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Support of Vent Stack
The weight of the vent stack or chimney must not rest on
the heater vent connection. Support must be provided 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.
Vent Terminal Location
NOTE: During winter months check the vent cap and
make sure no blockage occurs from build-up of snow
or ice.
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 termination
is installed near windows.
4. Prevailing winds, in combination with below-freezing
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. (305 mm) above grade,
including normal snow line.
6. Uninsulated 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 appliances
shall not terminate over public walkways or over
an area where condensate or vapor could create
a nuisance or hazard or could be detrimental to
the operation of regulators, relief valves, or other
equipment.
8. Locate and guard vent termination to prevent
accidental 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 masonry
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.
WARNING: The Commonwealth of Massachusetts
A
requires that sidewall vented heaters, installed in every
dwelling, building or structure used in whole or in part
for residential purposes, be installed using special
provisions as outlined on page 56 of this manual.
Vent termination requirements are as follows:
1. Vent must terminate at least 4 ft (1.2 m) below, 4 ft
(1.2 m) horizontally from or 1 ft (30.5 cm) above any
door, window or gravity air inlet to the building.
2. The vent must not be less than 7 ft (2.1 m) above
grade when located adjacent to public walkways.
3. Terminate vent at least 3 ft (.9 m) above any forced
air inlet located within 10 ft (3 m).
4. Vent must terminate at least 4 ft (1.2 m) horizontally,
and in no case above or below unless 4 ft (1.2 m)
horizontal distance is maintained, from electric
meters, gas meters, regulators, and relief equipment.
5. Terminate vent at least 6 ft (1.8 m) away from
adjacent walls.
6. DO NOT terminate vent closer than 5 ft (1.5 m) below
roof overhang.
7. The vent terminal requires a 12 in. (305 mm) vent
terminal clearance from the wall.
8. Terminate vent at least 1 ft (305 mm) above grade,
including normal snow line.
9. Multiple direct vent installations require a 4 ft (1.2 m)
clearance between the ends of vent caps located on
the same horizontal plane.
Canadian Installations
Refer to latest edition of the B149 Installation Code.
A vent shall not terminate:
1. Directly above a paved sidewalk or driveway which
is located between two single-family dwellings and
serves both dwellings.
2. Less than 7 ft (2.1 m) above a paved sidewalk or
paved driveway located on public property.
3. Within 6 ft (1.8 m) of a mechanical air supply inlet to
any building.
4. Above a meter/regulator assembly within 3 ft (.9 m)
horizontally of the vertical centerline of the regulator.
5. Within 6 ft (1.8 m) of any gas service regulator vent
outlet.
6. Less than 1 ft (305 mm) above grade level.
7. Within 3 ft (.9 m) of a window or door which can
be opened in any building, any non-mechanical air
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