HVAC Sheet Metal Block 1 Practice Exam

The correct answer indicates that a field fabricated single cut mitered duct can have a maximum angle of 15 degrees. This standard is important because it directly impacts airflow and system efficiency. A mitered duct is created by cutting the duct at an angle to create a joint, which helps to change the direction of airflow without a significant loss of pressure.

Having a maximum angle of 15 degrees ensures that the duct maintains more streamlined airflow, reducing turbulence and minimizing energy losses. This angle is a practical compromise, allowing ductwork to fit into spaces while maintaining system performance standards, as sharper angles can create additional resistance and noise within the HVAC system.

Larger angles, such as 20 degrees or higher, would likely introduce more turbulence and pressure drop that could hinder the duct's efficiency, making them impractical for most HVAC applications. Therefore, adhering to the 15-degree rule ensures that the duct remains effective in directing airflow without compromising the overall efficiency of the HVAC system.