18
TEE (OPTIONAL)
12 " Min To Roof
Or Highest Anticipated
Snow Level
Vertical Termination (Single Pipe)
12" MIN.
TO ROOF OR
HIGHEST
ANTICIPATED
SNOW LEVEL
Alternate Vertical Termination (Single Pipe)
_______________
MIN.
12"
FROM
WALL
12" TO GROUND OR
HIGHEST ANTICIPATED
SNOW LEVEL
Horizontal Termination (Single Pipe)
_______________
ENT/FLUE TEE (OPTIONAL)
or
45° ELBOW
TURNED DOWN or
90° ELBOW TURNED
DOWN
12" MIN. ABOVE
HIGHEST ANTICIPATED
SNOW LEVEL
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.
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.
Pipe
Size
(4)
(in.) 2345678
Standard
2 or 2 1/268656259565350
Alternate
2 or 2 1/255524946434037
Standard
2 or 2 1/268656259565350
Alternate 2 or 2 1/255524946434037
Standard
2 or 2 1/2 46 43 40
Alternate
2 or 2 1/2 33 30 27
Standard
3686562
59 56 53 50
Alternate 3 54 51 48 45 42 39 36
Standard
3 68656259565350
Alternate 3 55 52 49 46 43 40 37
Standard 2 or 2 1/237343128252219
Alternate 2 or 2 1/22421181512 9 6
Standard 3 68 65 62 59 56 53 50
Alternate 3 55 52 49 46 43 40 37
Standard 3 68 65 62 59 56 53 50
Alternate 3 55 52 49 46 43 40 37
Standard
3 68656259565350
Alternate 3 55 52 49 46 43 40 37
GMH_090_4
070_4
070_4
Not Recommended
080_5 or
090_5
GMH_090_4
100_5 or
115_5
Direct Vent ( Dual Pipe)
Maximum Allowable Length of Vent/Flue & Combustion
Air Intake Pipe (ft)
Unit Input
(Btu)
Number of Elbows
(1)(2)(3)
GCH_090_4
Vent/Flue/Air Intake
Termination
040_3 or
045_3
060_3 or
070_3
1) Minimum requirement for each vent pipe is five (5) feet in length and one
elbow/tee.
2) Tees and/or elbows used in the vent/flue termination must be included
when determining the number of elbows in the piping system.
3) 2 1/2” or 3” diameter pipe can be used in place of 2” diameter pipe.
4) Increased Clearance Configurations using (2) 45 deg.
Long Sweep
elbows should be considered equivalent to one 90 deg. elbow.
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.
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