102a) that performs heat exchange between a first fluid of high-temperature, high-pressure gas refrigerant and a second fluid of a heating target fluid; and a heat transfer plate group (102b) that performs heat exchange between a first fluid of low-temperature, high-pressure liquid refrigerant and a third fluid of low-temperature, low-pressure two-phase liquid refrigerant. The heat transfer plate group (102a) forms refrigerant channels including a stack of plates, has a configuration that a flow of the first fluid of high-temperature, high-pressure gas refrigerant and a flow of the second fluid are alternately aligned in the refrigerant channels, and causes the second fluid to flow in the outermost refrigerant channel.

A plate heat exchanger can reduce thermal contact between a second fluid (water and a third fluid (low-temperature, low-pressure two-phase refrigerant) to enhance thermal efficiency. A plate heat exchanger (1b) includes a heat transfer plate group (102a) that performs heat exchange between a first fluid of high-temperature, high-pressure gas refrigerant and a second fluid of a heating target fluid; and a heat transfer plate group (102b) that performs heat exchange between a first fluid of low-temperature, high-pressure liquid refrigerant and a third fluid of low-temperature, low-pressure two-phase liquid refrigerant. The heat transfer plate group (102a) forms refrigerant channels including a stack of plates, has a configuration that a flow of the first fluid of high-temperature, high-pressure gas refrigerant and a flow of the second fluid are alternately aligned in the refrigerant channels, and causes the second fluid to flow in the outermost refrigerant channel.

A combined hot water and air heating and conditioning system including a first heat exchanger, a heat pump, a chilling tower loop, a burner and a second heat exchanger to provide hot water, air heating and air cooling. The system provides hot water, air heating and cooling all in one single unit. The system utilizes a heat pump to remove heat from ambient air and transfer the rejected heat into a hot water system, thereby using waste heat to heat the hot water system. The system utilizes a heat exchanger not only for the purpose of transferring heat from a heating source to a fluid in the heat exchanger but also for the purpose of dissipating heat from the fluid in the heat exchanger to the surroundings of the heat exchanger, thereby allowing a heat pump to act both as an air heating and conditioning device.

A combined hot water and air heating and conditioning system including a first heat exchanger, a heat pump, a chilling tower loop, a burner and a second heat exchanger to provide hot water, air heating and air cooling. The system provides hot water, air heating and cooling all in one single unit. The system utilizes a heat pump to remove heat from ambient air and transfer the rejected heat into a hot water system, thereby using waste heat to heat the hot water system. The system utilizes a heat exchanger not only for the purpose of transferring heat from a heating source to a fluid in the heat exchanger but also for the purpose of dissipating heat from the fluid in the heat exchanger to the surroundings of the heat exchanger, thereby allowing a heat pump to act both as an air heating and conditioning device.