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For diameters 14" to 30", the termination must
terminate as per Figures 38 and 39.
A cap or chimney housing offers resistance
to the entrance of rain, snow and debris, as
well as birds, and will minimize the effect of
wind on the vent. It will protect the vent from
down drafts due to a wind that impinges
directly upon the vent. A reminder also to
homeowners to check the rain cap for icing
during low ambient temperatures.
However, no vent cap, cowl, or top can
overcome the adverse effect of a region
of high static pressure around the vent
terminal or the effect of an interior region
of low pressure. Regions of high static
pressure around the vent terminal can be
avoided by following the general rule for the
vent termination given previously. Low or
negative interior pressures in the building
may be caused by (1) failure to provide for
combustion air, (2) excessive use of exhaust
fans, and (3) tight construction resulting in the
lack of infiltration air.
10' MIN
1. To ensure a waterproof roof structure,
use the appropriately sized flashing and
storm collar where the vent penetrates the
roof. Place the Storm Collar over the vent
until it is level. Apply a thick horizontal ring
of nonhardening, high-temperature sealant
such as silicone, around the vent at the top
of the Storm Collar.
2. Vents in excess of 5 feet above the
roof should be securely guyed to prevent
unnecessary movement. Attach guying to the
vent. Never attach guying to the cap.
2' MIN
Fig. 38
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
10' OR LESS
2' MIN
2' MIN
WALL OR
PARAPET
Fig. 39
3. To prolong life and appearance of
galvanized steel parts located outside, use
proper painting procedure.
a. Remove oil and dirt with a solvent.
b. Paint with primer specifically recommended
for adhesion to galvanized steel.
c. Apply finish coat.
Checking Vent Operation
After adjusting appliance and lighting
main burner, allow several minutes for
w a r m - u p t o b e g i n v e n t i n g a c t i o n .
For water heaters and equipment with draft
hoods, hold a lighted match along the rim of
the draft hood relief opening of the appliance.
Proper venting will draw the flame up or into
the draft hood. Improper venting, indicated
by escaping or spilling of burned gas, will
cause the match to flicker or go out. When
consulting Standard NFPA 54 or CSA-
B149.1-00., follow procedures for conducting
safety inspections of existing appliances
and placing equipment in operation, paying
particular attention to the section titled
Checking the Draft (see Fig. 18).
Painting
For any CAN/ULC-S605 applications any
exterior exposed gas vent above the roofline
will require painting to prolong the life and
appearance of the galvanized steel outer
casing. Use proper painting procedure at
time of installation. Remove oil and dirt with
a solvent. Paint first with a good quality
zinc primer or other primer recommended
for use on galvanized steel. Next apply an
appropriate finish coat.
2' MIN
NOTE: NO
HEIGHT ABOVE
PARAPET
REQUIRED
WHEN DISTANCE
FROM WALLS
OR PARAPET IS
MORE THAN 10'
25
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