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Actuator Override
To override the control signal (for freeze protection or similar
applications), connect the 24 Vac common (T2) to either
terminal O1 or O2. Connecting to terminal O1 fully extends
the actuator stem. Connecting to O2 fully retracts the actuator
stem.
The control signal (+) is ignored when the override signal is
applied to terminal O1 or O2. This override can be achieved
with a switch or a relay. See Fig. 12.
Direction of Action
The direction of action can be changed by repositioning the
selector plug W3.
CHECKOUT
The actuator can be checked out either directly or using a controller.
Direct Checkout
1. Mount the actuator for the required application.
2. Check the valve position and make sure that 24 Vac is
correctly applied to the actuator.
3. Apply the control signal to the appropriate leadwires to
move the valve in the required direction.
4. If the actuator does not move, make sure the actuator is
properly installed.
5. If the actuator is correctly installed and does not run,
replace the actuator.
ML6421, ML7421 NON-SPRING RETURN ELECTRIC LINEAR VALVE ACTUATORS
Fig. 12. Connections for overriding control signal to drive
Controller Checkout
1. Adjust the setpoint of the controller to call for opening or
2. If the valve is closed, it should begin to open.
3. If the valve remains closed, move the setpoint further
4. If the valve does not move, check for 24 Vac in the
5. If 24 Vac is present and the actuator does not operate,
6. If wiring is correct, 24 Vac is present on the power input
7
ML7421
WIRING
2
STRIP
F
F
+
+
–
–
T2
T1
O1
O2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
2
2-10 Vdc FEEDBACK SIGNAL. SEE OUTPUT SIGNAL
FEEDBACK SECTION.
3
0-10Vdc OR 2-10 Vdc CONTROL SIGNAL. SEE SIGNAL
INPUT (+) SECTION.
SEE OVERRIDE SECTION FOR DETAILS ON
4
OVERRIDE OPERATION.
actuator to a specific position.
closing the valve. Observe the actuator.
toward the open setting.
actuator power input.
reverse the controller leadwires to determine if the
device is incorrectly wired.
terminals, and the actuator does not run, replace the
actuator.
INPUT
(FEEDBACK)
OUTPUT
3
SP3T
OVERRIDE
SWITCH
4
1
L1
(HOT)
L2
M17438
63-2515—4
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