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Author Topic: Vents on VTech solar kiln  (Read 478 times)

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Offline RussMaGuss

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Vents on VTech solar kiln
« on: January 02, 2019, 06:07:07 PM »
So I finished my kiln this fall and got my first load of 500bf of pine in there. I'm in IL, SW of chicago. The MC was around 18% and after about 10 days (maybe 2-3 cloudy days) It was down to 15% so I figure I get it down to 11 or so and it'll be fine for my purposes for it. 

My question however is more about solar kiln vent operation because I haven't seen much on here about what people do with the vents.

Do you guys ever open the vents at night to let the humid air out or will it just slowly trickle out by itself? I sealed my kiln pretty well. Currently, I have the vents closed at all times, day and night. First day I had the vents all open, fans on for 24 hrs, then closed them all with fans on when the sun was out. Saw a good amount of humidity built up on the polycarbonate roof panels during the day. Any advice about the vents on these solar kilns is appreciated. I also have a load of around 400bf of elm at 50%MC waiting to go in right after. 

One more question too: What kind of readers would you guys suggest to keep in the kiln to measure temp/humidity? Thanks,


Offline GeneWengert-WoodDoc

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Re: Vents on VTech solar kiln
« Reply #1 on: January 04, 2019, 08:43:35 AM »
The kiln vents are the major, perhaps only, way to remove water from the kiln.  If they are not opened, then the kiln humidity will rise until drying stops and you get 100% RH or close to 100% RH.

When the vents are open, they also exhaust hear.  So, we do not want to open the vents too far.  With a slow drying wood, they are opened just an inch or two; with fast drying perhaps 50% to 65% open.

We only run the fans when there is enuf sunshine to heat the kiln.  When there is no sun, the fans should be off, as without sun energy input the kiln temperature will drop which increases humidity and slows or stops drying.

The vents are opened an appropriate amount and left open all day. And night too.  With the fans off at night, you do not need to close them.

I have seen almost all of the VT solar kilns run without measuring temperature or humidity.  Fans are run with timers...turning on perhaps at 9AM and off at 6PM, but these vary depending on the time of year...turn them on when there will be energy or heat input, and off when the cover no longer has direct sunlight.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Offline OlJarhead

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Re: Vents on VTech solar kiln
« Reply #2 on: May 14, 2019, 05:04:47 PM »
I was thinking solar attic fans would work since they would only come on when the sun was beating down on them.

2016 LT40HD26 and Mahindra 5010 W/FEL WM Hundred Thousand BF Club Member

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