6
OPERATION AND MAINTENANCE
OF ALTERNATE HEATING SYSTEMS
COAL-WOOD MULTI-FUEL BOILERS
Alternate Heating Systems Coal-Wood Boilers
are designed for burning coal with maximum
efficiency and convenience but will also burn
wood. Each unit is manufactured to burn
primarily wood or primarily coal. Units that are
manufactured to burn primarily wood have a
secondary combustion area where un-combusted
gases from the wood have a second chance to be
combusted. When burning wood the unit will
have to be loaded three to four times per day on
average (if the unit is loaded less often, then
creosote buildup in the chimney will occur).
WOOD VS COAL
The conditions required for burning the two
fuels efficiently are considerably different.
With coal the combustion air must be drawn up
through the bed of coal, whereas with wood the
air should enter through the door and the live
coals should be held in the center of the fire to
maintain a higher temperature for most efficient
combustion. Therefore Alternate Heating
Systems, LLC. Coal-Wood Boilers have two
different draft systems so that the proper system
can be used for each fuel. The grate system is a
unique rotary design which allows the air
opening size to be increased from a nearly solid
bottom to a very large exposed area.
When burning wood, the grates should be
rotated so that one side on all the grates are
horizontal, and the ashes and coals should also
be allowed to build up to a depth of four inches
or more. This will have the effect of sealing off
the bottom of the firebox, preventing
combustion air from entering from below. The
grates should only be rotated when it is
necessary to remove some ash, being careful to
maintain sufficient ashes to insulate the bottom.
When burning coal the draft control linkage on
the loading door must be disconnected and
replaced with the chain linkage that is provided.
When burning coal it may be necessary to rotate
the grates slightly to increase airflow through
the fire.
COAL TYPES
Alternate Heating Systems, LLC. Coal-Wood
Boilers operate best when a good grade of hard
coal is burned since it has a high output of
energy and low ash and sulfur content. Either
“stove” or “nut” size should be used. The larger
size of these two produces the hottest fire
because it allows freer movement of air through
the burning mass. However “nut” size hard coal
will burn longer at a more even rate and a
mixture of the two sizes may prove to be the
most ideal.
Good grades of soft coal can be burned in the
Alternate Heating Systems, LLC. Coal-Wood
Boilers provided the ash and sulfur content is
low enough. Soft coals generally produce
considerably more ash than do hard coals and
also tend to “clinker” (or fuse together)
producing lumps of ash residue. When adding
soft coal to the fire it is important not to smother
the fire, preventing a free flow of combustion
air though the burning fuel.
