Which factor primarily controls the cycle of a gas furnace fan?

The cycle of a gas furnace fan is primarily controlled by the temperature of the heated air. In a typical heating system, the fan is designed to circulate air throughout the living space after the furnace has heated it to a certain temperature. Once the air reaches a predetermined temperature, the fan is activated to distribute the warm air effectively, ensuring even heating throughout the area.

The temperature of the heated air is crucial because it determines when the fan should turn on and off. If the heated air hasn't reached the desired temperature, the fan may not engage, allowing the furnace to continue heating. Once the air is adequately warmed, the fan's operation helps maintain comfort levels by ensuring that the heat is well-distributed, rather than just accumulating near the heating unit.

Other factors, while they may influence overall system operation or comfort, do not directly dictate when the fan cycles on or off. For instance, room temperature provides insight into overall comfort but does not control the fan directly. Similarly, furnace latency and burner efficiency may impact heating performance but are not the direct determinants of the fan cycle. Thus, the temperature of the heated air is the primary factor managing this aspect of a gas furnace's operation.