Table L: 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:
1.
Vent must terminate at least 4 ft below or 4 ft hori-
zontally from any door, window or gravity air inlet
to the building.
2.
The vent must not be less than 7 ft above grade
when located adjacent to public walkways.
3.
Terminate vent at least 3 ft above any forced air
inlet located within 10 ft.
4.
Vent must terminate at least 4 ft horizontally, and
in no case above or below unless 4 ft horizontal
distance is maintained, from electric meters, gas
meters, regulators, and relief equipment.
NOTE:
During winter months check the vent cap
and make sure no blockage occurs from build-up of
snow or ice.
from combustible materials. Use insulated vent pipe
spacers where the vent passes through combustible
roofs and walls.
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
CAT IV
AL29-4C
Galvanized Steel
PVC
ABS
CPVC
California Hot Water Supply, Inc.
(800) 249-7244
23
