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GENERAL INFORMATION
Woodchuck furnaces represent the ultimate in solid fuel
and dual fuel heating appliances. From the massive
model 4000 to the economy model 526, each unit is de-
signed to be attractive, durable and efficient while pro-
viding the safety and comfort you and your family
deserve.
HIGH QUALITY CONSTRUCTION
Constructed of high grade, heavy gauge, hot rolled
steel plate, the firebox is continuously welded for an air-
tight seal and structural strength. The heavy duty cast
iron doors are equipped with a positive latching device
for your safety. The loading door has a two-step safety
latch. The large cast iron grates provide for durability
and help promote efficient combustion of the fuel. The
firebox is lined with heavy duty firebrick and is done so
without any retainers to warp or burn out. These fea-
tures together with high quality electrical components
provide the safety, efficiency and total control possible
only in a Woodchuck. Total control means that you can
better avoid overheating the unit and developing exces-
sive and unsafe temperatures.
Woodchuck furnaces are subjected to the most strin-
gent test criteria applicable by an independent third
party testing laboratory and listed/labeled as having
met or exceeded those standards. Finally, any ma-
chine, even this Woodchuck, is only as safe as the per-
son operating it. This is why we have compiled this
comprehensive manual to assist you in operating your
Woodchuck properly and safely. Please read and follow
all instructions.
EFFICIENCY
The total efficiency of a unit is broken down into com-
bustion efficiency and transfer efficiency. We know that
when woodburning, 20% of it burns as fixed carbon.
The other 80% is in the gaseous state as it burns.
Therefore, to obtain efficient combustion of the wood it
is necessary to introduce 20% of the oxygen “under”
the fire to promote combustion of the solid material and
80% “over” the fire where it can readily react with the
gaseous material. Coal burns just the opposite of wood.
80% of it burns as fixed carbon and 20% burns in the
gaseous state. Therefore, before a furnace can burn
coal or wood efficiently, it must provide the 80/20 ratio
of combustion air and allow the operator to reverse the
ratio depending on the fuel being used. Combustion air
must be warm when it enters the firebox to further pro-
mote complete combustion. Your Woodchuck furnace
provides all these features and more. Here is how:
when combustion air enters a Woodchuck furnace it en-
ters into a “draft
channel." Here it comes into contact with the hot fire-
box front and is warmed before entering the firebox.
The draft channel is equipped with adjustable orifices
which provide for the 80/20 distribution of the com-
bustion air. A lever on the front of Models 2900/4000
allows for quick and easy adjustment of these orifices
to correspond to the fuel being used. As the air enters
the firebox it strikes a deflector which creates a turbu-
lence and causes the oxygen to mix thoroughly with
the gases for complete combustion.
Finally, Woodchuck Model 2900/4000 furnaces are
designed to accept a catalytic combustor. This device
will cause the small amount of unburned fuel to ignite
before entering the secondary heat exchanger. The
benefits of all this are threefold:
A.) You obtain very high combustion efficiencies,
meaning you use less fuel.
B.) You reduce the amount of unburned fuel that can
collect in your chimney as creosote and hence reduce
the hazard of a chimney fire.
C.) You virtually eliminate pollution of the air we all
breathe.
Transfer efficiency refers to how effectively we trans-
fer the heat generated inside the firebox to the rooms
we want to heat. Insufficient blower capacity will result
in poor transfer allowing the unused heat to escape
up the chimney. This is why we utilize a blower with
such large air handling capacity. The large surface
area of the firebox and secondary heat exchanger
provide for efficient transfer.
COMFORT
Comfort and efficiency are closely related. The more
efficient the heating system is, the more comfortable
you and your family are. Not only are the Woodchuck
furnaces efficient, they can actually increase the effi-
ciency of your home.
On a furnace with a conventional single speed
blower, the speed of the blower is a compromise
between comfort and efficiency. If the blower has a
large enough capacity to heat the home in the cold-
est weather it will cycle rapidly in milder weather so
the system air is not as warm. If this air is moved
too rapidly it can actually feel cool. Air that is mov-
ing at 3 ft. per second will feel 4° cooler than sta-
tionary air at the same temperature. If the blower
capacity is enough to operate properly in mild
