What is the purpose of a forced draft fan in a boiler?

Question

If it has any other usage other than supplying air to the combustion chamber?

Will it play any role in allowing a quantity of air to the stack for clearing the exhaust?

Answer 1

yes it help to keep the exhaust exhausting by creating positive pressure in the stack. I am assuming you had problems with negative pressure and it backing up and shutting down your boiler?

Forced draft: Draft is obtained by forcing air into the furnace by means of a fan (FD fan) and ductwork. Air is often passed through an air heater; which, as the name suggests, heats the air going into the furnace in order to increase the overall efficiency of the boiler. Dampers are used to control the quantity of air admitted to the furnace. Forced draft furnaces usually have a positive pressure.

Thats the definition, But yes it provides the combustion air if you have limited breathing room for you boiler , and keep the positive pressure in your stack.

Answer 2

It also helps prevent suet build up in the boiler and keeps the exhaust that goes out the chimney from being as dirty.