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Can I Use This Dehumidifier for Kiln

Started by Believer, May 31, 2013, 10:04:24 PM

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Believer

Is a dehumidifier that is 130 pints and 300 cfm for suitable for a small kiln?

Ianab

How much wood are you planning to dry, and how fast does it need to be done?

If it's a small scale "hobby" kiln that you want to put 500 bd/ft in and get it from air dried to ~8% in a couple of weeks, then any portable D/H unit will work. A couple of box fans, maybe a small heater, or just the heat from the D/H

All a simple "kiln" like that needs is constant warm dry air circulating though the wood stack, and the wood will eventually dry.

Ian
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

ancjr

I've used a regular "home" type of dehumidifier in a 10x20 room, which worked better than I expected it to.  My dogwood had 1/2" checks in less than a week!   :-\

Ianab

Hence my suggestion to use it to finish off air dried wood. Without the normal kiln controls keeping the humidity and temp correct it's possible to dry some woods TOO fast.

But once you get the moisture down to ~15% or so it's hard to mess it up.

Ian
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

Kcwoodbutcher

The 300 cfm sounds reasonable but the 130 pints sounds very high. Most small dehumidifiers will run 16 to 32 pints a day. Whats the time frame for the 130 pints. If it's over a days time you better be drying a lot of lumber.
My job is to do everything nobody else felt like doing today

ancjr

The "130 pint" capacity is how much water it can possibly extract from air at optimal temperature & dew-point over 24 hours. 

It's not that it will extract that much water out of X amount of wood over Y amount of time which is present in that air, necessarily.

Assuming a volume of wood and temperature that were enough to keep the air saturated, setting the humidistat at 99% RH would equalize to about 27% wood moisture. 65% RH will bring the wood to about 12%.  The only way I would know how long it would take to arrive at these values would be experimenting with a particular humidifier, in a particular room, at a particular temperature, with a particular amount of a particular species of wood.

Then, it would seem to me that reducing the humidistat in increments, while allowing the wood to equalize in moisture content should easily provide a safe & predictable drying rate for small volumes of wood.

Relative Humidity / Wood moisture data: http://www.csgnetwork.com/emctablecalc.html

Al_Smith

If you care to you can Google plans for small dehumidity type kilns or dryers using small units .

A guy who is now deceased I used to work with made a larger unit from an old refer truck box with an electric dehumidifier and internal circulation  fans which worked pretty well .I'm thinking it took maybe a month or so .It had heat too which I'd well imagine being electric it wasn't cheap to operate .On the other hand a refer box is pretty well insulated .

GeneWengert-WoodDoc

Although 300 cfm is fine for the DH, you will need more fans for circulating the air through the lumber pile. 

Technically, 130 pints is 130 pounds of water.  For many hardwood species, that weigh about 2200 pounds oven dry for 1000 bf, that is 6% MC loss per day...which is pretty good.  But if you have a stack that is 22 layers high with 3/4" stickers, and you need about 500 fpm air velocity, you need 16 x .75 /12 x 20 x 500 com = 10,000 cfm
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Planman1954

Go to flea markets. I found 3 in no time flat! $10!
Norwood Lumbermate 2000 / Solar Dry Kiln /1943 Ford 9n tractor

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