Getting to 8% KD250

[Woodslabs]

Hi All, 

Running my second load now and am stuck at 10-12%.  Kiln has ash and walnut at 2 and 1/4.  The manual says 120 dry and 98 wet.  I was stuck at 14 and turn wet down to 95.  After 4-5 days i got it down a few%.  I know bonded water can be hard to get out, do you guys turn down the humidity lower or turn compressor off and turn up the temp.

I would like to be able to unload in a month or so.  Please let me know.  I would like it between 6-8%

[WDH]

Keep the DB at 120 degrees.  Drop the WB to 75 degrees.  This will ensure that the compressor runs 100% of the time.  Anytime that you are below 20% moisture content, you can run the compressor full blast.  This will do the trick.

[GeneWengert-WoodDoc]

Heat does indeed make the water move within the wood.  Drying Hardwood Lumber, Drying Eastern Hardwood Lumber and I suggest raising the heat to 140 or 145 F for a few hours and then let it slowly get back to 120 or even 125 F.  Use a reasonable humidity...at least 3% EMC drier than the MC.

[WDH]

With the L53 unit, if you exceed about 133 degrees, you will trip the compressor.  There is a high temp limit at which you can run the compressor.  If you exceed 133 to heat up the kiln to 145, then turn the compressor off before you exceed 133 degrees DB.  Once you cool down below 130 degrees, you can turn it back on.  You might want to partially open the vents so that the water vapor can exit the unit while the compressor is shut down. 

If you trip the compressor, you have to take the side panel off the unit and hit the re-set button which is located on one of the refrigerant lines.

At wood moisture content of 12%, I run the DB at 125 degrees and the WB at 75 degrees to ensure the humidity is at least 3% EMC drier than the MC of the wood.

[Geeg]

Thanks for the info guys, I am running an Elm load witch was air dried to 30ish% and ran into the same problem, I am now seeing a drop in MC. Guess you have to be flexible with that scheduled as it seems to be just a starting point. I figured a max drop of 1.4% per day as it is 10/4

[123maxbars]

With the L53 unit, if you exceed about 133 degrees, you will trip the compressor.  There is a high temp limit at which you can run the compressor.  If you exceed 133 to heat up the kiln to 145, then turn the compressor off before you exceed 133 degrees DB.  Once you cool down below 130 degrees, you can turn it back on.  You might want to partially open the vents so that the water vapor can exit the unit while the compressor is shut down.  

If you trip the compressor, you have to take the side panel off the unit and hit the re-set button which is located on one of the refrigerant lines.

At wood moisture content of 12%, I run the DB at 125 degrees and the WB at 75 degrees to ensure the humidity is at least 3% EMC drier than the MC of the wood.

I 2nd what Danny is saying here, 

[GeneWengert-WoodDoc]

There is always the issue on how to measure MC when using an electric moisture meter- - pin or pin-less.  Example: You will often find that 50% true average moisture content in the lumber may read just 34% MC on the meter.  As the wood dries from 50% MC to 30% average MC, the meter will only go from 34% to 30%, indicating a 4% MC loss instead of the 20% MC actual loss.  Under 30% MC, the meters work much more accurately.

One issue with the pin meter is that if you measure the core MC, the outer layers of the wood can be drying quite a bit, but the core very little.  So, it appears that there is very slow drying when there is actually quite a bit of drying.  This is why the insulated pins should be driven 20% of the thickness to get the average and not 50% to the middle or to the core.  This happens even with drier lumber.

Then, there is the issue of exactly what depth are the needles...the lumber's surface can be at 15% MC and the core at 45% MC.  So, that is with 4/4 lumber roughly 1% MC for each 1/64” of depth...this makes a difference indeed, but we seldom measure the depth of the needles very precisely.

If you use uninsulated needles, they will read the wettest MC anywhere along their length, so will usually not detect that the wood is actually drying for quite a while.  This happens even under 30% MC.

[Woodslabs]

With the L53 unit, if you exceed about 133 degrees, you will trip the compressor.  There is a high temp limit at which you can run the compressor.  If you exceed 133 to heat up the kiln to 145, then turn the compressor off before you exceed 133 degrees DB.  Once you cool down below 130 degrees, you can turn it back on.  You might want to partially open the vents so that the water vapor can exit the unit while the compressor is shut down.  

If you trip the compressor, you have to take the side panel off the unit and hit the re-set button which is located on one of the refrigerant lines.

At wood moisture content of 12%, I run the DB at 125 degrees and the WB at 75 degrees to ensure the humidity is at least 3% EMC drier than the MC of the wood.

125/75 is 14.5 RH in the air.  That is very low, is that RH ok for the wood?

[GeneWengert-WoodDoc]

Because a 50 F depression dries the outside of the wood to 3%MC, this outside wood will be brittle when machining...chipped grain.  Cupping will be worse.  Many operations use 5.0% EMC, 5.5% or 6.0% EMC as the driest condition at any time in the kiln to produce higher quality lumber.

[WDH]

Those are just the set points.  These set points just keep the compressor running 100% of the time, like a switch.  The actual humidity in the kiln is much higher.  I usually end a load in the kiln with he humidity at about 5% or 6 % equilibrium moisture content which brings the wood to about 8% to 9% moisture content.