Honeywell ML7421 Proportional Integral Control Electric Two-Way Temperature Valve Dynamic Balancing Copper Contact Material

FEATURES • Quick and easy installation. • No separate linkage required. • 3/4 in. (20 mm) stroke on ML7421A; 1-1/2 in. (38 mm) stroke on ML7421B. • No adjustments required. • Accurate valve positioning. • Selectable 0(2) to 10 Vdc/0(4) to 20 mA input signal. • Position feedback. • Force-limiting end switches. • Manual operator. • Direct or reverse acting. • Synchronous motor. • Corrosion resistant design. • Maintenance free. • Conduit connector knockout

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. 7) to open or close the valve in the event of power failure. Turn off or diconnect the power supply before manuallly operating the ML7421. To operate, push down the manual operator knob and turn the knob counterclockwise to move the stem downward or clockwise to move the stem upward. If 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 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 the manual operator knob so the manual operator automatically disengages on power resumption. 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. Changing the W4 position to mA (see Fig. 8.) the ranges are 0(4) to 20 mA. Selector plugs W1, W2, W3 and W4 are positioned on the back side of the PCB protection sheet. See Fig. 8 for location of the selector plugs. Fig. 7. ML7421A,B manual operator knob. 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 50% . If W4 is set to mA-position, the actuator runs always to 0% . W1 (W4 ) W3 W4 V