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CHAPTER 2
CHAPTER 2 - DIRECT VENT INSTALLATION OF VENT/AIR PIPING
2. The combustion air piping must terminate in an up-
side down “U” shape fashion using two 90° elbows,
as shown in Fig. 1 on page 12. The termination
must be located 12” [30.5 cm] (18” [45.7 cm] Cana-
da) above the highest anticipated snow level.
3. The vent piping must terminate vertically with a
coupling to accept the bird screen and must be lo-
cated 12” to 24” [30.5 cm to 61 cm] above the com-
bustion air inlet as shown in Fig. 1 on page 12.
4. The vent and combustion air terminations must be
located at a radial distance of 12” to 24” [30.5 cm to 61
cm] from centerline of vent termination to centerline
of air termination as shown in Fig. 1 on page 12.
5. The following should be considered when deter-
mining the location of the vent and combustion air
terminations:
a. Locate the vent termination where ue vapors
will not damage surrounding shrubs, plants, air
conditioning equipment or be objectionable to
the homeowner.
b. The ue products will form a noticeable plume
of water vapor as they condense in colder air.
Avoid terminating the vent in areas where the
plume could obstruct window views.
c. Prevailing winds could cause freezing of ue
gas condensation and a buildup of water / ice
on surrounding plants, building surfaces or
combustion air inlet.
d. Avoid locations where prevailing winds could
aect the performance of the boiler or cause
recirculation of the ue gases, such as inside
corners of buildings, near adjacent buildings,
vertical surfaces, window wells, stairwells, al-
coves, courtyards, or other recessed areas.
e. Do not terminate the vent above doors or win-
dows, ue condensate could freeze causing ice
formations.
f. Locate the vent termination to prevent possible
condensate damage to exterior nishes.
g. Avoid locations of possible accidental contact
of ue vapors with people or pets.
6. The vent termination must also maintain the fol-
lowing clearances, as shown in Fig. 2 on page 13:
a. At least 3 feet [0.9 m] from adjacent walls
b. At least 3 feet [0.9 m] below roof overhangs
c. At least 7 feet [2.1 m] above any public walkways
A Direct Vent appliance utilizes uncontaminated outdoor
air (piped directly to the appliance) for combustion.
2.1. Direct Vent - Vertical - Through the Roof
or Unused Chimney
• The installation must conform to the re-
quirements of the authority having jurisdic-
tion or, in the absence of such requirements,
to the National Fuel Gas Code, ANSI Z223.1/
NFPA 54, and/or Natural Gas and Propane
Installation Code, CAN/CSA B149.1.
• When using an inoperative chimney as a
means of a chase for the vent, the surrounding
space within the chimney cannot be used to
draw combustion air or vent another appliance.
A gas vent extending through a roof must not
terminate near an adjacent wall or below any
building extensions such as roof eaves, balco-
nies or decks. Failure to comply with the required
clearances in this manual can result in substantial
property damage, serious injury, or death.
The information and diagrams outlining the fit-
tings and method of terminating the vent/com-
bustion air are directly related to PVC/CPVC vent
systems. When utilizing an AL29-4C® or Polypro-
pylene vent system, there may be some varia-
tions. Consult the appropriate vent manufactur-
er for recommendations and clarifications.
2.1.1 Determine Termination Location
Locate the vent and combustion air termination using
the following guidelines:
1. The total length of the vent or combustion air piping
must not exceed the limits given in Table 6 on page 7.
Do not include the 90º elbows used to terminate
the combustion air inlet exterior of the building
when determining the total length of pipe.
NOTICE
WARNING
NOTICE
NOTICE
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