The Model DM Actuators provide positive and precise modulating control of boiler draft control dampers, combustion air louvers, or other final control elements.  Thousands of DM Actuators are in use in Preferred Instruments boiler control systems. The actuator is used to position combustion air & fuel gas dampers and fuel control valves. An integral interlock switch proves an open damper position for purge proving or a low-fire position for fuel valves prior to light-off, thereby assuring a safe burner light-off. The DM Actuator is used on control dampers that have a maximum 6.5 sq. ft. area. For heavier-duty service, use the Preferred Instruments PL-2 linear actuators.

The Model DM Rotary Actuator is used in remotely controlled, manual or fully automatic combustion or process control systems. Responding to a SPDT snap-action or floating contact switch, the actuator may be started, stopped, or instantly reversed with out over heating or loss of power.

Operation: The DM Actuator utilizes an instantly reversible motor to rotate a hardened steel output shaft through a reduction of precision hobbed gears. The output shaft actuates four adjustable cam operated switches: two (2) travel limit switches to stop motor operation at pre-selected positions and auxiliary switch to provide damper position proving interlocks. The motor has an integral brake for positive positioning, and can be stopped, started, or instantly reversed at any time within its travel without overheating or loss of power. For maximum durability, the motor and gear train are sealed in an oil filled compartment.

• 160° Rotary Electric Actuator (Adjustable From 45°To 270°)
• 12.5 ft-lb. Torque Output
• Designed For Modulation Service
• All Gears and Roller Bearings Submerged In Oil
• Self-Locking Drive System To Hold In Last Position
• One Auxiliary Limit Switch Position Output

Power: 24 VAC - 50 / 60 Hz, 20 VA

Ambient Temperature: +10º to 125° F

Input: Switching SPDT or Floating Contacts

Torque: 25 ft-lbs (300 in-lb) Breakaway 12.5 ft-lb (150 in-lb) Running

Rotation: 160° in 60 seconds Adjustable 45°-270°

Auxiliary Switch: Integral SPDT, Adjustable 10 Amps. @ 120 VAC

Integral Brake: Fail-Safe, Self Locking

Linkage: Actuator Lever Arm Included; Connecting Linkage Optional

Output Shaft: Hardened Steel

Motor: Reversible, Split Phase, Capacitor Type, Oil Submerged

Gear Train: Precision Hobbed, Hardened Steel Gears, Oil Submerged

Application Example: Fuel Control Valves and Balanced Boiler Outlet Damper For Up To 6.5 Sq. Ft. Duct

Dimensions: 8 ¼" H x 5 27/32" L x 5 1/32" D

Enclosure: Die Cast Aluminum, Dust Tight, Splash Proof

The control damper or fuel valve actuator shall be totally enclosed in a dust-tight, splash-proof housing; have integral, snap action, travel limit and damper open proving switches; and maintenance-free oil immersed motor and gear train. A double ended output shaft shall have an integral brake for precise positioning without backlash, be field adjustable from 45°-270°, and rotate 160° in 60 seconds. The actuator shall be rated at 25 ft-lbs (300 in-lbs) breakaway, 12.5 ft-lbs (150 in-lbs) running torque and be capable of being stopped, started, or instantly re versed with out loss of power or over loading. The actuator shall be suit able for application to combustion air and flue gas damper and fuel flow control valve positioning and be a Preferred Instruments, Danbury, CT, Model DM.