Buderus Logano plus GB312 Applications Manual page 22

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5.5 Venting system calculation/sizing chart
GB312 are Cat. IV positive pressure, induced draft
condensing gas boilers
Note:
Total equivalent lengths in tables 10, 11 and 12 are
guidelines and for reference only. Please contact chimney
manufacturer directly for specifi c chimney design.
Calculation example
Calculate the vent pipe and combustion air pipe for the
following:
Vertical vent and vertical combustion air pipe
vent pipe:
• 1 each - 90 degree elbow = 7ft equivalent length
• 1 each - rain cap
• 68 lineal feet of pipe
• Total
What size vent (exhaust) pipe is needed?
What size combustion air pipe is needed?
5.5.1 Vertical Vent and Vertical Combustion Air Inlet (Nat-
ural Gas)
(See Figure 15)
Operating Conditions:
• Total fl ue & combustion air supply system pressure:
0.40"WC
- Vent calculated on 0.2" WC
- Combustion air calculated on 0.2" WC
• Min. Gross Stack Temp: 150 F
• CO2 percentage: NG: 9 %
GB312 Venting System Table
Models Input (MBH)
GB312-90 328
GB312-120 440
GB312-160 588
GB312-200 733
GB312-240 881
GB312-280 1029
GB312 Venting System Table
Models Input (MBH)
GB312-90 328
GB312-120 440
GB312-160 588
GB312-200 733
GB312-240 881
GB312-280 1029
Note: Breeching pressure measured at outlet of
boiler vent connection.
Technical specifi cations are subject to change without prior notice
= 10ft equivalent length
= 68ft equivalent length
= 85ft total equivalent length
5"diameter
5"diameter
Vent (Exhaust) Outlet Vertical
Vent Venting
Connection Diameter
at Boiler (inches)
6" 6"
6" 6"
6" 6"
8" 8"
8" 8"
8" 8"
Combustion Air (inlet) Vertical
Combustion Combustion
Air Inlet Air Pipe
Connection Diameter
at Boiler (inches)
4" 5"
4" 6"
4" 6"
4" 8"
4" 8"
4" 8"
combustion air pipe:
• 3 each - 90 degree elbow = 21ft equivalent length
• 1 each - inlet termination =10ft equivalent length
• 50 lineal feet of pipe
• Total
Venting Parameters:
• Exhaust horizontal: termination tee
• Exhaust vertical: rain cap
• Sealed Comb. Intake (all models): PVC piping with 90°
downward elbow
• 90° elbow = 7ft equivalent length
• 45° elbow = 4ft equivalent length
• Rain cap termination = 10ft equivalent length
• 1 lineal foot of pipe = 1ft equivalent length
Total Equivalent Vent Diameter for (minus
Length of Vent (max) one) size diameter and
TEL in feet
100 5" = 100ft
100 5" = 80ft
100 5" = 50ft
100 7" = 100ft
100 7" = 100ft
100 7" = 100ft
Total Equivalent Combustion Air Pipe
Length of Combustion Diameter (minus one
Air Pipe (max) inch) maximum TEL
in feet
100 4" = 55ft
100 5" = 95ft
100 5" = 50ft
100 7" = 100ft
100 7" = 100ft
100 7" = 100ft
GB312 Applications Manual
= 50ft equivalent length
= 81ft total equivalent length
Table 10
Vent Diameter for (minus
two) size diameter and
TEL in feet
4" = 55ft
4" = 30ft
4" = NA
6" = 70ft
6" = 55ft
6" = 35ft
Combustion Air Pipe
Diameter (minus two
inch) maximum TEL in
feet
3" = NA
4" = 30ft
4" = NA
6" = 70ft
6" = 55ft
6" = 35ft
Logano plus GB312 applications manual | 04.2008