Abstract: An ignition system for a gas furnace being controlled by a main controller and having at least one burner is provided. The ignition system may include at least one flame sensor and an interface module. The flame sensor may be disposed in close proximity to the burner and configured to output a flame check signal indicative of a status of a flame at the burner. The interface module may be configured to receive the flame check signal and generate a fault check signal based on the flame check signal.

Abstract: A flame sensor for sensing flame produced by the burner of a furnace. The sensor includes a closed end tube having a photosensitive element located therein. The photosensitive element is sealed off from any external light so as to only respond to infrared wavelengths of light emitted from the end of the tube when subjected to a flame produced by the burner of the furnace.

Abstract: A method of controlling a current defrost cycle for an outdoor coil of a heat pump system, the heat pump system having a plurality of supplemental heating elements for heating an air stream passing from an indoor coil to an air supply duct during defrost operation, wherein an initial quantity of supplemental heating elements energized is a function of a most recent previous defrost cycle. The initial quantity of supplemental heating elements is energized upon initiation of a defrost cycle. Whether the initial quantity of supplemental heating elements provided is insufficient or excessive is determined. At least one of the supplemental heating elements is deactivated if the initial quantity of supplemental heating elements being provided is excessive.