draft regulator. A flue-gas analysis should be made and the unit adjusted so that between a 8% and 10%
CO
2
is registered.
TYPES OF COMBUSTION AIR FOR WOOD HEATING
Unlike older airtight box heating appliances, low emission furnaces have more than one location and
control for supplying combustion air into the firebox. These additional air inlets allow for near complete
combustion of wood gases and particulates. Thus it is important to understand how these different air
supplies work.
PRIMARY AIR starts the fire. Opening or closing this air supply then regulates how fast the furnace will
burn. A hot coal bed requires less Primary Air to restart a fresh load of firewood.
It is very important to keep the secondary flames burning to maximize heat output and minimize air
pollution, so some experimentation will be necessary because each installation is different. Wood
moisture content will also affect the amount of time that a unit will need to burn on high after each reload.
By means of a slide Draft Control above the fire door, you can control the amount of combustion air
allowed into the fire box. Move this slide plate to the open position that allows sufficient combustion air in
for the type of solid fuel you are burning. For added efficiency, when heating with oil only, close the slide
plate and adjust your solid fuel thermostat to its lowest temperature setting.
FURNACE LABEL ILLUSTRATION
SECONDARY AIR allows the appliance to burn clean. This preheated air enters the upper firebox just
above the fire. This superheated air mixed with the wood gases and flames ignites, reaching
temperatures in the 1100F to 1600F range. Without Secondary Air these volatile gases would exit the
furnace unburned as creosote, smoke, particulates, and high levels of Carbon Monoxide, greatly
decreasing efficiency. Heat comes from burning the wood gases, not the wood, which itself turns into
black charcoal after the gases are all released. Secondary air increases the efficiency by approximately
40% greatly reducing the amount of wood required for a heating season (up to 1/3 less wood).
SECONDARY AIR INLETS are located below the firedoor. (See Diagrams 4,5 & 6)
NEVER ATTEMPT TO BURN YOUR BOILER WITH THE SECONDARY AIR SLIDER CLOSED OR
YOUR BOILER WILL BURN DIRTY, PRODUCE CREOSOTE AND BE LESS EFFICIENT. THE
SECONDARY AIR INLETS MUST BE LEFT IN THE OPEN POSITION TO BURN OPTIMALLY.
WATCH YOUR CHIMNEY – If you cannot see any visible smoke coming out of your chimney, you are
operating your appliance correctly. If you can see smoke, then adjust the additional Primary Air until the
smoke disappears. Remember, smoke equals lost heat!
CAUTION: Do not operate the boiler with the loading door open. Continuous operation with the door
open may lead to overheating.
REFUELING
The loading door should be closed at all times except when refueling. Before opening the loading door,
make sure the draft fan is operating. Allow the fire to burn rather briskly for a few minutes. Then open
the loading door slowly. By allowing the fire to increase for a short period, a high draft condition has
eliminated smoke in the firebox and the temperature has been raised which prevents a back or down
draft.
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