Table 16
N9MSB & N9MSE - MAXIMUM EQUIVALENT VENT LENGTH - Feet (Meters)
Note: Maximum Equivalent Vent Length (MEVL) does NOT include elbows or terminations.
Use DEDUCTIONS FROM MEVL - Table 15 to determine allowable vent length for each application.
Note: Vent sizing for Canadian installations over 4500 ft. (1370 M) above sea level are subject to acceptance
Altitude Unit Size
FT (M) BTU/Hr
40,000
60,000
4501 to 5000 80,000
(1370 to 1524) 100,000
120,000
140,0004
40,000
60,000
5001 to 6000 80,000
(1524 to 1829) 100,000
120,000
140,0004
40,000
60,000
6001 to 7000 80,000
(1829 to 2134) 100,000
120,000
140,0004
40,000
60,000
7001 to 8000 80,000
(2134 to 2438) 100,000
120,000
140,0004
40,000
60,000
8001 to 9000 80,000
(2438 to 2743) 100,000
120,000
140,0004
40,000
60,000
9001 to 10,000 80,000
(2743 to 3048) 100,000
120,000
140,0004
* Not all families have these models
NOTES:
by the local authorities havin,q jurisdiction.
DIRECT VENT (2-PIPE) AND NON-DIRECT VENT (1-PIPE)
Vent Pipe Diameter
1-1/2 2 2-1/2 3
33 1(10.1) 171 1(52.1) 196 (59.7)
I 20 (6.1) I 111 I (33.8) I 198 (60.4) 221 (67.4)
54 (16.5) 146 (44.5) 195 (59.4)
16 (4.9) 91 (27.7) 200 (61.0)
80 (24.4)
60 (18.3)
I 27 (8.2) I 158 I (48.2) I 179 (54.6)
I 16 (4.9) I 103 I (31.4) I 186 (56.7) 207 (63.1)
49 (14.9) 137 (41.8) 183 (55.8)
12 (3.7) 85 (25.9) 188 (57.3)
74 (22.6)
50 (15.2)
I 21 (6.4) I 145 I (44.2) I 162 (49.4)
I 13 (4.0) I 96 I (29.3) I 174 (53.0) 194 (59.1)
44 1(13.4) 1 120 (36.6) 171 (52.1)
10 (3.0) I 79 (24.1) 178 (54.3)
68 (20.7)
41 (12.5)
I 15 (4.6) I 133 I (40.5) I 146 (44.5)
I 10 (3.0) I 89 I (27.1) I 163 (49.7) 181 (55.2)
40 1(12.2) 1 120 (36.6) 159 (48.5)
73 (22.3) 167 (50.9)
62 (18.9)
32 (9.8)
I 10 (3.0) I 121 I (36.9) I 130 (39.6)
I 7 (2.1) I 82 1(25.o) 1 152 (46.3) 168 (51.2)
35 1(10.7) 1 111 (33.8) 148 (45.1)
67 (20.4) 157 (47.9)
56 (17.1)
23 (7.0)
I 5 (1.5) I 110 I (33.5) I 115 (35.1)
76 I (23.2) I 142 (43.3) 156 (47.5)
31 (9.4) I 103 (31.4) 137 (41.8)
62 (18.9) 147 (44.8)
51 (15.5)
16 (4.9)
216 (65.8)
222 (67.7)
211 (64.3)
134 (40.8)
200 (61.0)
208 (63.4)
199 (60.7)
109 (33.2)
185 (56.4)
195 (59.4)
187 (57.0)
87 (26.5)
170 (51.8)
182 (55.5)
175 (53.3)
63 (19.2)
156 (47.5)
170 (51.8)
164 (50.0)
42 (12.8)
142 (43.3)
157 (47.9)
153 (46.6)
20 (6.1)
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 ft. for 40k BTUH furnaces from 0 to 2000 ft (0 to 610m) above sea level require use of
an inducer outlet choke. Failure to use an outlet choke may result in flame disturbance or flame sense lock-out.
4. Not all furnace families include 140,000 BTUH input models.
5. Vent sizing for Canadian installation 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 two 45° degree elbows equal one 90° degree 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 (1.5) linear feet (meters) for all applications.
10. Use 3-in (76 mm) diameter vent termination kit for installations requiring a 4-in (102 mm) diameter pipe.
440 01 4101 03 Specifications subject to change without notice. 55
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