Model SM, Servo Actuator


The Model SM Servo Actuator provides directly connected and precise modulating control of fuel valves and combustion air & flue gas control dampers.

  • Overview and Features
  • Application
  • Specifications
  • Documents
Overview and Features

The actuator opens, modulates, and closes the valves and/or dampers in accordance with the integrated combustion control and burner management system programs.  An integral interlock switch provides proof of open or closed position for safe burner operation.  In addition, the feedback potentiometer provides indication of the motor’s shaft position.  The SM Actuator is used on boiler control applications that have a maximum of 37 ft-lbs torque required.  For heavier-duty service consult the factory.

  • 90° Rotary Electric Actuator (Adjustable Over 270°)
  • 3, 15 or 37 ft-lb. Torque Output
  • Designed For Modulation Service
  • Self-Locking Drive System To Hold In Last Position
  • Electrically Isolated Feedback Potentiometer Provides Indication Of Shaft Position
  • Two Auxiliary Limit Switch Position Output

The Preferred SM series rotary actuator works on a triac input. Switching SPDT or floating contacts provide power directly to the CW or CCW motor windings. A 5000 Ohm feedback potentiometer provides precise servo position data back to the control device.

Two adjustable Auxilliary switches provide an additional level of safety proving actuator position.


​​​​​​Power: 120 VAC - 50 / 60 Hz

Ambient Temperature: 14° F to 104° F, (-10° C to + 40° C)

Input: Switching SPDT or Floating Contacts

Torque: 3, 15 or 37 ft-lbs (depending on model selected)

Duty cycle: 100%

Linearity:  ± 1%

Rotation:  90° in 30 Seconds, Maximum Rotation 270 Degrees

Feedback Potentiometer: 5000 OHM Change For 270° Stroke

Auxiliary Switch: Two (2) Integral SPDT, Adjustable 

Integral Brake: Fail-Safe, Self Locking

Installation Position: Any

Output Shaft: Hardened Steel (⅜" Sq-Dbl. Ended)

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

Enclosure: SM-3: NEMA 2, SM-17 & SM-37: NEMA 4


Servo Actuator (SM) Specification

Servo Actuator (SM) Cutsheet


Servo Actuator (SM) Manual After Jan 2020