Gas Fitter Practice Test

What is the best way to increase the speed of a furnace blower?

1. Open up the motor pulley

2. Close up the motor pulley

3. Install a higher horsepower fan motor

4. Increase the size of the return air duct

The correct answer is: Close up the motor pulley

To increase the speed of a furnace blower effectively, adjusting the motor pulley by closing it down is often the best method. When you close the motor pulley, which means reducing its diameter, it increases the rotational speed of the blower. This enhances the airflow produced by the blower, thereby improving the system's efficiency in distributing heated air. It's crucial to understand how blower systems work; the relationship between the pulley size and motor speed is fundamental. By reducing the pulley size, more revolutions per minute (RPM) are generated for the same motor input, increasing the velocity of the air being moved by the blower. Other methods, like installing a higher horsepower fan motor, could also increase airflow but might lead to other issues, such as increased energy consumption and potentially overwhelming existing ductwork, which can lead to noise or undue wear on the system. Additionally, increasing the size of the return air duct primarily improves airflow efficiency rather than directly increasing the blower speed; it's more about reducing restriction rather than escalating blower performance ratios. Adjusting the motor pulley tends to be the most immediate adjustment for achieving your goal of increased speed and airflow in a controlled manner.