Firewood moisture content debate for EPA FURNACE

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Micdrew

Member
Jan 15, 2021
53
Maryland
Ok so I’ve been reading a lot about how a lot guys here that are burning an EPA furnace like their wood super dry 15% or at least under 20% so I’ve been doing some research, let’s start with the kuuma which is what I’m running, Lampa posted a video on YouTube back in the fall talking about firewood basics, in that video they specifically say that it’s important not to have your wood too dry because you’re drying out burnable BTUs all you want to dry out is the water content, Lampa likes to see moisture contents between 18%-28% as stated in that video. the Caddy advanced according to their manual wants to see the same moisture content 18-28%, the heat commander wants to see moisture content between 15-20% Both the kuuma and the caddy seem high to me. I’d like to hear others input on this I’m also hoping Lampa sees the post and comments on it.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
28,696
central pa
Ok so I’ve been reading a lot about how a lot guys here that are burning an EPA furnace like their wood super dry 15% or at least under 20% so I’ve been doing some research, let’s start with the kuuma which is what I’m running, Lampa posted a video on YouTube back in the fall talking about firewood basics, in that video they specifically say that it’s important not to have your wood too dry because you’re drying out burnable BTUs all you want to dry out is the water content, Lampa likes to see moisture contents between 18%-28% as stated in that video. the Caddy advanced according to their manual wants to see the same moisture content 18-28%, the heat commander wants to see moisture content between 15-20% Both the kuuma and the caddy seem high to me. I’d like to hear others input on this I’m also hoping Lampa sees the post and comments on it.
Water is not burnable. Removing more water from the fuel doesn't remove potential BTUs plain and simple. Now if an appliance is designed to work with higher moisture content wood it is possible that low mc could overwhelm the secondary combustion system in the beginning. But that is a different issue
 
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Micdrew

Member
Jan 15, 2021
53
Maryland
Water is not burnable. Removing more water from the fuel doesn't remove potential BTUs plain and simple. Now if an appliance is designed to work with higher moisture content wood it is possible that low mc could overwhelm the secondary combustion system in the beginning. But that is a different issue
I probably worded it wrong but I just posted the video
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
28,696
central pa
I probably worded it wrong but I just posted the video
No you worded it correctly he is just full of it. The end of the video says it all. He says you can burn dryer wood you will just have to adjust for it so you don't overheat the furnace. If you are removing most of the BTUs by "over drying" how would that cause the furnace to over heat?
 

ABMax24

Minister of Fire
Sep 18, 2019
1,529
Grande Prairie, Alberta, Canada
I just lost a lot of respect for Lamppa Manufacturing with that video.

2/3 of the BTU comes from "combustible fluids" in the wood? Give me a break. Hemi-cellulose and lignins do make up almost 2/3 of wood, but you're not going to evaporate them away by drying the wood too long. With softwoods it's definitely possible to loose some of the more volatile lignins (aromatics) when drying, but it's still more beneficial to loose these compounds if water is evaporated from the wood at the same time.

Here's some much more accurate information:

 

bholler

Chimney sweep
Staff member
Jan 14, 2014
28,696
central pa
I think he was talking about older furnaces not the newer ones of today
It doesn't matter what he was talking about it was never the case. And below 10% isn't even achievable by air drying in most of the USA.
 
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maple1

Minister of Fire
Sep 15, 2011
10,933
Nova Scotia
Man that video was a real head scratcher. Was that really made by Kuuma? Seems so? Also made me lose some respect. No way you want up to 28% MC. And yes he really contradicted himself at the end - if you dried out all the heat why would the furnace overheat?

Also agree it is near impossible to get wood to air dry much or any below 15% where most of us live.

He may have a small point, in that there may be something flammable in the wood that goes away over time? I made a thread on here last year about some real old stuff I was burning that seemed to be burning funny. As in, not as good as expected.
 

laynes69

Minister of Fire
Oct 2, 2006
2,669
Ashland OH
Here is a screenshot from PSG's Caddy Advanced test. While I think the moisture content is a little high even for testing, this shows that it's a more achievable moisture level. The higher moisture can probably be accomplished due to the computer controls, 28% is awfully high.

