49
Table 17 – Maximum Equivalent Vent Length -- Ft. (M)
4501 to 10,000 Ft. (0 to 1370 M) Altitude
NOTE: Maximum Equivalent Vent Length (MEVL) includes standard and concentric vent termination and does NOT include elbows.
Use Table 16 - Deductions from Maximum Equivalent Vent Length to determine allowable vent length for each application.
Altitude
FT (M)
Unit Size
BTU/Hr
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
2
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)
140,000
4
NA
NA
NA
60
(18.3)
134
(40.8)
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)
140,000
4
NA
NA
NA
50
(15.2)
109
(33.2)
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)
140,000
4
NA
NA
NA
41
(12.5)
87
(26.5)
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)
140,000
4
NA
NA
NA
32
(9.8)
63
(19.2)
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)
140,000
4
NA
NA
NA
23
(7.0)
42
(12.8)
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)
140,000
4
NA
NA
NA
16
(4.9)
20
(6.1)
NOTES
:
1. Use only the vent pipe sizes shown for each furnace. It is NOT necessary to choose the smallest diameter pipe possible for venting.
2. NA --- Not allowed. Pressure switch will not close, or flame disturbance may result.
3. Total equivalent vent lengths under 10’ for 40,000 BTUH furnaces from 0 to 2000 ft. (0 to 610 M) above sea level require use of an outlet choke plate .
Failure to use an outlet choke when required may result in flame disturbance or flame sense lockout.
4. Not all furnace families include 140,000 BTUH input models.
5. Vent sizing for Canadian installations over 4500 ft (1370 M) above sea level are subject to acceptance by local authorities having jurisdiction.
6. Size both the combustion air and vent pipe independently, then use the larger size 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. Elbow 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. (2 M) linear feet (meters) for all applications.
10. Use 3 ---in. (76 mm) diameter vent termination kit for installations requiring 4 ---in. (102 mm) diameter pipe.
59SC
5
A
