54
McQuay IM 987
Mechanical Installation
Adjusting Seismic Restraints
Spring-mounted supply air and return air fans can be ordered
with factory-installed seismic restraints. The system consists
of four snubbers, one located next to each spring isolator.
These snubbers allow free movement of the fan assemblies
during normal operation because normal operation does not
cause fan movements that exceed .25" (6 mm). However, if an
abnormal condition occurs, they restrain the fan assembly and
limit movement to .25" (6 mm) in any direction.
The position the fan assumes during normal operation is
determined by actual job site airflow and static pressure.
Therefore, for proper operation, field adjust the seismic
restraints as part of the normal “Check, Test and Start”
procedure. When the fan is operating in a normal manner,
there should be no contact between the snubber restrainer
angle and the snubber neoprene bumper. However, in a
“seismic event,” the snubber limits movement of the spring
mounted fan assembly to 0.25" (6 mm) in any direction,
thereby helping to prevent the fan from being tossed about and
damaged, or causing damage.
When a seismic restraint is properly adjusted and the fan is
operating normally, the neoprene center bumper is centered
within the 2" (51 mm) diameter hole in the restrainer angle,
and the restrainer angle is centered vertically between the
flanges of the neoprene center bumper. This results in 0.25"
(6 mm) clearance in all directions. When the fan is turned off,
the restrainer angle may come to rest on the neoprene center
bumper.
Figure 67: Cross Section of Seismic Restraint
The seismic restraint is adjustable in all directions. Vertical
slots in the restrainer angle and horizontal slots in the blower
base allow the restrainer angle to be adjusted up and down and
back and forth. The neoprene center bumper is mounted on a
slotted hole allowing in and out adjustment.
Removing the neoprene center bumper bolt allows removal,
disassembly, and replacement of the neoprene components.
Fan base channel
Adjust up or down
or back and forth
Snubber neoprene
bumper
Snubber neoprene
bumper
.25 (6 mm) gap
(fan running)
Adjust in and out
Snubber restrainer angle