Indicator for the extent of clarification of waterheaters in electric household appliances

摘要

Calcification sufficient to cause material impairment of heat transfer is indicated in a water heater in an electric appliance, such as a coffee maker. The water heater has a first and a second temperature-dependent switch thermally coupled thereto. The first switch serves as a final interrupter or temperature control. The switching temperature of the second switch is below that of the first one in the range of temperatures which occur in the water heating operation if excessive calcification is present. A time delay member after a predetermined time actuates an indicating signal. The time delay member is in operation when only the second temperature-dependent switch is in responded condition. The time delay member ceases operation and returns to its original state when both temperature-dependent switches are in the responded state or the original condition.