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Form#7.2-248 Issue#2
7
3.
Competition for available air.
Third, there must not be too much
competition from other devices in the boat, such as exhaust fans, a
large engine or air-exchange systems. If something else is sucking the
air out of the boat, the chimney might not be powerful enough to
overcome it, and exhaust might be drawn back into the boat from the
chimney.
4.
Proper chimney design.
And finally, a chimney must be designed to
accommodate the volume and type of exhaust being emitted by the
appliances it serves. This involves correct sizing, adequate height, and
proper construction. See the “Chimney Pipe” section on pg. 9.
Since the chimney draft is affected by so many factors, draft problems
can be complicated to find.
Testing the Draft
To find where the air is being drawn, twist a paper towel into a wick, light it
and blow it out to create smoke. Placing the smoking wick near the open
hatches, windows or vents will lead you to the location. Installing or opening
opposing vents will allow the air to come in from a path of least resistance
and not disturb the draft in the chimney.
Downdraft
A common reason for downdraft is burning the heater too low (too much air
in the burner and not enough fuel). If the flames are burning below the top
burner ring and inside the burner pot then it is burning inefficiently causing
the draft to be too weak going up the chimney allowing downdraft down the
chimney. When the flames are burning above the top ring then the natural
draft is at its strongest so it can fight against downdraft.
5. Installing your Stove
Location
Plan your stoves location prior to installing to ensure the location chosen
will fit the specifications and safety clearances. Combustible material closer
to the stove then the specified safety clearances must be lined with insulation
or millboard and a metal liner with a .5” standoff for air movement behind.
Another alternative is using insulation or millboard and ceramic tile. The
back of the stove and the first length of chimney pipe should also be lined
with such material. See diagram below.
