In a duct system, how do you calculate the friction loss per 100 feet?

To calculate the friction loss per 100 feet in a duct system, it is essential to understand how friction loss is quantified in relation to both the length of the duct and the friction rate. The correct approach involves multiplying the length of the duct by the friction rate. This relationship stems from the principle that friction loss is directly proportional to both the distance air travels through the duct and the resistance encountered per unit length.

The friction rate is typically expressed in units such as inches of water column per 100 feet of duct. Therefore, when you multiply this rate by the length of the duct system (in hundreds of feet), you directly determine the total friction loss experienced over that length. This method provides a straightforward means to calculate total friction loss, allowing designers and technicians to assess system performance and ensure efficient air flow.

Understanding this concept is crucial for effective HVAC design and troubleshooting, ensuring that air systems operate within designed parameters to maintain comfort and efficiency.