Operation - Honeywell ML7421A Product Data

ML7421A,B ELECTRIC LINEAR VALVE ACTUATOR
Auxiliary Potentiometers
The 43191679 Dual 220 Ohm Auxiliary Potentiometer can be
used as feedback potentiometers and to provide remote
indication of the valve position. This dual potentiometer must
be used but will provide only a single auxiliary potentiometer
function with feedback of 135 ohm operating range. See the
Accessories section for the part numbers and the Installation
Instructions packed with the potentiometer for further details.
Auxiliary Switches
The 43191680 Dual Auxiliary Switch can be used on both the
ML7421A and ML7421B Electric Linear Valve Actuators.
Switching points are adjustable over the full length of the
actuator stroke; for example, the switch can be used to switch
pumps or to provide remote indication of any stroke position.
See the Accessories section for the part numbers and the
Installation Instructions packed with the auxiliary switches for
details.
IMPORTANT
Use the 43191680 Dual Auxiliary Switch only with
24 Vac applications.

OPERATION

General
In the ML7421, the drive of a synchronous motor is converted
into the linear motion of the actuator stem by using a worm
gear transmission. A button retainer clip connects the actuator
stem to the valve stem.
The internal force sensor, using installed microswitches, turns
off the actuator when the specified stem force is reached.
Manual Operation
The ML7421 is equipped with a manual operator knob (see
Fig. 10) to open or close the valve in the event of power
failure. Turn off or disconnect the power supply before
manually operating the ML7421.
To operate, push down on the manual operator knob and turn
the knob counterclockwise to move the stem downward or
turn the knob clockwise to move the stem upward. When the
actuator is returned to automatic control, the manual operator
knob unlocks automatically.
NOTE: If the manual operator knob is not pushed in while
turned, it turns only for a short distance before it
automatically disengages without power resumption.
IMPORTANT
Manual operation allows a very high closing force
that can jam the actuator spindle, exceeding the
rating of the force switches, and stopping the motor.
After a manual valve close-off operation, release the
spindle one turn by turning the manual operator
knob so the manual operator automatically
disengages on power resumption.
63-2517—1
Fig. 10. ML7421A,B manual operator knob.
Signal Input Failure
Using coding switch J1-J2, the actuator can be set to run to
one of three positions in the event of a signal failure:
Coding switch open:
The actuator goes to the middle position on signal input
(+) failure.
Coding switch in the upper position (J1):
The actuator goes to the upper position on signal input
(+) failure.
Coding switch in the lower position (J2):
The actuator goes to the lower position on signal input
(+) failure.
The coding switch is a hook-type switch mounted on the
component side of the printed circuit board. See Fig. 11.
IMPORTANT:
If the actuator (ML7421A1008 or ML7421B1007
only) is used with a Series 90, 135-ohm controller,
the coding switch must be open.
11 13 3 22 7 9
T1
S1
Fig. 11. Coding switch position and direction of action.
6
M6640
4 10 15 8 20 21
T2
J1
J2
M6752