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CHAPTER 2
CHAPTER 2 - DIRECT VENT INSTALLATION OF VENT/AIR PIPING
2.3. Direct Vent - Vertical Vent and Sidewall
Combustion Air
• The installation must conform to the re-
quirements of the authority having juris-
diction or, in the absence of such require-
ments, 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 sur-
rounding space within the chimney cannot
be used to draw combustion air or vent an-
other appliance.
A gas vent extending through a roof must not
terminate near an adjacent wall or below any
building extensions such as roof eaves, bal-
conies or decks. Failure to comply with the re-
quired clearances in this manual can result in
substantial property damage, serious injury, or
death.
The information and diagrams outlining the
fittings and method of terminating the vent/
combustion air are directly related to PVC/
CPVC vent systems. When utilizing an AL29-
4C® or Polypropylene vent system, there may be
some variations. Consult the appropriate vent
manufacturer for recommendations and clari-
fications.
NOTICE
WARNING
NOTICE
2.3.1 Determine Termination Location
Locate the vent and combustion air termination using
the following guidelines:
1. The total length of the vent or combustion air pip-
ing 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.
2. The combustion air piping must terminate with a
90º elbow. Fig. 12 on page 19 shows a snorkel
termination option. The combustion air pipe can
also terminate using a 90º elbow directed down as
shown in Fig. 6 on page 17. The termination must
be located 12” [30.5 cm] minimum above grade /
highest anticipated snow level.
3. The vent piping must terminate vertically with a
coupling to accept the bird screen and must be
located 12” [30.5 cm] (18” [45.7 cm] Canada) above
the highest anticipated snow level.
4. 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.
NOTICE
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