Alternate Unit Support (In Lieu Of Curb Or Slab Mount); Step 5 - Field Fabricate Ductwork; Step 6 - Rig And Place Unit; Positioning On Curb - Carrier 48LC Installation Instructions Manual

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
dimensions 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.
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.
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.
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 1 and
Fig. 6 for additional information.
Lifting holes are provided in base rails as shown in Fig. 6.
Refer 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 pan can
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be tightened with a / - - in. square socket drive extension.
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For further details see "Step 11 - - Install External Condensate
Trap & Line" on page 16.
Before setting the unit onto the curb, recheck gasketing on
curb.
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.
Positioning on Curb —
Position unit on roof curb so that the following clearances
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are maintained: / in. (6.4 mm) clearance between the
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roof curb and the base rail inside the front and back, 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 3- - 5/16
in (84 mm).
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 inches (1220 mm).
Flue gas can deteriorate building materials. Orient unit such
that flue gas will not affect building materials. Locate
mechanical draft system flue assembly at least 48 in. (1220
mm) from an adjacent building or combustible material.
NOTE: Installation of accessory flue discharge deflector
kit will reduce the minimum clearance to combustible
material to 18 in. (460 mm).
After the unit is in position remove all riggings, shipping
materials and top skid. Recycle or dispose of all shipping
materials.
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