Firewood moisture content debate for EPA FURNACE

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bholler

Chimney sweep
Staff member
Jan 14, 2014
28,701
central pa
Not entirely true.

There are a number of members here who are completely satisfied with burning the drier wood in their appliances that call for a "non-traditional MC".
Ok I am confused what you are saying here. I say dry wood is better and I am told I am wrong here. Then you provided a link saying wetter wood was better for gasifiers and I said ok that may be true for that type of appliance. And I am still wrong??
 

LogCabinFever

New Member
May 24, 2021
39
CT, USA
this is getting weird. Bottom line, drier = more BTUs. Period. However, according to the wood gun document, the driest fuel burns with less control and with a few downsides. Though both Wood Gun and Kuuma both recommend the same moisture content, it is for entirely different reasons. One says it’s for more BTUs, the other for more controllable burn and less “backpuffing”.

I could see the argument for wetter wood burning more controllably, but I would think the trade-off to sacrifice BTUs would not be worth it, especially if we are spraying wood!
 

woodey

Feeling the Heat
Feb 8, 2018
327
ST. Lawrence Valley N.Y.
Fortunately the Kuuma doesn’t require that you have a garden hose close by for safe burning. I would state that my Kuuma loves dry wood (stacked/ covered 3 years) but that would be repetitive to what others have already said, so I won’t mention it.
 

JRHAWK9

Minister of Fire
Jan 8, 2014
1,869
Wisconsin Dells, WI
Fortunately the Kuuma doesn’t require that you have a garden hose close by for safe burning.

;lol

You mean the holes on the front of the furnace which connect to "sprinkler like" tubes on the inside aren't for watering down the wood?? Crap, I better put my hose away then.
 

yooperdave

Minister of Fire
Oct 26, 2010
1,220
Michigan's U.P.
Let me try this again. Had no intentions to confuse @bholler !

We have been hearing that dry wood is better, right?

And with the systems (appliances) that "we" have used for decades, this has proven true, right?

And manufacturers recommend the lower MC in use of their appliances in order to reach the optimum efficiency, right?

And those manufacturers all had to undergo epa testing to get their certifications and ratings, right?

And said testing is under controlled conditions with controlled MC fuels, controlled draft, etc. ...right?

Well, now here we are with a couple of manufacturers that say they have designed appliances that will efficiently burn firewood with higher MC than what we are used to and burn it safely, cleanly and efficiently.

Don't you think that those same manufacturers would get an even higher efficiency rating from the epa if they used the lower MC firewood? It would only be to their advantage to require fuel with MC of ....14% (?) instead of 20%-30%.

There must be a reason why they want the higher MC fuels........
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
28,701
central pa
Let me try this again. Had no intentions to confuse @bholler !

We have been hearing that dry wood is better, right?

And with the systems (appliances) that "we" have used for decades, this has proven true, right?

And manufacturers recommend the lower MC in use of their appliances in order to reach the optimum efficiency, right?

And those manufacturers all had to undergo epa testing to get their certifications and ratings, right?

And said testing is under controlled conditions with controlled MC fuels, controlled draft, etc. ...right?

Well, now here we are with a couple of manufacturers that say they have designed appliances that will efficiently burn firewood with higher MC than what we are used to and burn it safely, cleanly and efficiently.

Don't you think that those same manufacturers would get an even higher efficiency rating from the epa if they used the lower MC firewood? It would only be to their advantage to require fuel with MC of ....14% (?) instead of 20%-30%.

There must be a reason why they want the higher MC fuels........
Because their designs can't handle the initial rapid off gassing from dry wood. That is the reason. The link you provided clearly said that. If they can't handle that off gassing they won't pass the emissions testing and can't be sold. It isn't anything complicated at all really. The are using that moisture to slow off gassing in the initial phases so their system is not overwhelmed.

But again drying wood absolutely does not reduce BTU content.
 

maple1

Minister of Fire
Sep 15, 2011
10,933
Nova Scotia
Air requirements vary greatly for widely differing moisture contents. And most wood burning appliances are not designed to vary the air supply (not just amount, but primary/secondary balance) as widely as the m/c of the fuel they might see. The main exception would be Lambda controlled gasifiers. That use an O2 sensor in the exhaust stream to control air supply and primary/secondary balance. Manufacturers could design for very dry wood, but kind of pointless when most users won't feed it that.
 
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stoveliker

Minister of Fire
Nov 17, 2019
4,590
Long Island NY
Well, that change in attitude ("when most users won't feed it very dry wood") may be part of the thing that is needed. In stoves that has been worked at by newer EPA standards that lead to design changes that lead to users being forced to use dry wood in order to get the performance they want.
 
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laynes69

Minister of Fire
Oct 2, 2006
2,669
Ashland OH
I think going from cribwood to cordwood was the right move for testing. The EPA site recommends wood at least 6 months seasoned and 20% and under for optimal burning. Using cordwood gives you a more realistic expectations on use. However, drier wood is obviously better. Having an automated furnace, I've burned fresh cut dead ash at 23 percent moisture without a hitch. I've also burned 15 percent ash without a hitch. Having an automated unit, the servos adjust based on firebox temperatures for a clean burn. Dry wood just means that the firebox gets hotter quicker and computer closes the dampers sooner. I've burned wood I never could've burned in the old unit thanks to the self regulation.
 
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salecker

Minister of Fire
Aug 22, 2010
1,813
Northern Canada
Types of wood make a difference as well
Econoburns are designed in the east,where hardwood rules
All i have to burn is spruce.Dry spruce off gasses way quicker than hardwood.I was told my splits should be the size of a playing card.Over the years my splits have gotten bigger and that has slowed down the back puffing at times,brought down my flue temps.Additional modifications have continued to bring down flue temps and very rarely do i get back puffing.Right after loading i get the highest fuel temps and back puffing if it happens.Now anything under 10" does not get split.
If i get a piece of bad wood or high moisture content i can tell right away the next time i reload.Storage temps will be lower than normal and the wet wood will still be there at the next reload.
 
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