Screenshot_20220123-133522_Drive.jpg
 
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brenndatomu

Minister of Fire
Aug 21, 2013
7,224
NE Ohio
Was that really made by Kuuma? Seems so?
Yes, yes it was.
This whole "too dry" with the wood has been something that myself and @JRHAWK9 have been discussing for quite some time already (years) and while we have come to the conclusion (through individual testing) that even for a Kuuma furnace there is no "too dry"...wood much over 20% simply means less heat to the house (although the Kuuma will still do a nice job burning >20% wood)...so while I disagree with their "too dry" statement, I still have to respect Lamppa Mfg...this is the guy (Daryl, the owner, not Dale the GM in the video) that designed and built a revolutionary clean burning furnace before clean burning efficient wood furnaces were cool, and all done in an old building the size of a 3-4 car garage (until 3-4 years ago) aaand, on a shoestring budget! Kinda makes you think that the larger companies, some with multi million dollar budgets, (and some now out of business) were just resting on their laurels, rather than pushing the envelope for new innovation, heck, not even keeping up with the times in many cases!
Now, are there some things about my Kuuma that I don't prefer? Yes...but overall, there is nothing out there any better! So for me, I still have to have respect for Daryl Lamppa and the Kuuma line...even if he does have some strange things to say about wood MC...which I would love to sit down with him and discuss what he is talking about! (wouldn't be the first time that "common knowledge" has been proven wrong! If he could prove himself correct that is)
The only thing that I have been able to determine in my research is that there can be "too dry" for how a certain model stove/furnace is designed/tuned, but not "too dry" to where the wood will actually contain less BTU's (as long as the wood has not degraded...and the stove/furnace is "tuned" for the dryer wood)

I really like the way HeatMaster has things set up on their latest generation of G series OWB's...they are downdraft gassifiers with lambda and active air control on both the primary and secondary side...they also allow the consumer to tailor the air settings (to some degree) to the MC of the wood you are burning. (the typical OWB operator with green wood, vs the guy that actually has truly dry wood)
My dad bought one to replace an old school Central Boiler this past fall, and now they that they have a couple months experience with it, including a nice cold spell, the difference in how clean it burns, and the efficiency compared to the CB is remarkable...looks like wood consumption will be cut by at least 50%, possibly 60...not that the CB's were known for their efficiency, but to me that's still impressive! But I digress...I guess my point was that I think this is where things will go in the future for forced air wood furnaces too. (downdraft lambda control)
 
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Micdrew

Member
Jan 15, 2021
53
Maryland
Yes, yes it was.
This whole "too dry" with the wood has been something that myself and @JRHAWK9 have been discussing for quite some time already (years) and while we have come to the conclusion (through individual testing) that even for a Kuuma furnace there is no "too dry"...wood much over 20% simply means less heat to the house (although the Kuuma will still do a nice job burning >20% wood)...so while I disagree with their "too dry" statement, I still have to respect Lamppa Mfg...this is the guy (Daryl, the owner, not Dale the GM in the video) that designed and built a revolutionary clean burning furnace before clean burning efficient wood furnaces were cool, and all done in an old building the size of a 3-4 car garage (until 3-4 years ago) aaand, on a shoestring budget! Kinda makes you think that the larger companies, some with multi million dollar budgets, (and some now out of business) were just resting on their laurels, rather than pushing the envelope for new innovation, heck, not even keeping up with the times in many cases!
Now, are there some things about my Kuuma that I don't prefer? Yes...but overall, there is nothing out there any better! So for me, I still have to have respect for Daryl Lamppa and the Kuuma line...even if he does have some strange things to say about wood MC...which I would love to sit down with him and discuss what he is talking about! (wouldn't be the first time that "common knowledge" has been proven wrong! If he could prove himself correct that is)
The only thing that I have been able to determine in my research is that there can be "too dry" for how a certain model stove/furnace is designed/tuned, but not "too dry" to where the wood will actually contain less BTU's (as long as the wood has not degraded...and the stove/furnace is "tuned" for the dryer wood)

I really like the way HeatMaster has things set up on their latest generation of G series OWB's...they are downdraft gassifiers with lambda control and active air control on both the primary and secondary side...they also allow the consumer to tailor the air settings (to some degree) to the MC of the wood you are burning. (the typical OWB operator...green wood, vs the guy that actually has truly dry wood)
My dad bought one to replace an old school Central Boiler this past fall, and now they that they have a couple months experience with it, including a nice cold spell, the difference in how clean it burns, and the efficiency compared to the CB is remarkable...looks like wood consumption will be cut by at least 50%, possibly 60...not that the CB's were known for their efficiency, but to me that's still impressive! But I digress...I guess my point was that I think this is where things will go in the future for forced air wood furnaces too. (downdraft lambda control)
Was waiting for you or @JRHAWK9 to chime in.
 

