Heater protection arrangement for a washing appliance

Abstract

In a washing appliance, such as a dishwasher, employing a high watt density heater for heating washing liquid in the wash chamber of the appliance, a control circuit which integrates a liquid level sensor employed for positive liquid fill control and heater protection with the sequence controller to prevent damage to the heater in the event of a malfunction of the liquid level sensor which causes the sensor to indicate a full liquid level regardless of the actual liquid level in the wash chamber. The level sensor includes a switch which assumes a reset position when the sensed liquid level is less than a full level and a full position when the sensed liquid level equals the full level. The switch is operative in its reset position to enable liquid fill and prevent heater energization and in its full position to terminate fill and enable heater energization. In a preferred form of the invention, first and second switches controlled by the sequence controller for actuation in a predetermined sequence at the end of the drain cycle are arranged in combination with the level sensor controlled switch. This switch arrangement is operative to prevent continued cyclic operation of the appliance by interrupting energization of the sequence controller timer motor in the event the level sensor controlled switch fails to assume its reset position at the end of the drain cycle.