How do you calculate pressure loss in a duct system?

To calculate pressure loss in a duct system, the correct approach involves understanding how friction loss accumulates over a distance within the duct. The formula involves taking the friction loss per foot and multiplying it by the total length of the duct. This means that if you have a certain friction loss for every foot of duct and you know how many feet of duct you have, you can determine the total pressure loss by performing this multiplication.

For example, if a duct has a friction loss of 0.5 inches of water column per foot and the duct is 20 feet long, the total pressure loss can be calculated as 0.5 inches × 20 feet, resulting in a total pressure loss of 10 inches of water column. This method effectively captures how losses compound over the distance of airflow through the duct system, making it a crucial formula for HVAC design and analysis.

The other options do not accurately reflect the relationship between friction loss and the length of ductwork required to calculate the overall pressure loss. Understanding this calculation is fundamental for HVAC professionals to ensure efficient system design and operation.