COMBUSTION AND VENTILATION AIR
(DIRECT/NON-DIRECT VENT MODELS)
22
Rev. 0
All 90° elbows must be medium radius (1/4 bend DWV) or
long radius (Long sweep 1/4 bend DWV) types conform-
ing to ASTM D3311. A medium radius (1/4 bend DWV)
elbow measures 3 1/16” minimum from the plane of one
opening to the centerline of the other opening for 2” diam-
eter pipe, and 4 9/16” minimum for 3” pipe.
Proper Vent/Flue and Combustion Air Piping Practices
Adhere to these instructions to ensure safe and proper fur-
nace performance. The length, diameter, and number of
elbows of the vent/flue pipe and combustion air pipe (when
applicable) affects the performance of the furnace and must
be carefully sized. All piping must be installed in accordance
with local codes and these instructions.
Piping must be adequately secured and supported to pro-
hibit sagging, joint separation, and/or detachment from the
furnace. Horizontal runs of vent/flue piping must be sup-
ported every three feet and must maintain a 1/4 inch per
foot downward slope, back towards the furnace, to prop-
erly return condensate to the furnace’s drain system. Al-
lowances should be made for minor expansion and con-
traction due to temperature variations. For this reason, par-
ticular care must be taken to secure piping when a long run
is followed by a short offset of less than 40 inches.
Precautions should be taken to prevent condensate from
freezing inside the vent/flue pipe and/or at the vent/flue pipe
termination. All vent/flue piping exposed outdoors or in un-
heated areas must be insulated with 1/2” thick closed cell
foam such as “Armaflex” or “Insultube.” Inspect piping for
leaks prior to installing insulation.
Termination Locations
Note: Refer to
Location Requirements and Considerations
section for combustion air contaminant restrictions.
The following bullets and diagram describe the restrictions
concerning the appropriate location of vent/flue pipe and
combustion air intake pipe (when applicable) terminations.
Refer to
Non-Direct Vent (Single Pipe) Piping and Direct
Vent (Dual Pipe) Piping sections for specific details on ter-
mination construction.
•
All terminations must be located at least 12 inches
above ground level or the anticipated snow level.
•
Vent terminations must terminate at least 3 feet above
any forced air inlet located within 10 feet.
Note: This provision does not apply to the combustion air
intake termination of a direct vent application.
•
The vent termination of a
non-direct vent application
must terminate at least 4 feet below, 4 feet horizon-
tally from, or 1 foot above any door, window, or grav-
ity air inlet into any building.
•
The vent termination of a
direct vent application must
terminate at least 12 inches from any opening through
which flue gases may enter a building (door, window,
or gravity air inlet).
•
The vent termination of vent pipe run vertically through
a roof must terminate at least 12 inches above the
roof line (or the anticipated snow level) and be at least
12 inches from any vertical wall (including any antici-
pated snow build up).
•
A vent termination shall not terminate over public
walkways or over an area where condensate or va-
por could create a nuisance or hazard or could be
detrimental to the operation of regulators, relief
valves, or other equipment.
•
The combustion air intake termination of a direct vent
application should not terminate in an area which is
frequently dusty or dirty.
Note: In Canada, the Canadian Fuel Gas Code takes pre-
cedence over the preceding termination restrictions.
12"
12"
Non-Direct Vent
Vent/Flue Termination
No Terminations
Above Walkway
12"
4'
4'
Non-Direct Vent
Vent/Flue Termination
Direct Vent
Vent/Flue Termination
12"
10'
3"
Forced Air
Inlet
Other Than
Combustion Air
Termination Intake
Grade or Highest
Anticipated
Snow Level
Vent Termination Clearances
Canadian Venting Requirements
In Canada, venting must conform to the requirements of
the current CAN/CGA-B149 Installation Code. Use only CSA
listed two or three inch diameter PVC or ABS pipe, solvent
cement, and fittings throughout. Carefully follow the manu-
facturers’ instructions for cutting, cleaning, and solvent ce-
menting PVC and/or ABS.
The vent can be run through an existing unused chimney
provided the space between the vent pipe and the chimney
is insulated and closed with a weather-tight, corrosion-re-
sistant flashing.
The vent shall
not be located:
•
Less than 12 inches above the finished grade line.
