Double check my numbers please

[Raym]

Looking for expert knowledge to double check my settings/results.
I put in a load (1800BF) of 8/4 white oak that has been air drying a little over a year. It went in at 37 and 44%. (I only set two probes). Probably could have air dried a little longer but I do have an order for a table from this (customers) wood.

I started off with dry bulb set at 95 and wet bulb set at 89. here are my daily readings

6/8.....37 and 44
6/9.....36 and 43
6/10.....35 and 43
6/11 ?
6/12.....34 and 42
6/13.....34 and 41
6/14.....34 and 41

here i changed the dry bulb to 100 and the wet bulb to 90

6/15.....33 and 40
6/16.....33 and 40
6/17.....33 and 40
6/18 ?
6/19.....32 and 39
6/20.....32 and 39

Please note that the compressor has never come on as the wet bulb reading has varied from 83 to 88 and the controller is calling for humidification but I do not have a humidifier.

should I continue at this rate or increase the dry bulb. The good news is that I am only using an average of 38KWH per day. My heat source is from a heat exchanger connected to an OWB.

Thanks in advance for any input......Ray

[GeneWengert-WoodDoc]

There is no moisture meter that can measure moisture accurately above 30% MC.  So, I do wonder if your readings are reliable.  How deep are the pins driven?  We would typically drive them 20% of the thickness to get the average.  What brand of meter are you using?

After a year of air dryinof 8/4 white oak, we would expect a much lower average MC than 37% and 44%. As white oak starts at around 65% MC and the outside conditions are around 13% EMC, for locations near Charlottesville, the wood should be under 25% MC.  With such slow drying as you seem to have, I would expect to see lots of mold.  So, I do wonder again about the MC readings.  Can you find another kiln operation near you (maybe in Orange) that could double check the MC, using an oven test?

Because the wood has been exposed to 13% EMC for a year in air drying, the kiln should be started at that condition or perhaps 1% EMC drier.  This would be around 10 F depression  In any case, the EMC in the kiln should not be wetter than outside as this more humid condition will cause the surface to swell and then small surface checks will go deeper.  So, why is the wood not drying faster at a 10 depression?  Perhaps the sensors are incorrect.  Do a quick check by taking the wick off the wet-bulb and thereby making it a dry-bulb.  Make sure the regular DB and the dry WB readings are the same.

The typical drying rate for 8/4 white oak would be around 3/4% per day.  The 100F DB is about the highest I would go above 30% MC...maybe 105F max.  The 10F depression is also a good setting at high MCs for well air dried.  The extremely slow drying could actually be because the wood is much drier than your meter indicates.  If it is actually 15-20% MC, then the kiln settings would be closer to 120F and 100F.

If you are losing moisture now, albeit real slowly, where is the water going?  With 1800 BF, a 1% MC loss is a loss of about 55 pints of water.  So since you started, if the MC readings were correct, the loss would be over 30 gallons. Where is this water going if the compressor is not running?  And, if the kiln is tight, this amount of moisture going into the air in the kiln should result in very humid conditions.  Yet you say the WB depression is around 15F.  Something is drying the air out.  Do you have vents that are running?

The 18 kWh use per day must be just for the circulating fans.  What else is running?  The controls do not use hardly any power.  I think that you are using 0.75 kWh per hour or about 7 amps draw for the fans...sound right?

Things just do not seem to add up.  Incorrect MCs would explain most of the questions.  That is, if the MC is 15% MC now and the kiln is 13% EMC, then the slow drying, lack of smaller depression, etc. then makes sense.  As a quick check on your moisture meter, measure some wood that is inside the liv9ng space of your home (not basement).  The readings should be around 7% MC.  Measure some wood 9nside an unseated barn or garage (not exposed to rain wetting) and you should see 13% MC.

[Raym]

Thanks for the input Gene. I have the probes driven in about 3/4" (based on l200 manual instructions) and they are the moisture probes on the L200 nyle unit. I will change them out and see what the shorter ones read. I will also take some lumber from my shop and use the probes for comparison.

You are correct that the only thing running are the circulation fans, compressor fan (not the compressor itself) and a separate heat exchanger. The vent fans are not running.

[K-Guy]

It sounds like you might have some case hardening. Do you have meter that could take surface moisture content?

[Raym]

I did verify the wet bulb reading....it reads the same as the dry bulb without the sock.
I removed the probes and installed shorter ones (1/2") and the readings went to 22 and 21. I upped the dry bulb temp to 110 and wet bulb to 96.

I guess its time to also by a quality meter to check the controller probes

as far as where is the moisture going? beats me. There is a lot of open space in there. my kiln is pretty tight except for two louvered vents (fan not running). My door is very well insulated but i know it needs to be sealed better than it is.

here is a photo of the kiln. it is 18 x 22 and is in the basement of a shed.


 

[GeneWengert-WoodDoc]

Nice looking kiln indeed.

If you are looking to upgrade you MC measuring equipment, I suggest that you look at Delmhorst and then compare any others, like Lignomat, to them.  You do want a meter that has insulated needles so you can measure a gradient with the auxiliary hammer probe.  

In addition to the meter, they sell a probe to find the wetter lumber within an air drying stack.  

They also have a switch and cables and probes for in-kiln measurement, so when you attach the meter to the box, you can check all the readings in a few seconds.  It is called Kiln-Mo-Trol (R).  It is designed for DH and smaller operations.  Big time saver, but takes careful procedures to use properly.  One issue with taking a meter into a kiln in cold or cool weather is that moisture will condense on the cool meter and give a false reading.  The bad readings continue until the moisture, which can be inside cables, evaporates.  Keep your meters warm or use the remote system.

In any case, get a made in USA meter.  Better service and repairs and better calibration for our species.

[YellowHammer]

8/4 white oak is cranky.  I'm also surprised that after a year of drying the wood is still so wet.  

My advice is to do an oven dry sample and see exactly what the moisture levels are on a daily basis.  It's very easy and is definitive, and I believe is a critical troubleshooting measurement that allows you to understand what the wood is actually doing as well as to calibrate your instruments. 

Delmhorst makes a good meter.