Troubleshooting guide

Page 11
Why Pellets Burn
Simply stated, wood is stored energy from the sun. This stored energy, when heated, breaks
down into a gaseous state much like natural gas and carbon.
When these gases and carbon are in the proper environment both of them will burn and produce
heat.
How Pellets Burn
When wood is heated above approximately 500°F, part of it begins to break down into a gaseous
state. These gases will burn when they are in the presence of oxygen and a temperature above
approximately 1100°F. These gases burn as a yellow, white flame.
The remaining energy in wood is carbon. Carbon will begin to burn in the presence of oxygen
and at temperatures around 500°F. Pure carbon burns as a flameless glow.
Approximately 70% of the energy in wood comes from gases. Approximately 30% of the energy
comes from carbon.
Temperatures in a pellet fire may run as high as 1,900° to 2,300°F. At these temperatures
complete combustion can take place. These temperatures are also hot enough for some minerals
to melt and fuse into clinkers.
The proper amount of oxygen must be mixed with the gases and carbon, in a hot enough
environment for combustion to take place. The three T's are often used to describe these
requirements of combustion. These are Time, Temperature, and Turbulence. An improper
balance of any one of these items will cause a loss of combustion efficiency or cause the fire to
go out.
A properly designed and operating wood pellet stove will provide for the correct balance of all
the requirements of combustion. These are:
- Time - Fuel
- Temperature - Oxygen
- Turbulence
When pellets are burned properly combustion efficiency can be in the 99.9% range.
Too low a draft setting may provide inadequate air for a high fuel setting. A plugged burn grate
will also reduce the amount of combustion air. Too high a draft setting may provide too much air
and velocity. This will cool the burn grate area too much for a low burn to be maintained and can
result in creosote forming in the stove and venting system.
Learning how a properly burning flame looks, what drafts are needed for various settings, the
quality of fuel burned and it's characteristics are essential in diagnosing and solving operating
problems related to the pellet fuel.