12
The gasketing of the unit to the roof curb is critical for a watertight
seal. Install gasket supplied with the roof curb as shown in Fig. 4.
Improperly applied gasket can also result in air leaks and poor unit
performance.
Curb should be level. This is necessary for unit drain to function
properly. Unit leveling tolerances are shown in Fig. 8. Refer to
Accessory Roof Curb Installation Instructions for additional infor-
mation as required.
Install insulation, cant strips, roofing felt, and counter flashing as
shown. Ductwork must be attached to curb and not to the unit. The
accessory thru-the-base power and gas connection package must
be installed before the unit is set on the roof curb. If field-installed
thru-the-roof curb gas connections are desired, use factory-sup-
plied
1
/
2
-in. pipe coupling and gas plate assembly to mount the
thru-the-roof curb connection to the roof curb. Gas connections
and power connections to the unit must be field-installed after the
unit is installed on the roof curb.
If electric and control wiring is to be routed through the basepan,
attach the accessory thru-the-base service connections to the base-
pan in accordance with the accessory installation instructions.
Fig. 8 — Unit Leveling Tolerances
SLAB MOUNT (HORIZONTAL UNITS ONLY)
Provide a level concrete slab that extends a minimum of 6-in.
(150 mm) beyond unit cabinet. Install a gravel apron in front of
condenser coil air inlet to prevent grass and foliage from obstruct-
ing airflow.
NOTE: Horizontal units may be installed on a roof curb if
required.
ALTERNATE UNIT SUPPORT (IN LIEU OF CURB OR
SLAB MOUNT)
A non-combustible sleeper rail can be used in the unit curb sup-
port area. If sleeper rails cannot be used, support the long sides of
the unit with a minimum of 3 equally spaced 4-in. x 4-in. (102 mm
x 102 mm) pads on each side.
Step 5 — Field Fabricate Ductwork
Cabinet return-air static pressure (a negative condition) shall not
exceed 0.35 in. wg (87 Pa) with economizer or 0.45 in. wg
(112 Pa) without economizer.
For vertical ducted applications, secure all ducts to roof curb and
building structure. Do not connect ductwork to unit.
Fabricate supply ductwork so that the cross sectional dimensions
are equal to or greater than the unit supply duct opening dimen-
sions for the first 18-in. (458 mm) of duct length from the unit
basepan.
Insulate and weatherproof all external ductwork, joints, and roof
openings with counter flashing and mastic in accordance with ap-
plicable codes.
Ducts passing through unconditioned spaces must be insulated
and covered with a vapor barrier.
If a plenum return is used on a vertical unit, the return should be
ducted through the roof deck to comply with applicable fire codes.
A minimum clearance is not required around ductwork.
Step 6 — Rig and Place Unit
Keep unit upright and do not drop. Spreader bars are required.
Rollers may be used to move unit across a roof. Rigging materials
under unit (cardboard or wood) must be removed PRIOR to plac-
ing the unit on the roof curb. Level by using unit frame as a refer-
ence. See Table 2 and Fig. 9 for additional information.
Lifting holes are provided in base rails as shown in Fig. 9. Refer to
rigging instructions on unit.
Rigging materials under unit (cardboard to prevent base pan dam-
age) must be removed PRIOR to placing the unit on the roof curb
When using the standard side drain connection, ensure the red
plug in the alternate bottom connection is tight. Do this before
setting the unit in place. The red drain plug an be tightened with
a
1
/
2
-in. square socket drive extension. For further details, see
“Install External Condensate Trap and Line” on page 19.
Before setting the unit onto the curb, recheck gasketing on curb.
B
C
MAXIMUM ALLOWABLE
DIFFERENCE IN. (MM)
A-B B-C A-C
0.5 (13) 1.0 (25) 1.0 (25)
CAUTION
PROPERTY DAMAGE HAZARD
Failure to follow this caution may result in damage to roofing
materials.
Membrane roofs can be cut by sharp sheet metal edges. Be
careful when placing any sheet metal parts on such roof.
CAUTION
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment damage.
All panels must be in place when rigging. Unit is not designed
for handling by fork truck when packaging is removed.
If using top crate as spreader bar, once unit is set, carefully
lower wooden crate off building roof top to ground. Ensure
that no people or obstructions are below prior to lowering the
crate.
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