ML6421, ML7421
Non-Spring Return
Electric Linear Valve Actuators
PRODUCT DATA
FEATURES
•
•
•
•
•
•
•
•
Quick and easy installation.
No separate linkage required.
3/4 in. (20 mm) stroke on ML6421A and ML7421A.
1-1/2 in. (38 mm) stroke on ML6421B and ML7421B.
No adjustments required.
Accurate valve positioning.
Low power consumption.
Selectable 0(2) to 10 Vdc or 0(4) to 20 mA input signal
with ML7421.
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•
•
•
•
•
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Position feedback with ML7421.
High close-off ratings.
Direct/reverse acting with ML7421.
Force-limiting end switches.
Manual operator.
Synchronous motor.
Corrosion-resistant design.
Maintenance free.
APPLICATION
The ML6421A,B Non-Spring Return Electric Linear Valve
Actuators are suitable for use with low-voltage, single-pole
double-throw (spdt), Series 60 two-position and floating
controllers. These actuators operate standard Honeywell
valves in heating, ventilating, and air conditioning (HVAC)
applications.
Conduit connector knockout.
The ML7421A,B Non-Spring Return Electric Linear Valve
Actuators are modulating control actuators used with controls
that provide an analog output of 0 to 10 Vdc or 2 to 10 Vdc.
These actuators operate standard Honeywell valves in HVAC
applications. An internal selector plug can be used to reverse
the direction of action.
Contents
Ordering Information ........................................................
2
®
® U.S. Registered Trademark
Copyright © 2002 Honeywell • All Rights Reserved
63-2515-4
ML6421, ML7421 NON-SPRING RETURN ELECTRIC LINEAR VALVE ACTUATORS
ML6421A,ML7421A
ML6421B, ML7421B
7 (178 ) X 7 (178)
7 (178 ) X 7 (178)
2-1/2
(64)
2-1/2
(64)
16-7/8
(430)
14-1/4
(360)
MINIMUM
MINIMUM
CLEARANCE
CLEARANCE
12-3/4
10-3/8
(326)
(264)
KNOCKOUTS
(2)
7/8 (22)
KNOCKOUTS
(2)
7/8 (22)
9-3/8
(239)
11-7/8
(301)
5-5/8
(142)
8
(204)
YOKE DIAMETER 1-3/8 (35)
M17430
YOKE DIAMETER 1-7/8 (48)
Fig. 1. Approximate dimensions of ML6421, ML7421 Electric Linear Valve Actuators in in. (mm).
INSTALLATION
CAUTION
Electrical Shock or Equipment Damage Hazard.
Can shock individuals or short equipment
circuitry.
When Installing this Product…
1. Read instructions carefully. Failure to follow them could
damage the product or cause a hazardous condition.
2. Check ratings and description given in the specifications
to make sure the product is suitable for your application.
3. Installer must be a trained, experienced service
technician.
Disconnect power supply before installation.
Location
Install the actuator in a location that allows enough clearance
for mounting accessories and for servicing.
4. After installation is complete, check out product
operation as provided in these instructions.
CAUTION
Equipment Damage Hazard.
Can damage actuator due to condensation or a
valve gland leak.
Install the actuator in a position above horizontal.
3
63-2515—4
ML6421, ML7421 NON-SPRING RETURN ELECTRIC LINEAR VALVE ACTUATORS
Mounting
Wiring
1. Place the actuator on the valve with the U-bolt around
the valve collar. See Fig. 2.
CAUTION
IMPORTANT
Electrical Shock or Equipment Damage Hazard.
Can shock individuals or short equipment
circuitry.
When tightening the set screws, first tighten the right
set screw. See Fig. 2.
Disconnect power supply before installation.
2. Place the U-bolt against the valve collar and secure the
actuator to the valve by turning each U-bolt nut clock-
wise.
IMPORTANT
1. All wiring must comply with local electrical codes,
ordinances and regulations.
2. Voltage and frequency of the transformer used with
the actuator must correspond with the characteristics
of the power supply and those of the actuator.
NOTE: To assure even pressure on the collar, first
tighten the nuts finger-tight and then alternate
turning each U-bolt nut until both are snug.
