Dehumidifier Kiln Advice

Detailed conversation about building, equipping, and operating a dehumidifier kiln to dry lumber. September 10, 2007

I currently have a solar kiln that I am happy with, but it doesn't work well without the solar part. I am now going to upgrade to a Nyle200. Can anyone out there that has a DH kiln tell me if this is easy to operate? I have heard that Nyle's manual is tough to follow. I am kinda dumb and would like to know if operating it is relatively foolproof. I have 1100 bd ft of 1/4 sawn oak to go in first. Oak really clogs the solar kiln for a long time.

By the way, thank you Dr. Wengert for your solar design. I copied it exactly and I am very happy with it. I have dried thousands of bd ft in mine, but it gets too backed up in the winter.

Forum Responses
(Sawing and Drying Forum)
From contributor J:
I have an older Nyle 150 (similar to the 200). I replaced the standard timer control with a humidistat from Nyle so I can just set the desired RH instead of using the timers. Kiln schedules have the recommended RH and temperature settings based on the MC of the lumber, and the species and thickness. You'll have to check it every day and make adjustments if needed. Attending a NHLA kiln drying class is a big help too.

From contributor D:
I have been using a Nyle 200 for over a year now. Operating it is fairly simple, although there are other factors involved that could cause problems if you aren't careful. Remember when drying oak, a little too slow is a lot better than a little too fast.

From contributor E:
I've had a Nyle L200 for 3 years and am well pleased with it. Most anyone with walking 'round sense can operate it. At first I was afraid I would mess a customer's lumber up, but with a good moisture meter and the help from Nyle, it's no problem getting lumber kilned properly. Your kiln needs to be very, very well insulated unless you like making donations to the power supplier. Go for it! Some of the best spent coins I've ever let loose. Nyle will be right there with you, especially Don Lewis.

From the original questioner:
Thanks for the advice everyone. I am going to get the Nyle because they have shown excellent service. Someone is always available when I call for questions, and all I have bought so far are the plans. The Amish around here know I have the solar kiln and always want me to dry lumber for them, but my little solar kiln is busy with all my own stuff. I already have the insulation bought. It is 3" of foam sheets. The inside will be aluminum sheet I bought as seconds. Everything is now ready to be put together, so I am getting close. I appreciate the info from all you experts that have already been there and done that. I am just a little nervous about that first load! The cost of the kiln is a little bit of a reach right now, so I need the push.

From Professor Gene Wengert, forum technical advisor:
If you can afford it, I suggest the L300 is a minimum system. It can do more. Do not forget that the compressor and the building together are a piece of equipment, so should be treated that way when doing your taxes.

From Professor Gene Wengert, forum technical advisor:
As a note tangentially related, always get a loan for the kiln and use your cash to purchase lumber, advertise, pay monthly bills if sales are slow, and so on - things that the bank will not loan you money for.

From contributor S:
I've been operating a Nyle 200/Wood-Mizer 4000 kiln for over 4 years. Without question the folks at Nyle are superb when it comes to customer service and support after the sale.

Contributor E provides some good advice; in addition, I would add to be sure to insulate your floor, build a solid kiln-cart system (the Nyle model is a good one to follow), and to put in man-doors on each side of the chamber to allow quick and easy means on ingress/egress for daily inspections. You lose a lot of heat and RH management if you have to open the big doors daily.

Pay attention to the recirculating fans - I have 5 in mine. Also, oak produces a very corrosive by-product so make sure that all of your interior components are corrosion resistant.

I started off with a metal interior, and ended up with a poly insulation on the inside in order to reduce moisture condensing on the surface. I would also recommend some type of surge arrestor on your incoming power lines to help improve the longevity of your controller. I installed one after replacing $800.00 of components and have not had a problem since.

From the original questioner:
Thanks for all of the information. I have already insulated the concrete floor before I poured it, and I have a stack of aluminum sheets to use on the interior which Nyle guys told me was the best stuff to use. Where did you get the surge arrestor? That sounds like a good idea. Have you, or anyone else, found that you have a lot of business from drying lumber from customer's wood, or is it all your own? I don't have a sawmill, and do not want one. The Amish will cut lumber for me for .15 cents a bd ft, so the sawmill would not work here, as that is pretty cheap. Where do you sell all of your lumber at - retail, or different companies? It is tough here in NE OH and NW PA; many mills are shut down right now, even the Amish ones. I was wondering how the small L200 kilns are fairing in these hard times. It is hard for me to part with the money for the L200 if I can't make it pay for itself. I have young kids that are getting more and more expensive as they age, kinda like wine.

From contributor E:
Contributor S is right -on about the interior walls. You want them to be impervious to interior climate. I used fiberglass sheeting that was intended for meat coolers that I picked up at a salvage outlet for pennies on the dollar. Used exterior halogen lights in the chamber for light when checking load. Used insulated 3' door for inspection entrance that opens out and made a Styrofoam door for same frame to open in, so this door is double insulated. Load kiln from one end and unload from other end into planer room. Haven't had any corrosion on circulation fans and have dried quite a lot of red and white oak. Blades look great.

From contributor S:
I bought the surge arrestor off of E-bay from an electrical supply house that was discounting old inventory. It is the "whole house" style for a 200 amp load center, and I paid around $40.00 for it (cost over $300 new). I think that these particular units were a fad in the electrical industry about 10 - 15 years ago.

Regarding the aluminum on the walls, I defer to the experts at Nyle. In my case, I had some early problems with moisture condensing on the walls of the kiln, which was making it more difficult for me to control the RH and rate of MC reduction. After insulating and placing a non-condensing surface inside the kiln, the problem went away. Perhaps this is not as much of an issue if you are well insulated behind the aluminum; my initial kiln was not well insulated and thus may have contributed to the problem.

