KBD Series Manual 23
For PVC/CPVC vent systems reduce the maximum
allowable length for each elbow and terminaon type
as follows:
Vent and combuson air intake pipe diameters to be as
specied in the maximum equivalent vent length tables
of this document.
Do not exceed vent and combuson air intake pipe
MAXIMUM lengths (Lengths are specic to models and
fuel type).
2.5 feet for every 45° elbow.
5 feet for every 90° elbow.
Terminaon (refer to the Approved Vent
Component table of this secon)
There are two opons for determining the vent lengths/
components necessary for the installaon.
The installer can use the vent length calculaon
sheet (below), lling in the quanty of the vent components
in order to calculate the total equivalent vent lengths.
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 specic terminaon
type and quanty of elbows.
Determining Total System Equivalent Length
Choose the vent type and ll out the calculaon sheet
(assume 3” diameter pipes for
natural gas unit):
Twin pipe (parallel) with snorkel terminal
Combuson air pipe length: 40 straight pipe with 3 x
90° elbows
Exhaust pipe length: 40 straight pipe with 3 x 90°
elbows
Equivalent Combuson air pipe length: [40+(3 X 5)+10]
= 65
Equivalent Vent Length: [40+(3 X 5)+10] = 65
Total = 65 . for both exhaust and combuson 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 conguraon
which is cered for up to 100 equivalent feet.
Maximum equivalent vent lengths are specic to the fuel
type of the water heater. It is imperave when performing
vent calculaons the following be taken into consideraon:
1) 90 elbow
3
5
15
2) 45 elbow
2.5
0
3) IPEX Low Prole Terminaon
5
0
4) IPEX 4" Concentric Terminaon
20
0
5) IPEX 3" Concentric Terminaon
20
0
6)
Royal 3” Concentric Terminaon
20
0
7)
Royal Low Prole Terminaon
5
0
8)
3" Tee Terminaon
5
0
9)
4" Tee Terminaon
5
0
10) 3" Snorkel Terminaon
1
15
15
11) 4" Snorkel Terminaon
15
0
12) Length of Straight Secon in feet NA
40
40
(add up lines
1 through 12)
70
below. When determining equivalent combuson air and
vent length, add 5 feet for each 90° elbow, 2.5 feet for each
45° elbow.
(A blank copy of the Equivalent Vent Length Calculaon Sheet is located at the end of this secon)
Ensure SW1 in DIPSW 1 is in OFF posion if vent length is greater than 21 (6.4m).
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