In a balanced draft system, how does the size of the forced draft fan compare to the induced draft fan?

In a balanced draft system, the forced draft fan is typically smaller than the induced draft fan. This size difference is due to the specific roles each fan plays in the system. The forced draft fan is responsible for supplying the necessary combustion air to the furnace, ensuring that there is sufficient oxygen for efficient combustion. It doesn't need to handle the same volume of gases as the induced draft fan, which is tasked with removing the flue gases from the combustion process.

The induced draft fan must operate at higher capacities, as its primary function is to create a vacuum that draws the combustion gases out of the furnace and into the exhaust stack. This requires a greater volume of airflow compared to the amount of air that is forced into the furnace by the forced draft fan. Thus, the forced draft fan is designed to be smaller in size relative to the induced draft fan to maintain the balance of airflow in the system.

While other options touch on relevant concepts, they do not directly address the size relationship between the two fans in a balanced draft system.