40
McQuay IM 987
Mechanical Installation
Damper Assemblies
The optional damper assemblies described in this section
normally are ordered with factory-installed actuators and
linkages. The following sections describe operation and
linkage adjustment of the factory option.
Economizer Dampers
Outside air intake is provided on both sides of the unit, and the
return air path is at the center of the damper set. As the single
actuator modulates the outside air dampers open, the return air
dampers close. Exhaust air exits the unit through the gravity
relief dampers provided at the end of the economizer section.
The outside air return air damper assembly (economizer)
comes with manually adjustable linkage. This adjustable
linkage also can be used for connecting a damper operator. The
damper is set so that the crankarm moves through a 90-degree
angle to bring the economizer dampers from full open to full
close (see
Figure 45
). Access to the actuator and linkage is
from the filler section. Mechanical stops are placed in the
crankarm mounting bracket. Do not remove stops. Driving the
crankarm past the stops results in damage to the linkage or
damper. The unit ships with a shipping bolt securing the
linkage crankarm. Remove shipping bolt before use.
Note:
For good airflow control, adjust linkages so damper
blades do not open beyond 70 degrees. Opening a
damper blade beyond 70 degrees has little effect on its
airflow.
Do not “over close” low leak damper blades. The edge
seal should just lightly contact the adjoining blade. The
blades will lock up if they are closed so far the seal goes
over center.
Figure 45: Economizer Dampers
OA
Closed
OA
Open
90°
Stroke
.25" (6mm)
Outside
Air
Outside
Air
Optional Return Air Fan
Economizer
.500 (13mm) Dia. Shaft
x 1.30" (33mm) Long
OA
Closed
OA
Open
3.00
.25
.75
90°
Stroke
Shaft .500 Dia.
x 1.50 Long
RAH 047C - 077C
RDS 800C & 802C
