9
Step 4
—
Field Fabricate Ductwork
On vertical units, secure all ducts to roof curb and building
structure.
Do not connect ductwork to unit.
For horizontal
applications, field-supplied flanges should be attached to horizontal
discharge openings and all ductwork 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
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. Cabinet
return-air static pressure (a negative condition) shall not exceed
0.35 in. wg with economizer or 0.45 in. wg without economizer.
These units are designed for a minimum continuous return-air
temperature in heating of 50
_
F (dry bulb), or an intermittent
operation down to 45
_
F (dry bulb), such as when used with a night
set-back thermostat.
To operate at lower return-air temperatures, a field-supplied
outdoor-air temperature control must be used to initiate both stages
of heat when the temperature is below 45
_
F. Indoor comfort may
be compromised when these lower air temperatures are used with
insufficient heating temperature rise.
Step 5
—
Make Unit Connections
Vertical Configuration
Unit is shipped for thru-the-bottom duct connections. Ductwork
openings are shown in Fig. 1 and 6. Duct connections for vertical
supply and return configuration are shown in Fig. 7.
Field-fabricated concentric ductwork may be connected as shown
in Fig. 8 and 9. The unit is designed to attach the ductwork to the
roof curb. Do not attach duct directly to the unit.
SEE
NOTE
SEE
NOTE
AIR
OUT
AIR
IN
ECONOMIZER
NOTE: Do not drill in this area. Damage to basepan may result in water leak.
C06378
Fig. 7
---
Air Distribution -- Vertical Supply and Return
SEE
NOTE
SEE
NOTE
AIR OUT
AIR IN
AIR OUT
ECONOMIZER
NOTE: Do not drill in this area. Damage to basepan may result in water leak.
C06379
Fig. 8
---
Air Distribution -- Concentric Duct
C06100
Fig. 9
---
Concentric Duct Details
UNIT DAMAGE AND PERSONAL INJURY HAZARD
Failure to follow this warning could cause equipment
damage and/or 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.
!
WARNING
Units with electric heat require a 1-in. clearance for the first 24 in.
of ductwork. Outlet grilles must not lie directly below unit
discharge.
NOTE
: A 90-degree elbow must be provided in the supply
ductwork to comply with UL (Underwriters Laboratories) codes
for use with electric heat.
50P
G
20
---
28
