All Belimo spring return actuators can be mounted to fail open or to fail closed upon loss of power based on how the actuator is mounted on the damper shaft. With the CW side facing away from the shaft the spring will rotate the damper shaft clockwise upon loss of power. Similarly, if the CCW side is facing out the actuator will rotate counter-clockwise upon loss of power. Determine proper fail-safe direction of rotation and relocate the mounting clamp to the opposite side of the actuator as needed.