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Curb should be level. This is necessary for unit drain to
function properly. Unit leveling tolerances are show in
Fig. 5. Refer to Accessory Roof Curb Installation
Instructions for additional information as required.
A
B
Fig. 5 - - Unit Leveling Tolerances
Install insulation, cant strips, roofing felt, and counter
flashing as shown. Ductwork must be attached to curb and
not to the unit.
IMPORTANT:
If the unit's gas connection and/or electric and control
wiring is to be routed through the basepan and the unit
is equipped with the factory- - installed Thru- - the- - Base
service option see the following sections:
S Factory- - Option Thru- - Base Connections
(Gas Connection) on page 11
S Factory- - Option Thru- - Base Connections
(Electrical Connections) on page 18
If using the field- - installed Thru- - the- - Base accessory
follow the instructions provided with the accessory kit.
NOTE:
If gas and/or electrical connections are not
going to occur at this time, tape or otherwise cover the
fittings so that moisture does not get into the building or
conduit in the interim.
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 obstructing 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.
C
MAXIMUM ALLOWABLE
DIFFERENCE IN. (MM)
A-B
B-C
A-C
0.5" (13)
1.0" (25)
1.0" (25)
C10001
Step 5 — Field Fabricate Ductwork
NOTE:
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.
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
When the unit is ready to be rigged and no longer will be
lifted by a fork truck, the wood protector under the basepan
must be removed. Remove 4 screws from each base rail.
Wood protector will drop to the ground. See instructions on
the unit base rails.
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.
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.
Before setting the unit onto the curb, recheck gasketing on
curb.
9
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