# Using a dehumidifier for home made kiln?



## Bjs1991 (Jun 26, 2017)

Hi I came across a large commercial dehumidifier and was wondering if this could be used in a home made kiln to dry lumber quicker I'm new to all this would this work or be practical


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## GeorgeC (Jul 30, 2008)

kiln
kiln/
_noun_
noun: *kiln*; plural noun: *kilns*


*1*. 
a furnace or oven for burning, baking, or drying, especially one for calcining lime or firing pottery




You could use the dehumidifier to dry wood but it would not be part of a "kiln." Just be a different process. Do not know just how the end point of moisture would compare.


The dehumidifier would be like taking the wood into your air conditioned house.


George


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## Larry42 (Jan 10, 2014)

There are commercial dehumidifier dry kilns made. They work very well. You will need to build your charge and provide fans to move the air through the stack uniformly. One disadvantage is they don't kill some of the bugs in the wood since they don't get hot enough. Their condensers are also made with corrosion resistant materials. Wood contains tannic acid and will attack some dehumidifier condenser materials. You can find drying schedules on the Forest Products Laboratory web site.


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## Tennessee Tim (Dec 15, 2010)

They make DH kilns EVERYDAY!!!! People need to quit just answering without knowledge. Sorry for the rant, I'm seeing more and more questions answered here without correct knowledge about the original post.....it doesn't actually help...it makes more confusion, just another post count.

YES... I have a homemade DH kiln....without knowledge on how a commercial one is differ from a consumer I can't answer whether that one would work. Nyle make s all sorts of DH's....even DH wood kilns ( that's the third one in the definition....for DRYING!!! leave off the example). The actual reading of moisture is done via the unit or other gauges?? as a consumer it's all built in

Yes DH's are for removing moisture in a kiln AND as Larry mentioned they're not the sterilizing part of the kiln for killing bugs.....MOST assume a kiln is a one step unit BUT it's most of the time actually 2 or more steps...drying ....sterilizing and depending on the set-up can have features of steaming and other wood related processing. Here's a thread I started amongst many re wood sawing and drying... http://www.woodworkingtalk.com/f26/kilning-sterilizing-much-confused-process-s-131825/ ...NO I AM NOT a pro at this BUT have studied many of the processes...I'm just a basic guy that doesn't have to have all the bells and whistles....YES I WOULD LOVE to have the Nyle DH unit driving my kiln just not in my budget at this time.
WHEN you have a homemade unit there are MANY variables that have to be done personally and logged/scheduled and watched more closely.... they're not a plug and play.... niether is a true commercial unit BUT they have better ranges and settings with more auto checks.

Please take the time to read about the basics on air. solar, DH drying.....this is a complex BUT simple procedure that can be done at home IF understood.

Now have fun reading and enjoying playing with wood....IF you short-cut it, IT WILL haunt you in time!!! Jay Whitecloud here can even give you some greenwood working advice as that's been his specialty in life in his studies.


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## 35015 (Nov 24, 2012)

Kilning wood is horrid for it and a modern approach to satisfy the impatient...and...Those that don't know any better...

I too (quite often...ha, ha) become very impatient...

Probably why I learned to work wood in the Green State (aka wet condition) as it has been done for thousands of years for everything from Harvest Farm Tables and Chairs to Living Room Floors...

There are only a handful of folks I would trust to "kiln" or "quick dry" my wood...BECAUSE...they actually take the time to do it correctly and painstakingly follow the appropriate steps to do it well...Even then (as Tim can contest to)...S_ _ _E Happens... and you get warp, case hardening, and other unwanted effects.

If "dry wood" is an absolute requirement for something (there are cases of such needs of course) then slow air drying in the shade will always yield the best lumber...That is simply a reality of woodworking...Kilns and Machine drying is a modern industrial process...NOT...a necessity...


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## Bjs1991 (Jun 26, 2017)

Thanks Tim and Jay these are the kinda the answers I was looking for not the definition of a kiln... No offence george...The application would be flooring 6 wide 4/4 or 1 inch cut. I have a home I'm currently remodeling to say the least at this point might as well be rebuilding it I have a bandmill coming and all the hard wood I could want . Would it be worth constructing a kiln or just air dry the wood and paint the sub floor and install when the wood is dry or at what MC can the floor be installed?? Again I am a new to all of this but anybody can do anything they put there mind to mistakes are learning I'm just trying to learn from others before making my own


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## freedhardwoods (Sep 7, 2008)

I agree with TN Tim.

I have dried a few hundred thousand feet of lumber with Nyle and Ebac kilns. Even with the guides and controls that come with one of these, there is a learning curve. I used an lp gas heater at the end of the dry cycle to kill bugs.

Many people dry lumber with regular dehumidifiers. The learning curve will be bigger without automatic controls.

