DIY Dehumidifier Kiln questions

Broncman · July 13, 2023, 10:43:22 AM

I am working on building dehumdifier kiln based on from the USDFA.

Without the fancy kiln controls how do you guys set a schedule on the DIY kilns?

I am thinking about adding halogen lights just to get the load up to temp quicker for woods like pine. Since these kilns run at lower Temps overall, how is equalization and conditioning accomplished?

K-Guy · July 13, 2023, 11:22:05 AM

Be aware that any commercial dehumidifier will have a thermal safety that will shut it down at 104°F

Broncman · July 13, 2023, 12:25:12 PM

Yes, that is what I meant by lower Temps. I am using a crawl space dehumdifier and it is ducted to and from the chamber. That might get me a little more temp, but not the 170 range of a true wood kiln dehumdifier.

I might play with the RTD for the temp switch in the dehumdifier and see if I can get it higher.

Is conditioning and equalization even an issue at these temps?

kelLOGg · July 17, 2023, 06:17:24 AM

Here's another thread on your topic.
Custom made kiln help in Drying and Processing (forestryforum.com)

Don P · July 17, 2023, 06:53:23 AM

Going the other way, I bought a "cool bot" for a window shaker AC that fools the thermostat and lets you use it as a refrigeration cooler. There's gotta be a way to go the other direction?

Broncman · July 17, 2023, 10:52:58 AM

I actually have the wiring diagram for the dehumdifier. It is really simple. Looks like I can unplug all their stuff and simply run the compressor from my Inkbird humidity controller. The fan and compressor simply plug into relays on the control board. Little bit of wiring and I can run the fan and compressor from the Inkbird.

Got everything almost ready to try. Need to get my fans wired in and door cam latch installed and some door weather stripping. Will have 6 fans at 800 cfm apiece all wired to separate switches.

K-Guy · July 17, 2023, 11:21:52 AM

Check with the manufacturer to see if the fan or compressor have built in thermal overloads. Also don't expect it to last for long as those units aren't made to resist the tannic acid that comes out of the wood with the water.

Southside · July 17, 2023, 12:32:30 PM

Sidetrack a bit but those Cool Bots DonP mentioned are awesome. Keeps my walk in at 38F with the A/C running under 25% of the time, much better economics than a true commercial cooler, and boy isn't it nice on days like today in there!

Broncman · July 17, 2023, 04:34:07 PM

Quote from: K-Guy on July 17, 2023, 11:21:52 AM

Check with the manufacturer to see if the fan or compressor have built in thermal overloads. Also don't expect it to last for long as those units aren't made to resist the tannic acid that comes out of the wood with the water.

This one has coated coils. We will see. The prints do not show thermals, but I will probably leave as is for awhile to get all the other stuff sorted out. Then I probably will not go above 120 if even that. The Nyle smaller units only go to 125 I believe.
I really don't plan on doing much red oak if any. Lot of poplar, ash, and pine.

KcMatt · July 20, 2023, 10:48:23 PM

Quote from: K-Guy on July 13, 2023, 11:22:05 AM

Be aware that any commercial dehumidifier will have a thermal safety that will shut it down at 104°F

Dri-eaze has one that is rated at 125* I have one but not going to check the model number right now. I think it's a 2000. They also have a 1200 that is rated at 104* but mine runs way beyond that. I'm gonna say it's been almost 120*. One thing is for sure, they don't pump out much water on the discharge tube when the moisture content is below 10% but they do maintain RH down to almost 20%.

For controllers I use Inkbird units. They have a few from cycle timers to humidity and or heat controllers and all of them work well and are accurate and durable. They run about $40 each. I've never had one fail.

Broncman · July 24, 2023, 01:12:29 PM

Got my kiln running over the weekend. No mods done to the dehumdifier. It does shut off around 100 degrees. My fans are generating a bit of heat. There are 6 fans that run off 12v DC power supplies. They are generating about 500 watts. Add that to the heat from the dehumdifier and it gets to 100 degrees pretty quick.

May have to add a temp controlled vent.

firefighter ontheside · July 24, 2023, 08:57:08 PM

I have been running a diy dh kiln for a few years. It has done ok with air dried lumber. I was using an old analog dh and had it connected to an inkbird controller that I could set to turn off the dh based on heat or rh. It worked pretty well. That dh bit the dust as I knew it would. The next dh I got is digital and if I use the inkbird with it, the power gets killed to the dh and then when power is restored the dh does not come back on. I've given up the diy and bought a nyle unit, but havent built the new chamber for it.

