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Thread: Finished my Solar Lumber Drier Today

  1. #16
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    Dec 2010
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    Quote Originally Posted by Jim Andrew View Post
    John, do you run your dehumidifier all the time, or do you have a timer so it runs at night? And did you close all the vents?
    I set the DH so that the RH would stay at about 45% and it's on all the time, as needed. I closed all the vents except for the 1" or so on one to run the hose and electric cord from the DH outside.

    John

  2. #17
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    Quote Originally Posted by John TenEyck View Post
    I'm using 3/4" stickers; 1" would definitely increase the velocity but reduce the BF in the kiln. The combined effect would be faster drying times and might be a good route for species that can tolerate that like ash.

    Are you drying green lumber in your solar driers or AD? The FPL document on drying hardwood lumber says there is no quality advantage for air drying. The drying season up here is coming to an end this year and probably doesn't allow me to do anything more than another batch of AD lumber, but there is next year to plan for, too.

    John
    Actually switching to 1 stickers would slow the velocity down - not speed it up (unless you had minimal plenum area on each side of your stacks).

    Glad to learn that your DH addition worked well.

  3. #18
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    Quote Originally Posted by Scott T Smith View Post
    Actually switching to 1 stickers would slow the velocity down - not speed it up (unless you had minimal plenum area on each side of your stacks).

    Glad to learn that your DH addition worked well.

    Yes, sorry about that.

    I'm getting RH values down in the 20's now when the sun is shining. My lumber is done!

    John

  4. #19
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    Sep 2009
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    Putney, Vermont
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    JOHN,
    I have been following your first drying adventure. Does the RH at 20% when the sun is shining mean that the wood will be approximately 7% moisture content. I noticed you were shooting for 7% in a earlier post. If so it has only been 2 weeks for you having the wood in your new kiln, If I am correct. That sounds really good to me.

    Your new kiln looks fantastic by the way.

  5. #20
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    Quote Originally Posted by michael langman View Post
    JOHN,
    I have been following your first drying adventure. Does the RH at 20% when the sun is shining mean that the wood will be approximately 7% moisture content. I noticed you were shooting for 7% in a earlier post. If so it has only been 2 weeks for you having the wood in your new kiln, If I am correct. That sounds really good to me.

    Your new kiln looks fantastic by the way.
    Thanks Michael. If you keep the wood long enough at about 38% it will reach an EMC of 7%. But short term exposure to 20% will get you there faster. The surface wood will go down well below 6% but inside it will be higher. Then when the sun goes down the moisture will equilibrate within the wood to some intermediate value. That's the benefit of solar driers; you can push the wood really hard during the day but the relaxation at night helps prevent checking, etc. My wood was already air dried to 14% when I put it into the kiln, so the likelihood of me damaging it was pretty low. By adding the dehumidifier for the last few days I was able to prevent the wood from reabsorbing moisture from the ambient air at night and also keep the temperature higher in the wood. The RH stayed at 40% overnight which was sort of lucky as I just guessed at a setting and that's what I got with it running essentially non-stop at night. Anyway, the dehumidifier allowed more of the sun's energy the next day to go into extracting the last couple of % moisture I was trying to remove rather than having to use the first few hours warming the load back up and removing moisture reabsorbed at night.

    You are correct. The load was in the drier for two weeks. But again, I started at 14%.

    Now I'm adding the door seals I should have installed before I just couldn't wait to put some wood in it. And I'm also installing plastic sheeting on the inside of the rafters to have double glazing. Those improvements should give me even better performance, especially as we get into Fall here in WNY. With help of a friend we got the kiln unloaded yesterday. Once I finish the upgrades I have a half load of walnut cut only about 3 months ago to put in that hopefully will be dry before Thanksgiving.

    John

  6. #21
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    Sep 2009
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    Thanks John. I'm glad you started this post. I may build a kiln similar to yours, and use your experiences to dry some wood in the future.
    It will be nice to see some of your projects with your own kiln dried wood, in the future. Having wood correctly dried will be such an asset in making some nice pieces, and at a savings also.

  7. #22
    I just got my lumber dryer going a couple weeks ago, and added 2 dehumidifiers this week. The high temperature is running about 111 degrees F, and I opened it up to see how the dehumidifiers are doing, and one was running and the other was still turned on, but had shut down. Do these things run 24-7, or does the high heat make them shut down? I put hoses on the things and run the moisture out through holes in the corners, so no worry about dumping the buckets.

