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Fans for a solar kiln???

Started by Whitetail_Addict, March 08, 2011, 08:25:25 PM

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Whitetail_Addict

I'm putting the material together to build a solar kiln this Spring.  So far I've got the lumber, roofing, paint, insulation...  but i'm having a hard time deciding on what fans to go with.  The location for the kiln does not have AC power available so I need something battery operated or solar operated.  I found a solar powered attic fan at Tractor Supply for $229.  It says it moves 1000 cfm which brings up another question.  How much air do I need to move?  I'm using a variation of the Virginia Tech solar kiln plans and the building is 17.5ft long to accommodate 16ft lumber.  Does anyone have any experience with DC solar powered fans or have any recommendations on what I can use?  Thanks
2010 WoodMizer LT28, John Deere 4520 w/ FEL, 2003 Chevy Silverado 2500HD Duramax Diesel, 2007 Polaris Ranger XP 700, 127 Acres of Northeast hardwoods in New York's Whitetail country

pineywoods

Whitetail, I can tell you this from experience. Stay away from plastic. It will get hot enough in there to melt most plastics. I built two solar kilns, used cheap plastic box fans from walmart in one of them. The blades on the fans melted and fell off.
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

pyrocasto

Sounds like exactly what I'm building, but I'm using the grid for the fans. Most of the guys who use solar fans have 3 of the ones you're talking about. The panels arent very big and the cfm rating is not realistic, but I think you'll be just fine. That's what I would use if I didnt have the grid.

I'm using 3 1600 cfm gable fans for mine.

flibob

Pineywoods,  on the fans how did you have them switched?
The ranch is so big and I'm such a little cowboy

pineywoods

Quote from: flibob on March 09, 2011, 08:57:19 AM
Pineywoods,  on the fans how did you have them switched?

No switch, just plug and unplug. Mostly I just leave them running all the time until the lumber is dry enough.
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

Whitetail_Addict

Yeh I thought about the inexpensive plastic box fans too but remember reading someplace to stay away from plastic due to the high temperatures inside the kiln.  The solar stuff is just so expensive.  I guess I'm going to have to get my butt in gear and start putting my new Woodmaster to work making some mouldings to sell so I can afford the solar powered fans!  I'm not sure if this is a hobby, a business or an obsession....    :-\
2010 WoodMizer LT28, John Deere 4520 w/ FEL, 2003 Chevy Silverado 2500HD Duramax Diesel, 2007 Polaris Ranger XP 700, 127 Acres of Northeast hardwoods in New York's Whitetail country

Hokiemill

Whitetail, I was in the same situation a few years ago.  I found a solar powered attic fan at Home Depot that was a little less expensive.  I got mine for about $179 each and I run three of them.  I was in HD yesterday and saw that they still carry them but I didn't pay attention to the price.  The HD website is listing them at $217.  They're rated at 500cfm.  Here's a link:
http://www.homedepot.com/h_d1/N-5yc1v/R-100548465/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

laffs

hit the scrap yards for electric car fans, you could probably use the schroud also for mounting
timber harvester,tinberjack230,34hp kubota,job ace excavator carpenter tools up the yingyang,

flibob

Good idea about the car fans.  I don't have power at the shed.  A photovoltaic cell direct to the fan(s) and it should be ready to go. 
The ranch is so big and I'm such a little cowboy

Whitetail_Addict

I thought about used radiator fans out of junk cars as well.  I looked up a new fan to see how much current it would draw.  11 Amps.  That totally scraps the idea of running one with a solar panel... Even running one from a set of batteries with the solar panel just keeping them charged.  If you compare to the current used by the solar gable roof vent fans for the attic of your home it's 130 mA.  They are rated for 1000cfm so maybe a couple of those would be sufficient to circulate the air inside my kiln. 
2010 WoodMizer LT28, John Deere 4520 w/ FEL, 2003 Chevy Silverado 2500HD Duramax Diesel, 2007 Polaris Ranger XP 700, 127 Acres of Northeast hardwoods in New York's Whitetail country

Sparty

Quote from: pineywoods on March 09, 2011, 09:50:48 AM
Quote from: flibob on March 09, 2011, 08:57:19 AM
Pineywoods,  on the fans how did you have them switched?

No switch, just plug and unplug. Mostly I just leave them running all the time until the lumber is dry enough.

I am no expert with solar kilns...but I thought one of the advantages of the solar kiln was that in the evenings the fans are turned off, the humidity rises, and the lumber "conditions" each night.  This is supposed to prevent case hardening and other defects.  The fans are designed to come on in the morning when the kiln temp rises to a certain temp and then shuts off in the evening as temps fall.  This can be done with temp/humidity probes...but I imagine you could get pretty good results with just a timer switch. 

Kansas

When we had solar kilns, we just used the cheap box fans. At that time you could pick them up for 10 bucks apiece. We never had one melt down, although they usually only lasted about a year or so. We had cheap thermostats that kicked them on at a certain temp. I don't think you would want to have temp so high you would melt blades in your kiln. You definitely want a thermostat to kick them off and on. That night time cool down is what makes the quality of lumber. The smaller of the two we had two in the baffles. The bigger one we had three. I can say that the quality of lumber coming out is as good as any I have seen from  a dehumidifier or steam kiln. With the vents, it shouldn't get that hot anyway. Why not just get a battery and a cheap inverter and use that? They can't pull that much juice. Maybe solar charger or swap out batteries as needed. What plans are you using for building it? We got ours from some college back east.

Notice I use the word "cheap" a lot.

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