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MAXIMUM EQUIVALENT VENT LENGTH -- FT. (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) 8 (2.4) 8 (2.4)
Medium Radius 90º Elbow 5 (1.5) 5 (1.5) 5 (1.5) 5 (1.5) 5 (1.5)
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) 4 (1.2) 4 (1.2)
Medium Radius 45º Elbow 2.5 (0.8) 2.5 (0.8) 2.5 (0.8) 2.5 (0.8) 2.5 (0.8)
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)
Concentric Vent Termination NA 0 (0.0) NA 0 (0.0) NA
Standard Vent Termination 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0)
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.
See Vent Manufacturers’ data for equivalent lengths of flexible vent piping.
DO NOT ASSUME that one foot of flexible vent pipe is equivalent to one foot of standard PVC vent pipe.
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)
No deduction for Concentric Vent Kit 0 ft. = - 0 ft. (From Table 2)
Maximum Vent Length = 115 ft. For EACH vent or inlet pipe
915SA