Step 1
Acquire the Damper Torque Rating, or DTR, from the manufacturer for the damper at the most severe operating conditions. If you cannot get the DTR right away, use general estimates until you can get the actual rating. For standard leakage dampers, which is more than 10 cubic feet per minute per square foot (CfM/ft2), estimate 2.5 pound-inch/square foot (lb-in/ft2). For low leakage, 5 to 10 CfM/ft2, estimate 5 lb-in/ft2, and for very low leakage of less than 5 CfM/ft2, estimate 7 lb-in/ft2.
Step 2
Calculate the area of the damper, or DA, by measuring the dimensions of the damper and multiplying the length by the height. The measurement should be in square feet.
Step 3
Multiply the DRT by the DA to get the Total Damper Torque, or TDT.
Step 4
Use a torque wrench on the shaft of the damper to acquire a measurement of the TDT if the DTR is not available.