What is generally assumed to be the maximum angle for an HVAC elbow?

The maximum angle for an HVAC elbow is generally assumed to be 90 degrees. This is because a 90-degree elbow is commonly used in ductwork to change the direction of airflow while maintaining efficient airflow and minimizing pressure loss. While elbows can exist at other angles, the 90-degree configuration is standard for most typical HVAC systems.

The 120-degree and 150-degree elbows may be used in specific circumstances to help further reduce turbulence and pressure loss, but they are not the norm and are less common. An elbow at 180 degrees would result in a U-turn in the ducting, which is not practical for most systems as it would significantly hinder airflow and increase resistance. Thus, 90 degrees remains the maximum angle most often referred to in HVAC applications.