3 NM, 5 NM SERIES SPRING RETURN DIRECT COUPLED ACTUATORS
9 62-0274—07
Fig. 20. Wiring for 3 position Economizer controllers, MS74 series.
Fig. 21. Wiring for Sylk BUS, MS31 series.
OPERATION
The actuator is designed to be used in ventilating and air 
conditioning installations to operate valves, dampers, 
ventilation flaps and louvers. (For ratings, see the 
Specifications section.) If the power fails, the actuator will 
spring return to the fail safe position.
When using a proportional controller, the actuator drives 
toward its fully open position when the input signal increases; 
the actuator drives toward the fully closed position when the 
input signal decreases. The actuator stops when the input 
signal reaches the desired proportional control point. This 
operates in reverse when set to a 10-2(0) position.
IMPORTANT
The actuator is designed to respond to DDC 
Controller instantaneous contact closures. Take care 
not to short cycle the actuator. Unstable damper 
control can cause premature actuator failure.
Actuator Override
To override the control signal (for freeze protection or similar 
applications):
1. Override to full open:
a. Disconnect the input signal (from terminal 3).
b. Apply 24 Vac to terminal 3.
c. See Fig. 22.
2. Override to full closed:
a. Disconnect the input signal (from terminal 3).
b. See Fig. 23.
Fig. 22. Override to full open.
ACTUATOR
V
FEEDBACK
5
4
3
1
2
M32679
3 POSITION
MINIMUM POSITION
1
EXTERNAL MINIMUM POSITION POT 
CAN BE APPLIED TO 4 90°-0°.
SET SWITCH TO 3 POSITION.
2
2-10 VDC
10-2 VDC
3 POSITION
MINIMUM POSITION
Fltg, fwd
Fltg, rev
2
SENSOR
24 VAC
–
+
1 = ADDRESS 11
2 = ADDRESS 12
3 = ADDRESS 13
4 = ADDRESS 14
5 = ADDRESS 15
6 = TEST
S-BUS
LINE VOLTAGE POWER SUPPLY.  PROVIDE 
DISCONNECT MEANS AND OVERLOAD 
PROTECTION AS REQUIRED.
24 VDC SUPPLY ACCEPTABLE.
0/2..10 VDC INPUT
0/2..10 VDC OUTPUT
M32548
1
2
1
2
S-BUS
24 VAC
ACTUATOR
MS3105J ONLY
1
2
3
4
5
S-BUS
S-BUS
V
S3 S2
S1
ACTUATOR 
0/2 TO 10 VDC 
PROPORTIONING 
CONTROLLER 
24 VAC 
1
1 
2 
3 
2 
LINE VOLTAGE POWER SUPPLY.  
PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED. 
 
24 VDC SUPPLY ACCEPTABLE. 
 
SET SWITCH TO MODULATING. 
V 
FEEDBACK
– 
 
+ 
 
FEEDBACK 
5
4 
3 
1 
2 
M27827
2-10 VDC 
10-2 VDC 
0-10 VDC 
10-0 VDC 
Fltg, fwd 
Fltg, rev 
3 
SPDT 
0°-90° OR +
90°-0° OR N/A