Damper Authority Calculator
Control authority of a modulating damper in a duct system.
Enter your values
ⓘ Live results
Results
- Damper authority
- 20%
- Rating
- Poor - control will be non-linear, oversized damper
- Total loop pressure drop
- 0.75 in wc
Quick answer
Damper authority equals the damper's own pressure drop divided by the total pressure drop of the damper plus the rest of the system it controls.
Authority = dP_damper / (dP_damper + dP_system)
How to use the Damper Authority Calculator
- 1Enter the damper's pressure drop when fully open at design flow.
- 2Enter the pressure drop of the rest of the branch or system the damper modulates.
- 3Read the damper authority — values above 0.5 give the most linear, stable control.
Worked example
Using the values the calculator loads with:
Inputs
- Damper pressure drop (wide open)0.15 in wc
- Rest-of-system pressure drop0.6 in wc
Results
- Damper authority20%
- RatingPoor - control will be non-linear, oversized damper
- Total loop pressure drop0.75 in wc
Frequently asked questions
Why is low authority a problem?
A damper with low authority does almost all its work near the closed position, making control jumpy and hard to tune.
How do I increase authority?
Select a smaller, higher-pressure-drop damper, or reduce the rest-of-system resistance.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.