What type of draft system is used to overcome resistance on boilers equipped with an economizer?

The induced draft system is the correct choice because it actively manages the flow of flue gases through the boiler and economizer, ensuring efficient operation. In this system, a fan is used to create a negative pressure within the flue gas path, which helps to draw the combustion gases out of the boiler and through the economizer.

By using an induced draft, the system can effectively compensate for any resistance caused by the economizer, which is designed to recover heat from flue gases before they exit the stack. This resistance can hinder the natural flow of gases if not properly managed, making the induced draft critical for maintaining optimal performance and efficiency.

Natural draft relies solely on buoyancy, which may not be sufficient to overcome the resistance presented by the economizer. A balanced draft system utilizes both induced and forced draft but might not be necessary for every boiler setup. A forced draft system creates positive pressure, which is not as suitable for situations where negative pressure is required to handle specific resistance issues. Thus, the induced draft system is the most effective method in this scenario.