A method of determining an abnormal condition in a water heater. The method including sensing, via a temperature sensor, a plurality of temperatures and filtering, using a first time constant, the plurality of temperatures to produce a first plurality of filtered temperatures. The method further including determining, via a controller, if at least one temperature of the first plurality of filtered temperatures crosses a first temperature threshold, and when at least one temperature of the first plurality of filtered temperatures crosses a second temperature threshold, filtering, using a second time constant, the plurality of temperatures to produce a second plurality of filtered temperatures. The method further including initiating, via the controller, a shutdown procedure when at least one temperature of the second plurality of filtered temperatures, crosses a third temperature threshold.