7
MAXIMUM EQUIVALENT VENT LENGTH -- FT. (M)
NOTE: Maximum Equivalent Vent Length (MEVL) does NOT include elbows or terminations. Use Table
2
- Deductions from
Maximum Equivalent Vent Length to determine allowable vent length for each application.
Table 1 – Maximum Equivalent Vent Length -- Ft. (M)
0 to 4500 Ft. (0 to 1370 M) Altitude
Altitude
FT (M)
Unit Size
BTU/Hr
DIRECT VENT (2-PIPE) AND NON---DIRECT VENT (1---PIPE)
Vent Pipe Diameter (in.)
1-1/2
2
2-1/2
3
4
0 to 2000
(0 to 610)
40,000*
50
(15.2)
210
(64.0)
250
(76.2)
NA
NA
60,000
30
(9.1)
135
(41.1)
235
(71.6)
265
(80.8)
NA
80,000
20
(6.1)
70
(21.3)
175
(53.3)
235
(71.6)
265
(80.8)
100,000
NA
25
(7.6)
110
(33.5)
235
(71.6)
265
(80.8)
120,000
NA
NA
15
(4.6)
100
(30.5)
250
(76.2)
2001 to 3000
(610 to 914)
40,000*
45
(13.7)
198
(60.4)
232
(70.7)
NA
NA
60,000
27
(8.2)
127
(38.7)
222
(67.7)
250
(76.2)
NA
80,000
17
(5.2)
64
(19.5)
165
(50.3)
222
(67.7)
249
(75.9)
100,000
NA
22
(6.7)
104
(31.7)
223
(68.0)
250
(76.2)
120,000
NA
NA
11
(3.4)
93
(28.3)
237
(72.2)
3001 to 4000
(914 to 1219)
40,000*
39
(11.9)
184
(56.1)
214
(65.2)
NA
NA
60,000
23
(7.0)
119
(36.3)
210
(64.0)
235
(71.6)
NA
80,000
15
(4.6)
59
(18.0)
155
(47.2)
210
(64.0)
232
(70.7)
100,000
NA
19
(5.8)
98
(29.9)
211
(64.3)
236
(71.9)
120,000
NA
NA
8
(2.4)
86
(26.2)
224
(68.3)
4001 to 4500
(1219 to
1370)
40,000*
36
(11.0)
177
(53.9)
205
(62.5)
NA
NA
60,000
21
(6.4)
115
(35.1)
204
(62.2)
228
(69.5)
NA
80,000
14
(4.3)
56
(17.1)
150
(45.7)
202
(61.6)
224
(68.3)
100,000
NA
17
(5.2)
94
(28.7)
205
(62.5)
229
(69.8)
120,000
NA
NA
NA
83
(25.3)
217
(66.1)
* Not all families have these models.
Note: See notes at end of venting tables.
Note: Table 3 for altitudes over 4500 ft. (1370 M)
Table 2 – Deductions from Maximum Equivalent Vent Length -- Ft. (M)
Pipe Diameter (in):
1-1/2
2
2-1/2
3*
4*
Mitered 90º Elbow
8
(2.4)
8
(2.4)
8
(2.4)
NA
NA
NA
NA
Medium Radius 90º Elbow
5
(1.5)
5
(1.5)
5
(1.5)
NA
NA
NA
NA
Long Radius 90º Elbow
3
(0.9)
3
(0.9)
3
(0.9)
3
(0.9)
3
(0.9)
Mitered 45º Elbow
4
(1.2)
4
(1.2)
4
(1.2)
NA
NA
NA
NA
Medium Radius 45º Elbow
2.5
(0.8)
2.5
(0.8)
2.5
(0.8)
NA
NA
NA
NA
Long Radius 45º Elbow
1.5
(0.5)
1.5
(0.5)
1.5
(0.5)
1.5
(0.5)
1.5
(0.5)
Tee
16
(4.9)
16
(4.9)
16
(4.9)
16
(4.9)
16
(4.9)
* Note: 3--- and 4---in. Vent pipe systems require long radius elbows.
Venting System Length Calculations
The maximum length for each vent pipe (inlet or exhaust) equals the Maximum Equivalent Vent Length (MEVL) from
Table
1 or
Table
3
minus the number of elbows multiplied by the deduction for each elbow in
Table
2.
Standard vent terminations and concentric vent terminations count for zero deductions.
Example
A direct--vent 60,000 Btuh furnace installed at 2100 ft. (640 M ) with 2--in. (51 mm) vent piping. Venting system includes,
FOR EACH
PIPE
, (3) 90
_
long radius elbows, (2) 45
_
long radius elbows and a concentric vent kit.
Maximum Equivalent Vent Length
=
127 ft.
(From
Table
1)
Deduct (3) 90 long radius
3
x
3 ft.
=
- 9 ft.
(From
Table
2)
Deduct (2) 45 long radius
2
x
1.5 ft.
=
- 3 ft.
(From
Table
2)
Maximum Vent Length
=
115 ft.
For
EACH
vent or inlet pipe
