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17
12" MIN.
TO ROOF OR
HIGHEST
ANTICIPATED
SNOW LEVEL
90º
MEDIUM RADIUS
ELBOWS
Alternate Vertical Termination (Single Pipe)
MIN.
12"
FROM
WALL
12"
TO GROUND OR
HIGHEST ANTICIPATED
SNOW LEVEL
WALL
INSIDE
OUTSIDE
TEE
or
90°ELBOW
TURNED
DOWN
COUPLING
ELBOW OR
COUPLING
Horizontal Termination (Single Pipe)
VENT/FLUE TEE
or
90° ELBOW TURNED
DOWN
12" MIN.
Horizontal Termination (Single Pipe)
Above Highest Anticipated Snow Level
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. Installation of screens, while strongly recommended, is
not required and will not affect performance of the unit.
Direct vent installations require both a combustion air intake and a
vent/flue pipe. The pipes may be run horizontally 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 resis-
tant flashing. Both the combustion air intake and a vent/flue pipe
terminations must be in the same atmospheric pressure zone.
Refer to Section IX, Vent/Flue and Combustion Air Pipe - Termina-
tion Locations or Concentric Vent Termination 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 Connections.
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 represents 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 objec-
tionable, insulation of the combustion air pipe may be required.
Use 1/2” thick closed cell foam insulation such as Armaflex™ or
Insultube™ where required.
12345678
Standard 2 71 68 65 62 59 56 53 50
Alternate 2 58 55 52 49 46 43 40 37
2 4946434037343128
3 7168656259565350
2 3633302724211815
3 5754514845423936
Standard 3 71 68 65 62 59 56 53 50
Alternate 3 57 54 51 48 45 42 39 36
Standard 3 49 46 43 40 37 34 31 28
Alternate 3 35 32 29 26 23 20 17 14
12345678
2 4946434037343128
3 7168656259565350
2 3633302724211815
3 5754514845423936
2 6158555249464340
3 7168656259565350
2 4845423936333027
3 5754514845423936
90,000
Standard
Alternate
70,000
Standard
Alternate
COUNTERFLOW
Direct Vent (Dual Pipe) Maximum Allow able Length
of Vent/Flue & Combustion Air Intake Pipe (ft)
Unit Input
(Btu)
Termination
Style
Pi p e
(4)
(inch)
Number of Elbow s
(1)(2)(3)
45,000
90,000
115,000
Termination
Style
70,000
Standard
Alternate
UPFLOW
Direct Vent (Dual Pipe) Maximum Allow able Length
of Vent/Flue & Combustion Air Intake Pipe (ft)
Number of Elbow s
(1)(2)(3)
Pi p e
(4)
(inch)
Unit Input
(Btu)
(1)
Elbows and/or Tees used in the terminations must be included when
determining the number of elbows in the piping system.
(2)
Number of elbows tabulated are for each (Vent/Flue & Combustion air
intake) pipe.
(3)
Minimum length of each Vent/Flue & Combustion Air Intake pipe is five feet
and one elbow/tee.
(4)
3” diameter pipe can be used in place of 2” diameter pipe.
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 following
figure. Refer to Section IX, Vent/Flue Pipe and Combustion 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.
TEE
12" MIN.
12" MIN.
TO ROOF OR
HIGHEST
ANTICIPATED
SNOW LEVEL
VENT/FLUE
90º
MEDIUM RADIUS
ELBOWS
COMBUSTION
AIR INTAKE
24" MAX.
3" MIN.
SCREEN
Vertical Terminations (Dual Pipe)