Installation Guide

Installation & Servicing Instructions Rinnai Q-Series
40
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 ft 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.
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
V
ent
ft ft ft ft ft 0.5 ft
ft
Total equivalent len
g
th
Concentric s
y
stem
Length concentric
tube, boiler to roof
horizontal
Number of
elbows 90°
x 6*
Number of
elbows 45°
x 3*
Concentric
terminal
A
dd 2 ft.
*
Total Multiply with
factor
Total equivalent
length
ft ft ft ft ft 1.0 ft
Boiler t
yp
e 3” Max Vent e
q
uivalent len
g
th 3” Max Air e
q
uivalent
l
Q85 100 feet 100 feet
Q130 100 feet 100 feet
Q175 80 feet 80 feet
Q205 40 feet 40 feet
Equivalent vent length table 9