Friction loss in an HVAC system is typically measured by loss per how many feet of straight duct?

Friction loss in an HVAC system is commonly expressed as the pressure drop that occurs over 100 feet of straight duct. This measurement standardizes the way engineers and HVAC technicians calculate and compare the performance of different duct systems, making it easier to design and optimize systems for efficiency.

Using a standard length of 100 feet allows for consistent calculations that can be applied across various duct sizes and materials. This value aids in understanding how much resistance the airflow encounters as it travels through the ductwork, enabling professionals to make informed decisions regarding air handling and system design.

In contrast, the other lengths provided do not align with this standard practice, which is why they are less relevant in the context of measuring friction loss in HVAC systems. Adhering to this accepted measurement helps ensure accurate assessments and evaluations in the field.