Small DH kiln/ Grain Bin question

DDobbs · October 26, 2012, 06:23:45 PM

Anyone have a home built kiln with a big box store DH in it?

I have seen talk about them but have never saw one .

I was at Home Depot today they have a dozen of the DH's from just a couple pints to 80 pints.

What size works best?

Was thinking of building in one end of my shed 12' wide x 8' high x 4' deep.

Will a small DH work in that size?

Thanks
Dave

jueston · October 26, 2012, 06:34:02 PM

i am no expert, but i think you need 3 things to make that work. the DH unit, air movement, and heat.

if you live someplace really hot you might not need a heater, and if you could direct it, you might be able to use the fan built into the DH unit to make the air circulate.

Kcwoodbutcher · October 26, 2012, 09:11:20 PM

It will work. For that size unit I think a DH with a capacity of about 30 pints a day will be adequate. The DH unit itself will give off enough heat to heat the unit most of the time but a small milkhouse heater might be needed in real cold weather. You will need another fan for air circulation and that circulation should be even through the stack or you will end up with temperature variations and MC variations. I think Ebac has some plans available. It's nice to have a power vent controlled by a thermostat for temperature control..The store bought DH unit will have a shorter life than a commercial unit, but they're cheap.

DDobbs · October 26, 2012, 10:29:59 PM

Thank guys for the replys. Is it the acid in the wood that eat the units? I am just guessing it eats the coils? Why do the other units last longer? Are the coils coated?

Kcwoodbutcher · October 27, 2012, 08:21:28 PM

Some are coated, some maybe stainless. A lot of the home DH units use aluminum. They still last quite a while and not all woods are high in acidity.

kelLOGg · October 27, 2012, 08:54:54 PM

I have a well insulated DH kiln w/ a home DH unit in it. It does dry wood (down to ~7% MC) in 10 to 14 days. It does have drawbacks 1) you have to air dry first to ~20% MC because of lack of sufficient controls it will dry green wood too fast and crack it, 2) the home DH units are designed for home use and can't take the heat so, in my experience, last only about 2 years. (I am about to buy my third one). I have never seen corrosion on the coils due to tannic acid in oak. My units look new when they die so I assume heat did them in. With the DH only running it can achieve 130°F easily in a few days.
(When I get the new unit I am considering shutting it off at ~90°, turning on the aux heaters to ~130°F, allowing it to cool back to 90°F and turning on the DH again)

A Nyle L53 would cost me 3000 - 4000$ which is way out of my league so I plan to just replace the unit as needed :(.

Bob

DDobbs · October 28, 2012, 12:30:03 AM

thanks guys for all the info

scsmith42 · October 28, 2012, 12:34:10 PM

Daren Neeson (FF member) sells plans for small DIY DH kilns, primarily aimed at hobbiest woodworkers.

He is the most active on Woodworkingtalk.com; you can contact him there about buying his plans. I recall that they are only around 25 bucks, and worth the investment.

DDobbs · November 19, 2012, 05:06:36 PM

I was just at HD and they have most all of the DH units on sale/markdown $50 plus

DDobbs · November 30, 2012, 11:03:13 AM

I got my small kiln up an going will try to load a few pics soon.

But had another brainstrom I have 3 grain bins at the farm not being used. All 3 have drying floors. Has anyone ever dried wood in a bin?
There is no power an it will be a load it an forget type deal as I live 100 miles from them. I have some walnut stored in one now but it was dry when I put it in there.
Being in central IL. the winter time wont yeild much drying. But the summer would.
It would have a natural draft which I could control by making some dampers on the lower inlet where the blower/drying fans were.

They would be a pain to load. It would be all by hand. They are 24' across by 21' high
so lot of free dry storage.
Any thoughts ? Anyone done it?

Thanks
Dave

treefaller · November 30, 2012, 11:27:43 AM

Dave, I have a grain bin that i have used to dry lumber.If the sun is out those things get very hot inside.I do have power so had a big box fan running and it worked great! Hedj

learner · December 09, 2012, 12:09:17 AM

Most people don't realize this but an air-conditioner is a Dehumidification unit if you make a couple small modifications.
You have to vent the cooled air and circulate the heated air. The condensation from the coils can be gravity drained by drilling a hole in the base of the unit and attaching a piece of hose.
A small wooden frame can be attached to the cool air exhaust vent and a vacuum cleaner hose used to vent the air through the side of the building.
An air tight and insulated case around the unit will contain and direct the hot air through the exhaust of the unit. From there you use a blower unit to direct the hot air through a series of ductwork to vents that blow through the stacked lumber(this also helps to keep the unit from overheating by increasing the movement of air across the coils and internal units). Additonal heat can be added with a small propane heater which will add to the de-humidification process(The reason Humidifiers are reccomended when using gas type heating). A simple thermostat controlled louver vent can be used to controll the internal temperature of the kiln.
Safety note; The lumber must be thoroughly cleaned of sawdust before placing in the kiln. Otherwise there is a small chance that any drying sawdust can be circulated back to the gas heater and cause a fire.

ForestMan · December 28, 2012, 08:46:06 AM

I built my kiln half your size. It is 12x4x4. I use a DH unit, a fan, and I was using two 500 watt halogen lights for heat, but both of the lamps died within one month. So I'm looking for a solution to heat it right now. The DH unit will kick off some heat, but you will need more. To solve the pint issue, or having to open the kiln to dump out water every day or so and loose all the good heat, I took the water collection bucket at the bottom of the unit, used two blocks of wood on either side of the plastic, drilled holes through them and screwed them together. Then I drilled a 1" hole through the wood and the plastic, and I epoxied a piece of used water hose to it and ran the hose out of the kiln. It works great. No need to ever dump the water out.

I have just dried my very first load of wood. It works great. I need to purchase a moisture meter to see how dry it got, but the wood is lighter and looks very dry to me after one month. Once I figure out my heating problem, I'll have a working kiln.

pineywoods · December 28, 2012, 09:31:50 AM

Forestman, you are halfway there. Go solar for the heat. A clear plastic top and a chunk of black painted metal between the plastic and the stack of lumber. Mine will hit 160 degrees. I use a room dh unit to pull out the moisture, no fancy vents or controls. Only gotcha is don't use plastic fans to circulate the air. They will melt. Do a search on pineywoods solar kiln.

ForestMan · December 29, 2012, 12:07:00 AM

Right, I have thought of that. My fan is all metal.

clusterbuster75 · March 12, 2013, 08:41:27 AM

Yes I have dried wood in a grain bin!

More than once and still have wood in there.

The 1st time, when I put a bunch in there (few thousand board ft), on advisement from my Master sawyer(I didn't know what an expert he was until he retired and I have dealt with wanna-be's), I covered my stacks (approx 8' x 8' x 4-5' high) with tarps and put a box fan under the tarp to keep the air moving.. I guess the tarps were to keep it from drying too fast.. Later years I added small stacks(log or two) to the grain bin, with no tarp or fan and had no drying issues.

Good luck,

Eric

Tim Lea · March 12, 2013, 09:32:57 AM

I also use a grain bin to dry lumber it works great.. I have one that had been taken apart that we bought and never put up.. I have been thinking about using it to make domes to go over stakes of lumber to dry them..We will see how they work and let you all know.