What is an important feature of forced draft fans in a balanced draft system?

In a balanced draft system, forced draft fans play a crucial role in ensuring proper airflow through the combustion system. One of the notable features of forced draft fans is that they are typically smaller than induced draft fans. This size differential is primarily due to their different functions within the system: while the forced draft fans are responsible for delivering combustion air to the furnace, the induced draft fans are tasked with removing flue gases from the system.

The smaller size of forced draft fans contributes to their efficiency in moving the required volume of air directly into the combustion chamber. This enables better control of the combustion process which ultimately leads to improved efficiency and emissions control. In contrast, induced draft fans, which need to handle the exhaust gases and maintain the necessary draft pressure, tend to be larger to accommodate the greater airflow demands and pressure differentials associated with removing exhaust from the system.

Other choices regarding materials and temperature operation are not defining characteristics of forced draft fans in a balanced draft system, which adds further clarity to why the smaller size is significant in their design and functionality.