CSLB Class B General Contractor's License Practice Exam

What is the primary function of a return duct system in HVAC?

1. To supply fresh air to rooms

2. To regulate humidity levels

3. To return cooled or heated air to the air handler

4. To filter pollutants from the air

The correct answer is: To return cooled or heated air to the air handler

The primary function of a return duct system in an HVAC system is to return cooled or heated air to the air handler. This process is crucial for maintaining the overall efficiency and comfort level within a building. Once air has circulated through various rooms and has absorbed heat or cooled down, it needs to be collected and sent back to the air handler for reconditioning. This allows the HVAC system to effectively regulate the indoor temperature by continuously circulating air. While the other functions listed, such as supplying fresh air, regulating humidity, and filtering pollutants, are important components of HVAC systems, they are not the main function of the return duct system. Fresh air is typically introduced via separate systems or through fresh air intakes, humidity regulation is usually managed through humidifiers or dehumidifiers, and filtering is done through air filters located in the air handling unit. Therefore, the primary focus of the return duct system is specifically to facilitate the return of air to the air handler for further conditioning.