Common Vent Piping Size - Watts Aerco Modulex EXT Series Technical Application Manual

Modulex EXT Vent and Combustion Air Application Guide

3.5. COMMON VENT PIPING SIZE

Refer to Figures 6, 7 and 8 in Section 2 for typical common vent installations. The maximum length
is the sum of the equivalent straight length of horizontal runs, vertical runs, and fittings of the
individual vent connector and the common vent pipe. The maximum length is the combined length
of straight horizontal and vertical runs, and the equivalent straight length of fittings. The required
diameters for a given Modulex total BTU/hr. Input are shown in Table 6, below.
TABLE 6: Common Venting Pipe Run Lengths
TOTAL
BTU/HR
INPUT
Common Vent
(UP TO
Diameter
AND
INCLUDIN
G)
4"
606,000
(102 mm)
6"
1,284,000
(152 mm)
8"
2,407,500
(203 mm)
10"
3,825,000
(254 mm)
12"
5,355,000
(305 mm)
14"
6,885,000
(358 mm)
16"
9,180,000
(407 mm)
NOTES:
•
The chart above shows equivalent pipe lengths of the fittings for the common vent pipe. See
section 3.4 for equivalent lengths for fittings for the individual boiler connector.
•
The maximum equivalent length shown is the sum of the equivalent length of the longest individual
connector plus the equivalent length of the common vent pipe. If the maximum equivalent
length exceeds 100 equivalent ft., contact your AERCO sales representative or AERCO
International for design assistance and approval.
•
It is important to use a WYE as a means to connect the individual vent into the common vent pipe.
This will ensure the least amount of pressure drop. Do NOT use a TEE, 90°, or 45° elbow.
Page 26 of 28
09/25/2017
EQUIVALENT COMMON VENT LENGTHS
EXAMPLES
Sharp 90° Sweep 90°
Elbow Elbow
Equiv. Ft Equiv. Ft
(m) (m)
10 ft. 5 ft.
(3.05 m) (1.5 m)
10 ft.
N/A
(3.05 m)
10 ft.
N/A
(3.05 m)
10 ft.
N/A
(3.05 m)
10 ft.
N/A
(3.05 m)
10 ft.
N/A
(3.05 m)
10 ft.
N/A
(3.05 m)
AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913
Phone: 800-526-0288
WYE or
45° Elbow Termination
Equiv. Ft Tee or
(m)
Vent Cap
Equiv. Ft (m)
5 ft. 5 ft.
(1.5 m) (1.5 m)
5 ft. 5 ft.
(1.5 m) (1.5 m)
5 ft. 5 ft.
(1.5 m) (1.5 m)
5 ft. 5 ft.
(1.5 m) (1.5 m)
5 ft. 5 ft.
(1.5 m) (1.5 m)
5 ft. 5 ft.
(1.5 m) (1.5 m)
5 ft. 5 ft.
(1.5 m) (1.5 m)
MAX.
LENGTH 
INDIVIDUAL
CONNECTOR
PLUS
COMMON
VENT
EQUIVALENT
FT (M)
100 ft.
(30.5 m)
100 ft.
(30.5 m)
100 ft.
(30.5 m)
100 ft.
(30.5 m)
100 ft.
(30.5 m)
100 ft.
(30.5 m)
100 ft.
(30.5 m)
TAG-0054-0F
GF-136-V