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Valve and Actuator Manual 977
Actuators and Positioners Section
Product Bulletin VA-8051
Issue Date 0988
© 1988 Johnson Controls, Inc. 1
Part No.14-548-9 Rev. A
Code No. LIT-977305
VA-8051 Electric Valve Actuator
Floating Control, 50 lb. Force
The VA-8051 synchronous,
motor-driven actuator provides
floating control of valves with up
to 3/4 in. stroke in heating,
ventilating, and air conditioning
applications. This compact,
non-spring return actuator has a
50 lb. force and is compatible
with a 3-wire, 24 VAC signal.
A ± 12 VDC signal from a
DSC-8500 may be used with a
VA-8000-104 drive card to
position the VA-8051. A
3400 ohm (nominal) position
feedback potentiometer is also
included for remote position
indication to meters or a
DSC-8500. The VA-8051 can be
ordered factory coupled to
VB Series Valves. See AV-8051
bulletin for code numbers.
Operation
A controller sends 24 VAC to
the up or down terminal on the
circuit board depending on the
desired movement of the valve.
This signal causes the motor to
rotate in the proper direction,
and through the lead screw and
lever, move the valve up or
down. When the controller stops
sending a signal, the valve
remains in place.
When the controller closes the
valve, a shutoff force will build
up. When this force reaches
50 lbs., the lever activates a
force sensor which stops the
motor. Field calibration of the
force sensor is not required. The
actuator maintains the shutoff
force even if power to the
controller is lost. When the
controller signals the valve to
move in the opposite direction,
the shutoff force will be reduced
and the valve will modulate.
The internal position feedback
potentiometer is connected to
the R, W, and S terminals.
Specifically, the wiper is
connected to W. The wiper will
be at the R end when the
actuator is retracted and at the
S end when the actuator is fully
stroked.
Specifications
Product VA-8051-1 Electric Valve Actuator
Control Mode Floating Control, 3-Wire
Supply Voltage 24 VAC + 6 V, -4V, 200 mA, 50/60 Hz
Power Consumption 6 VA
Feedback 3400 Ohms ± 25%, 20 VDC Max Input Voltage
Shutoff Force 50 lb. Force Minimum
Stroke Time 1/2 in. Stroke: Approx. 65 Sec
3/4 in. Stroke: Approx. 90 Sec
Ambient Operating Temperature 0 to 140°F (-18 to 60°C), 90% RH Max,
85°F Max Dew Point
Ambient Storage Temperature -40 to 150°F (-40 to 65°C)
Media Temperature Water: 190°F (88°C)
Steam (with Insulator Kit): 280 °F (138°C)
VA-8000-101 Steam Insulator Kit
Accessories VA-8000-102 Valve Position Indicator Kit
VA-8000-104 Auxiliary Interface Board
The performance specifications are nominal and conform to acceptable industry standards. For application at conditions
beyond these specifications, consult the local Johnson Controls office. Johnson Controls, Inc. shall not be liable for
damages resulting from misapplication or misuse of its products.
Fig. 1: VA-8051-1 Connected to VB-3754