Desperately seeking kiln help

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Forum topic by SoftWood2 posted 05-13-2022 12:17 PM 338 views 0 times favorited 2 replies Add to Favorites Watch
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2 posts in 68 days

05-13-2022 12:17 PM

I just built this dehumidification kiln after looking around at how they are generally designed. However after loading my first charge in it today, my setup doesn’t work. I’d like to think I’m a decent problem solver but am a little stuck as to where I’ve gone wrong.
I am barely getting enough airflow through my stack to move a flame around on a lighter, and it’s far from being even.
I had planned on having 3 fans suspended from the ceiling but am waiting on the 3rd one to arrive and am not holding my breath on it fixing my issue.
The stack is 6.5’ tall, 3/4” stickers, 4.5’ wide and the bottom 1/3 is 10’ lumber while the top 2/3 is 8’. There is 39” of airspace on each side of the stack to the wall and I am using 2 fans from an Ebac dehumidifier system. Can’t see it in the photo but I’ve got plywood seaing the fans to each other and I cross to each wall, a sheet of plywood covering the top of the stack, plywood going from the bottom of the fans to the front edge of the stack as well as baffling sealing the sides of the stack to the walls. I even tried mounting some plywood on the ceiling/wall corner in front of the fans to help direct the air downward.
There seems to be decent airflow, albeit quite chaotic, in front of the stack.
Does anyone have any ideas? Or anything obvious that jumps out?

2 replies so far

View CaptainKlutz's profile


5618 posts in 2954 days

#1 posted 05-14-2022 06:25 AM

Request is a little vague? How is it not working?

Taking to long to reach equilibrium moisture content, or some random air flow measurements?

Have you calculated CFM air flow through stacks?
Have you tried using a digital handheld airflow measuring device?
What do your temp, humidity measurement logs show?

De-humidification works on principle of vapor pressure. You remove moisture via a difference in moisture content of surrounding air.
The fans in kiln direct the flow and move the air past the dehumidifier more consistently. If you want measurable airflow through each layer of stack, you have to design the drying chamber for that purpose.
I.E. lumber all same length, wide gaps between layers, and minimal space on ends to force higher air pressure into stack and not around it. A picture stolen from wood workers journal:

If ends of boards are not all same length, you need to block air from entering the dead space on the ends.
One thing I see missing is deflector down the front side end of stack to direct airflow into stacked lumber?
You must minimize any air path that is not through the stack, as airflow takes the path of least resistance. Don’t need to blow air across the ends of stack.

Best Luck.

-- If it wasn't for bad luck, I wouldn't have no luck at all, Doom, despair, agony on me… - Albert King - Born Under a Bad Sign released 1967

View SoftWood2's profile


2 posts in 68 days

#2 posted 05-14-2022 03:34 PM

I’m just not getting any airflow through the stack. My meter is not showing proper numbers but just for reference it’s showing 300cfm coming off each fan and between 0 and 7 on the negative side of the stack. I have the ends of the stack baffled but took it off the front side to get a photo. The actual length of the stack between baffling is close to 7’.

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