ML6984, ML7984 DIRECT COUPLED VALVE ACTUATORS
TO REPLACE ML784 or ML984:
1. The old ML784 or ML984 actuators cannot be used
with new ML7984 valve actuators in the same circuitry,
unless the old models are each powered by their own
transformer to prevent cross-talking.
2. The ML7984 is a direct replacement for all old ML784
and ML984, except:
a) When replacing the old reverse acting models, the signal
input wires to the new devices no longer need to be
reversed. Just follow the terminal polarity designations
and DIPswitch settings.
b) When replacing the old actuator which has an Electronic
Series 90 controller, i.e., T775, W973, H775, W7100,
the old interface resistor must be removed. The new
ML798 will work directly with the controller without the
external 240W resistor.
c) When replacing the old ML784 (mA model) in multiple-
actuator installations, resistor(s) will be needed. Use
Resistor Kit part # 272822 and set DIP switches
accordingly. See Figure 12 & 13.
1. Make sure the valve stem is completely screwed
into the actuator drive shaft with no threads
showing before applying power.
2. Make sure the valve stem is locked in place with
the set screw.
ML6984 - 5-Wire Installation
3. Connect 24 Vac or 28 Vdc power to T5 and T6.
4. Jumper R & B. The valve stem should move up.
5. Jumper R & W. The valve stem should move
6. For Floating operation, open R connection Valve
stem should remain in position.
7. Re-connect all control wiring.
8. Operate the system (valve, actuator and
controller) for several cycles to ensure proper
9. When checkout is complete, return the controller
to the desired setting.
3. Make sure the Configuration DIPswitches are set
4. With 24Vac or 28Vdc power source connected to T5
and T6, actuator operation can be verified by
connecting appropriate control signal (Series 70/90)
from controller to the signal input terminals (Fig. 8-11).
For direct acting: A modulating action can be obtained
simply by increasing the control signal. The actuator
will travel from full stem down to full stem up. On signal
failure (disconnected /no signal), actuator defaults to
closed position. For reverse acting: Decreasing
controller signal will drive actuator from full stem down
to full stem up. On signal failure (disconnect/no signal),
actuator defaults to open position.
5. Operate the system (valve, actuator and controller) for
several cycles to ensure proper installation.
6. When checkout is completed, return the controller to
the desired setting.
NOTE: Device will ignore any input changes until it has
completed its repositioning relative to the initial signal