D. How to Use the Vent Graph
1.Measure the distance from the top of appliance to the center of the 90° elbow. On the graph below, draw a horizontal line from that measurement on the vertical axis across until it intersects with the slanted line.
2.From the point of this intersection, draw a vertical line to the bottom of the graph.
3.The point at which this line meets the bottom line of the graph is the maximum length of the horizontal run.
EXAMPLE 1: If the vertical dimension from the center line of the flue vent to the center of the 90° elbow is 7 ft. (2 m), the horizontal run to the outer wall flange must not exceed 13 ft. 2 in. (5m).
EXAMPLE 2: If the vertical dimension from the center line of the flue vent is 21 ft. (6m), the horizontal run to the outer wall flange must not exceed 10 ft. (3m).
4.Each 90° elbow is equivalent to 3 ft. (914mm) of vent pipe and each 45° elbow is equivalent to 1 ft. (305mm) of vent pipe, and must be subtracted from vent pipe run. A single vertical to horizontal 90° elbow is already calculated into the allowable 15 ft. (5m) run. Each additional 90° elbow reduces the maximum horizontal distance by 3 ft. (914mm).
Example: The use of 3 elbows would reduce the allowable horizontal run to 9 ft. (3 - 1 = 2 elbows x 3 ft. = 6 ft.; 15 ft. max. - 6 ft.= 9 ft. max.)
E. Venting Guidelines for Horizontal Runs
Standard Horizontal Run
Max Horizontal Run, | 3 ft (914mm) |
Rear Vent |
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Max Horizontal Run | 15 ft (5m) when vertical rise is |
| 10 ft (3m |
Max Horizontal Run | 14 in. (356mm) |
with 45o Elbow |
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Min Horizontal Run | 11 in. (279mm) |
Max Wall Thickness | 20 in. (508mm) |
Min Wall Thickness | 4 in. (102mm) |
Exterior Vent Diameter | |
Inner Vent Diameter | 4 inches (101mm) |
Rear Vent with Vertical | Min of 2 ft vertical (610mm) |
Rise | must be used prior to any hori- |
| zontal run |
Horizontal Run requires a 1/4 in. (6mm) rise for every 1 ft toward the termination.
Horizontal Run requires a
Horizontal Run with Snorkel Kit.
A rear vent configuration with 3 ft. (914mm) maximum horizontal run with no vertical pipe and with 1/4 in. (6mm) rise per foot.
40 ft. (12m) | 40' |
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Maximum Run if | 38' |
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36' |
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Steel Inner Pipe |
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Material | 34' |
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30 ft. (9m) Maxi- | 32' |
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mum Run if using | 30' |
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Aluminum Inner | 28' |
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Pipe Material |
| Flue Restrictor more |
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| 26' |
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| 24' |
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Example 2 |
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22' |
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| 20' |
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Vertical Distance | 18' |
| Flue Restrictor |
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from Appliance Top | 16' |
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to 90o Elbow | 14' |
| 50% CLOSED in |
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| this area |
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| 12' |
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Example 1 | 10' |
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8' |
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| 6' |
| Flue Restrictor |
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| 4' |
| OPEN in this area |
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| 2' |
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| 0' | 11" | 2' | 4' | 6' | 8' | 10' | 12' | 14' | 15' |
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Figure 5.2 | TOTAL HORIZONTAL RUN TO THE OUTER |
| WALL FLANGE (EXCLUDING ELBOWS) |
•A snorkel kit must be used. Figure 5.3 below and
Figure 5.4 on page 12.
•A derating orifice must be installed. The appropriate orifice is supplied with the rear vent kit.
Snorkel Kit
C
L
Figure 5.3
NOTE: IF YOUR INSTALLATION FALLS WITHIN A SHADED AREA ON THE GRAPH, THE FLUE RESTRICTOR MUST BE USED.
INDIVIDUAL INSTALLATIONS MAY VARY.
Percentage closed based on full range of the flue restric-
tor travel.
WARNING! Fire Risk!
•Never allow the vent to run downward.
•This could cause high temperatures and may present the possibility of a house or structure fire.
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