How is the fan cycled during heating in a gas furnace with an electric control board?

In a gas furnace with an electric control board, the fan is cycled during heating primarily based on time. This means that the control board manages the operation of the fan by setting it to run for a specified duration after the burners have ignited and reached operational temperature.

Cycling the fan on a timed basis allows it to continue to circulate warmed air throughout the space even after the burners have turned off, ensuring that the heat produced is effectively distributed. This timed operation is crucial because it allows for the efficient use of the heat generated, maximizing comfort while avoiding unnecessary wear on the fan and the system. It also prevents abrupt temperature drops in the living space, maintaining a more consistent and pleasant environment for occupants.

In contrast to the other options listed, which pertain to various forms of mechanical and environmental controls, the timed cycling provides a straightforward and consistently effective method of regulating the fan's operation in relation to the furnace heating cycles.