Help with why mc wont go down?

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Forum topic by SRfinewoodworking posted 09-06-2013 06:37 AM 981 views 0 times favorited 4 replies Add to Favorites Watch
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2 posts in 1753 days

09-06-2013 06:37 AM

Hello my name is Shane. I built a VT type solar kiln about 8 months ago. The kiln in 10ft by 4ft, front wall is about 4ft and back wall is about 7ft. I loaded it with a stack of 8/4 wet Black Walnut. Some of the boards are almost 3in. The boards on the top are at 16% and the board on the bottom is at 32%. The mc has not changed for about two months. It has been getting up to 140 degrees inside on a hot day. I have been leaving the vents totally open. The vents are 5in by 15in, two at top and two at bottom. I am using a electrophysics pin type meter which has settings for species and temp. I became so frustrated with the lack of drying that I converted it to a DH kiln. I bought a GE 30pint dehumidifier from home depot and added 1inch foam insulation to the vents and the top of the kiln. I have two 20in box fans from walmart in the top of the kiln. Also I just recently realized most of the air was blowing around the stack so I completely blocked everything off so the air must move through the stack. My stickers are 3/4 by 3/4. When I put my hand behind the stack I am getting nice strong air movement throught he stack. I also have a basic radio shack remote thermometer which is reading 110 at night and 127 at hottest point. The RH is saying 20% but the Dehumidifier is saying the RH is 30%. I just converted this yesterday. So far I have collected about 1/3 gallon of water. I have a hose running from the dh out into a gallon jug. I just tested the mc and nothing has changed. It has been roughly 20hr. I have two small brad nails with wires running out of the kiln to test mc. When I connect the meter to the wires I set the meter for black walnut and changed the temp to whatever my thermometer is showing. I also tested my meter with the calibration cap that it came with and it is correct. Any advice on what I am doing wrong would be greatly appreciated. I was hoping Daren could chyme in on the conversion to the DH kiln. I bought the 30pint unit instead of the 50 due to post that I have been reading from him.

4 replies so far

View REO's profile


928 posts in 2102 days

#1 posted 09-06-2013 09:07 AM

often the DH will shut down the compressor when the temp is above 110. then all you are left with is a fancy fan. check the current draw and be sure the compressor hasnt shut down.

View Nomad62's profile


726 posts in 2986 days

#2 posted 09-06-2013 10:03 PM

Walnut that thick will take a long time to dry. 1/3 gallon water per 24 hours wouldn’t be bad if you have 200-300 bf of wood in it, maybe even too much; 2000 bf, it would be low, but still not terrible. Remember that you are leeching the water thru the wood as a vapor, then returning it to a liquid; this takes a lot of energy, and a lot of time. The water can only travel thru the wood at the pace it is allowed, and that is slow. I’d figure on another couple of months to get 3” wood dry.

-- Power tools put us ahead of the monkeys

View bondogaposis's profile


4770 posts in 2379 days

#3 posted 09-06-2013 10:40 PM

Patience, patience, 3” walnut is going to be a slow go, that’s the way you want it, too fast and it is going to warp. Water has to move through the cell walls molecule by molecule, in 3” stock that is a lot of cell walls.

-- Bondo Gaposis

View SRfinewoodworking's profile


2 posts in 1753 days

#4 posted 09-07-2013 12:57 AM

Thanks for your input guys. It has been 48 hrs since I converted the solar kiln to a dh kiln and the bottom board has droped 5%mc. Tomorrow I am going to take out the 30pint dh and add a 50pint dh. I will also vent the hot exhaust air from the dh out of the kiln. I am hoping this will keep the temp around 100 degrees in the kiln. When I dont have the dh running it stays around 100 degrees.

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