Abstract: A water heater appliance includes a heat exchanger, a first temperature sensor disposed on a front surface of the heat exchanger, a second temperature sensor disposed on an elbow extending from the heat exchanger, and a controller. A method of operating the water heater appliance includes monitoring a first temperature of the front surface of the heat exchanger with the first temperature sensor while the water heater appliance is running, monitoring a second temperature of the elbow with the second temperature sensor when the water heater appliance stops running, calculating a difference between the first temperature and the second temperature, and determining scale buildup in the heat exchanger based on the difference between the first temperature and the second temperature.

Abstract: A water heater includes a case, and a water line disposed within the case. The water line extends between an inlet and an outlet, and a heat exchanger is disposed in the case on the water line. A burner is disposed in the case, and a controller is also disposed in the case. A flue is coupled to the case. The flue defines an exhaust outlet contiguous with external air. The flue includes a temperature sensor, a fan, and a plate disposed within the flue. The plate is configured to rotate within the flue between an open position and a closed position. Also included in the case is a heating element coupled to the water line between the inlet and the outlet of the water line. The controller is in signal communication with the temperature sensor and the fan, and the controller is in operative communication with the heating element.

Abstract: A water heater includes a case, and a water line disposed within the case. The water line extends between an inlet and an outlet, and a heat exchanger is disposed in the case on the water line. A burner is disposed in the case, and a controller is also disposed in the case. A flue is coupled to the case. The flue defines an exhaust outlet contiguous with external air. The flue includes a temperature sensor, a fan, and a plate disposed within the flue. The plate is configured to rotate within the flue between an open position and a closed position. Also included in the case is a heating element coupled to the water line between the inlet and the outlet of the water line. The controller is in signal communication with the temperature sensor and the fan, and the controller is in operative communication with the heating element.