On Jan 27, 1:37*pm, "Bob F" wrote:
Andrew wrote:
On Jan 25, 4:29 pm, "Bob F" wrote:
FBWNDR wrote:
I'm trying to determine the pros and cons of having a wood boiler
installed on my property. *If you haven't heard of these, the boiler
is built to circulate water around the firebox. *The water gets
pumped into a heat exchanger which is located in the main heating
duct of the house. *The existing indoor furnace pushes the air
around the house.

Anyway, I'm looking at aHeatmorboiler, and I'm now looking for
people who have experience with these. *The website says that the
boiler has a forced draft fan (75 cfm). *It also says that the
boiler can heat a 3000 square foot house. *I know a little about
combustion, and I calculated that with 75 cfm, you cannot burn more
than 10 lbs of wood an hour. *And if the wood is 45% moisture, then
the available BTU is around 40,000 BTU. *A 40,000 BTU furnace is
very small for a 3000 square foot house.

45% seems awfully high for moisture content.
Fromhttp://extension.oregonstate.edu/news/story.php?S_No=829&storyType=garde

Seasoned firewood contains less than 20 percent moisture and
generally takes
from six to eight months - and sometimes up to more than a year - to
dry, or
cure. Much depends on the weather, the type of wood you have and how
you prepare
and store it. Hardwood such as oak takes longer to dry than softwood
like
Douglas fir or pine.

I do a lot of work on wood fired boilers - the large ones used in
power plants. *A 45% moisture content is not unusual. *Kiln dried wood
is only 10-20%. *But in looking over my numbers I noticed that made a
chemistry mistake, a big one, confusing moles of air for lbs of air.
I have recalculated my numbers based on ambient air of 20 degrees
(down from 40 degrees), and I used a series wood moisture contents.
This is assuming perfect combustion, and all the air is used is
combustion.

Fuel moisture content * * *Wood fuel lbs/hr * Available BTU/Hr in fuel
45% * * * * * * * * * * * * * * *71 * * * * * * * * * *246918
35% * * * * * * * * * * * * * * *60 * * * * * * * * * *260936
25% * * * * * * * * * * * * * * *52 * * * * * * * * * *268641
15% * * * * * * * * * * * * * * *46 * * * * * * * * * *275632

So, I guess that little fan does push enough air to burn enough wood.
So now I have to look into the pollutant problem. *According to this
thread, there are a few states where these are being outlawed.

That chart says something significant for drying your wood well, expecially when
you consider the cleaner burning of dry wood. Even if you calculate in that 15%
wood is lighter than 45%, you still get way more heat out of less wood.

I agree that drying the wood will save some money. But the boilers
are rated at 100,000 BTU, which is less than half of the energy
released from the wood. If the wood is not combusted, then it is
going out of the stack in the form of gases and particulates. I sure
would like to know what kind of smoke to expect.