Micdrew

Member
Jan 15, 2021
53
Maryland
I will say I’ve been burning 1-1/2 year old red oak that’s testing on a fresh split 19.6mc seems to be burning just fine no smoke and good heat output.
 

brenndatomu

Minister of Fire
Aug 21, 2013
7,224
NE Ohio
Was waiting for you or @JRHAWK9 to chime in.
He'll be around sooner or later...seems to be AWOL today...but he is the dry wood master...and has the data/records to prove it!
 

brenndatomu

Minister of Fire
Aug 21, 2013
7,224
NE Ohio
I will say I’ve been burning 1-1/2 year old red oak that’s testing on a fresh split 19.6mc seems to be burning just fine no smoke and good heat output.
Yeah, like I said, the Kuuma will still burn >20% wood just fine, but unless you really get hardcore with it, weighing the wood, taking moisture reading, keeping records, including heating degree days, you'll likely not notice that much difference between < and > 20% MC Kuuma chow...but when you start keeping records of things, it becomes apparent that the lower MC wood makes the house a lil warmer.
 

stoveliker

Minister of Fire
Nov 17, 2019
4,555
Long Island NY
I just lost a lot of respect for Lamppa Manufacturing with that video.

2/3 of the BTU comes from "combustible fluids" in the wood? Give me a break. Hemi-cellulose and lignins do make up almost 2/3 of wood, but you're not going to evaporate them away by drying the wood too long. With softwoods it's definitely possible to loose some of the more volatile lignins (aromatics) when drying, but it's still more beneficial to loose these compounds if water is evaporated from the wood at the same time.

Here's some much more accurate information:


That is one clear slide deck!

Good to see that my back of the envelope calc is similar to his:
 

woodey

Feeling the Heat
Feb 8, 2018
325
ST. Lawrence Valley N.Y.
I still have to respect Lamppa Mfg..
Yes...but overall, there is nothing out there any better
Couldn't agree more. If you know the history of this company and are familiar with the quality of their products and what they have achieved it's hard to imagine anyone losing respect of them over one confusing video.
 

brenndatomu

Minister of Fire
Aug 21, 2013
7,224
NE Ohio

JRHAWK9

Minister of Fire
Jan 8, 2014
1,869
Wisconsin Dells, WI
I'm here, was just away for the weekend.
I hope he didn’t go to the packers game....
That would be my guess...

;em yep........

Anyway, I'm burning 6.5 year old stuff now that measures anywhere from 12-18% or so.....from my stacks outside.

Before I left, I loaded 90lbs of 7-8 year old Black Locust that has been sitting down the basement for that last 3 years or so. I stuck a meter in it for $hits and giggles after re-splitting a piece to make smaller pieces to stick in voids. Anyway, that stuff was so damn hard I could hardly get the pins in, but it measured 8% on the face of the fresh split.

I have zero issues with dry wood. Like mentioned before, in our climate, I will probably never see much under 12-15%. Wood is hydroscopic, so it will reach an equilibrium moisture level at some point and then just continue to fluctuate with the atmospheric conditions.

As far as the video goes, I saw that right after they uploaded it. It didn't make sense to me either. That's all I'm going to say about that, mainly because I just simply don't know enough about it. I just know I don't have issues burning what I am burning and I am seeing better results vs when I was burning 20%+ the first and second winters.
 
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sloeffle

Minister of Fire
Mar 1, 2012
988
Central Ohio
When I built custom furniture we were happy to see kild dried wood <10% moisture in the summer time. The shop I worked at the longest didn't have AC so that didn't help either. All through college we were told just because the tree is dead doesn't mean the wood is dead. As @JRHAWK9 said, wood is hydroscopic, it's going to lose and gain moisture throughout the various times of the year. That's why you see tables with bread board ends look so odd during the winter time, and that's why there are some doors that don't close in the summer but do in the winter.

If you are bored, there's a book by R. Bruce Hoadley will tell you more about wood then what you ever wanted to know. I was introduced to this book as part of my studies.
 
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RockCastile

Member
Nov 9, 2015
54
VA
Could the guy in the video be thinking (or misconstruing) something to do with extremely dry wood vaporizing so much more rapidly that it escapes without combustion? I think Mr. Gulland mentions something about that on woodheat.org (can't locate it at the moment) although he adds it's mostly a theoretical point as real world firewood rarely if ever gets so extremely dry.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
28,696
central pa
Could the guy in the video be thinking (or misconstruing) something to do with extremely dry wood vaporizing so much more rapidly that it escapes without combustion? I think Mr. Gulland mentions something about that on woodheat.org (can't locate it at the moment) although he adds it's mostly a theoretical point as real world firewood rarely if ever gets so extremely dry.
Like I said initially. If their furnaces are designed and tested to run on higher moisture content wood that's one thing and perfectly understandable. But some of the stuff he said was just absurd.