Valemo VDM10B, 24 VAC General Purpose Spring Return Damper Motor Actuator , Replace Honeywell M847D & other damper Actuators (see more below), with adjustable stopper.

Valemo VDM10B, Spring Return Damper Actuator & Motor with Adjustable Stop on Power Open for Bleeding, Replacement Damper Motor Actuator for Honeywell ARD ZD M847D & Similar Actuators, 24VAC, No Switch 

• VDM10B 2-wire Spring return damper actuator motor is designed to be compatible with  and drop-in replacement for  following models:
  Honeywell's M847D, M847D1004, and old ARD and  ZD   series of damper motors.
  DuroZone #35105 damper Motor.
  Zone First, EWC,  and Erie, and other 2-wire damper actuators.
• Most reliable and trusted choice on Amazon since 2013.
  Well tested, no-hassle installation, most popular  purchases by home owners as well as contractors.
  Longest 3-Year Warranty available online.
• Extra unique  feature: Adjustable operating angle  60 to 90 degrees, allowing partial  close (air bleed when necessary).
  To be Used in either HVAC air ducts, or venting  installations.
• Tested to last 15+ years. Heavy-duty motor with all METAL gears inside, stainless steel housing.
• Input Power: 24 VAC, 50/60 Hz.
  Direct coupling to 5/16" damper shaft.
  Comes with detailed installation manual.

User Manual / Specification (PDF)