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DH Drying ?

Started by steveST, April 22, 2004, 07:57:12 AM

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steveST

I have a lumber storage building that is dehumidified by a large residential DH unit. The RH stays right around 30% and the temp is usually around 70-80 degees (the DH supplies the heat).

If I put material that is air-dried to <20% will the extremely low RH cause me troubles from it drying too quickly?? I have some AWESOME material in the currently that I want to be sure is dried correctly.

Thanks!

Den Socling

I don't think that you will get any water out if the temperature is 70-80 and the MC is <20%.

steveST

This is from Gene Wengert....

"When drying wood, the free water leaves first. It requires less energy to evaporate than the bound water. At about 30% MC, all the free water is gone and just bound water remains. At 99.9% RH, the MC of the wood will stay at about 30%. But, if the RH is lower, the bound water will evaporate--for example, 80% RH is 16% MC, 50% RH is 9% MC, and 30% RH is 6% MC."

old3dogg

And the Doc is right but.......
If you try to remove the bound water to fast you will crack the wood.

Den Socling

Steve,

If your dry bulb is 75 and the humidity is 30%, you will reach 6% eventually (according to the table in the DKOM). I wonder how long. I imagine it will seem like you're getting nothing out.

Den

steveST

I am in NO hurry...some of my material has been in there a year, some two.

I put some 6/4 maple material in 2 weeks ago that was air-dried to 16-20%. Checking it today it was down to 10-12. That seems kinda fast to me, but the RH is ALWAYS no more than 35%. (Usually it's 29-32).

If it takes 6 months it's ok by me. It is all very high-end material (curly walnut, curly cherry, curly maple (some 18" wide!).

Thanks for all the input. Back to my original question though...is that RH at  70-80 degrees too much, too fast?

Thanks.

Norm

My personal opinion is you will not have a problem with it drying too fast. Most times if you have wood under 20% when you put it in the kiln you can go full bore drying it. White oak, red oak and very thick wood are the exceptions to this.

Brian_Bailey

Sounds like the perfect place to store and acclimate your AD lumber to me.

30%rh is not to harsh for lumber that has a 20% mc.
WMLT40HDG35, Nyle L-150 DH Kiln, now all I need is some logs and someone to do the work :)

Don_Lewis

When you bring wood in the room, the humidity will rise and the unit should have a hard time bringing the humidity back down. That is a safety factor. The dehumidifier probably won't last very long because the acid in the wood will eat the wet coil away faily quickly.

dewwood

One other consideration is every time you introduce new higher moisture content wood you are raising the MC of all of the wood in the building.  Storing your dried lumber in a climate controlled room is a great way to go but you might want to consider a separate chamber for the actual drying process.
Selling hardwood lumber, doing some sawing and drying, growing the next generation of trees and enjoying the kids and grandkids.

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