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WHAT ACTUATOR TORQUE IS REQUIRED?
One of the bits of information we always want to know in selecting damper actuators is the required torque. Actuators are rated in inch pounds or newton meters. The inch pound rating equals the energy required to move a one pound load one inch. Newton meters are for the metric world, mostly in Europe. One hundred eighty inch pounds roughly equals twenty Newton meters. A torque wrench would demonstrate the required torque to open a damper but that is not always practical. Square area and face velocity of the damper factor into mathematical calculations or required torque. The manufacturer of orange actuators has a table showing in-lbs. per square foot (in-lbs./sq ft)at 1000 feet per minute, 1000-2500, and 2500-3500. A 36”x36” damper at 1000 feet per minute would follow this formula. 3’x3’= 9 square feet times 5 in-lbs. per square foot equals 45 in-lbs. torque required.
So in order to calculate the actuator you need you will need to do the following:
- Using the damper type vs velocity table; find the type of damper you are working with in the first column
- Then figure out the velocity of the system you are working on. Columns 2,3 and 4 are giving the value of in-lbs per square foot of damper.
- Now that you have extracted the value needed from the table, we can now calculate. L (Feet) * W ( Feet) = Damper Area (Square Feet)
- Then Take your Damper Square Feet and then multiply by the torque value you got from the table. This will give you the required torque needed when selecting an actuator.
| Damper Type | Velocity @ 1000 Feet Per Minute | Velocity @ 1000-2500 Feet Per Minute | Velocity @ 2500-3500 Feet Per Minute |
|---|---|---|---|
| parallel blade edge seals | 7 in-lbs | 10.5 in-lbs | 14 in-lbs |
| opposed blade edge seals | 5 in-lbs | 7.5 in-lbs | 10 in-lbs |
| parallel blade no edge seals | 4 in-lbs | 6 in-lbs | 8 in-lbs |
| opposed blade no edge seals | 3 in-lbs | 4.5 in-lbs | 6 in-lbs |
| round | 10 in-lbs | 14 in-lbs | 20 in-lbs |
With the torque established, other questions determine the selection. Is the fail safe or fail in place required? Stated another way, is it spring return or non-spring? What is the power supply voltage? What is the control signal?
Belimo LF at 35 in-lbs. would not be enough. JCI M9208 at 70 in-lbs. would be acceptable. Siemens GMA at 62 in-lbs. would be good. Honeywell MS7505 probably would do. It is rated at 44 in-lbs. These are spring return options. The return spring torque is usually the same as the driving torque.
Non-spring options include Belimo LMB, Siemens GDE, JCI M9308, Honeywell MN7505.
