How is the total external static pressure in an HVAC system calculated?

The total external static pressure in an HVAC system is determined by measuring the resistance that airflow encounters as it moves through the entire system, which includes both the unit and the ductwork. This pressure can be influenced by various factors such as bends in the ducts, friction along the duct surfaces, and the layout of the duct system. By measuring the pressure drop across the unit and the ducts, technicians can understand how efficiently the air is being distributed and any adjustments that may be needed for optimal performance.

Using a digital pressure gauge is one practical approach to measuring static pressure directly in ducts, but it is important to consider it within the context of the entire system. Similarly, while analyzing duct material properties and calculating airflow velocity and area can provide valuable insights about system performance, they do not directly give a total external static pressure measurement in the context needed for this specific question. Therefore, assessing the overall resistance at the unit and ducts combined provides the most applicable method for determining total external static pressure.