Slab Mount (Horizontal Units Only); Alternate Unit Support; Slab Mount); Step 5 - Field Fabricate Ductwork - Bryant Preferred Series Installation Instructions Manual

NOTE: 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. 3. Improperly applied gasket can also result in air leaks and
poor unit performance.
Curb should be level. This is necessary for unit drain to func-
tion properly. Unit leveling tolerances are shown in Fig. 4. Re-
fer to Accessory Roof Curb Installation Instructions for addi-
tional information 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-supplied
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 base-
pan, attach the accessory thru-the-base service connections to
the basepan in accordance with the accessory installation
instructions.
A
B
Fig. 4 — 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 ob-
structing 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
support 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 dimen-
sions are equal to or greater than the unit supply duct opening
dimensions for the first 18-in. (458 mm) of duct length from
the unit basepan.
/ -in. pipe coupling and gas plate
1
2
C
MAXIMUM ALLOWABLE
DIFFERENCE IN. (MM)
A-B B-C A-C
0.5 (13) 1.0 (25) 1.0 (25)
Insulate and weatherproof all external ductwork, joints, and
roof openings with counter flashing and mastic in accordance
with applicable 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
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.
Keep unit upright and do not drop. Spreader bars are required.
Rollers may be used to move unit across a roof. Rigging mate-
rials under unit (cardboard or wood) must be removed PRIOR
to placing the unit on the roof curb. Level by using unit frame
as a reference. See Table 2 and Fig. 5 for additional information.
Lifting holes are provided in base rails as shown in Fig. 5. Re-
fer to rigging instructions on unit.
Rigging materials under unit (cardboard to prevent base pan
damage) 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 / -in. square socket drive extension. For further details, see
1
2
"Install External Condensate Trap and Line" on page 16.
Before setting the unit onto the curb, recheck gasketing on
curb.

POSITIONING ON CURB

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.
Position unit on roof curb so that the following clearances are
maintained: / -in. (6.4 mm) clearance between the roof curb
1
4
and the base rail inside the front and rear, 0.0-in. clearance be-
tween the roof curb and the base rail inside on the duct end of
the unit. This will result in the distance between the roof curb
and the base rail inside on the condenser end of the unit being
approximately / -in. (6.4 mm).
1
4
Although unit is weatherproof, guard against water from higher
level runoff and overhangs.
Flue vent discharge must have a minimum horizontal clearance
of 4 ft (1220 mm) from electric and gas meters, gas regulators,
and gas relief equipment. Minimum distance between unit and
other electrically live parts is 48-in. (1220 mm).
10
CAUTION
CAUTION