KcMatt · July 26, 2023, 08:46:09 PM

The drieaz dehumidifiers come on after being shut off by a controller. FYI the unit that's rated to 125* is a 2800i. These are nearly 4,000 new and obviously a Nyle is a much better purchase at that price. They can occasionally be found for a tiny fraction of that used.

JoshNZ · July 27, 2023, 02:29:40 AM

In summer I absolutely have to vent my kiln with only the DH running (diy setup). I have two axial fans sitting inside the roof frame on top of the container, ducted to gravity louvres siliconed into the side of the container. One pushes and one pulls. It might vent 1-3 times a day depending on how hard it's working.

firefighter ontheside · August 12, 2023, 10:35:13 AM

I have a big dri-eaz that does not come on unless the power button is pressed, so if it is shut off by a controller it does not come back on. That is why I quit trying to use it in my kiln. I had limited success with it in cooler months and it did not overheat the kiln.

Broncman · August 13, 2023, 07:06:12 PM

I got my temp controlled exhaust fan and vents installed today. Doing a test run right now to see if I need more vents. It is a 4" fan and vent with a 4 " inlet vent as well. I will add another inlet vent first if more is needed.

I did figure out how to controll the dehumdifier with my inkbird controller. I will have to add a time off relay in the circuit . The Inkbird has a time on delay for the compressor but no time off delay for the fan.

Once I get the relay I can make the fan come on first, then after "x" seconds or minutes, the compressor will come on using the Inkbirds setup, Then when it cycles off, I can make the compressor shut off first, then with the off delay, let the fan run for another minute to cool the unit off.

K-Guy · August 14, 2023, 08:19:09 AM

Quote from: Broncman on July 17, 2023, 04:34:07 PMThe Nyle smaller units only go to 125 I believe.

The Nyle units can dry up to 120°F but once the compressor is turned off the can go as high 160°F for setting pitch or sterilizing.

Broncman · August 14, 2023, 08:23:01 PM

So, I figured out one of my issues today. Now I got some more figuring to do. I have six 12 volt fans. They put out about 500 watts. The heat from just the fans alone kept the kiln at 100 degrees WITH the 4 inch exhaust fan running! No dehumidifier running at all.

Turned off the fans and have the dehumdifier alone running. Will track Temps and see where it gets me with just the dehumdifier.

After that, I will run the fans in series. This will cut the heat output to about 240 watts but will reduce the speed of the fans as well.

I may have to find some 120 volt fans instead of the 12 volt fans. They generate less heat.

KcMatt · August 16, 2023, 07:20:44 PM

I have switched the 12v fans out of mine because they were unreliable but I don't see how the heat would be different unless you reduce the wattage consumed by your replacement fan.

You could put the fans on a temp controller like I did. All my components have a regular 110v plug and all the controllers have receptacles. In the summer it gets hot easily so I run both the Dri-Eaz and the fans on a single Johnson Controls temp controller set to run up to 105*. In the cooler weather the Dri-Eaz is plugged into an Inkbird humidity controller and the fans left to run or set on the temp controller.

When it's cold I have a 1500w ceramic heater that runs off the temp controller (through a contactor) the fan stays on, and the DH runs on the humidity controller.

When I put fresh sawn wood in my kiln, the fan goes on an inkbird cycle timer to keep from drying it out too fast.

Broncman · August 17, 2023, 06:36:34 AM

The AC fans are less wattage. I wired the existing fans in series and that cuts the wattage in half. Last cycle did ok.

Empties the kiln last night and going to reload it hopefully this weekend and see how it does.

Fortunately my dehumdifier has a power loss option and will resume operations if power is cycled. I may have to run it from the Inkbird or set it up on a timer.

It is slowly coming together and I am sure I will have to continue tweaking it.

I would NOT use the DC fans again, but have not figured out what AC fan I want to go with just yet.

Broncman · August 22, 2023, 05:26:20 AM

Adding the extra intake vent did the trick. The vent fan is on a temp controller. Fresh load of pine and it has been in going on 3 days. RH started at 86% and was at 66 yesterday. Been keeping the temp around 95 and the dehumdifier has not kicked out on high temp.

I have about 250 BF and got about 4-5 gallons of water a day .