Honeywell ML6421 User Manual

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.  
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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