Rinnai RUR98i - Determining Total System Equivalent Length; OPTION 1; OPTION 2

22 KBP Series Manual
Exhaust and Combuson Air Intake Pipe Diameters and
Maximum Lengths:
 For PVC/CPVC vent systems reduce the maximum
allowable length for each elbow and terminaon type
as follows:
 Vent and combuson air intake pipe diameters to be as
specied in the maximum equivalent vent length tables
in this manual.
 Do not exceed vent and combuson air intake pipe
MAXIMUM lengths (Lengths are specic to models and
fuel type).
 2.5 feet for every 45° elbow.
 5 feet for every 90° elbow.
 Terminaon (refer to the Approved Vent
Component table of this secon)
IMPORTANT CONSIDERATIONS FOR LOCATION (connued):
There are two opons for determining the vent lengths/
components necessary for the installaon.
Opon 1: The installer can use the vent length calculaon
sheet (below), lling in the quanty of the vent components
in order to calculate the total equivalent vent lengths.
Opon 2: The installer can use the maximum vent lengths
tables on the next pages to determine the amount of
straight pipe that can be used with a specic terminaon
type and quanty of elbows.
Determining Total System Equivalent Length
(A blank copy of the Equivalent Vent Length Calculaon Sheet is located at the end of this secon)
Ensure SW1 in DIPSW 1 is in OFF posion if vent length is greater than 21 (6.4m).
Calculaon of equivalent piping lengths for venng system:
Choose the vent type and ll out the calculaon sheet
below. When determining equivalent combuson air and
vent length, add 5 feet for each 90° elbow, 2.5 feet for each
45° elbow.
OPTION 1:
Example of calculaon (assume 3” diameter pipes for
natural gas unit):
 Twin pipe (parallel) with snorkel terminal
 Combuson air pipe length: 40  straight pipe with 3 x
90° elbows
 Exhaust pipe length: 40  straight pipe with 3 x 90°
elbows (include all interior and exterior elbows)
 Snorkel Terminaon: 10 equivalent feet (reference
Approved PVC/CPVC Terminaon Components table)
Calculaon:
 Equivalent Combuson air pipe length: [40+(3 X 5)+10]
= 65 
 Equivalent Vent Length: [40+(3 X 5)+10] = 65 
 Total = 65 . for both exhaust and combuson air
pipes, which is the maximum allowable vent length for
3” PVC/CPVC on a natural gas unit. If longer lengths
are required, go to the 4” diameter pipe conguraon
which is cered for up to 100 equivalent feet.
Fing / Terminaon Type
Number of
ngs
Equivalent Vent
Length
Total Equivalent
Length
1) 90 elbow
3
x
5
=
15
2) 45 elbow x
2.5
=
0
3) IPEX Low Prole Terminaon x
5
=
0
4) IPEX 4" Concentric Terminaon x
20
=
0
5) IPEX 3" Concentric Terminaon x
20
=
0
6)
3" Tee Terminaon
x
5
=
0
7)
4" Tee Terminaon
x
5
=
0
8) 3" Snorkel Terminaon
1
x
15
=
15
9) 4" Snorkel Terminaon x
15
=
0
10) Length of Straight Secon in feet NA
40
=
40
Total (add up lines
1 through 10)
70
Equivalent Vent Length Calculaon Sheet
Maximum equivalent vent lengths are specic to the fuel
type of the water heater. It is imperave when performing
vent calculaons the following be taken into consideraon:
ATTENTION