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converting solar to Dehumidifier over winter

Started by Woodslabs, March 28, 2016, 05:53:59 PM

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Woodslabs

Hi All,

I recently built a solar kiln and it works great.  I have some questions about adding a dehumidifier to the solar kiln and converting it to full dehumidifier over the winter months.

1) at what moisture content can i add the dehumidifier and should i run it 24 hour or night only (what do i set the RH to?)
2) Does anyone have a dehumidifier they recommend using?

I have the option to run natural gas to my kiln and heat it during the winter.  I can also insulate the collector with insulation fitted in-between the rafters. Would you recommend running a on off cycle like a solar kiln or just run it 24 hour a day with high heat and dehumidifier?
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GeneWengert-WoodDoc

Although you probably know I developed the Virginia Tech kiln in 1978, you will find that if you want a DH in the winter, you need to insulate the kiln better than a VT solar kiln.  So, it sounds like you would be best with 100% DH.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Woodslabs

I can convert it back and forth between the 2.  I can insulate the collector for the winter and remove it for the summer.  I may convert it 100% to dehumidifier depending on the results i get.  I will be running natural gas to the kiln this spring and maybe eventually get the L200 from nyle.  In the mean time i was wondering if i can run household dehumidifiers?  I need one that will safely run from 30-50C (86-122f)

I was thinking of putting two 70 pint dehumidifiers and see how it goes.  I know it will dry slower than with the L200 but i'm ok with that as i need around 4 loads a year.

Will two of these work?:
http://www.costco.ca/Gree-Electronic-33.1-L-(70-pint)-Dehumidifier-.product.100147779.html

if not can someone recommend some?  My kiln holds around 4500 bf. 
check out www.woodslabs.ca

pineywoods

Woodslabs, look here....https://forestryforum.com/board/index.php/topic,50281.0.html
Three of these locally. They work well. With the room dh, you don't need vents. All 3 dh's are different, just whatever the local flea market had available. They usually have a high temp auto shutoff, and will generate some heat in the kiln. The black sheet metal under the rafters makes a huge difference in the max temp obtainable.
1995 Wood Mizer LT 40, Liquid cooled kawasaki,homebuilt hydraulics. Homebuilt solar dry kiln.  Woodmaster 718 planner, Kubota M4700 with homemade forks and winch, stihl  028, 029, Ms390
100k bd ft club.Charter member of The Grumpy old Men

Woodslabs

Any idea what the usual shut off temp is?  I would like some that can at least get to 120 without turning off.
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pineywoods

Quote from: Woodslabs on March 31, 2016, 08:37:38 PM
Any idea what the usual shut off temp is?  I would like some that can at least get to 120 without turning off.
On some, it's a thermostatic shut=off, others use a pressure switch on the high side of the compressor, some have no cut-off. Mine still runs at 120 F, but I generally run the fans during the day and fans plus dh at night.
1995 Wood Mizer LT 40, Liquid cooled kawasaki,homebuilt hydraulics. Homebuilt solar dry kiln.  Woodmaster 718 planner, Kubota M4700 with homemade forks and winch, stihl  028, 029, Ms390
100k bd ft club.Charter member of The Grumpy old Men

GeneWengert-WoodDoc

The upper temperature is limited oftentimes by the gas used in the compressor.  At higher temperatures (above the rated value), lubrication is not adequate.

Now, 4500 BF of oak is about 130 pints per 1 % MC loss.  So, 70 pints is a bit small.  The risk with a small unit with that much lumber is that you will have high humidities and mold, mildew and sap staining.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Woodslabs

I plan to run two 70 pint dehumidifiers.  If that is not enough i may add a 3rd.
check out www.woodslabs.ca

GeneWengert-WoodDoc

We typically try to dry pine, ash, maple and others close to 10% MC per day.  With 2 units, you will be drying 1% MC to 1-1/2% MC per day.  In other words, you are under powered by quiet a bit.  Would you like to dry a load of pine in 50 days, green to 19% MC?  If you want ten days, you probably need at least 10 hp compressor.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Woodslabs

Hmm I usually only dry hardwood. I would be ok with a 2-2.5 month turn around as long as the results are solid. I may need to invest in a l200 sooner than I had planned.

Can't I just dry it slower with a lower temp (95f) so that the dehumidifiers can keep up and increase the temp towards the end?
check out www.woodslabs.ca

Fedge

I can't directly comment on a solar/dehumidifier hybrid would work. I can say that I used to use a 50pt dehumidifier in a foam box to dry about 350bd/ft per load. The dehumidifiers do not last in that environment. I ran maybe 6 loads a year and that was all I could get out of the dehumidifier. I believe that the kickout temp on those units was 110F. I built a larger kiln (800 bd/ft) when i purchased a used Ebac ld800 for $800. I have had no problems with that unit to date. To sum it up, I'd find a used nyle or ebac or spend the bucks and go new. Not say it doesn't work but it was costing about $.09 per bd/ft just for the dehumidifiers. Oh yeah, oak will eat the home units almost immediately.

Geoff
A smart man knows a lot, a smarter man knows what he doesn't know.

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