18
Nondirect Vent (Single Pipe) Piping
Nondirect vent installations require only a vent/flue pipe. The vent
pipe can be run horizontally with an exit through the side of the
building or run vertically with an exit through the roof of the
building. The vent can also be run through an existing unused
chimney; however, it must extend a minimum of 12" (30.5 cm)
above the top of the chimney. The space between the vent pipe
and the chimney must be closed with a weather-tight, corrosion-
resistant flashing. For details concerning connection of the vent/
flue pipe to the furnace, refer to “Vent Pipe Installation and
Combustion Air—Standard Furnace Connections” or “Vent Pipe
Installation and Combustion Air—Alternate Furnace
Connections” for specific details.
Refer to the following “Nondirect Vent (Single Pipe) Piping—Vent/
Flue Pipe Terminations” for specific details on termination
construction.
Although nondirect vent installations do not require a combustion
air intake pipe, a minimum of one 90° elbow should be attached
to the furnace’s combustion air intake if an upright installation
uses the standard intake location, or a horizontal installation uses
the alternate air intake location. This elbow will guard against
inadvertent blockage of the air intake.
Vent/Flue Pipe Lengths and Diameters
Refer to the following tables for applicable length, elbows and
pipe diameter for construction of the vent/flue pipe systems of a
nondirect vent (single pipe) installation. In addition to the vent/
flue pipe, a single 90º elbow should be secured to the
combustion air intake to prevent inadvertent blockage. The tee
used in the vent/flue termination must be included when
determining the number of elbows in the piping system.
NOTES:
■
One 90º elbow should be secured to the combustion air
intake connection.
■
Minimum requirement for each vent/flue pipe is 5 ft (1.5 m)
and 1 elbow/tee.
■
Tee used in the vent/flue termination must be included when
determining the number of elbows in the piping system.
■
2
¹⁄₂
" or 3" (6.4 cm or 7.6 cm) diameter pipe can be used in
place of 2" (5.1 cm) diameter pipe.
■
Increased clearance configurations using two 45º long-sweep
elbows should be considered equivalent to one 90º elbow.
Vent/Flue Pipe Terminations
NOTE: If either a 90º or 45º elbow is used for termination, it must
be pointed downward.
■
The vent/flue pipe may terminate vertically, as through a roof,
or horizontally, as through an outside wall.
■
Vertical vent/flue pipe terminations should be as shown in
“Vertical Vent Termination (Single Pipe)” illustration. Refer to
“Termination Locations” in this section for details concerning
location restrictions.
■
The penetration of the vent through the roof must be sealed
tight with proper flashing such as is used with a plastic
plumbing vent.
■
Horizontal vent/flue pipe terminations should be as shown in
“Horizontal Vent Termination (Single Pipe)” illustration. Refer
to “Termination Locations” in this section for details
concerning location restrictions.
■
A 2
³⁄₈
" (6.1 cm) diameter wall penetration is required for 2"
(5.1 cm) diameter pipe.
■
A 3" (7.6 cm) diameter hole is required for a 2
¹⁄₂
" (6.4 cm)
pipe.
■
A 3
¹⁄₂
" (8.9 cm) diameter hole is required for 3" (7.6 cm)
diameter pipe.
■
To secure the pipe passing through the wall and prohibit
damage to the piping connections, a coupling should be
installed on either side of the wall and solvent cemented to a
length of pipe connecting the 2 couplings.
■
The length of pipe 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.
■
In a basement installation, the vent/flue pipe can be run
between joist spaces.
NOTE: 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.
Vertical Vent Termination (Single Pipe)
Nondirect Vent (Single Pipe) Maximum Allowable Length
of Vent/Flue Pipe—ft (m)
Models
(kBtu Tons)
Pipe—in.
(cm)
2
3
4
5
6
7
8
040_3 or
045_3
2 or 2
¹⁄₂
(5.12 or 6.4)
68
(21)
65
(20)
62
(19)
59
(18)
56
(17)
53
(16)
50
(15)
060_3 or
070_3
2 or 2
¹⁄₂
(5.12 or 6.4)
68
(21)
65
(20)
62
(19)
59
(18)
56
(17)
53
(16)
50
(15)
070_4
2 or 2
¹⁄₂
(5.12 or 6.4)
46
(14)
43
(13)
40
(12)
Not
Recommended
3
(7.6)
68
(21)
65
(20)
62
(19)
59
(18)
56
(17)
53
(16)
50
(15)
A. Tee (optional)
B. 12" (30.5 cm) minimum to roof or
highest anticipated snow level
A
B
