Combustion Air And Vent Piping Lengths - Rinnai Q Premier QP85N Instructions D'installation Et D'entretien

6.7.7 Combustion air and vent piping lengths.

Parallel system
Length tube
Combustion air
ft
Vent
ft
Concentric system
Length concentric
tube, boiler to roof
horizontal
ft
In the table below you will fi nd the maximum equivalent pipe length of the vent/air
system based on 3" diameter. These lengths are for single pipe (room air), twin pipe,
and concentric venting systems.
Boiler type
QP85N
QP130N
Equivalent vent length
Calculation of equivalent length vent system
Choose the vent type and fi ll out the corresponding table.
* When determining equivalent combustion air and vent length, add 6 feet for each
90° elbow, 3 feet for each 45° elbow, 5 feet for the concentric terminal in the Parallel
System, 2 feet for the concentric terminal in the Concentric System and 12 ft for the
combustion room air fi lter.
Number of Number of
elbows 90° elbows 45°
x 6* x 3*
ft
ft
Number of Number of
elbows 90° elbows 45°
x 6* x 3*
ft
Example of calculation:
Twin tube (parallel) with terminal
Combustion air length
Vent length
Calculation:
Equivalent Air Length
Equivalent Vent Length
3" Max Vent equivalent length
100 feet
100 feet
Concentric Total
terminal
Add 5 ft.*
ft ft
ft ft
Total equivalent length
Concentric Total
terminal
Add 2 ft.*
ft ft
: 24 ft with elbow 3 x 90°
: 24 ft with elbow 2 x 90°, elbow 2 x 45°
: (24+3x6+2) x 0.5
: (24+2x6+2x3+2) x 0.5
Total
3" Max Air equivalent l
100 feet
100 feet
Multiply with Equivalent
factor length
ft 0.5
ft 0.5
Multiply with Total equivalent
factor length
ft 1.0
= 23 ft
= 23 ft +
= 46 ft.
table 9
ft
ft
ft
ft
41