What does 'balanced draft' refer to?

The term 'balanced draft' actually refers to a system where the airflow in the combustion chamber is controlled in such a way that the pressure within the furnace is generally kept negative, or below atmospheric pressure. This is achieved using both forced draft and induced draft fans, which work in conjunction to create the necessary pressure conditions.

In a balanced draft system, the induced draft fan removes flue gases from the furnace, creating a slight negative pressure that keeps combustion air flowing into the furnace efficiently. The forced draft fan then pushes air into the combustion area, ensuring that there is an adequate supply of oxygen for the fuel being burned.

This method enhances combustion efficiency and helps prevent the escape of combustion gases into the boiler room or surrounding environment, promoting safety and better performance. The way in which these fans are regulated ensures that the system remains stable and effective, maintaining the appropriate pressure balance.

Other options do not accurately represent the concept of balanced draft. For instance, equalizing airflow does not encompass the critical aspect of pressure control, and simply maintaining a furnace above or below atmospheric pressure does not provide a complete understanding of the operational balance necessary for this system.