I would spend several hours reading about drying lumber before you even start. I spent hundreds of hours reading everything I could about it while I was drying and I wouldn't call myself an expert. I did have many people in this area recommended me to others to dry their lumber.


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## Larry42 (Jan 10, 2014)

I don't think you can reach the required moisture content for your application by only air drying out doors. That is, unless you are not going to have heating and/or air conditioning. In most parts of the country your target moisture content should be in the range of 6.5 - 7.5%. You can use wetter wood but you will end up with gaps between strips when it finally reaches equilibrium. For all the work that you will be putting into this project a $200 moisture meter is a cheap deal. There is a lot more to properly drying wood than what meets the eye. READ.


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## freedhardwoods (Sep 7, 2008)

Larry Schweitzer said:


> There is a lot more to properly drying wood than what meets the eye. READ.


I found that out when I started drying lumber. The heater in my very first (homemade) small kiln caught fire and I had a load of smoked lumber. Thats why I started reading everything I could find about it.


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## Steve Neul (Sep 2, 2011)

The main objective of a kiln is to reduce the moisture content in the wood. Of course a dehumidifier would help. Even seasoned wood the moisture content rises when the humidity is high so it would stand to reason wood kept in low humidity would dry better.


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## Tennessee Tim (Dec 15, 2010)

freedhardwoods said:


> I found that out when I started drying lumber. The heater in my very first (homemade) small kiln caught fire and I had a load of smoked lumber. Thats why I started reading everything I could find about it.


LOL...I about done the same with a small piece I wanted to sterilize over night....the limit switch stuck on and melted my temp sending unit and insulation board....Looked for some pics BUT I can't find them in all them folders I've created to be easy to find !?!? LOL.


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## Bjs1991 (Jun 26, 2017)

Thanks for all the input on the topic I'm just starting out have a Turner band mill coming next week and can't wait to get a feel for it... The gap wouldn't be a big deal because I'm going for an older wide plank look anyways and I plan on getting a mc reader very soon haha


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## Roybrew (Nov 2, 2016)

Ooh good thread. I dried out a peach log in my basement a couple of years ago using box fan, dehumidifier, and time. I never used a moister meter or anything I had no idea. I really enjoyed working it into small boards and making trinket boxes. I never thought about the bugs tho... um I did have to remove a funny looking larvae from one of my boards. I probably infested my basement with God knows what.

Wish you the best Bjs1991. Please post how it's going.

Sent from my SM-G900V using Tapatalk


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## substratum (Apr 11, 2017)

As I read through these threads and links, I didn't see a recommended temperature for sterilizing wood. What is the generally accepted temperature needed to kill critters in the wood?


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## freedhardwoods (Sep 7, 2008)

substratum said:


> As I read through these threads and links, I didn't see a recommended temperature for sterilizing wood. What is the generally accepted temperature needed to kill critters in the wood?


The short answer is the lumber must reach 130* at the core. How long that takes depends on how hot your air temp is.

Here is an article all about it to really confuse you - https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr190/chapter_20.pdf


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## Tennessee Tim (Dec 15, 2010)

freedhardwoods said:


> The short answer is the lumber must reach 130* at the core. How long that takes depends on how hot your air temp is.
> 
> Here is an article all about it to really confuse you - https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr190/chapter_20.pdf


LOL.....I didn't know ANYTHING that had "fed" attatched to it would be confusing.....like "affordable" health care or just rules and regs!!??!!?? LOL......oooops sorry couldn't pass it up.

That is CORE (center of board) temp and held there for 3+ hrs (that varies with different articles BUT a general ule of thumb).....I get my kiln to approx 140 and leave 24- 36 hrs to be sure the core is heated long enough.


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## Tennessee Tim (Dec 15, 2010)

Note.....there are ways to build as Jay mentioned above in a greener state of moisture BUT there's a lot more to know about movement process and the wood.....even with hvac systems in most homes, proper build skills are must at any level for heirloom pieces to last, really what's the sense in building IF you don't want it to last....a waste of time IMO.

A couple of factors do play into this also :
1) we're cutting too many trees in the juvenile stage and mature lumber wood is getting less and less.
2) Most don't saw qtr sawn anymore....this is your premium wood for building.....how many "mission" style pieces of furniture you see issues with...????
3) Our lack of craftsman joinery is falling to the wayside....that includes knowing how parts should float and not be locked.
4) some of our finishes maybe hindering the older style of building due to they are harder, less forgiving to movement and not breatheable/flexible.


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## delelan (Jul 6, 2017)

I have a very small homemade kiln and a homemade dehumidifier it seems to work well for drying my turning blanks. I normally run it at 135 for a couple weeks with the humidifier also on during that time. If interested I have a couple build videos of it online if others want to take a look. 

