Operation; General; Output Signal Feedback (F); Actuator Override - Honeywell ML7425A Series Product Data

CAUTION
Equipment Damage Hazard.
Improper voltage through the 43191680 Dual
Auxiliary Switch will damage the switch beyond
repair.
Use the 43191680 Dual Auxiliary Switch with 24 Vac
applications only .

OPERATION

General

In the ML7425, the drive of a synchronous motor is converted
into the linear motion of the actuator stem by using a spur
gear transmission. A button retainer clip connects the actuator
stem to the valve stem.
An integrated spring package limits the stem force to a
factory-adjusted value in either direction. Installed
microswitches turn off the actuator when the specified stem
force is reached.
The ML7425A,B Spring Return Valve Actuators provide a
safety valve position in event of power failure. On power
failure, the ML7425A returns the stem to the bottom position.
On power failure, ML7425B returns the stem fully upward.
The ML7425 actuators are shipped from the factory with a
spring handle retaining clip installed, so that the actuator can
be connected to the valve without applying power. This clip is
removed after the actuator is installed on the valve. See
Installation section.
Signal Input (+)
The analog input signal (+) range is set at the factory to 0 to
10 Vdc. Changing the position of the W2 selector plug sets
the range to 2 through 10 Vdc. Selector plugs W1, W2, and
W3 are positioned on the back side of the PCB protection
sheet. See Fig. 12 for location of the selector plugs.
Signal Input Failure
Using selector plug W1, the actuator can be set to run to one
of three positions in event of a signal failure:
1. 0% — Actuator position corresponds with 0 or 2 Vdc
signal
2. 50% — Actuator stem in mid-position
3. 100% — Actuator position according to 10 Vdc signal
NOTE: W1 is factory set at the mid-position.
ML7425A,B SPRING RETURN ELECTRIC LINEAR VALVE ACTUATOR

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.
When the actuator stem is up, the output signal is 0 or 2 Vdc.
The output of the signal does not change when the action of
the actuator is reversed using W3. See Direction of Action.

Actuator Override

The output signal override function can be used for 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 a relay, see Fig. 14.
1
2
3
4
Fig. 14. Connections for overriding control signal
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 the feedback (F) function is 10 Vdc.
The output of the signal does not change when W3 is used to
reverse the action of the actuator, see Fig. 12.
7
ML7425
WIRING
2
STRIP
F
F
+ +
–
–
T2
T1
O1
O2
TS
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
2-10 Vdc FEEDBACK SIGNAL. SEE OUTPUT SIGNAL
FEEDBACK SECTION.
0-10Vdc OR 2-10 Vdc CONTROL SIGNAL. SEE SIGNAL
INPUT (+) SECTION.
SEE OVERRIDE SECTION FOR DETAILS ON
OVERRIDE OPERATION.
to drive actuator to a specific position.
INPUT
(FEEDBACK)
OUTPUT
3
SP3T
OVERRIDE
SWITCH
4
L1
(HOT)
L2
1
M7906A
63-2518-3