McQuay IM 987 53
Mechanical Installation
Relief Damper Tie-Down
Economizer sections with a 30" or 40" return fan have a relief
damper that is tied down for shipping. Remove the two
brackets and two screws before operation to allow free
movement of dampers. Access is from inside the economizer
section.
Adjusting Scroll Dampers
Two sets of scroll dampers are provided in the housing of the
twin 15" x 6" supply fan to allow control of air volume to each
fan wheel. At the factory, these dampers are fully closed,
unrestricting airflow. If fan paralleling occurs, correct it by
loosening the adjustment screw on top of the fan housing (see
Figure 65) and slightly lowering the rod until air distribution
between the fans is even.
Figure 65: Scroll Damper Adjustment
Adjusting Supply Fan Thrust Restraints
Thrust restraints are provided when housed double-width fans
are mounted on springs. After the spring mounts are adjusted
for level operation when the fan is running, check the thrust
restraints. With the fan off, set the adjustment nuts so the
spring is slightly compressed against the angle bolted to the
fan housing frame. Refer to Figure 66. When the fan is turned
on, the fan moves back to a level position and the thrust
restraint spring compresses.
Figure 66: Thrust Restraint Adjustment
WARNING
Moving machinery hazard. Can cause severe injury or death.
Start the fans for the first time according to the “Check, Test,
and Start Procedures” on page 106. If this is not done,
equipment damage, severe personal injury, or death can occur.
Adjustment assembly
Scroll damper
Jam nut A
Nut B
Spring clip
Nut C
Jam nut A
Washer
Fan bulkhead
Thrust restraint angle
Fan housing frame
See Detail A
Detail A
Thrust restraint adjustment (with fan off)
Note: 1. Loosen jam nuts A.
Note: 2. Turn nut C until spring cup and washer contact thrust
restraint angle.
Note: 3. Turn nut B until spring is compressed by two turns of nut B.
Note: 4. Tighten jam nuts A.
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