3. Push aside the stem button retaining clip and hold. See
Fig. 2.
NOTE: See Fig. 5 through 8 for typical wiring hookups.
4. Lift the valve stem until the head of the valve stem
button is inside the large slot of the stem button
retaining clip on the actuator.
1. Feed power and control wires through the conduit
connector located on the bottom of the actuator case.
5. Release the stem button retaining clip to secure the
stem button. Check to make certain the stem button is
secured by the retaining clip.
6. Pull off the manual operation knob.
7. Remove the cover from the actuator using a Phillips or
crosspoint screwdriver. See Fig. 3.
CAUTION
Conduit connection or removal can break an
unsupported connector.
Equipment Damage Hazard.
When removing or attaching conduit, use a wrench to
support the motor connector.
2. Using the appropriate wiring diagram (see Fig. 5 through
8), connect power and control wires to the actuator.
Make sure that all wiring is correct.
3. For the ML7421 only: Check selector plugs for proper
settings. See Signal Input Failure section for details.
4. When wiring is complete, replace the actuator cover
and control knob (see Fig. 9).
TIGHTEN RIGHT
SET SCREW FIRST
5. Apply power and control signals to the actuator.
M17431
Fig. 2. Attaching actuator to valve.
M6630
Fig. 4. Connecting wiring to the actuator.
M17432
Fig. 3. Removing actuator cover.
63-2515—4
4
ML6421, ML7421 NON-SPRING RETURN ELECTRIC LINEAR VALVE ACTUATORS
ML6421A,B
ML7421
WIRING
STRIP
SENSOR
2
WIRING
STRIP
2
4
6
1
3
3
5
L1
(HOT)
T1
T2
T1
T2
+
W
B
L2
1
L1
(HOT)
R
L2
1
SPDT
O1
O2
SINGLE
W
B
CONTROLLER
1
2
TRANSFORMER
40 VA, 24 VAC
1
2
POWER SUPPLY. PROVIDE DISCONNET MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
T775 (WITH 2 TO 10 VDC OUTPUT)
ALL WIRING BLOCKS HAVE THE SAME NUMBER
OF TERMINALS (8), BUT THE ONLY TERMINALS
THAT ARE ACTIVE ON THIS BLOCK ARE T1,W,AND B.
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
M17436A
R
W
B
3
THE R-W-B AND T-Y-G TERMINALS ARE A SIX
TERMINAL WIRING BLOCK SEPARATE FROM THE
MAIN BLOCK. THEY DO NOT APPEAR ON ALL
MODELS BECAUSE R-W-B ARE FOR A SINGLE
FEEDBACK POTENTIOMETER AND T-Y-G ARE
FOR A SECOND FEEDBACK POTENTIOMETER
(BOTH POTENTIOMETERS ARE 220 OHMS). THE
REQUIRED WIRING BLOCKS ARE PART OF THE
POTENTIOMETER ACCESSORY KITS.
Fig. 8. ML7421 wiring using voltage input control and a
common transformer.
T
Y
G
3
M17433
Fig. 5. ML6421 typical wiring diagram.
ML7421
WIRING
STRIP
L1
L2
1
T1
T2
+
–
2
+
OUTPUT
O1
O2
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
1
2
0 TO 10 OR 2 TO 10 VDC CONTROL SIGNAL
(DEPENDING ON ACTUATOR MODEL).
M17464
M17434A
Fig. 9. Replacing actuator cover.
Fig. 6. ML7421 typical wiring diagram.
Auxiliary Potentiometers
The 43191679 Auxiliary Potentiometers can be used as feed-
back potentiometers and to provide remote indication of the
valve position. See the Accessories section for part numbers.
See Installation Instructions packed with the potentiometers
for details.
L1
L2
1
ML7421
WIRING
STRIP
SENSOR
2
2
4
6
1
3
3
1
5
T1
T2
+
Auxiliary Switches
L1
The 43191680 Dual Auxiliary Switch can be used on both the
ML6421 and ML7421 Electric Linear Valve Actuators.
Switching points are adjustable over the full actuator stroke.
