998659-YIM-C-0614
14
Johnson Controls Unitary Products
Figure 17: XP078-150 Roof Curb Cut Away
Ductwork
Ductwork should be designed and sized according to the
methods in Manual D of the Air Conditioning Contractors of
America (ACCA) or as recommended by any other recognized
authority such as ASHRAE or SMACNA.
A closed return duct system should be used. This will 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 pressure requirements of the job. They
should NOT be sized to match the dimensions of the duct
connections on the unit.
Refer to Figure 10 for bottom air duct openings. Refer to
Figures 12, 13 and Table 6 for side air duct openings.
Duct Covers
Units are shipped with the side duct openings covered and a
covering over the bottom of the unit. For bottom duct
application, no duct cover changes are necessary. For side
duct application, remove the side duct covers and install over
the bottom duct openings. The panels removed from the side
duct connections are designed to be reused by securing each
panel to its respective downflow opening. But keep in mind that
the supply panel is installed with the painted surface UP, facing
the heat exchanger, while the return panel is installed with the
painted surface DOWN, facing the downflow duct opening. The
supply panel is secured with the bracket (already in place from
the factory) and two screws. It’s a snug fit for the panel when
sliding it between the heat exchanger and unit bottom, but there
is room. The return panel is secured with four screws.
3/4” X 1-1/4” WIDE GASKETING FOR CURB
FRAME AND ALL DUCT SUPPORT SURFACES
2“
UNIT BASE
WOOD NAILER
8“ MIN. ABOVE FINISHED ROOF
CURB FRAME
INSULATION
UNIT BASE RAILS
COUNTERFLASHING
CAN’T STRIP
INSULATION AND ROOFING MATERIAL
ROOF DECK AND SUPPORT STRUCTURE
14”
3.56”
3.75”
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 water-proofed.
