Dry kiln owners - does this sound right ......

[TexasTimbers]

"A low temperature dehumidification process is rapid enough to dry timber in a reasonable period of time, is energy efficient enough to be cost effective, and is gentle enough to cause very little stress and fiber distortion in the timber........ As we have become more adept at operating these kilns, we have been able to dry timbers down to 15% moisture content virtually from surface to core in about 28 days. We regularly dry Southern Yellow Pine and have also dried Douglas Fir. This process allows us to use dry, stable wood in our frames without having to resort to the expense of recycled timber."

My B.S. Meter went off when I read this. I won't mention names but I found this on a website of a TF Guild member. Is this for real? Because if it is then drying timbers doesn't sound like a problem.

Right before these paragraphs they were discussing how air drying was not acceptable to them because of time constraints with large timbers, so I am left with the impression they are not air drying the timbers any long lengths of time before going into the kiln if at all.
Is 28 days, with little or no air drying, realistic for SYP with little or no air drying?
If so, this is great news. For some reason, I have been under the impression I was looking at 2 - 3 months to dry large timbers in a DH kiln not counting air drying, especially on days like today when it's raining in sheets.

[Gilman]

Maybe they are drying really short beams?  In the range of 1-4"?

[twoodward15]

They never mentioned how much wood was in the kiln and how big the dehumifier was did they????  If they put one 2X4 in a kiln designed for 4000 feet and ran that bad boy full boar while strapping the lumber to the floor it might work.
Actually, I was just talking to the sawyer I buy from.  He sawed up a couple cedar logs, 5 footers and through them immediately in his attic.  Said they've been there for a few weeks now and he's gonna take them out and use them this weekend. 
I was alos under the assumption that pine and cedar and the like would pretty much air dry (with good airflow and being about 5/4) in just a couple months here in Jersey.  I would assume that it could be sped up in a dehu-kiln.  You can pretty much dry that stuff as fast as humanly possible with very little degrade, and it's framing lumber.  You ever see that stuff they sell at lowes and HD????? ;D

[Don_Lewis]

SYP timbers for log homes, (6" x 8") can be and are dried in 7-10 days in DH kilns that are able to go to 160F. You would double the time in a 120F kiln. Sizing the unit is critical. Douglas Fir takes longer and Eastern White Pine takes longer. Some EWP operators dry in 2 weeks, some 4 and some 6. The longer time reduces, but does not eliminate, checking. The important thing is to be sure that stickers are at least 1-1/2" when timbers are over 4". We tested a SYP kiln drying 8x8's with 3/4 and 1-1/2" stickers, all other factors equal, and drying time went from 10 days to seven days (green to 15% 1" in). But some of the best and biggest operators use 3/4" stickers on timbers and take 4 weeks because the feel the get a better result.

[Den Socling]

Don,

You say 15% 1" in? What is the core?

A forum member recently told me it took him more than 3 weeks in his DH kiln for Doug fir that was only 4" thick.

Den

[kilndry]

I agree, 15% at the core would be a trick. I wonder if the company actually measures the core of the timber?

[Don_Lewis]

15% 1" in is pretty standard because that is about all that is practical to measure. We do have customers on the West Coast who do nothing but 4" Douglass Fir for the European and Japanese market and they dry to 6% to the core. This is very high end product and they take 4 weeks.

Drying time is directly related to vapor pressure deficit which is more dependent on temperature than EMC or RH. Then you have to consider what the capacity of the dh unit is at the conditions. Timbers generally require bigger depressions and dh units take less water out at bigger depressions just as conventional kilns require about twice as much energy at bigger depressions.

[Den Socling]

And that is why vacuum kilns do well with thick stock. The pressure gradient is set by the chamber pressure and you do not need to drive up the vapor pressure with high heat. The high heat approach has the added disadvantage of drying that outer inch which then becomes an insulator to the water in the core.

[TexasTimbers]

So then for me to do this in a Nyle 200 or comparable unit is not really doable, at least in any quantity I take it.
Oh well. Thanks. KJ.

[Den Socling]

You know how it goes. If it was easy, everyone would be doing it and then it wouldn't be worth the big bucks.  ;)

[Don_Lewis]

It will work with an L200 but you have to be aware of the drying time difference. You can still set pitch and sterilize with an L200

[Frank_Pender]

If I am not mistaken, out here in Oregon, kiln dried lumber is required to be at 15%.   For the purpose of cabinetry and such it needs to be to at lest 6-8% for the folks doing business with me.

[Don P]

For construction kd19% is the code throughout the country I believe.
Typically timbers over 5" have been exempt from that portion of the code.
The new proposed log building standard interrelates settlement allowances with moisture content, among other things. Don brings up a good point, how the measurement is taken. My meter does have 3" insulated pins.  I have met shell driers in court who had advertised 19%...they lost ;).