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2
Curb should be level. Unit leveling tolerances are shown in
Fig. 3. This is necessary for unit drain to function properly. Re-
fer to Accessory Roof Curb Installation Instructions for addi-
tional information as required.
SLAB MOUNT (Horizontal Units Only) — Provide a level
concrete slab that extends a minimum of 6 in. 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.
Step 2 — Field Fabricate Ductwork —
Secure all
ducts to roof curb and building structure on vertical ducted
units. Do not connect ductwork to unit. For horizontal applica-
tions, field-supplied flanges should be attached to horizontal
duct openings and all ductwork should be secured to the
flanges. Insulate and weatherproof all external ductwork,
joints, and roof openings with counter flashing and mastic in
accordance with applicable codes.
Ducts passing through an unconditioned space must be in-
sulated 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 applica-
ble fire codes.
A minimum clearance is not required around ductwork.
Cabinet return air static shall not exceed –.20 in. wg with
EconoMi$er, –.35 in. wg with Durablade economizer, or
–.45 in. wg without economizer.
These units are designed for a minimum continuous heating
return-air temperature of 50 F (dry bulb), or an intermittent op-
eration down to 45 F (dry bulb), such as when used with a night
set-back thermostat.
Step 3 — Install External Trap for Condensate
Drain —
The unit’s
3
/
4
-in. condensate drain connections are
located on the bottom and side of the unit. Unit discharge con-
nections do not determine the use of drain connections; either
drain connection can be used with vertical or horizontal
applications.
When using the standard side drain connection, make sure
the plug (Red) in the alternate bottom connection is tight before
installing the unit.
To use the bottom drain connection for a roof curb installa-
tion, relocate the factory-installed plug (Red) from the bottom
connection to the side connection. See Fig. 4. The piping for
the condensate drain and external trap can be completed after
the unit is in place.
All units must have an external trap for condensate drain-
age. Install a trap at least 4-in. deep and protect against freeze-
up. If drain line is installed downstream from the external trap,
pitch the line away from the unit at 1 in. per 10 ft of run. Do not
use a pipe size smaller than the unit connection (
3
/
4
in.).
Step 4 — Rig and Place Unit —
Inspect unit for
transportation damage. File any claim with transportation
agency. Keep unit upright and do not drop. Spreader bars are
not required if top crating is left on unit. Rollers may be used to
move unit across a roof. Level by using unit frame as a refer-
ence. See Table 1 and Fig. 5 for additional information.
Lifting holes are provided in base rails as shown in Fig. 6.
Refer to rigging instructions on unit.
POSITIONING — Maintain clearance around and above unit
to provide minimum distance from combustible materials,
proper airflow, and service access. See Fig. 6. A properly posi-
tioned unit will have the following clearances between unit and
roof curb:
1
/
4
-in. clearance between roof curb and base rails on
each side and duct end of unit;
1
/
4
-in. clearance between roof
curb and condenser coil end of unit. (See Fig. 2, section C-C.)
Do not install unit in an indoor location. Do not locate unit
air inlets near exhaust vents or other sources of contaminated
air.
Be sure that unit is installed such that snow will not block
the combustion intake or flue outlet.
All panels must be in place when rigging.
Fig. 1 — Horizontal Conversion Panels