According to the present invention, a heat exchanger comprises a fin having a plurality of through holes. The plurality of through holes include mutually adjacent first and second through holes disposed on a side closest to a heating gas's inlet side. The fin has a slit located between the first through hole and the second through hole and cut into the fin from an edge thereof located on the heating gas's inlet side to a side farther from the heating gas's inlet side than a reference line connecting a center of the first through hole and a center of the second through hole. Furthermore, the fin has at least one opening between the slit and the first and second through holes. The opening includes a first opening having a portion located on the side farther from the heating gas's inlet side than the reference line.

A hot water supply system includes a hot water storage tank configured to store hot water, a plurality of temperature sensors that are installed in the height direction of the water storage tank and that detect temperatures at their installed positions, a main-unit-side hot water supply device that heats hot water in the hot water storage tank, a sub-unit-side hot water supply device, a main-unit-side control board equipped with control means that controls the corresponding hot water supply device, and a sub-unit-side control board. Signals sent from the temperature sensors are input in a distributed manner among the main-unit-side control board and the sub-unit-side control board, and each of the control boards are communicably connected to each other by a transmission line.

In one aspect, the present invention is directed to boiler heating system, comprising: a hollowed-walls cylinder, for storing therein water to be heated; a partition in a form of a cylinder, disposed inside the hollowed-walls cylinder, distantly from its vertical walls; the partition having an upper water passage and a lower water passage, for allowing water transition between the inner side of the partition and the outer side of the partition; a heating element based on induction heating, said heating element being disposed inside the inner space of the hollowed-walls cylinder; a water inlet, disposed in the lower side of the hollowed-walls cylinder; and a water outlet, disposed in an upper side of the hollowed-walls cylinder, thereby (a) allowing heating the water without being in direct contact between the heating element and the water, resulting with no scale accumulation, and (b) separation between ascending water and descending water, thereby accelerating the water warming.

An energy efficient heat pump system capable of operating in extreme low and high temperature environments. The heat pump system includes an evaporator, a heater operatively associated with the evaporator, compressor and condenser. In an exemplary embodiment, the heat pump system may further include a plasma pulse-spark system to facilitate removal of scale deposits. The heater heats an environmental medium prior to the environmental medium exchanging energy with a refrigerant located in an evaporator coil of the evaporator in order to maintain a predetermined minimum temperature differential between the environmental medium when it contacts the evaporator coil and the refrigerant when located in the evaporator coil. The system allows efficient operation at low temperatures.

A method for controlling a system including a heat pump, a space heater, a space cooler, a thermal battery, an electrical battery and a grid access system, the method including turning on at least one of discharging of the thermal battery and discharging of the electric battery, if a hot water demand exists; turning on at least one of the heat pump, charging of the thermal battery, charging of the electric battery and discharging of the electric battery, if a space heating demand exists; turning on charging of the thermal battery, if a space cooling demand exists; and backfeeding electricity from the electric battery to a grid through the grid access system, if electricity sale is desired.

A method for operating a heat pump water heater appliance positioned with a building is provided. The method includes receiving a measurement of ambient temperature about the building via a network and also getting a measurement of ambient temperature about the heat pump water heater appliance within the building. The method further includes heating water within the heat pump water heater appliance with only a sealed system of the heat pump water heater appliance or with only a secondary heating element of the heat pump water heater appliance based upon the measurement of ambient temperature about the building and the measurement of ambient temperature about the heat pump water heater appliance within the building.

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.

Water heater appliances are provided. A water heater appliance includes a tank, a hot water conduit and a cold water conduit. The water heater appliance further includes a heat pump assembly configured to heat water within the chamber of the tank, and a thermo-electric assembly configured to generate an electrical current. The thermo-electric assembly includes a thermo-electric converter, a working fluid flowable through the thermo-electric converter, and a heat source configured to heat the working fluid within the thermo-electric converter. At least a portion of the electrical current generated by the thermo-electric assembly is flowed to the heat pump assembly to at least partially power the heat pump assembly.

A system powers a resistive load with switched direct current (DC) power. The high-speed switching of the resistive load heats up the resistive load with a pseudo-DC current. The resistive load can be a water heater element. The water heater can also have another heating element, which allows the pseudo-DC signal to pre-heat the water heater with local solar power, reducing the need for outside energy to power the other heating element.

Embodiments described herein generally relate to a domestic hot water (DHW) preheater operable to supply domestic hot water to a structure and/or to preheat a cold return of a space heating system.