What should be the maximum friction loss in duct systems to ensure efficient performance?

The maximum friction loss in duct systems is critical for ensuring efficient air distribution and overall system performance. A friction loss of 0.5 inch water gauge (wg) is often considered a standard maximum for typical air duct systems. This level allows for an effective balance between airflow and pressure drop, minimizing energy consumption while maintaining adequate airflow to all areas of a building.

When friction loss exceeds this value, it can lead to several issues, including insufficient airflow to the farthest ducts, increased energy use as the system works harder to push air through the ducts, and potential noise from turbulent airflow. Keeping friction loss around or below 0.5 inch wg helps HVAC systems run more efficiently and effectively without requiring excessive adjustments or compensatory measures.

Values greater than 0.5 inch wg can be encountered in specific scenarios, but they usually indicate that system design or duct sizing may need revision to prevent operational inefficiencies and ensure comfort levels are met in all spaces served by the ductwork.