How do I know what size damper I need?

With so many dampers being used in the HVAC industry the sizing of an electronic actuator like Belimo, Johnson Controls, and Honeywell is critical.

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No matter if the electronic actuator is spring return or non-spring return the proper torque rating (in-lb += inch pounds) of the actuator is necessary to drive the blades of the damper in a open or a closed position. So the first step in selection of the proper damper actuator is to find the damper&#;s square footage AREA. A simple formula of Width X Height divided by 144 will give you the square footage of a damper.

Example: The damper in question is 45 inches X 23 inches using the formula. 45 X 23 = divided by 144 = 7. square feet of damper area.

The next important piece of information is the type of damper you need the actuator for.

1.     NO SEALS&#;.. Usually an outside air damper

2.     WITH SEALS&#;.. Usually interior dampers like zone control dampers

3.     Fire/Smoke dampers

NO SEALS dampers require 7 in-lb of torque per square foot of damper area to open/close the damper blades *

WITH SEALS dampers require 8 in-lb of torque per square foot of damper area to open/close the damper blades *

FIRE/SMOKE dampers require 9 in-lb of torque per square foot of damper area to open/close the damper blades *

* ( Less than feet per minute air flow)

Multiply 7, 8, or 9 by the damper&#;s square footage to arrive at the minimum torque value needed by the actuator motor to open and to close the damper. Note: If the torque necessary is too close to the actuators maximum torque valve go to the next highest torque value actuator.

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With this in mind let&#;s look at the different torque requirements for the example above.

The square footage of our damper is 7. square feet

NO SEALS damper = 7. X 7 = 50. in-lbs of minimum torque necessary

WITH SEALS damper = 7. X 8 = 57.50 in-lbs of minimum torque necessary

FIRE/SMOKE damper = 7. X 9 = 67. in-lbs of minimum torque necessary

Industrial dampers will usually have different requirements for the sizing of electronic damper actuators but this simple formulas can be used on domestic and commercial sizing of actuatrors. If you need help sizing your damper actuators pleases give Stromquist and Company a call at 1-800-241- and we can help you in the selection process.

Damper Size Selection

Typically in an existing install, the duct size will determine the damper sizes needed.  But if starting with a new duct system 2 variables must be known to determine damper sizes.

• Total CFM of System

Calculate using the &#;whole house load&#; with maximum diversity.

• Zone CMF

  (needed for each Zone)

 Total the rooms associated with each zone separately to get the &#;Zone CFM&#; (No diversity)

Round Damper Sizes

Round damper sizes range from 4&#; to 18&#; typically in 1&#; increments up to 10&#; and in 2&#; increments up to 18&#;.  There are two numbers that must be used when designing a zoning system with regard to all dampers.  

If you are looking for more details, kindly visit Dampers for Domestic Equipment bulk supply.