Abstract: A solar hot water system is provided, comprising an ambient temperature sensor, a controller, a valve, a water storage tank, having an inlet and an outlet, and at least a first solar panel, having an inlet in fluid communication with the water storage tank outlet and an outlet in fluid communication with the water storage tank inlet. When the temperature sensor indicates to the controller that the ambient temperature is above a predetermined level, the controller controls the valve to direct flow from the water storage tank outlet to the solar panel inlet and from the solar panel outlet to the water storage tank inlet. When the temperature sensor indicates to the controller that the ambient temperature is below a predetermined level, the controller controls the valve to direct flow from the solar panel inlet to the valve and so to atmosphere.

Abstract: A heat exchanger (10) for a water heater. The heat exchanger (10) has a first part (12) and second part (14). A heat exchanging medium flows through the first and second parts. The majority of the length of the first part (12) is in direct heat exchanging contact with a substance to be heated and the majority of the length of the second part (14) is encased in an insulative material or substantially thermally isolated from the substance to be heated.

Abstract: A water heater (10) including a tank (12) adapted for mounting with its longitudinal axis substantially vertical and a duct (32) adapted for mounting with its longitudinal axis substantially vertical. The duct (32) is positioned within the tank (12) and extends through at least most of the height of the tank (12). The duct (32) defines a first volume (34) within the duct interior and a second volume (36) between the duct exterior and the tank interior. The first volume (34) being smaller than the second volume (36). The duct (32) has at least one upper opening (38) at or near the top of the duct (32) and at least one lower opening (40) at or near the bottom of the duct (32). The heater (10) also has a heating element (44) within, or forming all or part of, the duct (32). The element (44) extends at least substantially through the upper half of the duct (32). The heater (10) also has an inlet (24) at or near the bottom of the tank (12) and an outlet (22) at or near the top of the tank (12).

Abstract: A method for operating a heat pump (100) in low ambient air temperatures comprises periodically or temporarily halting flow of refrigerant through an evaporator (170) of the heat pump (100) and providing forced airflow across the evaporator (170) while the refrigerant flow is halted. The method enables operation of the heat pump (100) at low ambient temperatures and provides a means for de-icing the evaporator (170) when operating at low ambient temperatures. The method is particularly applicable to heat pumps having an evaporator located outdoors, such as domestic and industrial water heating systems.

Abstract: A solar hot water system is provided, comprising an ambient temperature sensor, a controller, a valve, a water storage tank, having an inlet and an outlet, and at least a first solar panel, having an inlet in fluid communication with the water storage tank outlet and an outlet in fluid communication with the water storage tank inlet. When the temperature sensor indicates to the controller that the ambient temperature is above a predetermined level, the controller controls the valve to direct flow from the water storage tank outlet to the solar panel inlet and from the solar panel outlet to the water storage tank inlet. When the temperature sensor indicates to the controller that the ambient temperature is below a predetermined level, the controller controls the valve to direct flow from the solar panel inlet to the valve and so to atmosphere.