Combustion Settings; Smoking Causes And Troubleshooting - HearthStone WFP-75 Owner's Manual

2.2.7 Combustion Settings

Accelerated Combustion (High)
The maximum heat output for the WFP-75 is achieved by burning with the door closed and
the combustion air opened. By this method, the WFP-75 can produce up to 75,000 BTU of
heat per hour. However, it will be necessary to reload with wood every one or two hours.
This is the least efficient method of burning the WFP-75. Use caution when firing with the
combustion air control wide open. Only burn cordwood in this manner. Small dry pieces
of softwood and construction scraps will burn very intensely using this method and may
damage the firebox.
Medium Combustion
This is the recommended mode of operating the WFP-75 and should be the one normally
used since it will deposit the least amount of creosote on the glass and in the chimney. The
combustion air control must be ¾ closed. The precise setting will depend on many factors,
including chimney length and the moisture content of the wood.
To obtain the proper combustion, close the combustion air control completely, then open
it about ¼" to ½". For shorter chimneys, open the combustion air control more, for longer
chimneys, open the combustion air control less. Three medium size pieces of wood should
be burning on a bed of hot coals. The heat output will be approximately 35,000 BTU per hour
and the loading time will be every 3-4 hours. Softwoods may be burned using this method
but the time will be substantially reduced.
Slow Combustion
When the air combustion control is completely closed, the fireplace is in a slow combustion
phase. If the fireplace is hot enough, slow combustion will not stop the fire, but there will be
a noticeable change in the flame pattern. The flames will be slow and may appear dirty if the
wood is too wet (moisture content of 20% and more). Do not allow the wood to burn without
flame, since this will produce excessive creosote in the unit.
Creosote may accumulate on the glass door. This method of burning should be used only
after operating the WFP-75 with the air control opened to produce a hot fire for about an
hour or at medium pace for at least 2 hours. Slow combustion can be used at night in order
to reduce the heat output and to prolong the burn. The loading time will be every 6-8 hours.

2.2.8 Smoking Causes and Troubleshooting

To reduce the likelihood of smoking when opening the door, set the combustion air controls
to the right (High) before opening the door. Occasionally, there may be a small amount of
smoking upon lighting the fire, until the chimney heats up but this should not continue. If the
fireplace continues to smoke it is probably for one of the following reasons:
A. Negative pressure in the house
As the fire burns, air goes up the chimney. This air must be replaced through leakage
into the house or by connecting to fresh, outside air. When operating the WFP-75, open a
nearby window temporarily to check if there is adequate air supply replacement. If opening a
window solves the problem, the house is under negative pressure.
Hearthstone Quality Home Heating Products, Inc ® 7 WFP-75 Model 8410