Modulex EXT Vent and Combustion Air Application Guide
TAG-0054_0F
AERCO International, Inc.
•
100 Oritani Dr.
•
Blauvelt, NY 10913
Page 25 of
28
GF-136–V
Phone: 800-526-0288
09/25/2017
3.4.
VENT PIPING SIZE
The maximum length is the combined length of straight horizontal and vertical runs, and the
equivalent straight length of fittings. The required lengths for each boiler are as shown on Table 5 and
11.
TABLE 5: Venting Pipe Run Lengths
MODEL NO.
VENT
PIPE
DIAM
ETER
EQUIVALENT VENT LENGTH EXAMPLES
MAXIMUM
LENGTH
EQUIV. FT
(M)
Sharp 90°
Elbow
Equiv. Ft.
(m)
Sweep 90°
Elbow
Equiv. Ft.
(m)
45° Elbow
Equiv. Ft.
(m)
Termination
Tee;
Equiv. Ft.
(m)
EXT 321
EXT 481/450
4”
(102
mm)
10 ft.
(3.05 m)
5 ft.
(1.5 m)
5 ft.
(1.5 m)
5 ft.
(1.5 m)
100 ft.
(30.5 m)
EXT 641/600
EXT 802/800
EXT 962
EXT 1123/1100
6”
(152
mm)
10 ft.
(3.05 m)
N/A
5 ft.
(1.5 m)
5 ft.
(1.5 m)
100 ft.
(30.5 m)
EXT 1530/1500
EXT 1912
10”
(254
mm)
10 ft.
(3.05 m)
N/A
5 ft.
(1.5 m)
TBD
100 ft.
(30.5 m)
EXT 2295/2300
EXT 2677/2600
EXT 3060/3000
12”
(305
mm)
10 ft.
(3.05 m)
N/A
5 ft.
(1.5 m)
TBD
100 ft.
(30.5 m)
The maximum pressure drop of the combustion air piping is also 100 equivalent feet (30.5 m). See
Section 2.2. Note that this does NOT mean the allowed combined pressure drop between the vent
and combustion air is 200 equivalent feet (61 m). That is, the vent cannot go above 100 equivalent
feet (30.5 m), even if the combustion air is less than 100 equivalent feet, and vice versa.
EXAMPLES:
1. A 40 foot (12.2 m) length of vent pipe and 1 sharp 90° elbow plus a termination vent cap (rain cap)
add up to 40 ft. + 10 ft. + 10 ft. = 60 equivalent ft. (18.3 m).
2. A 30 foot (10.4 m) length of vent pipe and 2 sharp 90° elbows plus a termination rain add up to 30
ft. + (2 x 10 ft.) + 10 ft. = 50 equivalent ft. (18.3 m).