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Variable inlet vanes are installed on the supply and return
fans of VAV units. They are also installed on the return fans
of constant volume units that have direct building static
pressure control capability.
The inlet vane assemblies consist of airfoil type inlet
funnels with integral sets of lever-actuated radial vanes.
Supply fans have one assembly on each side of the fan.
Return fans have one assembly on the inlet side of the fan
only. When they open, the inlet vanes direct air in the
direction of wheel rotation.
The vanes are able to rotate 90 degrees from full closed
to full open. A stop limits the amount of travel open and must
not be changed. Driving the vanes past this stop will cause
the vane hub cam linkage to disengage. The vanes will turn
independently of each other, and the hub assembly will have
to be overhauled. The moving parts of the vanes are perma-
nently lubricated. All threaded fasteners must be periodically
checked for tightness.
All fans with inlet vanes are provided without motor
actuators for field control installation, or may be shipped
from the factory with complete linkage and actuator assem-
blies. Field installed linkages and actuators would be con-
nected at Point B on Figures 31 and 32.
Minimum vane position
Operation with the inlet vanes closed completely may result
in fan pulsation and excessive vibration. In units equipped
with MicroTech controls, the vanes are automatically opened
approximately 5 degrees by the control system prior to fan
start-up. Field installed linkages and actuators should be
preset to close to no less than 5 degrees open.
Supply fan vane adjustment
Figure 31 shows the supply fan vane linkage assembly. Both
sets of vanes on the supply fan must operate in unison.
Adjustments to the motor rod end and locknut as well as to
the floating link ends (Point A) can be made to assure
uniformity between the linkage assemblies.
The vane actuators must have 180-degree rotation. Do
not make linkage adjustments to compensate for improper
actuator rotation, but correct the actuator rotation adjustment.
Refer to “Actuator Rotation Adjustment” section following.
Variable Inlet Vanes
On units with vane controls on both the supply and return
fan, it is important that both actuators have exactly 180-
degree rotation to assure proper “tracking” of the two
actuators.
NOTICE
Inlet vanes must not be adjusted to close tight during
fan operation.
A minimum operating position of 5 degrees open is
recommended to avoid pulsation.
Units with factory installed MicroTech controls will auto-
matically open vanes 5 degrees prior to start-up.
Return fan vane adjustment
Refer to Figure 32 for 30" and 40" wheels. The vane actuator
must have 180-degree rotation. Do not make linkage adjust-
ments to compensate for improper rotation, but correct the
actuator rotation adjustment. (Refer to the “Actuator Rota-
tion Adjustment” section following.)
As the actuator crankarm rotates from 0 degrees to 180
degrees, the vanes should move from 0 degree (closed) to 90
degrees (full open). This can be adjusted by changing the
linkage rod length by loosening the nut and sliding the rod at
Point A or Point B and retightening the nut.
Actuator rotation adjustment
The counterclockwise (as viewed from shaft end of actuator)
limit switch is adjustable on the Barber-Colman actuator.
The clockwise limit is not adjustable. The counterclockwise
limit setting can be changed in the field by inserting a
screwdriver through the opening in the top plate directly
ahead of the terminal block on the shaft side and engaging
the screwdriver blade with the edge of the notched cam
nearest the front of the actuator. Turning the cam clockwise
(as viewed from the shaft) increases the amount of actuator
rotation. Each click of the cam represents about 3 degrees
of change in actuator rotation. The actuator should be set for
180-degree rotation.
A convenience receptacle is provided in the main control box
on all units. To utilize this receptacle, a separate field sup-
plied 115V power wiring circuit must be connected to the
115V field terminal block TB1, located in the main control box.
Note that the National Electrical Code requires that this circuit
be protected by a ground fault circuit interrupter (GFI) device.
Optional lights are available for certain sections in the unit.
Each light includes a switch and convenience receptacle,
and is powered by the external 115V power supply connected
to TB1.
Convenience Receptacle/Section Lights
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