Step 3 - Field Fabricate Ductwork; Step 4 - Make Unit Duct Connections; 48A2, A3, A6, And A7 Units; 48A4, A5, A8, And A9 Units - Carrier WeatherMaker 48A020 Installation Instructions Manual

Step 3 — Field Fabricate Ductwork
Secure all ducts to building structure. Use flexible duct connectors
between unit and ducts as required. Insulate and weatherproof all
external ductwork, joints, and roof openings with counter flashing
and mastic in accordance with applicable codes.
NOTE: Due to width of the horizontal supply and return
ductwork, provisions should be made for servicing of the outdoor
air filters (i.e., catwalk over ductwork).
Ducts passing through an unconditioned space must be insulated
and covered with a vapor barrier. Outlet grilles must not lie
directly below unit discharge. The return duct must have a
90-degree elbow before opening into the building space if the unit
is equipped with power exhaust.
To attach ductwork to roof curb, insert duct approximately 10 to
11 in. up into roof curb. Connect ductwork to 14-gage roof curb
material with sheet metal screws driven from inside the duct.
Follow AMCA (Air Movement and Control Association) guide-
lines relating to ductwork connections to the unit. These
guidelines recommend a minimum 2
of straight duct connected to supply air inlet and outlet openings
before any transitions, fittings, dampers, etc. Failure to adhere to
these guidelines may result in system effects which can impact the
unit's ability to achieve published performance.
For vertical supply and return units, tools or parts could drop
into ductwork and cause an injury. Install a 90-degree elbow
turn in the supply and return ductwork between the unit and
the conditioned space. If a 90-degree elbow cannot be
installed, then a grille of sufficient strength and density should
be installed to prevent objects from falling into the conditioned
space. Use the full opening of the provided supply and return
openings. Failure to do so can lead to air balancing issues,
improper operation, or even failure of system components.
Step 4 — Make Unit Duct Connections

48A2, A3, A6, AND A7 UNITS

Unit is shipped for thru-the-bottom duct connections.
Field-fabricated ductwork should be attached to the roof curb.
Supply and return duct dimensions are shown in Fig. 5, 6, 9, and
12. Air distribution is shown in Fig. 15. Refer to installation
instructions shipped with roof curb for more information.
a48-8241
Fig. 15 — Air Distribution — Thru-the-Bottom
/ equivalent duct diameters
1
2
WARNING

48A4, A5, A8, AND A9 UNITS

Remove shipping covers from supply and return air openings.
Attach field-supplied ductwork to unit. Connect to the unit with a
single duct for all supply openings and with a single duct for all
return openings. Splitting of the airflow into branch ducts should
not be done at the unit. Sufficient duct length should be used prior
to branching to ensure the air temperatures are well mixed within
the ductwork. See Fig. 7, 8, 10, and 11 for duct opening dimen-
sions. Secure all ducts to building structure. Air distribution is
shown in Fig. 16. Verify the Outdoor Air Temperature (OAT) and
Return Air Temperature (RAT) sensors as outlined in Fig. 17 can
measure the OAT and RAT temperatures in the corresponding air
streams. Relocate the sensor locations if needed. Failure to do this
can lead to operational issues and possible future relocation of the
sensors.
Install accessory barometric relief or power exhaust in the field-
fabricated return ductwork. Refer to Step 11 — Position Power
Exhaust/Barometric Relief Damper Hood section on page page 30
for more information.
a48-8242
Fig. 16 — Air Distribution — Thru-the-Side
Fig. 17 — Outdoor Air and Return Air Sensors
Step 5 — Install Flue Hood

48A2020-050 UNITS

Flue hood is shipped inside gas section of unit. To install, secure
flue hood to access panel. See Fig. 18.

48A2060 UNITS

Flue hood and wind baffle are shipped inside gas section of unit.
To install, secure flue hood to access panel. Install the two pieces
of the wind baffle over the flue hood. See Fig. 19.
NOTE: When properly installed, flue hood will line up with com-
bustion fan housing. See Fig. 20.
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Location