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Installation: Piping
4. Any run of single wall vent pipe passing through an
unheated space must be insulated with an insulation
suitable to 550°F (288°C).
5. The combustion and exhaust vent air systems must be
installed to prevent collection of condensate. Pitch
horizontal pipes downward 1/4 inch per foot (21 mm/
m) toward the terminal cap to facilitate drainage (see
Figure 11, p.
21). Vertical vent pipes should be
arranged as depicted in
6. The equivalent length of the vent system must not be
less than five feet (1.5 m) and must not exceed 50 feet
(15.2 m). Equivalent length equals the total length of
straight pipe plus 15 feet (4.6 m) for each 90-degree
elbow and five feet (1.5 m) for each 45-degree elbow.
7. Each slip joint must be secured with at least three
corrosion resistant screws. Two full turns of 3M™ #425
Aluminum Foil tape or its equivalent must then be
used to seal each joint. General Electric RTV-108, Dow
®
Corning
RTV-732, or an equivalent may be used
instead of the tape.
8. For horizontal vent systems longer than five feet
(1.5 m), the system must be supported from overhead
building structures at three-foot (1-m) intervals.
9. The exhaust vent system must remain at a minimum of
six inches (152 mm) from all combustible materials.
Any part of the vent system that passes through a
combustible material must be properly insulated.
Note: Increasing the clearance distances may be
necessary if there is a possibility of distortion or
discoloration of adjacent materials.
For a VERTICAL vent pipe section that passes through
a floor or roof, an opening four inches (102 mm)
greater in diameter is required. The opening must be
insulated and flashed in accordance with applicable
installation codes.
A HORIZONTAL section of an exhaust vent system that
passes through a combustible wall must be
constructed and insulated as shown in
10. The top of a VERTICALLY VENTED exhaust system
must extend at least three feet (1 m) above the roof
surface that it passes through. The point of termination
for a HORIZONTALLY VENTED exhaust system must be
at least 12 inches (305 mm) from the exterior wall that
it passes through. In addition, the termination point
must be at least three feet (1 m) above the snow line,
more than six feet (2 m) from the combustion air inlet
of another appliance, more than three feet (1 m) from
any building opening, and more than four feet (1.3 m)
from, and not directly above, any electric meter,
regulator, or relief equipment (refer to
and
Figure 12, p.
21).
20
Figure 9, p.
21.
Figure 12, p.
Figure 10, p. 21
21.
GMND-SVX01B-EN
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