For example, the switch can be used to switch pumps or to
provide remote indication of any stroke position. See the
Installation Instructions packed with the auxiliary switch for
details.
1
L2
DUAL
TRANSFORMERS
O1
O2
T775 (WITH 2 TO 10 VDC OUTPUT)
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
M17435A
IMPORTANT
Use the 43191680 Dual Auxiliary Switch only with
24 Vac applications.
Fig. 7. ML7421 wiring using voltage input control and
separate transformers.
5
63-2515—4
ML6421, ML7421 NON-SPRING RETURN ELECTRIC LINEAR VALVE ACTUATORS
OPERATION
General
ML7421
The drive of the actuator 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.
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:
•
•
•
0%: Actuator position corresponds with 0 or 2 Vdc signal.
50%: Actuator stem in mid-position.
100%: Actuator position according to 10 Vdc signal.
The internal force sensor, using installed microswitches, turns
off the actuator when the specified stem force is reached.
NOTE: If W4 is set to the mA position, the actuator always
runs to 0 percent.
Manual Operation
The ML6421 and ML7421 are equipped with a manual
operator knob (see Fig. 10) to open or close the valve in the
event of power failure:
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.
1. Turn off or disconnect the power supply before manually
operating the actuator.
2. Push down on the manual operator knob and turn the
knob:
a. Counterclockwise to drive the stem downward.
b. Clockwise to draw the stem upward.
With the actuator stem fully down, the output signal is 10 Vdc.
The output of the signal does not change when the actuator
action reverses using W3 or W4 (see Signal Input Failure
section and Fig. 11).
IMPORTANT
Manual operation allows very high closing force that
can jam the actuator spindle, exceed the force switch
ratings, and stop the motor. After a manual valve
close-off operation, release the spindle one turn by
turning the manual operator knob. This will ensure
automatic disengagement of the manual operator
upon power resumption.
W1
W3
10V (20mA)
50% 100%
0%
W4
10V (20mA)
NOTE: If the manual operator knob is not pushed in while
turned, it will rotate only a short distance before
disengaging without power resumption.
mA
V
W2
2-10V
0-10V
(4-20mA) (0-20mA)
M17437
Fig. 11. Location of selector plugs.
M6640
Fig. 10. Manual operator knob.
63-2515—4
6
ML6421, ML7421 NON-SPRING RETURN ELECTRIC LINEAR VALVE ACTUATORS
Actuator Override
ML7421
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.
WIRING
STRIP
2
INPUT
(FEEDBACK)
OUTPUT
F
F
+
+
3
–
–
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.
T2
T1
O1
O2
SP3T
OVERRIDE
SWITCH
4
Direction of Action
The direction of action can be changed by repositioning the
selector plug W3.
1
L1
(HOT)
L2
1
2
3
4
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
M17438
OVERRIDE OPERATION.
Fig. 12. Connections for overriding control signal to drive
actuator to a specific position.
CHECKOUT
The actuator can be checked out either directly or using a controller.
Direct Checkout
Controller 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.
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
toward the open setting.
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.
4. If the valve does not move, check for 24 Vac in the
actuator power input.
5. If the actuator is correctly installed and does not run,
replace the actuator.
5. If 24 Vac is present and the actuator does not operate,
reverse the controller leadwires to determine if the
device is incorrectly wired.
6. If wiring is correct, 24 Vac is present on the power input
terminals, and the actuator does not run, replace the
actuator.
7
63-2515—4
Automation and Control Solutions
Honeywell International
Control Products
Honeywell Building
17 Changi Business Park Central 1
Singapore 486073
Honeywell Europe S.A.
3 Avenue du Bourget
1140 Brussels
Honeywell Latin American
Region
480 Sawgrass Corporate Parkway
Suite 200
Sunrise FL 33325
Honeywell
Honeywell Limited-Honeywell Limitée
1985 Douglas Drive North
Golden Valley, MN 55422
35 Dynamic Drive
Scarborough, Ontario
M1V 4Z9
Belgium
Printed in U.S.A. on recycled
paper containing at least 10%
post-consumer paper fibers.
63-2515—4 B.B. Rev. 1-03
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