Page 66 IM-738
Variable Inlet Vanes
Variable inlet vanes are installed on the supply and return fans
of VAV units. They are also installed on the return fans of con-
stant volume units that have direct building static pressure con-
trol capability.
The inlet vane assemblies consist of airfoil type inlet fun-
nels with integral sets of lever-actuated radial vanes. Sup-
ply 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 indepen-
dently of each other, and the hub assembly will have to be
overhauled. The moving parts of the vanes are permanently
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 fac-
tory with complete linkage and actuator assemblies. Field
installed linkages and actuators would be connected as shown
in Figure 69 on page 67 thru Figure 75 on page 70 .
Minimum Vane Position
Operation with the inlet vanes closed completely may result in
fan pulsation and excessive vibration. In units equipped with
MicroTech II 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 pre-
set to close to no less than 5 degrees open.
Supply Fan Vane Adjustment
Figure 69
& Figure 70 on page 67, Figure 71 on page 68 and
Figure 74 on page 69 thru Figure 75 on page 70 show the sup-
ply 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 provide 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” on this page.
On units with vane controls on both the supply and return fan,
it is important that both actuators have exactly 180-degree
rotation to provide proper "tracking" of the two actuators.
Inlet vanes must not be adjusted to close tight during fan oper-
ation. A minimum of 5° open is recommended to avoid fan
pulsation. Units with factory installed MicroTech II controls
will automatically open vanes 5 degrees prior to start-up.
As the actuator moves from 0° to 180°, the vanes should move
from 0° (closed) to 90° (full open). This can be adjusted by
changing the linkage rod length by loosening the nut and slid-
ing the rod at Point A or Point B and retightening the nut.
Return Fan Vane Adjustment
Refer to Figure 71 on page 68 for 30" wheels and Figure 70
on page 67 thru Figure 73 on page 69 for 40" wheels. The
vane actuator must have 180-degree rotation. Do not make
linkage adjustments to compensate for improper rotation, but
correct the actuator rotation adjustment. (Refer to the "Actua-
tor Rotation 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.
Inlet vanes must not be adjusted to close tight during fan
operation. A minimum of 5º open is recommended to avoid
fan pulsation. Units with factory installed MicroTech II con-
trols will automatically open vanes 5º prior to startup.
Actuator Rotation Adjustment
The counterclockwise (as viewed from shaft end of actuator)
limit switch is adjustable on the Siebe actuator. The clock-
wise limit is not adjustable. The counterclockwise limit set-
ting can be changed in the field by inserting a screwdriver
through the opening in the top plate directly ahead of the ter-
minal 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.
Table 19: Applicable Actuator Linkage Configurations
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 II controls will
automatically open vanes 5 degrees prior to start-up.
Supply Fan
Wheel Size
(In Inches)
Z
(Refer to
Figure 71 on
page 68)
Motor
HP
Figure 71 on
page 68
Reference
View
27 38.1 (968mm) 5—40 2
30 42.3 (1074mm) 5—40 2
33 46.4 (1179mm) 5—40 2
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