11
o
The equipment shall have clearances of at least 1 inch
from the sides and back and 6 inches from the front of the
appliance.
o
The opening shall directly communicate with the outdoors
and shall have a minimum free area of 1 square inch per
3000 BTU's per hour of the total input rating of all
equipment located in the enclosure, and not less than the
sum of the areas of all vent connectors in the confined
space.
Figure 3
– All Air From Outside, One Opening
3.2.4
– Exhaust Fans
Any fan or equipment which exhausts air from the equipment
room may deplete the combustion air supply and/or cause a
downdraft in the venting system. Spillage of flue products from
the venting system into an occupied space can cause a very
hazardous condition that must be immediately corrected. Sealed
combustion should be selected in cases where exhaust fans
cannot be avoided or isolated.
3.3
– Installation and Termination
3.3.1
– Vertical Configuration Guidelines
Rooftop Vent Terminations:
o
Rooftop vents can terminate vertically, but in areas where
heavy rainfall is projected, a rain cap should be
considered. Rain entering the venting will drain out
through the condensate removal system, but may waste
neutralizer media, so it should be avoided where possible.
o
Position terminations so they are not likely to be damaged
by foreign objects, or exposed to a build-up of snow, ice
debris, etc., which can cause a blocked flue condition.
o
Position vents away from points of roof top access (i.e.
hatches and walkways) whenever possible.
o
Flue gas condensation can freeze on the vent cap
causing a blocked flue situation. Select proper diameter
piping and cap designs to avoid excessive ice build-up.
o
NOTE:
If the hydronic system design uses high water
temperatures, uncondensed water vapour in the flue
products will find its way into the vent, and could form
large plumes of steam at the vent termination. This is not
harmful to the water heater but can be unsightly. The
steam can also cause discoloration on exterior building
surfaces. Adjacent brick or masonry surfaces should be
protected with a rust resistant sheet metal plate.
Rooftop Combustion Air Inlets:
o
A roof top air inlet consists of two 90° elbows. The first 90°
elbow is installed on the rooftop at the highest vertical
point of the air inlet pipe and turned horizontal; the second
90° elbow is screened and is installed on the horizontal
outlet of the first elbow and turned down. If a straight piece
of pipe is used between the two elbows, it should not
exceed 6" (150mm) in length. A bird screen should be
installed on the open end of the second elbow.
o
Combustion air supplied from outdoors must be free of
contaminants.
o
Incorrect installation and/or location of the air inlet cap can
allow flue products to be drawn back into the appliance.
This can result in incomplete combustion and potentially
hazardous levels of carbon monoxide in the flue products.
This will cause operational problems with the appliance
and if left uncorrected, will lead to conditions that can
cause personal injury or death.
Clearances
:
o
The vent terminal must exhaust outside the building at
least 2 feet (0.61M) above the highest point of the roof
within a 10 foot (3.05M) radius of the termination.
o
A vertical termination less than 10 feet (3.05M) from a
parapet wall must be a minimum of 2 feet (0.61M) higher
than the parapet wall.
o
The termination of the vent/air intake must be a minimum
of 3 feet (0.91M) above the roof penetration, and at least
12 inches (30cm) above the projected snow level.
o
The inlet MUST be at least 1 foot (0.3M) below the point
of flue gas termination (vent cap) if located within a 5 foot
(1.5M) radius of the flue outlet. Ensure that the 90° elbow
assembly is properly installed on the air inlet pipe.
Vertical Direct Venting Configuration
Concentric Venting
- Kits can be ordered to provide venting
and combustion air supply through one opening. Vent/air pipe
still limited a
maximum 100 equivalent feet (30.5M) in length.
Vertical Concentric Vent Clearances