KBD Series Manual
11
Maximum vent length
Maximum Vent Length with Concentric Venting
1. Determine the number of 90 degree elbows in
the vent system. (Two 45 degree elbows count as
one 90 degree elbow.)
2. Refer to the table to find the maximum vent
length based on the number of elbows.
3. Adjust SW1 in DIPSW 1 (tan switches) if required
by the applicable note.
If the length is greater than 21 ft (6.4 m) then
move SW1 to OFF.
If the length is greater than 15 ft (4.6 m) then
move SW1 to OFF.
If the length is greater than 9 ft (2.7 m) then move
SW1 to OFF.
Move SW1 to OFF.
If you have a longer vent length (see number 3
regarding max. vent length), SW1 in DIPSW 1 is
required to be in the OFF position. This ensures the
water heater will run properly. Blocked flue
diagnostic codes and shutdowns may result if SW1 in
DIPSW 1 is not in the correct position.
NOTICE
Vent length using short radius elbow
(Intake is the short UV protected 90° elbow)
Number of
90° Short
Radius
Elbows
Maximum
Straight Vent
Length
SW1 in DIPSW 1
If length is greater
than:
0
41 ft (12.50 m)
18 ft (5.49 m) move
SW1 to OFF
1
26 ft (7.93 m)
3 ft (0.91 m) move SW1
to OFF
2
11 ft (3.35 m)
move SW1 to OFF for
any length
Number of
90° Long
Radius
Maximum
Straight Vent
Length
SW1 in DIPSW 1
If length is greater
than:
0
41 ft (12.50 m)
21 ft (6.40 m) move
SW1 to OFF
1
35 ft (10.67 m)
15 ft (4.57 m) move
SW1 to OFF
2
29 ft (8.84 m)
9 ft (2.74 m) move
SW1 to OFF
3
23 ft (7.01m)
3 ft (0.91 m) move
SW1 to OFF
4
17 ft (5.18 m)
move SW1 to OFF
for any length
5
11 ft (3.35 m)
6
5 ft (1.52 m)
Vent length using long radius elbow
(Intake is the long UV protected 90° elbow)
Maximum Vent Length for Centrotherm 2 Pipe
InnoFlue Vent System (single wall SW, 3 inch diameter)
Propane Units Only
Ubbink Concentric
(90
° elbow is equivalent to 6 feet; 45° elbow is equivalent to 3 feet.)
Maximum Equivalent Vent Length 41 ft (12.5 m)
# of 90° Elbows
Maximum Vent Length in feet
(meters)
0
41 (12.5)
1
1
35 (10.7)
2
2
29 (8.8)
3
3
23 (7.0)
4
4
17 (5.2)
4
5
11 (3.4)
4
6
5 (1.5)
4
Natural Gas Units Only
Ubbink Concentric
(90
° elbow is equivalent to 6 feet; 45° elbow is equivalent to 3 feet.)
Maximum Equivalent Vent Length 65 ft (19.8 m)
# of 90° Elbows
Maximum Vent Length in feet
(meters)
0
65 (19.8)
1
1
59 (18.0)
2
2
53 (16.2)
3
3
47 (14.3)
4
4
41 (12.5)
4
5
35 (10.7)
4
6
29 (8.8)
4
Example: If you have one elbow then your
maximum vent length is 35 feet (10.7 m).
If your actual length is greater than 15 ft
(4.6 m) then move SW1 in DIPSW 1 to
OFF.
