How to split wood for a downdraft gassifier?

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DaveBP

Minister of Fire
Hearth Supporter
May 25, 2008
1,156
SW Maine
I would like to know if there is a consensus here among those who have been running their Tarms and EKOs (and now other brands, too) for more than just one season. I mean those who have learned to split and stack and dry their wood thoroughly before burning and have found their routine that works without any more tinkering.
I remember quite a few folks reporting problems with bridging, or not being able to maintain gassification, or possibly burning too fast and losing too much heat up the flue with exhaust temps much too high.

So with completely dry wood ( I think moisture content was the most common problem people were having ) what is the optimum size to split to? By dry I mean split, stacked and rain-covered for a second season.

Different sizes for different densities?

I've been working on some wood for burning in my Tarm 2 years from this coming winter. I notice that I'm splitting smaller than I used to split for my old woodstove. If I can see a 4X4 inside the stick (looking at the end of it) I will split it. I used to have a sawmill so this sort of hallucination is normal for me. Only rarely on a crotch will I not be able to touch my thumb-to-thumb and finger-to-finger around a split with room to spare. Split this small I know the wood will dry faster but ultimately I expect it would reach the same moisture content as larger splits.

So is there an ideal size?

And for those who can modulate their draft fan speed, does a slower fan speed work better with different size splits?
 
I find that "smaller is better" for the most part. Especially for starting. If I have anything over 4" on the end I'll throw it on top when I load the firebox. Otherwise I try to use a rule of thumb I heard here first - if the end is bigger than a playing card, split it again.

Fan speed for me varies by the stage of the burn more than by the type of wood. I crank it up to get a good hot start and then I slow it down once I have a good fire established and my flue temps are up...
 
It's nice to have a good selection, I've found. Smaller wood is always best for starting, but just like any other wood-fired boiler, bigger pieces are better for long burns on cold nights. Those of us who get our wood from standing trees always have plenty of branchwood to work with, so I don't split anything under around 6-8 inches in diameter. I let my wood dry for at least two years, so moisture content in the larger chunks isn't really an issue. If you have a shorter dring rotation, then by all means split smaller. As a practical matter--at least with an EKO 60--you can burn anything that will fit through the firebox door.
 
I think part of it is how your burning...My father likes to burn a little slower so that he can maintain a good coal bed because he has a large heat load and burns everyday so he likes to burn larger pieces. I burn really hot and fast so I can recharge my storage as fast as possible so then I live off the storage for a while while I work 12 hour days. I like small splits (4" or smaller) and they produce allot of BTU's but I reload and burn down faster.


Edit...Good to see you back Eric, I was wondering where you have been as I haven't seen any posts for a while.
 
I'm splitting down the the 2x4 size also...... I'm impressed... My oldest wood has only been split since April and is already down to 25%... So for me, small it important if I'm going to get wood decently dry in 6 months......
 
deerefanatic said:
I'm splitting down the the 2x4 size also...... I'm impressed... My oldest wood has only been split since April and is already down to 25%... So for me, small it important if I'm going to get wood decently dry in 6 months......

Any smaller and the birds are going to carry it away! :p ..sorry, I couldn't resist!
 
Garnification said:
deerefanatic said:
I'm splitting down the the 2x4 size also...... I'm impressed... My oldest wood has only been split since April and is already down to 25%... So for me, small it important if I'm going to get wood decently dry in 6 months......

Any smaller and the birds are going to carry it away! :p ..sorry, I couldn't resist!

Hey now...birds gotta be warm to!!!
 
sdrobertson said:
I think part of it is how your burning...My father likes to burn a little slower so that he can maintain a good coal bed because he has a large heat load and burns everyday so he likes to burn larger pieces. I burn really hot and fast so I can recharge my storage as fast as possible so then I live off the storage for a while while I work 12 hour days. I like small splits (4" or smaller) and they produce allot of BTU's but I reload and burn down faster.


Edit...Good to see you back Eric, I was wondering where you have been as I haven't seen any posts for a while.

Thanks, Shannon. I'm back.
 
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