7
MAXIMUM EQUIVALENT VENT LENGTH -- FT. (M)
Table 3 – Maximum Equivalent Vent Length -- Ft. (M)
4501 to 10,000 Ft. (0 to 1370 M) Altitude
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.
Altitude
FT (M)
Unit Size
DIRECT VENT (2-PIPE) AND NON---DIRECT VENT (1---PIPE)
Vent Pipe Diameter
1-1/2
2
2-1/2
3
4
4501 to 5000
(1370 to
1524)
40,000*
33
(10.1)
171
(52.1)
196
(59.7)
NA
NA
60,000
20
(6.1)
111
(33.8)
198
(60.4)
221
(67.4)
NA
80,000
13
(4.0)
54
(16.5)
146
(44.5)
195
(59.4)
216
(65.8)
100,000
NA
16
(4.9)
91
(27.7)
200
(61.0)
222
(67.7)
120,000
NA
NA
NA
80
(24.4)
211
(64.3)
5001 to 6000
(1524 to
1829)
40,000*
27
(8.2)
158
(48.2)
179
(54.6)
NA
NA
60,000
16
(4.9)
103
(31.4)
186
(56.7)
207
(63.1)
NA
80,000
11
(3.4)
49
(14.9)
137
(41.8)
183
(55.8)
200
(61.0)
100,000
NA
12
(3.7)
85
(25.9)
188
(57.3)
208
(63.4)
120,000
NA
NA
NA
74
(22.6)
199
(60.7)
6001 to 7000
(1829 to
2134)
40,000*
21
(6.4)
145
(44.2)
162
(49.4)
NA
NA
60,000
13
(4.0)
96
(29.3)
174
(53.0)
194
(59.1)
NA
80,000
NA
44
(13.4)
120
(36.6)
171
(52.1)
185
(56.4)
100,000
NA
10
(3.0)
79
(24.1)
178
(54.3)
195
(59.4)
120,000
NA
NA
NA
68
(20.7)
187
(57.0)
7001 to 8000
(2134 to
2438)
40,000*
15
(4.6)
133
(40.5)
146
(44.5)
NA
NA
60,000
10
(3.0)
89
(27.1)
163
(49.7)
181
(55.2)
NA
80,000
NA
40
(12.2)
120
(36.6)
159
(48.5)
170
(51.8)
100,000
NA
NA
73
(22.3)
167
(50.9)
182
(55.5)
120,000
NA
NA
NA
62
(18.9)
175
(53.3)
8001 to 9000
(2438 to
2743)
40,000*
10
(3.0)
121
(36.9)
130
(39.6)
NA
NA
60,000
7
(2.1)
82
(25.0)
152
(46.3)
168
(51.2)
NA
80,000
NA
35
(10.7)
111
(33.8)
148
(45.1)
156
(47.5)
100,000
NA
NA
67
(20.4)
157
(47.9)
170
(51.8)
120,000
NA
NA
NA
56
(17.1)
164
(50.0)
9001 to
10,000
(2743 to
3048)
40,000*
5
(1.5)
110
(33.5)
115
(35.1)
NA
NA
60,000
NA
76
(23.2)
142
(43.3)
156
(47.5)
NA
80,000
NA
31
(9.4)
103
(31.4)
137
(41.8)
142
(43.3)
100,000
NA
NA
62
(18.9)
147
(44.8)
157
(47.9)
120,000
NA
NA
NA
51
(15.5)
153
(46.6)
*Not all families have these models.
Notes:
1. 3--- and 4---in. Vent pipe systems require long radius elbows.
2. Total equivalent vent lengths under 10’ for 40,000 require the use of an outlet choke plate at altitude 0 to 2,000 ft (0 to 610M).
Failure to use an outlet choke when required may result in flame disturbance or flame sense lockout.
3. Vent sizing for Canadian installations over 4500 ft (1370m) above sea level are subject to acceptance by the local authorities having jurisdiction.
4. NA --- Not allowed; pressure switch will not close, or flame disturbance may result.
5. Do not use pipe size greater than those specified in table or incomplete combustion, flame disturbance, or flame sense lockout may occur.
6. Size both the combustion---air and vent pipe independently, then use the larger diameter for both pipes.
7. Assume the two 45
_
elbows equal one 90
_
elbow. Wide radius elbows are desirable and may be required in some cases.
8. Elbows and pipe sections within the furnace casing and at the vent termination should not be included in vent length or elbow count.
9. The minimum pipe length is 5 ft. (1.5 M) for all applications.
10. Use 3---in. (76 mm) diameter vent termination kit for installations requiring 4---in. (102 mm) diameter pipe.
