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TAMCO Installation Guidelines for medium-duty backdraft dampers

Weight and Counterweight Adjustment

Series 7000 WT backdraft damper showing adjustable weights


  • Series 7000 WT Weighted Backdraft Dampers have a round, adjustable weight and a threaded post secured to the center of each blade. A zert nut on the back of the blade is used to lock the threaded post in place.
  • Each cylindrical, steel weight measures 1¼” (32 mm) in diameter.
  • Weights are supplied, so that the required resistance to the opening of the blade against airflow can be achieved.
  • The cylinder can be adjusted away from or towards the blade, as far as the threaded post will allow.
  • Moving the weight away from the blade will increase the amount of additional pressure and airflow required to open the backdraft damper blades.
  • Moving the weight closer to the blade will decrease the amount of additional air pressure and airflow required to open the backdraft damper blades.
  • Additional weights may be added to increase the desired pressure build-up before the backdraft damper begins to open.
  • Adjust weight placement until desired pressure build-up is achieved. (Several re-adjustments may be necessary for desired operation.)
  • Once adjustment is completed, tighten the weight locking nut to prevent weight from moving out of position.
Series 7000 CW backdraft damper showing adjustable counterweights


  • Series 7000 CW Counterweighted Backdraft Dampers have an adjustable ¾” wide (19 mm) aluminum, counterweight bar attached to the back of the blades (with the exception of the top blade).
  • The aluminum bar bracket is centered along the length of the blade. This is designed to apply even pressure across each blade. Do not move the bar bracket away from the factory-aligned center of the blade.
  • Counterweights can be set to relieve air pressure differentials less than .01 in. w.g. (3 Pa).
  • To accelerate blade opening, move the aluminum counterweight bar further away from the blade.
  • To delay blade opening, move the aluminum counterweight bar closer to the blade.
  • To move the aluminum counterweight bar, first loosen the two socket head cap screws with a 3/16” (4.8 mm) Allen/Hex wrench. Do not remove the screws. (The socket head cap screws secure the aluminum counterweight bar in place, through the washer and the aluminum bar bracket.)
  • Slide the aluminum counterweight bar in the direction required to achieve desired blade operation. The counterweight bars should be adjusted to the same location on each blade, to ensure that even pressure is applied across the entire backdraft damper.
    (Several re-adjustments may be necessary. Keep in mind that depending on external conditions and damper size, moving the aluminum bar to the furthest point away from the blade might prevent the backdraft damper from closing.)
  • Once adjustment is completed, re-tighten socket head cap screws.


TAMCO Medium-Duty Backdraft Damper Installation Guidelines