NATE Gas Heating Practice Exam

What type of motors power the blowers in residential gas furnaces?

1. Poly-phase, two phase, single phase and capacitor start

2. Shaded pole, split-phase, capacitor start and PSC

3. Three phase, shaded pole and PSC

4. Split-phase, induction start-induction run and variable speed DC

The correct answer is: Split-phase, induction start-induction run and variable speed DC

In residential gas furnaces, blower motors are typically powered by split-phase, induction start-induction run, and variable speed DC motors. Split-phase motors are commonly used because they provide a good balance between efficiency and cost. These motors start with a phase shift created by the starter winding and run continuously on the main winding after they reach a certain speed. Induction start-induction run motors are another popular choice; they start up using an initial start current and then continue running using induction principles, which enhances their efficiency and reliability. Variable speed DC motors are also increasingly used in modern systems. They allow for precise control of airflow and can adjust speed based on demands, leading to better energy efficiency and comfort in heating applications. This versatility is particularly beneficial in achieving optimal indoor climate control, which residents value. In contrast, the other options may include motor types that are not typically found in residential gas furnace blowers, such as three-phase motors, which are more common in commercial and industrial settings, or shaded pole motors, which, while used in some applications, do not offer the performance or efficiency that residential furnaces require.