12
Remove these covers
for horizontal duct
applications
Duct Cover Installation
Down Discharge Applications
Cut insulation around bottom openings and remove
panels from the bottom of the unit, saving the screws
holding the panels in place.
NOTE:
Single phase models require installation of
horizontal duct kit #20464501NGK (medium chassis) and
#20464502NGK (large chassis). See “Unit Dimensisons”
section for chassis sizes.
Ductwork
Duct systems and register sizes must be properly
designed for the C.F.M. and external static pressure rating
of the unit. Ductwork should be designed in accordance
with the recommended methods of Air Conditioning
Contractors of America Manual D (Residential) or Manual
Q (Commercial). All ductwork exposed to the outdoors
must include a weatherproof barrier and adequate
insulation.
A duct system should be installed in accordance with
Standards of the National Board of Fire Underwriters
for the Installation of Air Conditioning, Warm Air Heating
and Ventilating Systems. Pamphlets No. 90A and 90B.
The supply duct from the unit through a wall may be
installed without clearance. However, minimum unit
clearances as shown in the appendix must be maintained.
The supply duct should be provided with an access panel
large enough to inspect the air chamber downstream of
the heat exchanger. A cover should be tightly attached
to prevent air leaks.
For duct flange dimensions on the unit refer to the Unit
Dimension illustration in the appendix.
For down-discharge applications, the ductwork should
be attached to the roof curb prior to installing the
unit. Ductwork dimensions are shown in the roof curb
installation manual.
If desired, supply and return duct connections to the unit
may be made with flexible connections to reduce possible
unit operating sound transmission.
Filters
CAUTION
T
O PREVEN
T
PROPERTY
D
AMAGE
DU
E TO
F
IRE
A
ND LO
SS
OF
EQUIPMEN
T
EFFICIENCY OR EQUIPMEN
T DA
MAGE
D
UE
T
O
DUST A
ND LIN
T
BUILD
UP
ON INTERNAL
P
AR
TS
, NEVER OPER
AT
E UNIT WITHO
UT A
N AIR
FILTER INS
TA
LLED IN THE RETURN
A
IR
S
YSTEM.
Even though a return air filter is not supplied with this
unit, there must be a means of filtering all return air. All
units may be externally filtered.
Refer to the unit filter size chart in the appendix for filter
size information.
Filters installed external to the unit should be sized in
accordance with their manufacturer recommendations.
A throwaway filter must be sized for a maximum face
velocity of 300 feet per minute.
Filter Installation
Important:
When installing a filter, the air flow arrows on
the filter must point toward the circulator blower.
Unit
2 Ton
2 1/2 Ton
3 Ton
3 1/2 / 4
Ton
5 Ton
Min.Filter
Size
(1)20x20x1 (1)20x25x1 (1)25x25x1 (2)20x20x1 (2)20x25x1
Recommended Filter Sizes
VENTING
NOTE: Venting is self-contained. Do not modify or block.
Flue Hood Installation
Install the exhaust flue hood and combustion air intake
hood prior to operation of the unit.
To install the flue hood cover, please refer to the installation
instructions, included in the flue hood assembly package
located in the blower compartment.
Installation - Flue Hood Exhaust
1. Locate the flue hood assembly box in the unit.
2. Slide screen over flanges on the lower flue hood.
3. Slide screen and lower flue hood into hood.
4. Using the three screws provided, attach the hood (with the
opening facing down) over the flue exhaust opening in the
utility panel.
