Slab Mount (Horizontal Units Only); Alternate Unit Support; Slab Mount); Step 5 - Field Fabricate Ductwork - Carrier 50KC04 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. 7. Improperly applied gasket can also result in air leaks and
poor unit performance.

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 0.4-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.
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.

FOR UNITS WITH ACCESSORY ELECTRIC HEATERS

All installations require a minimum clearance to combustible sur-
faces of 1 in. (25 mm) from duct for the first 12-in. (305 mm)
away from unit.
Outlet grilles must not lie directly below unit discharge.
NOTE: A 90 degree elbow must be provided in the ductwork to
comply with UL (Underwriters Laboratories) code for use with
electric heat.
PERSONAL INJURY HAZARD
Failure to follow this warning could cause personal injury.
For vertical supply and return units, tools or parts could drop
into ductwork and cause an injury. Install a 90 degree turn in
the 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. Due to electric
heater, supply duct will require 90 degree elbow.
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. Level by using
unit frame as a reference. See Table 2 and Fig. 9 for additional in-
formation.
Lifting holes are provided in base rails as shown in Fig. 9. Refer to
rigging instructions on unit.
Before setting the unit onto the curb, recheck gasketing on curb.
Rigging materials under unit (cardboard or wood 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 set-
ting the unit in place. The red drain pan plug can be tightened with
a / -in. square socket drive extension. For further details see "Step
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10 — Install External Condensate Trap and Line" on page 14.
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.

POSITIONING ON CURB

Position unit on roof curb so that the following clearances are
maintained: / -in. (6.4 mm) clearance between the roof curb and
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the base rail inside the front and rear, 0.0-in. clearance between 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
(6.4 mm).
Although unit is weatherproof, guard against water from higher
level runoff and overhangs.
After unit is in position, remove rigging skids and shipping
materials.
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WARNING
CAUTION
/ -in.
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