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Configuring Supply and Return Openings for
Downflow Applications
Units may be converted to be installed as downflow
applications. To convert to downflow operation, use the
following steps:
1.
Remove the duct covers found in the bottom return and
supply air duct openings. There are four screws securing
each duct cover.
2.
Install the duct covers to the side supply and return air
duct openings. Secure with the four screws used in step
one.
3.
All ductwork must be in place and attached to the roof
curb before the unit is set into place.
Roof Curb
A field assembled or fabricated roof curb must be in place
before the unit is hoisted to the roof top.
The roof curb must be installed on a flat level section of the
roof (maximum of 1/4" per foot pitch) and provide a level
mounting surface for the unit.
Be sure the roof curb spans structural members (trusses) of the
roof providing sufficient support for the weight of the unit, the
curb, the duct(s), and any factory or field installed accessories.
Be sure the hole in the structure for the ducts is large enough
to accommodate the fabricated ducts and the insulation
surrounding them. See page 15 for roof curb dimensions.
Roof flashing must be installed to seal the roof curb cavity
and must conform to local building codes.
Check the appropriate building codes for weight
distribution requirements. Refer to the applicable roof curb
mounting instruction. The unit may be installed on class A,
B, or C roofing material.
3/4" x 1" wide gasketing for
curb frame and all duct
support surfaces
Unit Base
Wood Nailer
8" Min. above
finished roof
Curb frame
Insulation
Roof curb
installation -
side return
6
Unit base rail
Counter flashing
Cant strip
Insulation and
roofing material
Roof deck and
roofing material
Roof curb
installation -
bottom return
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