A water heater having an electric heating element therein is provided with apparatus for preventing dry firing of the heating element. The apparatus is operative to (1) power the heating element with electrical test pulses having first predetermined durations and being separated by rest periods of second predetermined durations during which the heating element is depowered, (2) determine the average electrical current flow through the element during each of the test pulses, and (3) preclude energization of the heating element if the average current flow therethrough during an electrical test pulse subsequent to the first test pulse is less by a predetermined magnitude than the average electrical current flow through the heating element during the first electrical test pulse.

A water boiler comprises an inner tank, an electric heating pipe, and a controller. A lower cover is attached to a mouth of the inner tank. The lower cover comprises an inlet pipe and an outlet pipe, wherein an outlet port at a lower part of the inlet pipe is in communication with lower part within the inner tank. An inlet port of a lower part of the outlet pipe is in communication with an upper part of the inner tank. The lower cover is arranged beneath the upper cover. An upper part of the inlet pipe passes through the upper cover. A cavity is formed between the lower cover and the upper cover. The cavity is partitioned into an upper chamber and a lower chamber by a diaphragm. The lower chamber is in communication with an outer space.

In an electric water heater having adjustable set point and differential temperatures, upper and lower heating elements, and associated temperature sensors respectively operative to sense upper and lower tank water temperatures, a specially designed control system is provided for controlling the heating elements. The control system is operative to prevent dry firing of the heating elements by measuring temperatures over time with the temperature sensors.

In an electric water heater having adjustable set point and differential temperatures, upper and lower heating elements, and associated temperature sensors respectively operative to sense upper and lower tank water temperatures, a specially designed control system is provided for controlling the heating elements. The control system is operative to prevent dry firing of the heating elements by measuring temperatures over time with the temperature sensors.

In an electric water heater having adjustable set point and differential temperatures, upper and lower heating elements, and associated temperature sensors respectively operative to sense upper and lower tank water temperatures, a specially designed control system is provided for controlling the heating elements. The control system is operative to automatically set a selected setpoint temperature to a second setpoint temperature less than or equal to a predetermined magnitude, and to reduced the second setpoint temperature and/or the differential temperature, as a predetermined function of the magnitudes of detected time intervals between successive heat demands of the water heater, to reduce the energy cost associated with the water heater.

A structure of an aquarium heater with off-water overheat protection, wherein a control box with a control circuit is set inside. The control circuit includes: setting a temperature-control module; connecting with an electric heater; and connecting with either an overheat sensor or an off-water protection sensor; wherein the control circuit consists of a single chip, an electric relay box, and a plurality of resistors, capacitors, diodes, and transistors to constitute a complete electric circuit. Therefore, saving the electric energy and avoiding the conditions which the heating temperature is too high or the electric heater is emptily burned to damage because of the off-water can be achieved through the overheat sensor senses the temperature or the off-water protection sensor senses weather the electric heater is off water or not, and then the temperature-control module does the temperature comparison to control the electric heater to heat or not.

A water heater has a tank defining an interior volume, a heating element disposed within the interior volume, and a temperature sensor disposed with respect to the heating element so that the temperature sensor detects temperature of an area ambient to the heating element in the interior volume. The heating element is actuated at a predetermined actuation rate and for a cumulative actuation period so that the predetermined actuation rate maintains the heating element below a predetermined maximum temperature in air and so that the actuation period contributes a predetermined amount of energy to the ambient area when the heating element is immersed in water.

A water heater has a tank with at least one heating element. A non-invasive liquid level sensor is disposed in communication with a water containing volume encompassing the tank volume. If a signal received from the sensor indicates the at least one heating element is immersed in water, power is provided to the heating element. If the signal indicates the at least one heating element is not immersed in water, power is prevented from being provided to the heating element.

The invention relates to a method for managing the heating of water in a tank of a water heater which comprises a device for electrically heating the water in the tank, characterized in that it comprises, when a water heating phase is actuated: activation of heating by the heating device, determination of a variation of the temperature in the tank over time and determination of at least one water filling state in the tank according to the variation over time.

A water heater has a tank defining an interior volume, a heating element disposed within the interior volume, and a temperature sensor disposed with respect to the heating element so that the temperature sensor detects temperature of an area ambient to the heating element in the interior volume. The heating element is actuated at a predetermined actuation rate and for a cumulative actuation period so that the predetermined actuation rate maintains the heating element below a predetermined maximum temperature in air and so that the actuation period contributes a predetermined amount of energy to the ambient area when the heating element is immersed in water.