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POWER VENTER SIZING
In order to choose the correct size power venter for a particular installation, the total input firing rate and total equivalent
length of vent pipe to be used must be known. Refer to Table 2 to determine the maximum allowable equivalent feet of
pipe for each model used with the pipe diameters shown. When venting multiple appliances, add the input of each
appliance to determine the total input. Always choose a power venter that is capable of handling more than the system
requires. The choke plate can be adjusted to compensate for the difference.
Table 2
MAXIMUM EQUIVALENT HORIZONTAL PIPE LENGTH (FEET)
VENTER MODEL NO. AND VENT PIPE DIAMETER
PVO-300 PVO-600
BTU/HR INPUT
4” 5” 6” 5” 6“ 8”
0.75
287 --- --- --- --- ---
1.00
150 257 346 428 --- ---
1.50
75 120 172 212 --- ---
2.25
--- 51 70 86 143 211
3.00
--- --- --- 46 74 116
3.75
--- --- --- --- 51 84
4.00
--- --- --- --- --- 77
PROCEDURE FOR CALCULATING TOTAL EQUIVALENT PIPE LENGTH IN FEET
1. Calculate the total equivalent feet for each type of fitting used in the venting system from the following chart.
2. Calculate the total amount of feet for the straight lengths of vent pipe.
3. Add the equivalent feet for the fittings with the total amount of feet of straight lengths.
Table 3
EQUIVALENT LENGTH (FEET) OF VENT PIPE FOR VENT PIPE FITTINGS
VENT PIPE DIAMETER
VENT PIPE FITTINGS
3” 4” 5” 6” 7” 8” 9” 10”
TEE
19 25 31 38 44 50 56 63
90° ELBOW
5 7 9 11 12 14 16 18
45° ELBOW
3 4 4 5 6 7 8 9
1/4 8 11 14 17 19 22 25 28
1/2 5 7 8 10 12 13 15 17
REDUCER
(d/D)*
3/4 2 3 3 4 4 5 6 6
*
Reducer or increaser ratio (d/D) small diameter divided by the larger diameter. (See Figure 3)
Example: 4" to 8" reducer, the reducer ratio is d/D = 4/8 = 1/2. To estimate the equivalent foot
length for the fitting, use the smaller pipe diameter for the equivalent length figure. Example:
4" to 8" reducer; the reducer ratio is 1/2 and the smaller pipe diameter is 4". So, from the chart,
the equivalent feet would be 7 feet.
Example: System Pipe Size = 4"
Step 1 2 – 90° Elbows (4") = 14 Ft.
Step 2 10 - 2 Ft. Lengths of 4" Pipe = 20 Ft.
Step 3 Total Equivalent Feet = 14 Ft. + 20 Ft. = 34 Ft.
Figure 3