Sent from my SM-G928V using Tapatalk


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## djg (Dec 24, 2009)

Just my opinion, but don't pass on as much lumber you can get (or afford to pay for) just because you don't have a kiln setup next week. Have it sawn into lumber and then sticker it while you educating yourself on drying. Just let it air dry for a while.


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## Quickstep (Apr 10, 2012)

delelan said:


> I have a very small homemade kiln and a homemade dehumidifier it seems to work well for drying my turning blanks. I normally run it at 135 for a couple weeks with the humidifier also on during that time. If interested I have a couple build videos of it online if others want to take a look.
> 
> Sent from my SM-G928V using Tapatalk


I'm interested. I've tried to accelerate drying in turning blanks using a variety of methods and have always ended up with cracks.


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## Quickstep (Apr 10, 2012)

I'm become more interested in the drying process lately since I've begun to harvest turning blanks from trees that have been cut down. It's been my understanding that the key to drying is to regulate the humidity in the kiln so that the humidity slowly decreases so the wood doesn't dry out too quickly. In fact, I thought I'd seen reference to kilns where they actually _add_ humidity at first, then slowly bring the humidity down to avoid cracking. I guess it varies according to species also.


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## delelan (Jul 6, 2017)

Quickstep said:


> I'm interested. I've tried to accelerate drying in turning blanks using a variety of methods and have always ended up with cracks.


Here is a couple videos of my micro kiln. Size is about 42 wide and 30 x 30. It's made from a heat lamp, thermostat controller, old computer power supply, pelteir modules, couple heat sinks, computer fans and thick wall PVC. Generally I'll run the heat portion starting off around 100 for a day and then bump on up to 130. When ramping up the temp in the second day is when I turn on the dehumidifier I built. 

Micro Wood Kiln Project: http://www.youtube.com/playlist?list=PLbKMKxAKVoTU0flDXfQbjuGjzuAxGpatv

I have watched several videos online of people using old refrigerators and even a dishwasher and making kilns out of them. This is how I got my idea to make mine the way I did. 

One thing I did add to the kiln after I built it was a small cheap humidity sensor. When the wood is heated the sensor reads really high. Like 80% and slowly drops over time. Normally after several days at around 25% or less I'll turn the kiln off. 

If you want links to the items I purchased I can try and find me. So far my little itty bitty kiln is working great for me. I may doing it wrong but I had little to no knowledge about drying wood when I went to built this. 




Sent from my SM-G928V using Tapatalk


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## Catpower (Jan 11, 2016)

A dehumidifier is really just a window shaker ac with a drain in the bottom of it. It would also add some heat from the fan motor and compressor, and heat of compression, but that really wouldn't amount to squat (the heat of compression)

You can pick up a 6000 btu window unit for about $100 bucks at Wally world it will extract about 6.8 lbs of water per hour under the right conditions, the latent heat of vaporization of water is 970 BTU @ 212F, so subtract 112, figuring 100 degree internal temp of the kiln

Get some muffin fans to circulate the air so all the wood gets air movement and it should dry it out pretty good


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## Tennessee Tim (Dec 15, 2010)

delelan said:


> Here is a couple videos of my micro kiln. Size is about 42 wide and 30 x 30. It's made from a heat lamp, thermostat controller, old computer power supply, pelteir modules, couple heat sinks, computer fans and thick wall PVC. Generally I'll run the heat portion starting off around 100 for a day and then bump on up to 130. When ramping up the temp in the second day is when I turn on the dehumidifier I built.
> 
> Micro Wood Kiln Project: http://www.youtube.com/playlist?list=PLbKMKxAKVoTU0flDXfQbjuGjzuAxGpatv
> 
> ...


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## delelan (Jul 6, 2017)

Tennessee Tim said:


> delelan said:
> 
> 
> > Here is a couple videos of my micro kiln. Size is about 42 wide and 30 x 30. It's made from a heat lamp, thermostat controller, old computer power supply, pelteir modules, couple heat sinks, computer fans and thick wall PVC. Generally I'll run the heat portion starting off around 100 for a day and then bump on up to 130. When ramping up the temp in the second day is when I turn on the dehumidifier I built.
> ...


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## Tennessee Tim (Dec 15, 2010)

delelan said:


> Tennessee Tim said:
> 
> 
> > I do the higher temp to get the internal portion of the wood to 130 so it will kill off any bugs. Actually come think about it I run at 135. The peltier module dehumidifiers I have built don't pull a whole lot of moisture. Rather they slowly decrease the ambient moisture in the air. Also want to mention most of the wood I run in my kiln isn't straight from tree to kiln. Rather it has sat in my shop from anywhere to 3 or 4 months to even maybe a year. Friends bring me random logs. I cut them to reduce checking and then they sit for a while until I have enough to run the kiln.
> ...


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