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2. Refer to Table 4.2 for minimum and maximum vent
length allowed.
3. Maintain a minimum 2” (51 mm) clearance between
vent pipe and combustible construction.
4. When installing vent pipe through a combustible
wall, pipe must pass through a metal wall thimble;
maintain a 2” (51 mm) clearance between vent pipe
and thimble. Follow thimble manufacturer’s
instructions. Seal between thimble and exterior wall
using exterior-rated caulk or silicone to prevent water
damage and also to prevent recirculation of flue
products into the structure.
5. Determine vent terminal location.
a. Vent terminal shall be located at least 3 feet (1
meter) above any forced air inlet located within
10 feet (3 meters).
b. Vent terminal shall be located at least 4 feet (1.2
meters) below, 4 feet (1.2 meters) horizontally
from, or 1 foot (0.3 meters) above any door,
window, or gravity air inlet into any building.
c. Vent terminal shall be located at least 1 foot (0.3
meters) above ground level or normal snow lines.
See subsection 7 below if terminal needs to be
extended above ground level or snow line.
d. Vent terminal shall not be located over public
walkways where condensate could create a
nuisance or hazard.
e. When adjacent to a public walkway, vent
terminal shall be at least 7 feet (2.1 meters)
above grade.
f. Vent terminal shall be located at least 4 feet (1.2
meters) horizontally from electric meters, gas
meters, regulators and relief equipment. In
Canada, this dimension must be 6 feet (2 meters).
g. Vent terminal should not be located directly
under roof overhangs to prevent icicles from
forming.
6. Vent Pipe Assembly:
a. Horizontal portions of the vent pipe shall slope
down not less than 1/4” per foot (21 mm per
meter) from the boiler to the vent termination
elbow. If this horizontal run is pitched toward
boiler, provide a horizontal drain tee as per
instructions in section D. Direct Exhaust;
Vertical Venting.
b. Secure vent pipe using metal strapping, clamps
and/or other means. Do not screw into the vent
pipe.
• Horizontal portions of the vent pipe must be
supported at intervals no greater than four
feet to prevent sagging/separation.
• Secure vent pipe to the thimble/wall to
prevent possible movement from incidental
contact on the vent terminal.
c. Type vent material approved is AL29-4C, 3 inch
(76 mm) diameter stainless steel; manufactured
by Heat-Fab
®
(Saf-T-Vent); Z-Flex
®
(Z-Vent);
ProTech (FasNSeal
™
); Flex-L (StaR-34); Metal-
Fab (Corr/Guard).
d. Attach the fan adapter to blower outlet flange
using gasket and 1/4” (6 mm) -20 nuts and
washers, (parts located in miscellaneous parts
box).
e. Refer to Figure 4.3 that lists special vent adapters
for connection to boiler fan adapter. These
special adapters are not supplied with boiler.
f. Attach vent pipe adapter to boiler fan adapter by
applying a 1/4” (6 mm) bead of high
temperature silicone around diameter of fan
adapter and slip vent pipe adapter over the fan
adapter. Fill in any voids with silicone and
smooth out with moistened finger or flat tool.
g. If using Z-Flex
®
pipe, slide vent pipe over the first
2-1/2” (64 mm) of the fan adapter and secure
joint connection with the Z-Flex
®
looking bands
making sure that locking band has contact with
fan adapter at boiler end and vent pipe.
h. Attach remaining pipe and fittings per
manufacturer’s vent instructions. Use only the
silicone recommended by the vent pipe
manufacturer.
i. The only approved vent termination is a 3”(76
mm) 90° elbow. Refer to Figure 4.4. Vent pipe
must be sealed to the thimble (or outside wall if-
non-combustible construction) using silicone to
prevent recirculation of flue products into the
structure.
*Maximum Vent Length to be reduced by 5 feet (1.5
meters) for each 90° elbow added that is
manufactured by Z-Flex
®
, Heat-Fab
®
and Protech.
*Maximum Vent Length to be reduced by 7-1/2 feet
(2.3 meters) for each 90° elbow added that is
manufactured by Flex-L.
The outside vent terminal (90° Elbow) is not
included in Equivalent Vent Length.
7. Refer to Figure 4.2 for vertical offset option. The
maximum offset is 5 feet. With the exception of the
last 90° elbow which serves as the vent terminal, the
additional elbows and straight vent pipe must be
considered when determining maximum vent length.
Provide a horizontal drain tee as described in
Section D. Direct Exhaust; Vertical Venting.
VENTING
50 feet (15 m)
50 feet (15 m)
45 feet (13.7 m)
45 feet (13.7 m)
DE-03
DE-04
DE-05
DE-06
Boiler Model
2-1/2 feet (762 m)
2-1/2 feet (762 m)
2-1/2 feet (762 m)
2-1/2 feet (762 m)
Table 4.2.: Equivalent Vent Length
*Equivalent Length of 3” diameter
Stainless Steel Vent Pipe
Minimum Vent Length
Maximum Vent Length