Abstract: A method of heating water in a water storage tank. The method includes: selecting an outlet port and an inlet port from at least three ports located in the tank at different heights along a vertical direction. The outlet port is below the inlet port. The method further includes extracting water from the outlet port, supplying the extracted water to an external heat exchanger configured for heating the extracted water, and delivering heated water from the heat exchanger to the selected inlet port.

Abstract: A method of heating water in a water storage tank. The method includes: selecting an outlet port and an inlet port from at least three ports located in the tank at different heights along a vertical direction. The outlet port is below the inlet port. The method further includes extracting water from the outlet port, supplying the extracted water to an external heat exchanger configured for heating the extracted water, and delivering heated water from the heat exchanger to the selected inlet port.

Abstract: It is an object of the subject matter to disclose a water heating device, comprising a vaporizer for vaporizing refrigerant and a compressor for compressing the vaporized refrigerant. The device also comprises a shell; such as a condenser and a volume reducing member positioned within the shell. The member is configured to reduce the cross section area of the volume in which water is heated in the shell. The device may also contain a refrigerant coil positioned adjacent to the volume in which water is heated in the shell; the refrigerant coil contains a refrigerant material received from the compressor, said refrigerant material heats the water in the volume in which water is heated in the shell.