Electric Linear Valve Actuators
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.
ML6421, ML7421
Non-Spring Return
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.
• 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.
• 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.
® U.S. Registered Trademark
Copyright © 2002 Honeywell • All Rights Reserved
Contents
Application ........................................................................ 1
Features ........................................................................... 1
Specifications ................................................................... 2
Ordering Information ........................................................ 2
Installation ........................................................................ 3
Operation .......................................................................... 6
Checkout .......................................................................... 7
®
63-2515-4
ML6421, ML7421 NON-SPRING RETURN ELECTRIC LINEAR VALVE ACTUATORS
SPECIFICATIONS
Models:
Model
Stroke in
in. (mm)
Run Time in
sec at 60 Hz Description
ML6421A 3/4 (20) 95 Electric Linear
ML7421A
Valve Actuator
ML6421B 1-1/2 (38) 175
ML7421B
Dimensions: See Fig. 1.
Weight: 5.1 lb (2.3 kg).
Electrical Ratings:
Power Input: 24 Vac (+10%, -15%), 60 Hz.
Power Consumption: 11 VA maximum at 24 Vac.
Signal Inputs:
ML6421:
24 Vac across T1 and W: Drives stem downward.
24 Vac across T2 and B: Draws stem upward.
ML7421: 0 to 10 Vdc or 2 to 10 Vdc.
Actuator Material:
Cover: ABS plastic.
Yoke and Base: Diecast aluminum.
Stem Force: 405 lbf (1800N).
Close-off Pressure Ratings: See Table 1.
Cable Entry: Two knockout holes for 1/2 in. conduit standard
on actuator case.
Ambient Ratings:
Temperature:
Ambient Range: 14°F to 122°F (-10°C to +50°C).
Storage Range: -40°F to +158°F (-40°C to +70°C).
Humidity Range: 5 to 95 percent relative humidity,
noncondensing.
Approvals:
Canadian Standards Association Listed.
Underwriter’s Laboratories, Inc. UL94-5V Flame Retardant
(file E181716).
Meets CE requirements.
Protection Standard: IP54.
Accessories:
43191679-101 Single Auxiliary Potentiometer for ML6421A.
43191679-102 Single Auxiliary Potentiometer for ML6421B.
43191679-103 Dual Auxiliary Potentiometer for ML6421A.
43191679-104 Dual Auxiliary Potentiometer for ML6421B.
43191680-102 Dual Auxiliary Switch (for 24 Vac use only).
43196000-001 High Temperature Kit (for actuators with 3/4 in.
stroke). Increases maximum temperature to 428°F (220°C).
43196000-102 High Temperature Kit (for actuators with 1-1/2 in.
stroke). Increases maximum temperature to 428°F (220°C).
Table 1. Close-off Ratings for ML6421, ML7421 Electric Linear Valve Actuators and Honeywell Valves (psi).
Type Valve 1/2 in. 3/4 in. 1 in. 1-1/4 in. 1-1/2 in. 2 in. 2-1/2 in. 3 in. 4 in.a5 in.a6 in.
Flange V5011A,B,C — — — — — — 77 53 29 18 12
V5011B ———— — —— —
V3350/51/60/61;V3450/51/60/61 — — — — — —
NPT V5011F,G
V5011N1xxx, V5011N3xxx,
150
c
150c150c150
c
150
c
150
230 230 230 230 230 126 — —
b
63
c
100 61 — — —
45b25b16b11
V5013N
V5011N2xxx
100
d
100d100d100
d
100
d
100
d
V5013F 150 150 150 150 150 150
a
For use with ML6421B or ML7421B Actuators only.
b
Represents maximum pressure difference between the outlet and either of the two inlets.
c
Do not exceed 100 psi with V5011G valves used in steam applications.
d
Rating is for steam at maximum 100 psi. Ratings for water applications are the same as for the V5011N1xxx.
a
b
ORDERING INFORMATION
When purchasing replacement and modernization products from your TRADELINE® wholesaler or distributor, refer to the
TRADELINE® Catalog or price sheets for complete ordering number.
If you have additional questions, need further information, or would like to comment on our products or services, please write or
phone:
1. Your local Home and Building Control Sales Office (check white pages of your phone directory).
2. Home and Building Control Customer Relations
Honeywell, 1885 Douglas Drive North
Minneapolis, Minnesota 55422-4386
In Canada—Honeywell Limited/Honeywell Limitée, 35 Dynamic Drive, Scarborough, Ontario M1V 4Z9.
International Sales and Service Offices in all principal cities of the world. Manufacturing in Australia, Canada, Finland, France,
Germany, Japan, Mexico, Netherlands, Spain, Taiwan, United Kingdom, U.S.A.
63-2515—4 2
ML6421, ML7421 NON-SPRING RETURN ELECTRIC LINEAR VALVE ACTUATORS
ML6421A,ML7421A ML6421B, ML7421B
7 (178 ) X 7 (178)
KNOCKOUTS
(2)
7/8 (22)
YOKE DIAMETER 1-7/8 (48)
8
(204)
11-7/8
(301)
CLEARANCE
12-3/4
(326)
MINIMUM
M17430
2-1/2
(64)
7 (178 ) X 7 (178)
KNOCKOUTS
(2)
7/8 (22)
YOKE DIAMETER 1-3/8 (35)
5-5/8
(142)
9-3/8
(239)
CLEARANCE
10-3/8
(264)
14-1/4
(360)
MINIMUM
2-1/2
(64)
Fig. 1. Approximate dimensions of ML6421, ML7421 Electric Linear Valve Actuators in in. (mm).
