Instruction manual

47
NOTE: Maximum Equivalent Vent Length (MEVL) does NOT include elbows or terminations. Use Table 14 - Deductions from
Maximum Equivalent Vent Length to determine allowable vent length for each application.
Table 15 – Maximum Equivalent Vent Length -- Ft. (M)
4501 to 10,000 Ft. (1371 to 3048 M) Altitude
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
2
* 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 Btuh furnaces, require the use of an outlet choke plate at a ltitudes 0 --- 2000 ft. (0 to 610 M).
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 ar e subject to acceptance by th e 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.
986TA