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Condensing furnace combustion products have very little
buoyancy, so Table 2 is to be used without consideration
of any vertical rise in the piping.
Vent Pipe Material
Vent and combustion air pipe and fittings must be one of
the following materials in the list and must conform to the
indicated ANSl/ASTM standards. Cement must conform
to ASTM Standard D2564 for PVC and Standard D2235
for ABS. PVC Primer must meet standard ASTM F656.
When joining PVC piping to ABS, use PVC solvent cement.
(See procedure specified in ASTM Standard D3138).
Material ...............................................
Standard
Schedule 40PVC ....................................
D1785
PVC-DWV ...............................................
D2665
SDR-21 & SDR-26 .................................. D2241
ABS-DWV ...............................................
D2661
Schedule 40 ABS ....................................
F628
Foam/Cellular Core PVC ........................ F891
In Canada, all plastic vent pipes and fittings including
any cement, cleaners, or primers must be certified as a
system to ULC S636. However, this requirement does not
apply to the finish flanges or piping internal to the furnace.
Vent Pipe Installation
CAUTION:
Combustion
air
must
not
be drawn
from
a
corrosive
atmosphere.
This furnace has been certified for installation with zero
clearance between vent piping and combustible surfaces.
However, it is good practice to allow space for convenience
in installation and service.
The quality of outdoor air must also be considered. Be
sure that the combustion air intake is not located near a
source of solvent fumes or other chemicals which can
cause corrosion of the furnace combustion
system.
See list of substances on page 5.
Route piping as direct as possible between the furnace
and the outdoors.
Longer vent runs require larger
diameters. Vent piping must be sloped upwards 1/4" per
foot in the direction from the furnace to the terminal.
This is to ensure that any condensate flows back to the
condensate disposal system.
The combustion air intake and the vent exhaust must
be located in the same atmospheric
pressure zone.
This means both pipes must exit the building through
the same portion of exterior wall or roof as shown in
Figures 6 - 9 (page 12 - 13) and Figure 41 (page 44).
Piping must be mechanically
supported
so that its
weight does not bear on the furnace. Supports must
be at intervals no greater than 5 ft. Supports may be
at shorter intervals if necessary to ensure that there
are no sagging sections that can trap condensate.
Outdoor Terminations
= Horizontal Venting
Vent and combustion
air intake terminations
shall be
installed as depicted in Figures 6 - 7 (page 12) and in
accordance with these instructions:
Vent termination clearances must be consistent with the
NFGC, ANSI 2223.1/NFPA 54 and/or the CSA B149.1,
Natural Gas and Propane Installation Code.
All minimum clearances must be maintained to protect
building materials from degradation
by flue gases as
shown in Figure 7.
Vent and combustion
air intake terminations
must
be located to ensure proper furnace operation and
conformance
to applicable
codes. The minimum
distance from any door, open window, or air gravity inlet
is 1ft. below, 1ft. horizontally, or 1ft. above. In Canada,
CSA B149.1 takes precedence over these instructions.
Table 15 (page 43) lists the necessary distances from
the vent termination to windows and building air intakes.
The vent termination
shall be located at least 4 ft.
horizontally
from any electric
meter,
gas meter,
regulator and any relief equipment. These distances
apply ONLY to U.S. installations.
In Canada,
the
Canadian Fuel Gas Code takes precedence over these
instructions.
Do not install the vent terminal such that exhaust is
directed into window wells, stairwells,
under decks
or into alcoves or similar recessed areas, and do not
terminate above any public walkways.
If venting horizontally, a side wall vent kit is available
according to the pipe diameter size of the installation.
For 2 inch pipe use side wall vent kit #904617, and
for 3 inch pipe use kit #904349. Please follow the
instructions provided with the kit,
= When the vent pipe must exit an exterior wall close to
the grade or expected snow level where it is not possible
to obtain clearances shown in Figure 6, a riser may be
provided as shown in Figure 8 (page 12). Insulation is
required to prevent freezing of this section of pipe. For
vent freezing protection, see page 13.
WARNING:
The combustion air vent and exhaust vent
must be configured as shown in Figure 9.
Improper
vent terminations
can cause
the
recirculation
of flue gases which may result in
furnace vibration. In severe cases, the furnace
will
cycle,
due to the intermittent
contact
between
the flame
and
the flame
sensor.
If you
notice
these
oscillations
occurring,
check the vent configuration
to make sure
the exhaust vent does not have a 90 degree
termination.
11
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