Installation & Servicing Instructions Rinnai Q Premier
41
6.7.7 Combustion air and vent piping lengths.
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.
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 feet for
the combustion room air
fi
lter .
Example of calculation:
Twin tube (parallel) with terminal
Combustion air length
: 24 ft
with elbow 3 x 90°
Vent length
: 24 ft
with elbow 2 x 90°, elbow 2 x 45°
Calculation:
Equivalent Air Length
: (24+3x6+2) x 0.5
= 23 ft
Equivalent Vent Length
: (24+2x6+2x3+2) x 0.5
= 23 ft +
Total
= 46 ft.
Equivalent vent length
table 9
Parallel system
Length tube
Number of
elbows 90°
x 6*
Number of
elbows 45°
x 3*
Concentric
terminal
Add 5 ft.*
Total
Multiply with
factor
Equivalent
length
Combustion air
ft
ft
ft
ft
ft
0.5
ft
Vent
ft
ft
ft
ft
ft
0.5
ft
ft
Total equivalent length
Concentric system
Length concentric
tube, boiler to roof
horizontal
Number of
elbows 90°
x 6*
Number of
elbows 45°
x 3*
Concentric
terminal
Add 2 ft.*
Total
Multiply with
factor
Total equivalent
length
ft
ft
ft
ft
ft
1.0
ft
Boiler type
3” Max Vent equivalent length
3” Max Air equivalent l
QP85N
100 feet
100 feet
QP130N
100 feet
100 feet
