Vent Fitting Equivalent Length
| Vent Pipe: | 6” Vent | 7” Vent | 8” Vent | 9” Vent |
90º | Elbow | 8 feet | 9 feet | 10 feet | 11 feet |
90º | Long Radius Elbow | 5 feet | 5 feet | 5 feet | 6 feet |
45º | Elbow | 5 feet | 5 feet | 5 feet | 5 feet |
The following vent information is provided for use in design calculations, if needed.
Venting Specifications
Input MBtu | Combustion Air | Max Vent | |
Volume (cfm) | Press. ”W.C. | ||
| |||
399 | 136 | 0.5 | |
500 | 170 | 0.6 | |
750 | 255 | 1.0 | |
900 | 306 | 1.2 | |
1000 | 340 | 1.3 |
9.3Vertical or Horizontal Vent Termination:
1.The vent terminal must have a minimum clearance of 4 feet (1.22 m) horizontally from, and in no case be located above or below, unless a 4 foot (1.22 m) horizontal distance is maintained from electric meters, gas meters, regulators and relief equipment.
2.The vent cap must terminate at least 3 feet (0.91 m) above any forced air inlet within 10 feet (3.05 m).
3.The vent shall terminate at least 4 feet (1.22 m) below, 4 feet (1.22 m) horizontally from or 1 foot (0.3 m) above any door, window or building air inlet to the building.
4.The vent system shall terminate at least 1 foot (0.3 m) above grade and at least 1 foot (0.3m) above possible snow accumulation levels and shall terminate at least 7 feet (2.13 m) above grade when located adjacent to public walkways or gathering areas.
5.To avoid a blocked flue condition, keep the vent cap clear of snow, ice, leaves, debris, etc.
6.The vent must not exit over a public walkway, near soffit vents or crawl space vents or other areas where condensate or vapor could create a nuisance or hazard or cause property or could be detrimental to the operation of regulators, relief valves or other equipment.
7.A horizontal vent must extend one foot beyond the wall.
8.A horizontal vent terminal must not be installed closer than 3 feet (0.91m) from an inside corner of an
9.A vertical vent must exhaust outside the building at least 3 feet (0.91m) above the point of the exit and at least 2 feet (0.61 m) above the highest point of the roof within a
10.A vertical termination less than 10 feet (0.91 m) from a parapet wall must be a minimum of 2 feet (0.61 m) higher than the parapet wall.
9.4Combining Category IV Vents
Combined TRICON Category IV gas vent systems must incorporate an Exhausto or Tjernlund variable speed, modulating, mechanical draft inducer capable of maintaining the appropriate negative draft at the end of the common flue, to assure that all water heaters in the combined vent system operate with a negative draft. Do not exceed negative 0.25” W.C. See “Combining Vents with a Draft Inducer” illustration below.
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