-21-
Combustion Air & Balanced Draft
Sig Marine heaters only are unique in that they can be fitted with a balanced draft flue
installation. The draft system is, generally speaking, how the heater/stove gets
combustion air and how it expels the exhaust. To guarantee that sufficient oxygen (fresh
air) is available for your heater/stove, good ventilation is essential. It is necessary to
replace the air inside your boat at the same rate that the heater/stove is removing it. The
higher the heater’s burning rate, the more air the heater/stove will require. If the air flow
is blocked (the ‘draft’) or restricted, the heater/stove will burn inefficiently, create soot or
even blow out.
A permanently open fresh air inlet must be installed. This inlet must be at least 3" in
diameter. Ducting fresh air to the heater/stove is most satisfactory. It is important to
create and maintain a positive pressure inside the boat.
High winds can draw air from the boat and thus create a negative pressure. This
condition can result in down drafts. Ensure that when you do have widows open that they
do not create a suction effect in the cabin due to the window’s position and the wind
direction. In a similar way, it is possible for the air intake on your engine to suck the air
out of a cabin if it is not properly vented. Your heater/stove is a natural draft appliance
and
