Control of the woodburning section of the furnace is by adjustment of the primary air control located on the top
rear right corner of the HMF150/200. This control operates in two set positions - "Full Open" allowing maxi-
mum combustion air delivery to the
fi
re box and "Closed", providing minimum primary air to the
fi
re box to as-
sist the development of secondary or gasifying burn in the top of the
fi
re box (Note that secondary combustion
air enters through two inlets on the front of the furnace either side of the ash lip tray and is not adjustable).
In the automatic mode the adjustment of primary air is accomplished
using a shutter connected to a small servo motor. The control circuit-
ry will energize the motor if it detects the room thermostat is calling
for heat and the high limit sensor in the supply plenum has not been
surpassed (greater than 250°F (121°C)). The primary air shutter will
be fully opened and will remain so unless the room temperature has
been satis
fi
ed or too much heat is detected in the plenum.
H3.62
IN NO WAY SHALL THE PRIMARY AIR CONTROL SYSTEM BE ALTERED TO INCREASE COMBUSTION
AIR FLOW GREATER THAN THE FACTORY PRESET MAXIMUM.
Carbon monoxide is a colourless, odourless, and tasteless gas that is toxic when inhaled, and can be fatal
depending on concentration levels and exposure time. Note that although carbon monoxide will be present in
poor combustion process that creates smoke (as described above), it is not necessary for smoke to be pres-
ent while high levels of carbon monoxide are being created. An example of this takes place when a wood
fi
re
has reduced down to the coal state and the draft starts to reduce as less heat is available to keep the chimney
warm. Some level of carbon monoxide is being generated in all stages of the combustion process regardless
of the fuel.
Several precautions can be taken to minimize the risk of carbon monoxide poisoning occurring.
• The
fi
rst is to run the furnace in the most ef
fi
cient manner possible to reduce the levels of carbon monoxide
being generated. Using well seasoned dry wood and establishing the correct operating draft as laid out in
these operating instructions will help limit CO emissions.
•
Building Pressure - if the combustion air for an appliance (as with this wood furnace) comes from within the
building that the appliance is located there will be a tendency for the internal building pressure to become
negative. There must be adequate mechanical ventilation supplied to the building to neutralize the build-
ing pressure otherwise there is a risk of reversing the
fl
ow of exhaust
fl
ue products back into the building.
These
fl
ue products may not only come from the wood furnace but also from other combustion appliances
in the building. The Hybrid Wood Furnaces come supplied with a 4" (10 cm) vent for direct connection to
outdoor combustion air. Although the wood furnace still relies on room air for the secondary burn process
the connection of outdoor primary combustion air to the furnace will help reduce the amount of mechanical
ventilation required to prevent negative building pressures.
•
Smoke Alarms and Carbon Monoxide Detectors - Smoke alarms and carbon monoxide detectors are not
only important tools for protecting the inhabitants of a building but they are mandated in many jurisdic-
tions. Although these items should be located on every level of a building there are two locations that are
of prime importance. The
fi
rst is in the sleeping areas of the building, and the second is in the location to
where the combustion process is taking place. Check with local codes for details of alarm/detector re-
quirements.
8.3 CONTROL SYSTEM - WOOD FURNACE
W415-1506 / A / 12.04.15
72
IOM
EN
