Rinnai E75CN - Manual (Page 32)

Installation & Servicing Instructions Rinnai E-Series
32
6.7.6 Combustion air and vent piping lengths.
In the table below you find 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 fill 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, and 2 feet for the concentric terminal in the Concentric System .
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
Boiler type 3” Max Vent equivalent length 3” Max Air equivalent length
E75 100 feet 100 feet
E110 100 feet 100 feet
Parallel system
Length tube Number of
elbows 90°
x 6*
Number of
elbows 45°
x 3*
Concentric
terminal
A
dd 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
A
dd 2 ft.*
Total Multiply with
factor
Total equivalent
length
ft ft ft ft ft 1.0 ft