32
FIGURE 6-17 Mulitple Boilers With Common Venting Pipe
Model
Minimum
Diameter
050
2" (51mm)
075
3" (73mm)
100
3" (73mm)
150
3" (73mm)
200
3" (73mm)
299
3" (73mm)
Table 8 - Minimum Diameter for Individual
Boiler in Common Venting System
Total
Firing
Rate
Minimum
Diameter of
Common vent
pipes if
L< 50 ft (16m)
Minimum
Diameter of
Common vent
pipes if
L>50 ft (16m)
400
4" (101mm)
5" (127mm)
600
5" (127mm)
6" (152mm)
800
1000
6" (152mm)
7" (177mm)
1200
1400
1600
7" (177mm)
8" (203mm)
1800
2000
Table 9 - Common Venting Pipe Diameters
L
H
6 - COMBUSTION AIR AND VENT PIPING
Flow Check
Valve
Flow Check
Valve
Flow Check
Valve
6.8
Multiple Boiler Venting Installation
• Multiple boiler application boiler can vent individually or
use common vent pipes.
• If boilers vent individually follow guidelines as described
in figures 6-1 through 6-7.
• If boilers vent through common vent pipes, as shown
in Figure 6-17, choose common vent pipe per Table 8.
Choose size from Table 9 for pipes between boiler and
common vent pipes.
• Longest individual vent lengths and common vent length
together must be shorter than 100 ft. (30m).
H + L ≤ 100 ft (30m) (See Table 9)
•
Each boiler must have flow check valve to prevent flue
gas back flow.
• External terminals follow same rule as single boiler
venting as described in Section 6.6 and 6.7
• Locate combustion air and vent terminals as required by
authority having jurisdiction.
• Flow check valve and vent pipe shall be made by the
same manufacturer for proper compatibility. Check
common vent kit for more information on flow check
valve.
PN 240011320 Rev. G 10/01/2021]
Combustion
Air
Minimum 12" (305mm)
U.S. ; 18" (457mm)
Canada Above
Anticipated Snow Line
Ground Level
Vent
Snow Line