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Author Topic: house window fans for kiln circulation?  (Read 525 times)

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Offline ray299

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house window fans for kiln circulation?
« on: May 23, 2017, 09:05:28 am »
I got the idea off another member here who suggested it...
I want to use a 100watt solar panel to charge a car battery. Use a DC to AC 400 watt converter from the battery to two window fans (up to 1200 CFM) because they will turn on automatically with a preset temp. Each fan uses less than 100watts so there should be plenty of power there.... in fact I may not even need to charge a battery... just hook up the solar panel to the converter? But I was going to use the battery anyway just in case the panel needed help on cloudy days.
So my question is, anyone use these house window fans on their kiln? Here is what I was thinking about buying....
http://www.homedepot.com/p/9-in-Twin-Window-Fan-FW23-A1/100663385

Offline pineywoods

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Re: house window fans for kiln circulation?
« Reply #1 on: May 23, 2017, 01:03:05 pm »
Three local solar kilns. You might be surprised at the peak temps, I have documented 180 degrees in mine. Some problems with fans. On one, the plastic blades melted and fell off. Another one bought fans with metal construction, but the motors has an internal thermal fuse that blew. Mine uses an old fashioned box type fan, all metal, so far has worked fine.
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Offline bedway

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Re: house window fans for kiln circulation?
« Reply #2 on: May 23, 2017, 01:22:33 pm »
Ive burnt out 3 different fans in my kiln. Ive just finished up building my fan motor outside the kiln, powering the fan inside. It seems to be working great and now I don't have to be concerned about burning more fan motors out.

Offline GeneWengert-WoodDoc

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Re: house window fans for kiln circulation?
« Reply #3 on: May 23, 2017, 11:10:50 pm »
The original Virginia Tech kiln used three 20" 3-speed window fans, with the plastic grills removed.  All the rest was metal.  Bushing and not bearings.  We used them for over three years.  Each of these fans will draw about 2-1/4 amps or 250 watts an hour each.  This size gives us the required air flow.  Less wattage fans mean less air flow and slower drying.

Keep in mind that a solar array is at its peak at noon when the panel is adjusted to be perpendicular to the sun.  A panel will have less power output the rest of the day because of the sun angle; most of the day (before 9AM and after 3PM)  it will be under half.

Note that a kiln will get hotter inside with low air flow, as the low flow means the wood is not drying as fast, so evaporation is not using the energy or heat in the air.  It is a false assumption that if a solar kiln is a lot hotter than outside, that this shows the kiln is better.  With any heat in the air, you want this heat to be used for evaporation and not just heating the air.  So, an efficient kiln with lumber that needs drying, there should not be a lot of heat compared to outside...20 degrees F perhaps is all.

With an empty kiln, the vents should be opened to allow heat to escape.

Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Offline kelLOGg

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Re: house window fans for kiln circulation?
« Reply #4 on: May 27, 2017, 07:08:49 am »
Attic exhaust fans should work fine. That's what I use.
Bob
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Offline ray299

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Re: house window fans for kiln circulation?
« Reply #5 on: May 30, 2017, 08:07:06 am »
Am I over thinking this? It sounds like people have changed fans over the years... and I see people use both 120v and 12v fans, house fans and auto fans... I have the auto fans, I think I'll go with them and a timer as opposed to window fans with a temp control...

Offline Tree Dan

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Re: house window fans for kiln circulation?
« Reply #6 on: May 30, 2017, 08:39:16 pm »
I have 2 of the attic fans in my solar kiln ,they are ok but i dont think they blow enough air.
The old style 3 speed window fans blow more wind.

I use 3 speed honeywell fans in my shop...these really move the air fast,
and I think i would use them if i build another solar kiln.
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Offline YellowHammer

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Re: house window fans for kiln circulation?
« Reply #7 on: May 30, 2017, 10:55:31 pm »
My solar kiln uses 2 of the plain $20 Wal Mart 20 inch or so square, three speed, plastic bladed cheap window fans.  They work perfectly, I never turn them off, and they last about 3 years.  These are very effective for this application. 
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