ML7421A,B ELECTRIC LINEAR VALVE ACTUATOR
63-2517-2
6
Output Signal Feedback (F)
An analog output signal (2 to 10 Vdc) that represents the
actual actuator stem position is available at Terminal F. It
can be used for remote indication of the stem position.
When the actuator stem is fully extended, the output signal
is 10 Vdc.
The output of the signal does not change when the action of
the actuator is reversed using W3 or W4, which is set to
mA-position, see Direction of Action.
Actuator Override
The converter output signal override position can be used in
freeze protection or similar applications. it forces the
actuator into an end position, overriding the control signal.
To exercise this function, connect the 24 Vac common (or
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 relay, see Fig. 9.
Fig. 9. Connection for overriding control sigal to
drive actuator to specific position.
CHECKOUT
The ML7421 Electric Linear Valve Actuator can be checked
out either directly or using a controller.
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.
Direct Checkout
Controller Checkout
1. Adjust the setpoint of the controller to call for opening
or closing the valve. Observe the actuator.
2. If the valve is closed, it should begin to open.
3. If the valve remains closed, move the setpoint further
towards the open setting.
4. If the valve does not move, check for 24 Vac in the
actuator power input.
5. If 24 Vac is present and the actuator does not operate,
reverse the controller leadwires to determine if the
device is miswired.
6. If the wiring is correct, 24 Vac is present on the power
input terminals, and the actuator does not run, replace
the actuator.
Direction of Action
The direction of the actuator action can be changed by
repositioning selector plug W3, which is factory set so that
the stem extends on increasing signal and retracts on
decreasing signal. When the actuator stem is fully extended
the output signal from feedback (F) function is 2 Vdc.