  8. #23
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    Mar 2015
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    cleveland,tn.
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    it depends on the make and model as how they run, but dehumidifiers operate on a temp differential they get cold in a warmer surrounding and causes moisture in the air to condensate on the cooling coils and water drips off , so I believe that temps to hot or to cold will make them not function correctly. I would think that in the instructions they would cover the ideal operating temps. you might have to cycle the temps up and down with the dehum to come on when you lower the temp enough to let the dehum work. Like set a timer and let the dehum run at night when the temp drops and off during the day when temps are to high for the dehum to work. This is a WAG.

  9. #24
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    I use a 30 year old dehumidifier. I used to use it in my dehumidification kiln, which ran at a constant 110F. It never failed to work properly and easily condensed water out on the cold coils. The temp. in my solar kiln was 114F the last day or two when I had the dehumidifier inside and it was still running fine. As David said, check the temp. range for your dehumidifiers.

    John

    I looked up the temp. range for the new, digital dehumidifier I have in my shop. The high temp. limit is 95F. If yours was built to similar specs. that could explain why it shut down in the solar drier. If so, you'll need to find one that can handle higher temps. or only run it at night when the temps. are lower.

    John
    Last edited by John TenEyck; 09-11-2019 at 5:48 PM.

  10. #25
    The temperature this morning when I checked was 94, so that makes sense why the dehumidifiers aren't working. Guess I will have to turn off the blower for a couple days to let it get low enough for them to work.

  11. #26
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    Quote Originally Posted by Jim Andrew View Post
    The temperature this morning when I checked was 94, so that makes sense why the dehumidifiers aren't working. Guess I will have to turn off the blower for a couple days to let it get low enough for them to work.
    You must live somewhere really warm. My drier is in the low 70's in the morning. How will turning off the fans lower the temp? If you are using a solar drier covering the glazing with something opaque might be the best way to lower the temperature if opening all the vents doesn't do it. But if the ambient temp. is 90F in the morning I doubt there's much you can do to lower the temp. in the drier. In that case your best alternative would be to look for a dehumidifier that can operate at higher temps. like mine.

    John

  12. #27
    I have a 48' reefer trailer box, and 22' of solar hot air panels. The blower is a furnace blower that blows air from the inside of the reefer through the solar panels and back into the trailer, so that is my heat source. This morning I checked the dehumidifiers, and both were on 40, so clicked them down to 35 and both started blowing. Checked later in the morning, and water was dripping from the hoses. So they were working, as the temperature in the reefer this morning was 96 degrees. Checked the temperature at 2:00 pm, and it was 115 degrees. Located in Kansas.

  13. #28
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    Quote Originally Posted by Jim Andrew View Post
    I have a 48' reefer trailer box, and 22' of solar hot air panels. The blower is a furnace blower that blows air from the inside of the reefer through the solar panels and back into the trailer, so that is my heat source. This morning I checked the dehumidifiers, and both were on 40, so clicked them down to 35 and both started blowing. Checked later in the morning, and water was dripping from the hoses. So they were working, as the temperature in the reefer this morning was 96 degrees. Checked the temperature at 2:00 pm, and it was 115 degrees. Located in Kansas.
    That's an interesting set up. I imagine you can dry a lot of wood in a batch.

    John

  14. #29
    Have had a band mill since 05, and every place available for storage is full of lumber. Be nice to have some dry enough to use in my wood shop!

  15. #30
    Join Date
    May 2014
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    Washington State rainforest
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    Just wanted to chime in and say what a great job on the kiln!

    If you're drying wood mostly for your own use, a modification to consider down the road would be to add black metal roofing panels to the underside of the rafters creating a pocket between the glazing and the roof panel. By building a box for the fans that directs airflow through the pockets, out at the bottom, and through the pile, the kiln can be "turned off" simply by unplugging the fans. This is useful to use the kiln as a dry shed for lumber storage when not kiln drying (which is what I do). Temperature increase with fans off is 5-10 degrees above ambient in the summer. With fans on, temp increase is up to 45 degrees in my kiln (140F is the top temp I've recorded - I think the triple wall polycarbonate panels help a little). The kiln modification is a lot of extra work but I dry mostly for my own use and having an extra insulated, dry storage space while I work through my inventory has been a big plus.\
    Don't ask me how I know that!

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