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In cold climates, the use of type “B” double wall vent pipe or an
insulated single wall pipe for combustion air is recommended to
help prevent moisture in the cool incoming air from condensing
and leaking from the inlet pipe.
Termination point for the flue products must follow the clearance
requirements in the Vertical or Horizontal Vent Termination
sections of the Category IV Venting.
CAUTIONƽ
Appliances that are shut down or will not operate may
experience freezing due to convective airflow in the air
inlet pipe connected to the appliance.
TABLE - F
Direct Vent and Intelli-Vent Flue
and Air Inlet Pipe Sizes
Air Inlet
Input Btu/hr Flue Size Pipe Size
1,500,000
________________
1,700,000
________________
2,000,000
6"
______________
7"
_____________
8"
6"
________________
7"*
________________
8"
*Piping from the appliance to the air inlet cap may be either 7"
or 8". An 8" diameter sidewall air inlet cap is provided in the
vent kit.
Length of Air Inlet Pipe
The maximum total length of the sidewall or vertical roof top
combus tion air inlet pipe as installed from the appliance to the air
inlet cap must not exceed 100 equivalent feet (30.5 m) in length.
Subtract 5 feet (1.52 m) of equivalent length for each 90° elbow
installed in the air inlet pipe system. Subtract 2 1/2 feet (0.7 m)
of equiv a lent length for each 45° elbow in stalled in the air inlet
pipe system.
Do not exceed limits for the combustion air inlet piping lengths.
Air Inlet Pipe Materials
The air inlet pipe(s) must be sealed. Choose acceptable
combustion air inlet pipe materials from those specified in this
section.
Select air inlet pipe material from the following specified
materials:
• PVC, CPVC or ABS (6", 7"or 8" I.D.)*.
• Dryer Vent or Sealed Flexible Duct (not recommended
for roof top air inlet).
• Galvanized steel vent pipe with joints and seams
sealed as specified below.
• Type “B” double wall vent with joints and seams
sealed as specified below.
* Plastic pipe may require an adapter (not provided) to transition
between the air inlet connection on the ap pli ance and the plastic air
inlet pipe.
WARNINGƽ
Using vent or air intake ma te ri als other than those specified,
fail ure to properly seal all seams and joints or failure to
follow vent pipe manufacturer’s instructions can result in
personal injury, death or property damage. Mixing of
venting materials will void the warranty and cer ti fi ca tion
of the appliance.
Sealing of Type “B” double wall vent material or galvanized vent
pipe ma te ri al used for air inlet pipe on a sidewall or vertical roof top
Com bus tion Air Supply System.
a. Seal all joints and seams of the air inlet pipe
using either Aluminum Foil Duct Tape meeting
UL Standard 723 or 181A-P or a high quality
UL Listed silicon sealant such as those
manufactured by Dow Corning or General
Electric.
b. Do not install seams of vent pipe on the
bottom of horizontal runs.
c. Secure all joints with a minimum of three sheet
metal screws or pop rivets. Apply aluminum
foil duct tape or sil i cone sealant to all screws
or rivets installed in the vent pipe.
d. Ensure that the air inlet pipes are properly
supported.
The PVC, CPVC or ABS air inlet pipe should be cleaned and sealed
with the pipe manufacturers recommended solvents and standard
commercial pipe cement for the material used. The PVC, CPVC,
ABS, Dryer Vent or Flex Duct air inlet pipe should use a silicone
NOTE:
The use of double wall vent or insulated material for the
combustion air inlet pipe is recommended in cold climates
to prevent the condensation of airborne moisture in the
incoming com bus tion air.