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Certified
Model
Material
503
753
1003
Category IV
1253
(AL29-4C)
1503
1753
2003
* Vent length may be extended up to 40 ft. using a barometric damper installed at 15 equivalent feet from
the heater where the category of the vent changes from Cat IV to Cat II. NOTE: Special vent materials
are still required.
1
Vent lengths are based on a lateral length of 2 ft. Refer to the latest edition of the NFGC for further
details.
** Subtract 10 ft per elbow. Max. 4 elbows.
t Adapters supplied by others.
AL29-4C vent is: 6 in. (152mm) for Models 503-1003;
and 8 in. (203mm) for Models 1253-2003.
The connection from the appliance vent to the stack
must be as direct as possible and shall be the same di-
ameter as the vent outlet. The horizontal breaching of
a vent must have an upward slope of not less than 1/4
inch per linear foot from the heater to the vent termi-
nal. The horizontal portions of the vent shall also be
supported for the design and weight of the material
employed to maintain clearances and to prevent physi-
cal damage or separation of joints.
NOTE: A vent adapter (field-supplied) may be re-
quired to connect the Category IV vent to the heater.
Termination
The vent terminal should be vertical and should termi-
nate outside the building at least 2 ft above the highest
point of the roof that is within 10 ft. The vent cap
should have a minimum clearance of 4 ft horizontally
from and in no case above or below (unless a 4 ft hori-
zontal distance is maintained) electric meters, gas
meters, regulators and relief equipment.
The distance of the vent terminal from adjacent public
walkways, adjacent buildings, open windows and
building openings must be consistent with the NFGC
(U.S.) or B149 (Canada). Gas vents supported only by
flashing and extended above the roof more than 5 ft
should be se-curely guyed or braced to withstand
snow and wind loads.
Vertical Vent
Vent Size
Height
Vent
(in.)
Min.
6
8
Table L: Category IV Vertical Venting
Combustion Air
1
(Ft)
Intake Pipe
Material
Max.
15*
15
*
75
Galvanized Steel,
75
PVC,
0
40
ABS,
75
CPVC
75
75
CAUTION: A listed vent cap terminal suitable for
connection to the Cat IV vent materials, adequately
sized, must be used to evacuate the flue products
from the building.
25
Air Inlet
Max. Length** (Ft)
6" Ø 8" Ø 10" Ø
t
45
100
N/A
N/A
45
85
Fig. 23: Vertical Venting
t
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