What fan operates at higher temperatures than a forced draft (FD) fan?

An induced draft fan operates at higher temperatures than a forced draft fan. This is due to the specific roles these fans play in the combustion and ventilation processes of boilers and other systems.

Induced draft fans are used to pull flue gases from the combustion area and force them through the exhaust system. During this process, they deal with hot gases that exit from the combustion chamber, which can have elevated temperatures due to the combustion process. This requires the induced draft fan to be designed to withstand and operate efficiently under these higher temperature conditions.

In contrast, a forced draft fan is used to supply air to the combustion process. While it does involve air, the temperature of the air being moved is generally lower than the exhaust gases that the induced draft fan handles.

This distinction in function and the nature of the gases or air being moved explains why the induced draft fan operates at higher temperatures, making it the correct choice for this question.