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Table-3 Assembly Configuration Chart
Valve Body
Valve Body Action
VB-721x
Two-Way Stem Up Open
b
VB-921x
VB-722x
Two-Way Stem Up Closed
b
VB-922x
VB-731x
Three-Way Mixing
b
VB-931x
VB-732x
Three-Way Diverting
b
VB-932x
a
Proportional models shipped with RA/DA jumper set for DA (actuator extends with increasing signal).
b
Discontinued 1/2" to 1-1/4" VB-9xxx.
THEORY OF OPERATION
MAINTENANCE
FIELD REPAIR
F-27169-3
as determined by the control signal. Refer to Table-3 for valve flow.
2. Break power to the actuator. Actuator and valve should return to the spring return
position (retracted position).
Normal Position
Valve Stem
Up
Up
Up
Up
Note: Check that the transformer(s) are sized properly.
•
If a common transformer is used with multiple actuators, make sure that polarity is
observed on the secondary. This means connecting all black wires to one leg of the
transformer and all red wires to the other leg of the transformer.
•
If multiple transformers are used with one control signal, make sure all black wires are
tied together and tied to control signal negative (-).
•
If the controller uses a full-wave power supply and does not provide isolated outputs, a
separate transformer is required.
The MA, MF and MS series actuators are directly mounted onto the valve without the use of
a separate linkage. They are equipped with true mechanical spring return operation for
reliable, positive close-off on valves. When power is applied, the actuator moves to its
powered position, at the same time tensing the spring return safety mechanism. When the
power is removed, the spring returns the actuator to its normal position (retracted position).
The spring return system provides consistent close-off force to the valve.
MA series two-position actuators use a DC motor controlled by on board electronics. When
the actuator encounters a stall or end of travel position, the motor current is automatically
reduced, preventing damage to the actuator or motor.
MF or MS series floating or proportional actuators use a DC motor which is controlled by a
microprocessor. The microprocessor supplies the intelligence to provide a constant speed
and to know the actuator's exact position. The microprocessor monitors and controls the DC
motor's rotation and provides a digital rotation sensing function to prevent damage to the
actuator in a stall condition.
All actuators may be stalled anywhere in their normal rotation without the need of a
mechanical end switch.
Regular maintenance of the total system is recommended to assure sustained optimum
performance. The Linear series actuators are maintenance free.
None. Replace with a functional actuator.
© Copyright 2004 Invensys Building Systems, Inc. All rights reserved.
Flow
Open
A to AB flow decreases as actuator extends
Closed
A to AB flow increases as actuator extends
A to AB flow increases as actuator extends
B to AB
B to AB flow decreases as actuator extends
B to A flow increases as actuator extends
B to AB
B to AB flow decreases as actuator extends
a
Action
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