SYSTEM OPERATION
11
9.3.8.1
Ducts shall be constructed of galvanized steel or a
material having equivalent corrosion resistance, strength,
and rigidity.
Exception: Within dwellings units, unobstructed stud and joist
spaces shall not be prohibited from conveying combustion
air, provided that not more than one fireblock is removed.
9.3.8.2
Ducts shall terminate in an unobstructed space, al-
lowing free movement of combustion air to the appliances.
9.3.8.3
Ducts shall serve a single space.
9.3.8.4
Ducts shall not serve both upper and lower combustion
air openings where both such openings are used. The separa-
tion between ducts servicing upper and lower combustion air
openings shall be maintained to the source of combustion air.
9.3.8.5
Ducts shall not be screened where terminating in an
attic space.
9.3.8.6
Horizontal upper combustion air ducts shall not slope
downward toward the source of combustion air.
9.3.8.7
The remaining space surrounding a chimney liner,
gas vent, special gas vent, or plastic piping installed within a
masonry, metal, or factory built chimney shall not be used to
supply combustion air.
Exception: Direct vent appliances designed for installation in
a solid fuel-burning fireplace where installed in accordance
with the manufacture’s installation instructions.
9.3.8.8
Combustion air intake openings located on the exterior
of the building shall have the lowest side of the combustion
air intake openings located at least 12 in. (300 mm) vertically
from the adjoining grade level.
Horizontal Applications and Considerations
Horizontal applications, in particular, may dictate many of
the installation’s specifics such as airflow direction, ductwork
connections, flue and/or combustion air pipe connections,
etc. The basic application of this furnace as a horizontal fur-
nace differs only slightly from an upright installation. When
installing a furnace horizontally, additional consideration
must be given to the following:
Drain Trap and Lines
In horizontal applications the condensate drain trap is se-
cured to the furnace side panel, suspending it below the fur-
nace. A minimum clearance of 5.5” below the furnace must
be provided for the drain trap. Additionally, the appropriate
downward piping slope must be maintained from the drain
trap to the drain location. Refer to
Condensate Drain Trap
and Lines
section in this manual or the installation instruc-
tions for further details. If the drain trap and drain line will be
exposed to temperatures near or below freezing, adequate
measures must be taken to prevent condensate from freez-
ing.
NOTE:
The use of insulation and/or heat tape is recom-
mended. Failure to provide proper condensate drainage can
result in property damage.
Leveling
Leveling ensures proper condensate drainage from the heat
exchanger and induced draft blower. For proper flue pipe
drainage, the furnace must be level lengthwise from end to
end. The furnace should also be level from back to front or
have a slight tilt with the access doors downhill (approxi-
mately 3/4”) from the back panel. The slight tilt allows the
heat exchanger condensate, generated in the recuperator
coil, to flow forward to the recuperator coil front cover.
In horizontal installations with the furnace laying on the left
hand side, the alternate vent connection may be used. In this
configuration the internal elbow is removed. The standard
piping connections may also be used in these positions. Re-
fer to
Vent/Flue Pipe and Combustion Air Pipe
section in the
installation instructions for details concerning the conversion
to the alternate vent/flue and combustion air connections on
the 90% furnace.
The 34.5” single stage furnace is one of the products in our
newly redesigned line of shorter chassis furnaces. It is avail-
able in 92% / 96% AFUE up flow / horizontal model and a
down flow / horizontal model.
The up flow / horizontal 34.5” single stage furnace is avail
-
able in the following models:
*M9S920403ANAA
*M9S920603BNAA
*M9S9S0803BNAA
*M9S920804CNAA
*M9S920805CNAA
*M9S921004CNAA
*M9S921005CNAA
*M9S921205DNAA
*M9S960403ANAA
*M9S960603BNAA
*M9S960803BNAA
*M9S960804CNAA
*M9S960805CNAA
*M9S961005CNAA
*M9S961205DNAA
The down flow / horizontal 34.5” single stage furnace is
available in the following models.
*C9S960403BNAA
*C9S960603BNAA
*C9S960804CNAA
*C9S961005CNAA
*C9S961205CNAA
