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Combustion
Air Supply
Exhaust
Configuration
Heater Venting
Category
Certified
Materials
Combustion Air
Inlet Material
Vertical
Venting
From Inside Building
(Non-Direct Venting)
Horizontal Through-
the-Wall Venting
Vertical
Venting
From Outside Building
(Direct Venting)
Horizontal Through-
the-Wall Venting
IV
Stainless Steel
AL29-4C
Galvanized Steel
PVC
ABS
CPVC
T
able K: Venting Category Requirements
Vent Terminal Location
1. Condensate can freeze on the vent cap. Frozen
condensate on the vent cap can result in a blocked
flue condition.
2. Give special attention to the location of the vent
termination to avoid possibility of property dam-
age or personal injury.
3. Gases may form a white vapor plume in winter.
The plume could obstruct a window view if the ter-
mination is installed near windows.
4. Prevailing winds, in combination with below-freez-
ing temperatures, can cause freezing of
condensate and water/ice build-up on buildings,
plants or roofs.
5. The bottom of the vent terminal and the air intake
shall be located at least 12 in. above grade, includ-
ing normal snow line.
6. Un-insulated single-wall Category IV metal vent
pipe shall not be used outdoors in cold climates for
venting gas-fired equipment without insulation.
7. Through-the-wall vents for Category IV appli-
ances shall not terminate over public walkways or
over an area where condensate or vapor could
create a nuisance or hazard or could be detrimen-
tal to the operation of regulators, relief valves, or
other equipment.
8. Locate and guard vent termination to prevent acci-
dental contact by people or pets.
9. DO NOT terminate vent in window well, stairwell,
alcove, courtyard or other recessed area.
10. DO NOT terminate above any door, window, or
gravity air intake. Condensate can freeze, causing
ice formations.
11. Locate or guard vent to prevent condensate from
damaging exterior finishes. Use a rust-resistant
sheet metal backing plate against brick or mason-
ry surfaces.
12. DO NOT extend exposed vent pipe outside of
building beyond the minimum distance required
for the vent termination. Condensate could freeze
and block vent pipe.
U.S. Installations
Refer to the latest edition of the National Fuel Gas
Code.
Vent termination requirements are as follows:
NOTE: During winter months check the vent cap
and make sure no blockage occurs from build-up of
snow or ice.
Use only the special gas vent pipes listed for use with
Category IV gas burning heaters, such as the AL29-4C
stainless steel vents offered by Heat Fab Inc. (800-
772-0739), Protech System, Inc. (800-766-3473),
Z-Flex (800-654-5600) or American Metal Products
(800-423-4270). Pipe joints must be positively sealed.
Follow the vent manufacturer’s installation instructions
carefully.
Support of Vent Stack
The weight of the vent stack or chimney must not rest
on the heater vent connection. Support must be pro-
vided in compliance with applicable codes. The vent
should also be installed to maintain proper clearances
from combustible materials. Use insulated vent pipe
spacers where the vent passes through combustible
roofs and walls.