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TFTN 085-199
4.8
Power Vent / Indoor Combustion Air (non-Direct Vent)
When the installation uses Indoor Combustion Air (i.e. piping is not directly connecting the appliance air intake to the
outdoors), provisions for combustion and ventilation air, in accordance with section "Air for Combustion and Ventilation,"
of the National Fuel Gas Code, ANSI Z223.1/NFPA 54 (U.S.), or Clause 8.2, 8.3 or 8.4 of Natural Gas and Propane Installation
Code, CAN/CSA B149.1 (Canada), or applicable provisions of the local building codes, must be adhered to.
The boiler shall be located so as not to interfere with proper circulation of combustion, ventilation,
and dilution air.
Make up air requirements for the operation of exhaust fans, kitchen ventilation systems, clothes
dryers, and fireplaces shall be considered in determining the adequacy of a space to provide
combustion air requirements. Failure to ensure adequate make up air to all appliances may
result in personal injury or death.
4.9
General Venting Rules and Guidelines
1. Prevailing Winds: Ensure the vent is located where it will not be exposed to normal prevailing winds.
2. Combustion Air Intake Contamination: Air for combustion must be drawn from an area free of dust and contaminants.
Combustion air containing chemicals such as chloride, fluoride, bromine or iodine or dust and debris will cause corrosion
damage of the heat exchanger voiding your NTI warranty. Refer to Table 4-1 for a list of corrosive products and
contaminants sources to avoid.
3. Vertical Separation: The exhaust must be a minimum of 18" above the air inlet, and the air inlet must always be a
minimum of 12" plus snow allowance above any surface that will support snow. (2' plus snow allowance is highly
recommended). Consult your weather office for the maximum typical snowfall for your region.
Example: New Brunswick Canada - typical maximum snowfall is 19", thus the inlet must be (12"+19") = 31" above grade
and exhaust must be (31"+18") = 49" above grade.
4. Horizontal Separation: The horizontal distance between the inlet and exhaust must be a minimum of 4" center to center.
5. Wall Flashing: Under normal operating conditions this boiler will produce a plume of white gases, and should be taken
into consideration when selecting an adequate location. A 36" diameter stainless, plastic, or vinyl shield can be used to
flash the exterior of the residence.
6. Flue Gas Hazard: Position the vent termination where vapors cannot make accidental contact with people and pets or
damage nearby shrubs and plants.
7. Elbow Extensions: Elbows on outside of wall must be no more than 1/2" away from the wall.
8. Vent Sloping: All indoor exhaust piping must be on a slope back to the boiler a minimum of 1/4" per linear foot of vent.
For applications where excessive condensation is possible 1/2" per linear foot is recommended.
9. Vent Supports: Where required Exhaust and Air Intake piping shall be secured to the wall for more rigidity. All interior
vent pipe shall be supported a minimum of every 36".
10. Roof Exhaust: In all roof applications the discharge must point away from the pitch of the roof.
11. Roof Flashing: Install adequate flashing where the pipe enters the roof, to prevent water leakage.
12. Rain Cap: Install and seal a rain cap over existing chimney openings, in vacant chimney applications.
13. Venting Below Grade: For installations that exit the wall below grade refer to Figure 4-5.
14. Vent Screens: Install factory supplied vent screens on the outside of the last elbow for both the inlet and exhaust vent
terminal elbows. Install the screen into the female opening of the elbow, and then cut a small piece of pipe to sandwich
the screen into the elbow. NOTE: ensure the small piece of pipe cut, does not extend past the end of the elbow. Two
screens are provided in the package. See Figures 4-3 and 4-4.
15. Condensate Hazard: Do not locate vent over public walkways, driveways or parking lots. Condensate could drip and freeze
resulting in a slip hazard or damage to vehicles and machinery.
16. Warning Plate: For Sidewall Venting, install the warning plate "Gas Vent Directly Below", above (within 4 ft. vertically) the
location of the air intake pipe, so it is visible from at least 8 ft. away. See Figure 4-3.
17. Wall Thickness: Direct vent terminations are designed to work with any standard wall thickness. Installation guidelines
for min/max wall thickness are as follows: Min. = 1", Max. = 60".
18. Venting Options: Due to potential moisture loading (build-up) along the exterior wall, sidewall venting may not be the
preferred venting option. Refer to Figures 4-2(c), 4-2(d), 4-2(e) and 4-4 for roof top venting options.
Installation and Operation Manual
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