Troubleshooting a Dehumidifier Kiln

A newly acquired (but secondhand) dehumidifier kiln has some performance issues, and the Sawing and Drying forum offers advice. March 26, 2013

Question
I have my Nyle L200 up and running with 2500 bf of oak. It is not producing much water though the drain line (lots of water on floor). The oak lumber is between 22% and 26% moisture.

I have the temp up to 120 degrees, compressor running 35 minutes per hour. My wireless thermometer for the RH is not reading correct (flashes 1-99, then 99-1). What should I use to get the RH in the chamber? Why would the kiln unit only produce a small amount of water?

Forum Responses
(Sawing and Drying Forum)
From Professor Gene Wengert, forum technical advisor:
A t this low MC, if your readings are correct, it is virtually impossible to damage the wood by using the wrong conditions. Normally, at this low MC, we would run the compressor more. Do not add any more heat at this point. 115 would have been better. Slow drying is the result of poor air flow or high RH. The RH will be lowered if the compressor runs more.

The water on the floor indicates that the floor is cold. You need to provide a warmer floor in the future. It also indicates a high RH in most situations, so again, run the DH more.

Take your RH probe out of the kiln and see if it is working outside correctly.

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From contributor T:
How new is this kiln/building? If it's all new (at least the concrete floor) the excess floor moisture could be from the concrete still being green (not fully cured), lack of vapor barrier under concrete drawing moisture up from a damp subsurface. Also, as Gene mentioned, a cold floor condensing. Cold climate (not here in Tennessee now), building not sealed good at floor.

After those being okayed, it's up to Doc's opinion on the mechanicals per numbers. My kiln is just too simple of a setup to give correctly good advice on the numbers (I watched the numbers and occasionally logged them but not as a daily journal or to a schedule). My setup is too small to damage/dry too fast.

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From the original questioner:
The wireless RH sensor works correct outside the chamber. What brand of RH device would you recommend to use for measuring the RH inside the chamber? The slab is about a year old and it does have a moisture barrier underneath. Because of the hot weather here in East Texas I did not insulate under the slab. I hope that doesn't become an issue.

I purchased the Nyle L200 unit from a fellow that never hooked it up. It was made in 2003. Could it be low on Freon? I turned the heat down to 115 degree and turned up the compressor to run 45 minutes per hour. I measured the amount of water from the first hour and it pulled out 7 pints. I also noticed a lot of moisture around the vents.

Click here for higher quality, full size image

Click here for higher quality, full size image

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From Professor Gene Wengert, forum technical advisor:
You will find that for 1000 BF of oak, 32 pints of water is equal to 1% MC loss. So, with 2500 BF (is your pile 24' long, 4' wide and 25 layers?), this means about 100 pints will be a 1% MC loss. So, 7 pints per hour x 24 hours = 168 pints is actually a good loss rate, although you could go even faster. It does seem like the compressor is not working correctly.

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From contributor S:
I have used a Nyle for seven years and have had the same problem. After some investigating, I discovered several problems. First, check the hose, it will plug up. Pull it off the unit and blow through it, now reattach to unit. Check the flow. If, when you remove the hose and water does not flow freely, the plug is in the nipple or the trough in the unit. Clean them out and replace hose. Check flow and floor morning and night. I think you will see results immediately.