21
Rev. 0
COMBUSTION AND VENTILATION AIR
(DIRECT/NON-DIRECT VENT MODELS)
4. When ducts are used, they shall be of the same cross-
sectional area as the free area of the openings to which
they connect. The minimum dimension of rectangular
air ducts shall not be less than 3 inches.
5.3.4 Specially Engineered Installations:
The requirements of 5.3.3 shall not necessarily govern when
special engineering, approved by the authority having ju-
risdiction, provides an adequate supply of air for combus-
tion, ventilation, and dilution of flue gases.
5.3.5 Louvers and Grilles:
In calculating free area in 5.3.3, consideration shall be given
to the blocking effect of louvers, grilles or screens protect-
ing openings. Screens used shall not be smaller than 1/4
inch mesh. If the area through a design of louver or grille is
known, it should be used in calculating the size of opening
required to provide the free area specified. If the design
and free area is not known, it may be assumed that wood
louvers will have 20-25 percent free area and metal lou-
vers and grilles will have 60-75 percent free area. Louvers
and grilles shall be fixed in the open position or interlocked
with the equipment so that they are opened automatically
during equipment operation.
5.3.6 Special Conditions Created by Mechanical Ex-
hausting or Fireplaces:
Operation of exhaust fans, ventilation systems, clothes dry-
ers, or fireplaces may create conditions requiring special
attention to avoid unsatisfactory operation of installed gas
utilization equipment.
Vent/Flue Pipe and Combustion Air Pipe
General
WARNING
Failure to follow these instructions can result in bodily
injury or death. Carefully read and follow all instruc-
tions given in this section.
WARNING
Upon completion of the furnace installation, carefully
inspect the entire flue system both inside and outside
the furnace to assure it is properly sealed. Leaks in the
flue system can result in serious personal injury or
death due to exposure to flue products, including car-
bon monoxide.
A condensing gas furnace achieves its high level of effi-
ciency by extracting almost all of the heat from the prod-
ucts of combustion and cooling them to the point where
condensation takes place. Because of the relatively low flue
gas temperature and water condensation requirements,
PVC pipe is used as venting material.
This furnace must not be connected to Type B, BW, or L
vent or vent connector, and must not be vented into any
portion of a factory built or masonry chimney except when
used as a pathway for PVC as described later in this sec-
tion. Never common vent this appliance with another appli-
ance or use a vent which is used by a solid fuel appliance.
Do not use commercially available “no hub connectors” other
than those shipped with this product.
It is the responsibility of the installer to follow the manufac-
turers’ recommendations and to verify that all vent/flue pip-
ing and connectors are compatible with furnace flue prod-
ucts. Additionally, it is the responsibility of the installer to
ensure that all piping and connections possess adequate
structural integrity and support to prevent flue pipe separa-
tion, shifting, or sagging during furnace operation.
Dual Certification: Non-Direct/Direct Vent
This furnace is dual certified and may be installed as a non-
direct vent (single pipe) or direct vent (dual pipe) appliance.
A
non-direct vent installation requires only a vent/flue pipe,
while a
direct vent installation requires both a vent/flue pipe
and a combustion air intake pipe. Refer to the appropriate
section for details concerning piping size, length, number
of elbows, furnace connections, and terminations.
Materials and Joining Methods
WARNING
To avoid fire, explosion, or bodily injury, solvent ce-
ments must be kept away from all ignition sources (i.e.,
sparks, open flames, and excessive heat) as they are
combustible liquids. Avoid breathing cement vapors
or contact with skin and/or eyes.
Two- or three-inch nominal diameter PVC Schedule 40 pipe
meeting ASTM D1785, PVC primer meeting ASTM F656,
and PVC solvent cement meeting ASTM D2564 specifica-
tions must be used. Fittings must be DWV type fittings
meeting ASTM D2665 and ASTM D3311. Carefully follow
the manufacturer’s instructions for cutting, cleaning, and
solvent cementing of PVC.
As an alternative to PVC pipe, primer, solvent cement, and
fittings, ABS materials which are in compliance with the
following specifications may be used. Two-or-three-inch
ABS Schedule 40 pipe must meet ASTM D1527 and, if
used in Canada, must be CSA listed. Solvent cement for
ABS to ABS joints must meet ASTM D2235 and, if used in
Canada, must be CSA listed. The solvent cement for the
PVC to ABS transition joint must meet ASTM D3138. Fit-
tings must be DWV type fittings meeting ASTM D2661 and
ASTM D3311 and, if used in Canada, must be CSA listed.
Carefully follow the manufacturers’ instructions for cutting,
cleaning, and solvent cementing PVC and/or ABS.
