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Example
1
A direct-vent
140,000
Btuh furnace
installed
at 2100 ft. (640 M).
Venting system
includes,
FOR EACH
PIPE, 52 feet (16 M) of vent pipe,
50 feet (15 M) of combustion
air inlet pipe, (3) 90 ° long radius elbows,
(2) 45 ° long radius elbows
and a factory
accessory
concentric
vent
kit.
Can this application
use 4-in. (102 mm ND) PVC/ABS
DWV vent piping'?
Measure the required linear length of air inlet and vent pipe; insert the
longest of the two here:
Add equiv length of (3) 90 ° long-radius
elbows
3 ft.
(use the highest number of elbows for either
3
x
the vent or inlet pipe)
(0.9 M)
Add equiv length of (2) 45 ° long-radius
elbows
2 ft.
(use the highest number of elbows for either
2
x
the vent or inlet pipe)
(.6 M)
Add equiv length of vent termination
52 ft.
(16 M)
9ft.
(2.7 M)
4ft.
(1.2 M)
Oft.
Oft.
65 ft.
(20 M)
Use length of the longer of the vent
or air inlet piping system
From Table 16
From Table 16
From Table 16
From Vent Manufacturer's
instructions;
zero for PVC/ABS DWV
Add all of the above lines
Add
correction
for flexible
vent
pipe,
if any
Total Equivalent
Vent Length
(TEVL)
68 ft.
Maximum
Equivalent
Vent
Length
(MEVL)
(20.7
M)
For 4" (102 mm)
pipe
from
Table
15
Is TEVL
less
than
MEVL?
YES
Therefore,
4" (102 mm)
pipe
may be used
Example
2
A direct-vent
140,000
Btuh furnace installed
at 1800 ft. (549 M) Venting system
includes,
FOR EACH
PIPE, 31 feet (9 M) of vent pipe, 30
feet (9 M) of combustion
air inlet pipe, (3) 90 ° long radius elbows,
and a polypropylene
concentric
vent kit. Also includes
20 feet (6 M) of
flexible
polypropylene
vent pipe, included
within the 68 feet (21 M) of vent pipe.
Assume
that one meter
of flexible
3-in.
or 4-in.
polypropylene
pipe equals
1.8 Meters
of PVC/ABS
pipe.
VERIFY
FROM
VENT
MANUFACTURER'S
INSTRUCTIONS.
Can this application
use 3-in. vent piping'?
If not what size piping
can be used'?
Measure the required linear length of air inlet and vent pipe; insert the
longest of the two here:
Add equiv length of (3) 90 ° long-radius
elbows
3 ft.
(use the highest number of elbows for either
3
x
the vent or inlet pipe)
(0.9 M)
Add equiv length of (2) 45 ° long-radius
elbows
(use the highest number of elbows for either
0
x
the vent or inlet pipe)
Add equiv length of vent termination
Add correction for flexible vent pipe, if any
Total Equivalent Vent Length (TEVL)
3.3 ft.
9
x
(1 M)
lOft.
1.8
x
(6 M)
31 ft.
(9 M)
9ft.
(2.7 M)
=
Oft.
30 ft.
(9 M)
18ft.
(5.5 M)
88 ft.
(26.8 M)
Use length of the longer of the vent
or air inlet piping system
From Vent Manufacturer's
instructions
From Vent Manufacturer's
instructions
From Vent Manufacturer's
instructions
From Vent Manufacturer's
instructions
Add all of the above lines
20 ft.
Maximum Equivalent Vent Length (MEVL)
(6 M)
For 3" pipe from Table 15
Is TEVL less than MEVL?
NO
Therefore,
3-in. pipe may NOT be used;
try 4-in.
90 ft.
Maximum Equivalent
Vent Length (MEVL)
(27.4 M)
For 4" pipe from Table 15
Is TEVL less than MEVL?
YES
Therefore,
4" pipe MAY be used.
45
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