Johnson Controls VA-8051 User Manual

VA-8051 Electric Valve Actuator

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.

Valve and Actuator Manual 977

Actuators and Positioners Section

Floating Control, 50 lb. Force

Fig. 1: VA-8051-1 Connected to VB-3754

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.

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

Ambient Operating Temperature 0 to 140°F (-18 to 60°C), 90% RH Max,

Ambient Storage Temperature -40 to 150°F (-40 to 65°C)
Media Temperature Water: 190°F (88°C)

Accessories VA-8000-102 Valve Position Indicator Kit

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.

3/4 in. Stroke: Approx. 90 Sec

85°F Max Dew Point

Steam (with Insulator Kit): 280 °F (138°C)
VA-8000-101 Steam Insulator Kit

VA-8000-104 Auxiliary Interface Board

Product Bulletin VA-8051

Issue Date 0988

Specifications

© 1988 Johnson Controls, Inc. 1

Part No.14-548-9 Rev. A
Code No. LIT-977305

Wiring

All wiring must be in accordance
with applicable electrical code
requirements. Input lines to the
actuator must be wired correctly
for the valve to move in the
proper direction.

2 VA-8051 Product Bulletin