Regarding business, I built my kiln primarily for my own use, but I offer drying services to others that either own sawmills, need large beams sterilized, or buy in bulk from sawmills. I really can't comment on the general market, other than to say that here in NC most of the furniture manufacturing is moving off shore, so the market becomes more of the woodworker end user. If you're planning to do this as a business, you are right to find your end market first and then proceed accordingly.

From the original questioner:
I hear that all over from the local sawmills. Most of them say the same thing - overseas imports are killing them. This is the reason for my concern. I am hoping the Amish will keep me busy around here as they have no practical way of kiln drying their lumber, but it all seems to be a roll of the dice. I hope both of you guys end up millionaires whether you want to be or not! Both of you are a lot of help.

From contributor R:
I bought a Nyle 200 about 4 years ago, after much debate on the payback potential for the machine. Excluding my labor for loading and unloading, the machine paid for itself within one year. I have mine set up in a used reefer shipping container... very good insulation and a stainless interior. They are about $3000 and well worth it. The kiln itself is profitable, but you won't get rich. The real value to me is the doors that it has opened to other markets. I can now easily sell my lumber to cabinet shops, hobby workers, and further process it into value added products such as moulding and flooring. These markets were not open to me before the kiln. I also use it to differentiate my business for other portable sawmills. There are many around, but not many other kilns. All said and done, buying the kiln was probably the best investment I've made since starting up in 2000.

From contributor T:

Are you talking about using the same container as the solar kiln? On a very related note, I am considering converting my solar kiln to a Nyle L150 or 200 system. Since the capacity of my box is only ~1000bf, I figure the L200 is enough power. I hope I can find room for the DH!

In the heat of the summer here in St. Louis, I get all the drying speed I want from the solar panels and would probably just keep the DH off, but for the other ~8 months, this DH will keep my insulated box active. But of course the roof is not insulated (being just two layers of polycarb panels) and it still lets in light. Do I lose too much control trying to use such a box for DH drying? Aside from installing drainage and finding a place for the DH itself, what other mods might make this work? I don't look forward to building another big insulated box! Do I have a choice? Can this work?

From the original questioner:
No, I am going to keep the solar kiln up and running for small loads. I built a large barn this past summer with the intention of adding a kiln. I put a drain in the floor, and wired it for 100 amp service. I also put foam under the cement, and added lights strategically with the kiln in mind. I think if I lived where the solar kiln worked for 8 months like you do, I would build another solar kiln instead. Why would you pay to dry wood when you can do it for free? Here in NE OH we rarely see the sun, even in the summer! It really put a constraint on what I can dry. I have 1000 ft of 1/4 sawn oak backed up right now. Forecast says rain and snow for the next two weeks. No drying is going to happen here in April either.

All you guys here have been a great help to me. I always wondered why everyone on this thread talks about sawmills mostly, and not too much about kilns. I would think this would be more profitable than running a sawmill, but I have been known to be wrong in the past (just ask my wife).

From contributor C:
Avoid a cart system at all costs. I have one that works well, but at great expense. A front load kiln that you can load with a forklift would be a much better solution.

From contributor G:
I have been using Nyle kilns since '89. Started with a L50, added a second, then a third. Sold them and bought a L200. Added a second, then a third. Thought I would downsize, so I sold one and rebuilt the two others. I also started shed drying so I could get lumber through the kilns faster. Takes a big shed. Works very well for me. They are very easy to run and service can't be beat. They are money makers if you charge enough and use a forklift as much as possible. I can't keep up, so I am thinking about adding a third one again. I dry some for myself, but most is custom drying. I like the 200 over a larger kiln because it gives me more flexibility for small or large loads.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor O:
Congrats on getting a Nyle DH. We’ve had L200 online 12 years now and are in our 216th load. We are a small family 5th generation sawmill in central Connecticut. In addition to sawing for ourselves and custom orders, we custom saw people’s logs, air dry, kiln dry and make a lot of wide plank flooring as well as do custom drying and offer milling services for the same. We got old reefers that were already insulated and have stainless walls. We built a 36’ long lumber cart and made the cart 40” wide with 15” on positive side and 12” between dryer and load. We load 3000’ per load and do 75-85M per year. The L200 works just fine. We use 5 fans and if/when we get a 2nd unit going, we’ll put in 6 fans especially for doing pine.

With a many different lengths of lumber, we have not been able to successfully pre-stack units for ease of loading. That takes time too. Instead, we unload and reload right on the cart and it’s a “puzzle” to get the courses as tightly packed as possible to maximize your load. It works pretty well. Three of us can usually do the job in six hours or less. This also gives us the opportunity to take our kiln samples from the center of the piles instead of off the edges or the top of piles where you’d be getting drier samples.

Everyone has given you good advice based upon their experience. Whatever you spend now, you will not regret; you will make it up down the road and remember it is a long road.

To summarize, taking a class in kiln drying would be a big help to understanding exactly what you are doing. Having a good moisture meter (Delmhorst J2000 and RDM# are good ones) is a big help. We use the true and tried method of daily weighing kiln samples and use the Delms as backup.

We air dry all species before drying, pine 2-3 months and oak 6 months. Why? Because mother nature will take ½ - 2/3 of the moisture out for you. Example: 8-9 years ago we did some mid-winter sawing of oak and we needed it in a hurry. It took three weeks to saw and prep and then it was in the kiln with no air dry time - frozen wood too. It sat there 45 days, what seemed like an eternity. We took 350 gallons of water out of it. With air drying, that is cut to 75-100 gallons and 21-24 days, a big difference. We save that water and later put it back into the kiln when conditioning.

And above all, don’t be afraid to ask questions. There are apparently a lot of us out here more than willing to give you advice. Hope this has been helpful.