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Fans Size and Drying Kiln Dimensions
Question
Forum Responses
Regarding the fans, are you thinking of a load that is 8' x 16' x 74"? What species? What will the entering MC be? What is your sticker thickness? If you are drying a wood like oak that is air dried first and using 3/4" stickers and there are two adjacent piles so the air flow path is 8' long, you will have an air flow channel that is 3/4" high, 16' long. There will be 40 of these in your load. You should have about 200 fpm air velocity. Note: 3/4" is 3/48 feet. So, 3/48 x 16 x 40 x 200 = 8000 cfm. Add 50% for air losses and this means you need fans that can provide 12,000 cfm.
From the original questioner: My plans are to stack 8 ft wide x 16 long with 1" x 1" stickers. I will dry 4 quarter #1 com red oak, right off the mill. I have 4" spray foam insulation in interior covered with plywood. You mentioned I would have 50% air loss; can you explain? From Professor Gene Wengert, forum technical advisor: I suggest that you plane your stickers (dry, I hope) to 3/4. The air losses are due to air sneaking under, over and around the piles and not going through them. From contributor J: I have a L200 Nyle and have five 1/2 hp 16" fans in my drier. Three of them run on a speed rheostat together and the other two on a separate switch for more air flow with softwoods. I have an air flow meter to let me know how many cubic feet of air per minute is going through the stacks. For 4000 feet of hardwoods I use three fans most of the time with 450-500 cubic feet of flow. Pine needs all five and I don't put more than 3000 board feet of pine in at a charge when MC is over 60% or your pine will mold with the L200. If your pine has been air drying for awhile, more than 3500 is okay. From contributor S: My experience with an L200 for green oak is, keep your stack no wider than 6' by 16' long, using 3 fans, keep your temp at 95 deg with kiln cycle at 100%. When your charge is at 40% moisture kick the heat to 120 and run it out. I never dry green oak. Let nature do the work for you. We always air dry for at least 1 month. From the original questioner: If you air dry 4/4 red oak for a month off the mill, what is your MC at that point? I also put three fans in the kiln, and stacked 6' wide, 40 layers high. My intentions are to always have a kiln load air drying while there is a load in the kiln, 4/4 RO. I have my kiln inside another building, so the lumber air drying will be under roof, with wind blowing through the open doors east to west. I am in Southeastern Pa, where we don't get a lot of humid air for long periods of time. So, my question is what MC do you lose in 30 days during the months of March through Oct. (4/4 red oak)? Would you like to add information to this article? Interested in writing or submitting an article? Have a question about this article? Have you reviewed the related Knowledge Base areas below? 
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