McQuay IM 777-3
9
Installation Guidelines
If the unit has a top mixing box or economizer damper or a top
duct connection, field fabricate and install flashing to divert
moisture from the connection. The flashing must lap over the
standing seams of the top panels. The flashing also must lap
over the side edges of the unit. See Figure 14
.
Figure 14: Flashing Over Top Panels and Sides of Units
Dampers and Hoods
Side dampers may be provided in the mixing box and
economizer sections of units. When dampers are provided, a
removable panel is located above the weather hood to provide
access to the damper drive shaft. Other access may be available
depending on the specific construction of the unit. See Figure 15.
Figure 15: Filler Panel Over the Weather Hood
When units are ordered with exhaust hoods and intake hoods
adjacent to each other, install a field-supplied barrier to
prevent recirculation of exhaust air into the intake openings.
See Figure 16.
Figure 16: Field-Installed Barrier Between Hoods
Mounting Actuators
The installing contractor is responsible for the mounting of all
field-installed actuators. No provisions are made for the
location of these actuators due to the number of options and
arrangements available and the variety of specific applications.
Typically, actuators are mounted inside the cabinet. Provide
proper support for the actuator to avoid excessive stress in the
cabinet, linkage, or damper shafts.
Note:
Damper blades are at full flow when open to 70 degrees.
Do not open blades further than 70 degrees.
Fresh air and return air dampers can be linked together and
driven from the same actuator if the dampers are the same size.
If the dampers are different sizes, they must be driven by
separate actuators and controlled appropriately. Exhaust
dampers are always driven by a separate actuator.
A typical rotary electric actuator can handle up to 40 sq. ft. of
damper. For pneumatic actuators, allow 5 in-lb per square foot
of damper area.
F l a s h i n g
D u c t
F l a s h i n g
U n i t t o p
p a n e l
F l a s h i n g
D u c t
F l a s h i n g
Remove screws
and panel to access
damper control shaft.
Hood
E x h a u s t
I n t a k e
B a r r i e r
