15
Nondirect Vent Applications
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
■
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.
Upflow
Nondirect Vent (Single Pipe) Maximum Allowable Length of Vent/Flue Pipe—ft (m)
Number of Elbows
Unit Input (Btu)
Pipe—in. (cm)
1
2
3
4
5
6
7
8
45,000
2 or 2
¹⁄₂
(5.12 or 6.4)
71 (21.6)
68 (20.7)
65 (19.8)
62 (18.9)
59 (18)
56 (17.1) 53 (16.2) 50 (15.2)
70,000
2 or 2
¹⁄₂
(5.12 or 6.4)
49 (14.9)
46 (14)
43 (13.1)
40 (12.2)
37 (11.3) 34 (10.4) 31 (9.5)
28 (8.5)
3 (7.6)
71 (21.6)
68 (20.7)
65 (19.8)
62 (18.9)
59 (18)
56 (17.1) 53 (16.2) 50 (15.2)
90,000
3 (7.6)
71 (21.6)
68 (20.7)
65 (19.8)
62 (18.9)
59 (18)
56 (17.1) 53 (16.2) 50 (15.2)
115,000
3 (7.6)
49 (14.9)
46 (14)
43 (13.1)
40 (12.2)
37 (11.3) 34 (10.4) 31 (9.5)
28 (8.5)
Counterflow
Direct Vent (Dual Pipe) Maximum Allowable Length of Vent/Flue Pipe—ft (m)
Number of Elbows
Unit Input (Btu)
Pipe—in. (cm)
1
2
3
4
5
6
7
8
70,000
2 or 2
¹⁄₂
(5.12 or 6.4)
61 (18.6)
58 (17.7)
55 (16.8)
52 (15.8)
49 (14.9) 46 (14)
43 (13.1) 40 (12.2)
3 (7.6)
71 (21.6)
68 (20.7)
65 (19.8)
62 (18.9)
59 (18)
56 (17.1) 53 (16.2) 50 (15.2)
90,000
2 or 2
¹⁄₂
(5.12 or 6.4)
61 (18.6)
58 (17.7)
55 (16.8)
52 (15.8)
49 (14.9) 46 (14)
43 (13.1) 40 (12.2)
3 (7.6)
71 (21.6)
68 (20.7)
65 (19.8)
62 (18.9)
59 (18)
56 (17.1) 53 (16.2) 50 (15.2)