DuraVent DuraFlex AL Installation - Manual (Page 5)

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Figure 1
Figure 2
For complete sizing instructions, refer
to the National Fuel Gas Code , the
International Fuel Gas Code, or the
DuraVent Sizing Handbook. Failure
to properly size the venting system
may result in draft hood spillage, back
pressure, and corrosive condensation
in the relining system.
As an alternate method, for draft
hood-equipped appliances and
decorative gas fireplaces only, the
venting system may be sized to the
outlet of the appliance. For two or
more draft hood-equipped appliances,
the effective area of the vent shall not
be less than the area of the largest
appliance, plus 50% of the areas
of additional draft hood outlets. For
fan-assisted gas appliances, the vent
system must be sized using the sizing
instructions and tables referenced
above.
PRIOR TO INSTALLATION
Before installing the Chimney Liner
System, the chimney passageway
should be examined to ascertain that
it is clear and free of obstructions,
and must be cleaned if it has been
previously used for venting solid or
liquid-burning appliances or fireplaces.
CHIMNEY LINER SELECTION
The basic DuraFlex AL Chimney
Liner System consists of a continuous
flexible liner from the top of the
chimney to the appliance connection
(Figure 1). This system is relatively
easy to install, even in masonry
chimneys that are constructed with an
offset. This single-wall flexible system