66369-YIM-D-1004
Unitary Products Group
17
DUCTWORK
Ductwork should be designed and sized according to
the methods in Manual Q of the Air Conditioning Con-
tractors of America (ACCA).
A closed return duct system shall be used. This shall
not preclude use of economizers or outdoor fresh air
intake. The supply and return air duct connections at
the unit should be made with flexible joints to minimize
noise.
The supply and return air duct systems should be
designed for the CFM and static requirements of the
job. They should NOT be sized to match the dimen-
sions of the duct connections on the unit.
Refer to Dimensions and Clearances Figure 13 for
information concerning side and bottom supply and
return air duct openings.
NOTE:
It is recommended that, in Canada, the outlet
duct be provided with a removable access
panel. It is recommended that this opening be
accessible when the unit is installed in service,
and of a size such that smoke or reflected light
may be observed inside the casing to indicate
the presence of leaks in the heat exchanger.
The cover should be attached in a manner
adequate to prevent leakage.
FIXED OUTDOOR AIR INTAKE DAMPER
This damper is shipped inside the return air compart-
ment. It is completely assembled and ready for installa-
tion. A damper baffle inside of the hood is adjustable to
provide variable amounts of outdoor air intake on units
that are not provided with an economizer or a motor-
ized damper option. Refer to the Fixed Outdoor
Damper Figure 3.
Gasketing and mounting screws are provided in a parts
bag attached to the hood assembly. Apply gasketing to
the three flange surfaces on the hood prior to installing
the hood. Extend gasketing 1/4 inch beyond the top
and bottom of the two side flanges to insure adequate
sealing.
Adjusting the damper to the desired air flow may be
done before mounting the hood into position or after
installation by removing the front hood panel or the
screen on the bottom of the hood. Damper baffle in
position 1 will allow approximately 10% outdoor air
flow, position 2 approximately 15% and, to allow
approximately 25%, remove the damper baffle.
On units with bottom return air application install the
damper assembly over the opening in the side return
air access panel. Remove and discard the opening
cover and the covering over the hood mounting holes
(used for shipping) before installing. Secure with the
screws provided.
On units with side return air applications, install the
damper assembly on the return air ductwork as close
to the unit as possible. Cut an opening 16 inches high
by 18 inches wide in the ductwork to accommodate the
damper. Using the holes in the hood flanges as a tem-
plate, drill 9/64 inch dia. (#26 drill) holes into the duct-
work and secure with the screws provided.
Do not permit overhanging structures or shrubs
to obstruct outdoor air discharge outlet, com-
bustion air inlet or vent outlets.
When fastening ductwork to side duct flanges
on unit, insert screws through duct flanges
only. DO NOT insert screws through casing.
Outdoor ductwork must be insulated and
waterproofed.
If outdoor air intake will not be required on
units with bottom return air applications, the
damper assembly should still be mounted on
the side return air access panel, per the
instructions above, to insure moisture is not
drawn into the unit during operation. The cov-
ering over the mounting holes only need be
removed. Do not remove the opening cover.
