Lennox GWM-050IE, Installation Instructions Manual

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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 figure 6-17)
• 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
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)
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
12" (305mm)
Anticipated
Snow Line
Vent
Combustion
Air
Ground Level