Kiln drying by RH

[foresterstan]

Recently bought and set up used Koetter 4000 dry kiln.  Does anyone have experience running a kiln using RH readings as opposed to Depression?

[DR Buck]

The Wood-Mizer DH-4000 uses RH and Temp to dry.   Been using mine for almost 10 years without problems.

[foresterstan]

Does it run with a dehumidifier, or direct heat to the chamber?
if it is direct heat, I would be interested in a schedule example to compare with the Koetter

I have just installed an Extech RH sensor, and am hoping to use it to run the drying schedules. 

thanks

[scsmith42]

I also have a DH4000.  It uses both heat as well as dehumidification.  Typically you set a targeted temp and DH range based upon the species, thickness, and initial moisture content.  You change the settings (increase temp and lower RH%) as the load dries.

Schedules vary depending upon the species, thickness and IMC%.

It's a good idea to take chamber size as well as load size into account.  If you have a large chamber and try to dry a small quantity of a slow drying species, it can be difficult to control the RH% during the early and mid drying stages unless you augment with steam or fog.

[foresterstan]

thanks SC,
some more questions if you have time, on load size etc. 
if you don't have a full load, (both length and height) how do you buffer the empty spaces for good airflow,
also, what adjustments do you make to the schedule if any?

[GeneWengert-WoodDoc]

Is the Koetter 4000 a DH kiln?  I think not.

I have been involved with running many Koetter kilns.  You can easily convert depressions to RH and also the reverse.  Go to DRYING HARDWOOD LUMBER and use the chart on p. 16 and 17.  This book is available at many sites on the Internet.  The chart is available in many texts as well.

Let me know if you have more questions about operation.

[foresterstan]

thanks, I just posted for someone with experience with koetter.
I have a lot of questions, I will post them under Koetter Dry Kiln experience wanted...

thanks in advance.

[GeneWengert-WoodDoc]

Are you using Koetter schedules?  They are different than the schedule that most people use. 

The basic schedule for most people uses the same humidity as a steam schedule but might use a lower temperature.

If you do not fill the kiln, you can use the standard schedule.  With air dried, blocking the air spaces with fabric or plywood etc., is not as critical as with green lumber.

The standard schedule is based on the Moisture Content of the lumber and not time...are you familiar with the MC method of running a kiln?

[DR Buck]

thanks SC,
some more questions if you have time, on load size etc. 
if you don't have a full load, (both length and height) how do you buffer the empty spaces for good airflow,
also, what adjustments do you make to the schedule if any?

I have drop down curtains (tarps) to close in the top over the stack.   I also block the ends as needed with small pieces of roofing tin and Styrofoam insulation board pieces.   I normally follow the schedule Nyle has in the owners manual.  I try not to run with less than half load (~1000 bf) because it is not economical as it takes just about a long as a full load and costs the same to operate.   If I have small amounts I end up mixing species which is not really a good idea unless their drying schedules are close.  So far I've been lucky.  Right now I have a mixed load of 8/4 walnut, 4/4 cedar and 5/4 yellow pine.   Maintaining close to the 8/4 walnut  schedule.   I did get a small amount of blue stain on a few of the pine boards during the first week of the cycle but otherwise things are looking pretty good.

[scsmith42]

thanks SC,
some more questions if you have time, on load size etc. 
if you don't have a full load, (both length and height) how do you buffer the empty spaces for good airflow,
also, what adjustments do you make to the schedule if any?

Drying schedule is based upon species, thickness and initial moisture content.  You should never modify a schedule based upon having a small load, otherwise you will damage the lumber. 

I typically staple some Tyvek housewrap to the bottom of my kiln baffles and run it to the floor, and use some 4 x 4's to hold it in place.  Fast and easy.

[foresterstan]

Thanks all for the input!  unbelievable amount of resource here...
probably the best now is to try a few loads and start posting more questions then...
I'm sure i'll be back for more....
thanks again
-fs