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(This information is based on emission test results done with a
Finnish contraflow heater design with a grate and air supply from under and in
front of the grate)
Whether you're a seasoned masonry heater owner or are reading this as a new
owner, there are some newly discovered firing techniques you will want to employ
to get the most out of your hearth.
- Use regular cordwood! Yes, it is not necessary to burn sticks 2" to
3" across to get the rapid, complete combustion that masonry heaters are noted
for. Actually, 4" to 6" pieces such that 9 to 12 pieces will fill your firebox
when cross hatched will provide better air/fuel ratio for complete, and more
usable combustion. The bigger pieces allow more time for the masonry mass to
soak up the fire's heat - yielding better heat transfer to your home.
- Place smaller wood, kindling and paper on top of this load and light
from the top! The revolutionary top burn greatly reduces emissions during the
dirtiest part of a firing - the first 10 minutes or so. Lighting the load from
the top of the pile yields a candle-like burn, allowing the firebox to heat up
as the volatile gases are being more evenly released.
- Take a little extra care in laying up your fire. A good "fuel load
configuration" is well balanced and won't topple over prematurely. Allow a 1"
airspace between pieces, placing the largest pieces first and the bottom row
running "front to back" in the firebox.
- Don't admit air from below the grate until the fire is down to coals. Use
the air slots in the door, if provided. If not, cut scrap dimensional lumber so
that a piece will cover the grate and air is admitted from the front. With a top
burn fire the piece will block grate air until it is burned through - well into
the firing. Alternately, you can adapt your doors so that they will 3/4 inch of
air between them but can not be accidentally be opened further. This
modification was lab tested for emissions with excellent results. During the
coal burning phase, rake the coals so they evenly cover the grate with air
coming from below.
- It is more efficient to have one full firing than 2 fires half as large.
If you've been burning small pieces kindled at the bottom in your contraflow
heater, chances are there is soot in the heat exchange channels. This can
effectively be cleaned from the cleanout door usin a rod and brush designed for
cleaning pellet stove chimneys. This will better allow them to absorb heat from
future fires.
Burning cordwood has so many benefits, economy-wise. And as you're probably
aware, masonry heaters provide the cleanest burning solid fuel appliances
available. Now, following these simple practices you can be assured that you are
providing yourself and your loved ones simple, yet state-of-the-art heat more
cleanly than ever. |
Great explanation, thanks for the posting! Performance Parts
ReplyDeleteVery informative content. After reading this, dealing with the heating issue becomes quite interesting and easy. Keep on sharing such fruitful concepts in future as well.
ReplyDeleteThis is exactly what I have been doing with my TempCast masonry stove. It did not come with air access below the grate, so I inserted a 2" black iron pipe through the wall about three inches below the grate. I screw a cap onto the pipe until the fire has burned down to a bed of coals, then I remove the cap and partially close the opening that feeds around the door frame. This reduces burn-time by about an hour and saves valuable heat from escaping through the chimney.
ReplyDeleteMy question is, "Can a fire burn too hot for the stove?" I use very dry black locust and hedge-apple wood, and it burns extremely fast and hot. I must wear gloves and long sleeves when I use a 30 inch poker to level out the burning coals on the grate, and any exposed flesh will burn quickly from the radiant heat. The firebrick has a vertical crack between the door frames and a vertical hairline crack in the back just above the grate. The brick enclosure also has a vertical hairline crack between the two doors. This is the second year firing the stove. Are cracks inevitable, or am I doing something wrong that is causing them? I have not exceeded the recommended 100 pounds of wood per day, and average about 1.5 burns per day.
I would like to see proof that it is better to burn 4-6 inch pieces of wood than 2-3 inch pieces. Longer burning times mean longer times for heat to escape up the chimney. I close the damper as soon as possible, even before all coals are out. But I never do that unless all doors to the stove have been opened to allow sufficient oxygen to get to the remaining live coals. Not opening all doors will starve the live coals from oxygen and cause the formation of deadly carbon monoxide. I have a carbon monoxide detector located a few feet from the masonry stove and will know if any carbon monoxide is generated. The main drawback of closing the damper early and opening the stove doors is the release of a small amount of ash dust into the air.
ReplyDelete