Oak at 7.1

[tacks Y]

In my solar kiln the wood is now at 7.1%. Running at 150 degrees in the after noon with the fans  on. Cools to about 125 at 8pm on sunny days. To get my wood down to 6% how open should my vents be? I have them about 1 or 2 inches. This am temp is about 10 degrees over out side.  Thanks Tom

[GeneWengert-WoodDoc]

To achieve the lowest MCs, you need as much heat as possible, so close the vents.  Then, run the fans only when the kiln is about 20 F hotter than the outside and the sun is shining on the roof.  In other words, run the fan only when the interior air will be low in humidity.

It takes very little heat to heat the air in the kiln.  It also does not take much to heat the lumber.  However, what uses the heat the most is evaporation of water.  If you have little or no water to evaporate, you will see very hot temperatures in the kiln (with the fans running) and the kiln will cool off slowly at night even though the sun is no longer shining directly on the roof.  In other words, you are not using heat for evaporation, so then the heat slowly leaves the kiln through the walls, roof and floor, which are well insulated.

So, based on the 150 F temperature and still 125 F at 8PM, I suspect that your MC reading is incorrect and that the wood is drier than you indicate.  What brand of meter are you using?  Insulated pins?  How deep?    Did you make a temperature correction for the kiln air temperature of 150 F or 125 F?  Did you make a species correction?

Note that a pinless meter inside the kiln is going to respond more to the surface MC, so it is not the best meter for running a solar kiln.  In the morning, due to the higher humidity in the kiln during the early morning, the pinless will read higher as the surface MC is higher.  

Do you have a piece of lumber that you can take out of the kiln?  If so, measure the MC correctly, put it in a very dry spot, and then measure the MC after about six hours.  If you do not have a dry spot, wrap the board with plastic film so no moisture can get in or out while it is waiting to be measured.

[YellowHammer]

Close the vents, get the temps as high as possible.  


I try not to get to 6%, the wood just starts to over-react and actually begins to move, cup and warp as it gets into this range.  5% is really bad news.  

If you are at 7.1%, I'd say the pizza is done.

  

[tacks Y]

Gene, I have the J2000 w/26es w/insulated pins. I have it set for the insulated pins and 31 for red oak. Checked it in the am and set temp for 80, so it was close. I checked the wood in my shop at 5.9 after this so I think it is working fine. I ran the fans with vents closed today. So at what m/c should I keep the vents closed? I only reached 155 degrees today as it was kind a cloudy. At 8:30pm it was 135 * and cooling, I shut the fans off. Should I run them longer in the evening if the temp is still up?

Mr Hammer, so you say good enough? I will recheck in the am.

Thank you both for the input.