21
All minimum clearances specified must be
maintained to protect building materials from
degradation by flue gases.
1.
The termination tee must be 12 inches
above snow level or grade level which
ever is higher. See Figure 22 for alter-
nate method to achieve 12" above snow
level.
2.
Avoid areas where condensate drainage
may cause problems such as above
planters, patios, or adjacent to windows
where the steam from the flue gases
may cause fogging. Do not terminate
above any public walkway.
3.
Select the point of wall penetration where
the minimum 1/4 inch per foot of upward
slope can be maintained.
4.
When penetrating a noncombustible
wall, the hole through the wall must be
large enough to maintain the pitch, pipe
clearance for passage, and provide for
proper sealing. Penetrating a combus-
tible wall requires the use of a wall
thimble. (See Figure 22.) A 6-1/2 inch
square framed opening is required to
insert the thimble halves. The thimble is
adjustable to varying wall thickness and
is held in place by applying sealant to the
male sleeve before assembly. Also run
a bead of sealant around the outer wall
thimble.
5.
The vent pipe must extend 1-1/4 inches
through the outer thimble half for a
combustible wall. Be sure to check this
carefully before cutting the vent pipe.
6.
Attach a 3 inch coupling to the end of the
pipe that extends through the wall or
thimble. This prevents the vent pipe
from being pushed inward.
7.
Cut an 8 inch minimum piece of vent pipe
and connect the coupling to the
termination tee. The inside of the tee
must be a minimum of 12 inches from
the outside of the wall. (See Figure 23.)
Flexible Vent Systems
Flexible gas vent is approved for use in vertical
single vent or common vent installations only.
The minimum distance to combustibles is 1" for
type B insulated and 6" for single wall. The
venting system must be installed in accordance
with the local authorities, the vent manufacturer's
instructions and the instructions listed below.
The flexible vent must be installed in accor-
dance with the venting tables for vertical or
common venting only. The vent system must
be supported in horizontal runs with
3/4" pipe strap at a maximum of 5 foot intervals.
All horizontal sections must have a slope to-
ward the furnace of not less than 1/4" per foot.
The vent must not sag, or have any bends
greater than 90 degrees.
CIRCULATING AIR SUPPLY
General
Plenums and air ducts must be installed in
accordance with the Standard for the Installa-
tion of Air Conditioning and Ventilating Systems
(NFPA No. 90A) or the Standard for the Instal-
lation of Warm Air Heating and Air Conditioning
Systems (NFPA No. 90B).
Use Wall Thimble at
Vent Points
Support vent pipe
every 5 feet
Ground Level
Termination Tee
Figure 22. Alternate Horizontal
Vent Installation
Wall Thimble
(Inner Half)
Inner Shield
4
1
/
2
" Dia.
Wall Thimble Outer Half
Outer Overlapping
Shield 6
1
/
2
" Dia.
3" Termination
Tee
Protective
Screen
Inside
Combustible
Wall
Inside
Combustible
Wall
3" Vent
Pipe
Outside
Combustible
Wall
Inner
Overlapping
Shield 6
3
/
8
" Dia.
Locking Band
12" Min
Figure 23. Typical Termination
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