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12" MIN.
Horizontal Termination (Single Pipe)
Above Highest Anticipated Snow Level
In a basement installation, the vent/flue pipe can be run
between joist spaces. If the vent pipe must go below a joist
and then up into the last joist space to penetrate the header,
two 45° elbows should be used to reach the header rather
than two 90° elbows.
DIRECT VENT (DUAL PIPE) PIPING
The inlet air screens provided in the installation instruction
packet are available for the installer to use in the inlet of the
combustion air pipe to prevent animals from building nests
in the combustion air pipe. The installation of the screens
is not a requirement and will not effect performance if not
installed in the combustion air pipe.
Direct vent installations require both a combustion air
intake and a vent/flue pipe. The pipes may be run horizon-
tally and exit through the side of the building or run vertically
and exit through the roof of the building. The pipes may be
run through an existing unused chimney; however, they
must extend a minimum of 12 inches above the top of the
chimney. The space between the pipes and the chimney
must be closed with a weather tight, corrosion resistant
flashing. Both the combustion air intake and a vent/flue
pipe terminations must be in the same atmospheric pres-
sure zone. Refer to Section IX, Vent/Flue and Combustion
Air Pipe - Termination Locations or Concentric Vent Termi-
nation for specific details on termination construction. For
details concerning connection of pipes to the furnace, refer
to the Section IX, Vent/Flue Pipe and Combustion Pipe -
Standard Furnace Connections or Alternate Furnace Con-
nections.
Vent/Flue and Combustion Air Pipe Lengths and
Diameters
Refer to the following table for applicable length, elbows,
and pipe diameter for construction of the vent/flue and
combustion air intake pipe systems of a direct vent (dual
pipe) installation. The number of elbows tabulated repre-
sents the number of elbows and/or tees in each (Vent/Flue
& Combustion Air Intake) pipe. Elbows and/or tees used in
the terminations must be included when determining the
number of elbows in the piping systems.
If the combustion air intake pipe is to be installed above a
finished ceiling or other area where dripping of condensate
will be objectionable, insulation of the combustion air pipe
may be required. Use 1/2" thick closed cell foam insulation
such as Armaflex or Insultube where required.
VENT/FLUE TEE
or
90° ELBOW TURNED
DOWN
12" MIN. ABOVE
HIGHEST ANTICIPATED
SNOW LEVEL
Direct Vent (Dual Pipe)
Maximum Allowable Length of Vent/Flue & Combustion
Vent/Flue/Air
Unit Input
Intake
(Btu)
Termination
Standard
45,000
Alternate
Standard
70,000
Alternate
Standard
90,000
Alternate
Standard
115,000
Alternate
Standard
115,000
Alternate
Elbows and/or Tees used in the terminations must be included when
(1)
determining the number of elbows in the piping system.
Number of elbows tabulated are for each (Vent/Flue & Combustion air
(2)
intake) pipe.
Minimum length of each Vent/Flue & Combustion Air Intake pipe is
(3)
five feet and one elbow/tee.
3" diameter pipe can be used in place of 2" diameter pipe.
(4)
Vent/Flue and Combustion Air Pipe Terminations
The vent/flue and combustion air pipes may terminate
vertically, as through a roof, or horizontally, as through an
outside wall.
Vertical pipe terminations should be as shown in the follow-
ing figure. Refer to Section IX, Vent/Flue Pipe and Com-
bustion Pipe - Termination Locations for details concerning
location restrictions. The penetrations through the roof
must be sealed tight with proper flashing such as is used
with a plastic plumbing vent.
COMBUSTION
AIR INTAKE
12" MIN.
12" MIN.
TO ROOF OR
SCREEN
HIGHEST
ANTICIPATED
SNOW LEVEL
Vertical Terminations (Dual Pipe)
Horizontal terminations should be as shown in the following
figure. Refer to Section IX, Vent/Flue Pipe and Combustion
Pipe - Termination Location for location restrictions. A
2 3/8 inch diameter wall penetration is required for 2"
diameter pipe while a 3 1/2 inch diameter hole is required
for 3" diameter pipe. To secure the pipe passing through
the wall and prohibit damage to piping connections, a
coupling should be installed on either side of the wall and
solvent cemented to a pipe connecting the two couplings.
The pipe length should be the wall thickness plus the depth
of the socket fittings to be installed on the inside and outside
of the wall. The wall penetration should be sealed with
silicone caulking material.
19
Air Intake Pipe (ft)
Pipe
Number of Elbows
(4)
Size
(in.)
2
3
4
5
2
68
65
62
59
2
55
52
49
46
2
68
65
62
59
2
5
52
49
46
2
55
52
49
46
2
42
39
36
33
2
26
23
20
Not Recommended
2
7
10
Not Recommended
3
88
87
80
76
3
74
70
66
62
TEE
VENT/FLUE
90º
MEDIUM RADIUS
ELBOWS
24" MAX.
3" MIN.
(1)(2)(3)
6
7
8
56
53
50
43
40
37
56
53
50
43
40
37
43
40
37
30
27
24
72
68
64
58
54
50
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