What scenario requires the use of a forced draft?

A forced draft is necessary in scenarios where there is insufficient natural draft. This typically occurs in situations where the natural atmospheric conditions are not adequate to create the necessary airflow through the system. An insufficient natural draft can lead to poor combustion efficiency, as the lack of a proper draft may hinder the supply of air needed for the combustion process.

In such cases, forced draft fans are used to mechanically introduce additional air into the combustion system, ensuring that there is a consistent and adequate supply of oxygen. This enhances the combustion efficiency and helps maintain optimal operating temperatures and pressures within the system, thereby promoting better overall performance and preventing safety hazards associated with incomplete combustion.

Normal operation conditions don't typically require additional mechanical assistance, as the natural draft is usually sufficient to handle airflow needs. Low ambient temperatures might also support natural draft by increasing the temperature differential that drives draft without necessitating a forced draft. Lastly, too much natural draft could lead to situations where excessive air dilutes the fuel, but this scenario does not call for a forced draft either. Therefore, forced drafts are specifically beneficial when natural drafts are inadequate.