16-7/8
(430)
INSTALLATION
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.
4. After installation is complete, check out product
operation as provided in these instructions.
CAUTION
Electrical Shock or Equipment Damage Hazard.
Can shock individuals or short equipment
circuitry.
Disconnect power supply before installation.
Location
Install the actuator in a location that allows enough clearance
for mounting accessories and for servicing.
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
1. Place the actuator on the valve with the U-bolt around
the valve collar. See Fig. 2.
IMPORTANT
When tightening the set screws, first tighten the right
set screw. See Fig. 2.
2. Place the U-bolt against the valve collar and secure the
actuator to the valve by turning each U-bolt nut clockwise.
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.
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.
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.
Wiring
CAUTION
Electrical Shock or Equipment Damage Hazard.
Can shock individuals or short equipment
circuitry.
Disconnect power supply before installation.
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: See Fig. 5 through 8 for typical wiring hookups.
1. Feed power and control wires through the conduit
connector located on the bottom of the actuator case.
CAUTION
Equipment Damage Hazard.
Conduit connection or removal can break an
unsupported connector.
When removing or attaching conduit, use a wrench to
support the motor connector.
TIGHTEN RIGHT
SET SCREW FIRST
M
Fig. 2. Attaching actuator to valve.
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).
5. Apply power and control signals to the actuator.
17431
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
WIRING
STRIP
2
T1
T2
W
B
R
W
B
T
Y
G
3
W
R
B
SPDT
CONTROLLER
1
POWER SUPPLY. PROVIDE DISCONNET MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
2
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.
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. 5. ML6421 typical wiring diagram.
ML7421
WIRING
STRIP
T1
T2
+
O1
O2
M17434A
–
2
+
OUTPUT
POWER SUPPLY. PROVIDE DISCONNECT MEANS
1
AND OVERLOAD PROTECTION AS REQUIRED.
2
0 TO 10 OR 2 TO 10 VDC CONTROL SIGNAL
(DEPENDING ON ACTUATOR MODEL).
Fig. 6. ML7421 typical wiring diagram.
L1
(HOT)
L2
1
L1
L2
ML7421
WIRING
STRIP
T1
T2
+
O1
O2
1
1
3
T775 (WITH 2 TO 10 VDC OUTPUT)
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
4
2
3
1
2
6
5
SENSOR
L1
(HOT)
L2
SINGLE
TRANSFORMER
40 VA, 24 VAC
M17436A
1
Fig. 8. ML7421 wiring using voltage input control and a
common transformer.
M17433
1
M17464
Fig. 9. Replacing actuator cover.
L1
1
L2
ML7421
WIRING
STRIP
T1
T2
+
O1
O2
2
4
1
3
1
2
3
T775 (WITH 2 TO 10 VDC OUTPUT)
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
6
5
SENSOR
L1
1
L2
DUAL
TRANSFORMERS
M17435A
Fig. 7. ML7421 wiring using voltage input control and
separate transformers.
Auxiliary Potentiometers
The 43191679 Auxiliary Potentiometers can be used as feedback 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.
Auxiliary Switches
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.
IMPORTANT
Use the 43191680 Dual Auxiliary Switch only with
24 Vac applications.
5 63-2515—4
ML6421, ML7421 NON-SPRING RETURN ELECTRIC LINEAR VALVE ACTUATORS
OPERATION
General
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.
The internal force sensor, using installed microswitches, turns
off the actuator when the specified stem force is reached.
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:
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.
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.
NOTE: If the manual operator knob is not pushed in while
turned, it will rotate only a short distance before
disengaging without power resumption.
ML7421
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.
NOTE: If W4 is set to the mA position, the actuator always
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.
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).
runs to 0 percent.
W3
10V (20mA)
10V (20mA)
W2
0%
W1
100%50%
W4
VmA
Fig. 10. Manual operator knob.
M6640
2-10V
(4-20mA)
0-10V
(0-20mA)
Fig. 11. Location of selector plugs.
M17437
63-2515—4 6
ML6421, ML7421 NON-SPRING RETURN ELECTRIC LINEAR VALVE ACTUATORS
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
ML7421
WIRING
STRIP
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.
2
F
+
–
INPUT
(FEEDBACK)
OUTPUT
3
SP3T
OVERRIDE
SWITCH
4
L1
(HOT)
L2
M17438
1
Fig. 12. Connections for overriding control signal to drive
actuator to a specific position.
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.
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
toward 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 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
Printed in U.S.A. on recycled
paper containing at least 10%
post-consumer paper fibers.
Automation and Control Solutions Honeywell International Honeywell Europe S.A. Honeywell Latin American
Honeywell Honeywell Limited-Honeywell Limitée Control Products 3 Avenue du Bourget
1985 Douglas Drive North 35 Dynamic Drive Honeywell Building 1140 Brussels 480 Sawgrass Corporate Parkway
Golden Valley, MN 55422 Scarborough, Ontario 17 Changi Business Park Central 1 Belgium Suite 200
M1V 4Z9 Singapore 486073 Sunrise FL 33325
Region
63-2515—4 B.B. Rev. 1-03 www.honeywell.com
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