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98618/035-20009-001
Rev. B (1205)
Clearances
for access:
Ample clearances should be provided to permit easy access to the unit.
The following minimum clearances are recommended:
1.
Twenty-four
(24) inches (61 cm) between the front of the furnace
and an adjacent
wall or another
appliance,
when access
is
required for servicing and cleaning.
2.
Eighteen (18) inches (46 cm) at the side where access is required
for passage to the front when servicing or for inspection or replace-
ment of flue/vent connections.
In all cases, accessibility
clearances
shall take precedence
over clear-
ances for combustible
materials
where accessibility
clearances
are
greater.
Installation
in a residential
aaraae:
1.
A gas-fired furnace for installation in a residential garage must be
installed so the burner(s)
and the ignition source are located not
less than 18 inches (46 cm) above the floor, and the furnace must
be located or protected to avoid physical damage by vehicles.
TABLE 1: Unit Clearances to Combustibles
APPLICATION
UPFLOW
ROOF JACK
TOP
In, (cm)
1 (2.54)
0 (0.0
FRONT
In. (cm)
2 (5.08)
0 (0.0)
REAR
In. (cm)
0 (0.0)
0 (0.0)
SIDES
In. (cm)
0 (0.0)
0 (0.0)
FLOOR/
BOTTOM
COMBUSTIBLE
COMBUSTIBLE
CLOSET
YES
YES
ALCOVE
YES
YES
ATTIC
YES
YES
LINE
CONTACT
NO
NO
SECTION
Ih DUCTWORK
DUCTWORK
GENERAL
INFORMATION
The duct system's design and installation must:
1.
Handle an air volume appropriate
for the served space and within
the operating parameters of the furnace specifications.
2.
Be installed in accordance with standards of NFPA (National Fire
Protection
Association)
as outlined
in NFPA pamphlets
90A and
90B (latest editions), in Canada CAN/CGA-B149.1-00
Natural Gas
and Propane Installation
Code. or applicable
national, provincial,
or state, and local fire and safety codes.
3.
For Manufactured
(Mobile)
Home and Modular Home Return
Duct System
Installations:
The return air duct and the return air plenum are not required by
the furnace manufacturer,
provided a return air duct and plenum
are not required by state, local, or regional codes. The only vent
system that is approved
for use on this furnace is a Roof Jack
which is a Sealed Combustion
Direct Vent System.
4.
Complete a path for heated or cooled air to circulate through the
air conditioning
and heating equipment and to and from the condi-
tioned space.
CAUTION1
The coolingcoilmust be installed i n the supply airduct,down-
stream ofthe furnace. Cooled air may notbe passed over theheat
exchanger.
When the furnace is used in conjunction
with a cooling coil, the coil
must be installed parallel with, or in the supply air side of the furnace to
avoid condensation
in the primary heat exchanger. When a parallel flow
arrangement
is used, dampers
or other means used to control airflow
must be adequate
to prevent chilled air from entering
the furnace.
If
manually operated,
the damper must be equipped with means to pre-
vent the furnace or the air conditioner from operating unless the damper
is in full heat or cool position.
_WARNING
The duct system must be properly sized to obtain the correct airflow
for the furnace size that is being installed.
Refer to Table 8 and the furnace rating plate for the correct rise
range and Table 3 for static pressures.
If the ducts are undersized,
the result will be high duct static pres-
sures and/or high temperature
rises which can result in a heat
exchanger
OVERHEATING
CONDITION.
This condition can result
in premature
heat exchanger failure, which can result in personal
injury, property damage, or death.
DUCTWORK
INSTALLATION
Upflow
Instructions
Attach the supply plenum to the furnace
outlet duct
connection flanges. This is typically through the use of
S cleat material when a metal plenum is used. The use
of an approved
flexible
duct connector
is recom-
mended on all installations.
This connection should be
sealed to prevent air leakage. The sheet metal should
be crosshatched
to eliminate any popping of the sheet
metal when the indoor fan is energized.
When replacing an existing furnace,
if the existing plenum is not the
same size as the new furnace,
then the existing plenum
must be
removed and a new plenum installed that is the proper size for the new
furnace. If the plenum is shorter than 12" (30.5 cm) the turbulent air flow
may cause the limit controls not to operate as designed, or the limit con-
trols may not operate at all.
The duct system is a very important part of the installation.
If the duct
system
is improperly
sized the furnace
will not operate
properly,
The ducts attached to the furnace plenum, should be of sufficient size
so that the furnace operates
at the specified
external static pressure
and within the air temperature rise specified on the nameplate.
Table 2 is a guide for determining
whether the rectangular
duct system
that the furnace is being connected to be of sufficient size for proper fur-
nace operation.
Use the Example below to help you in calculating the duct area to deter-
mine whether the ducts have sufficient
area so that the furnace oper-
ates
at the specified
external
static
pressure
and within
the air
temperature
rise specified on the nameplate.
Example: The furnace input is 80,000 BTUH, 1,200 CFM. The recom-
mended duct area is 280 sq.in, there are two 8 x 14 rectangular
ducts
attached to the plenum and there are two 7 inch round ducts attached to
the furnace.
1.
Take 8 x 14, which equals 112 sq.in. X 2, which equals 224 square
inch then go to round duct size located in Table 2.
2.
The square inch area for 7 inch round pipe is 38.4, multiply by 2 for
two round ducts which equals 76.8 square inch.
3.
Then take the 224 square inch from the rectangular duct and add it
to the 76.8 sq.in, of round duct. The total square inch of duct
attached to the furnace plenum is 300.8 square inch. This exceeds
the recommended
280 square inch of duct.
In this example, the duct system attached to the plenum has a sufficient
area so that the furnace operates at the specified external static pres-
sure and within the air temperature rise specified on the nameplate.
4
Unitary Products Group
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