What size fan for grain bin?

[tomstractorsandtoys]

I have a 21 ft. diameter grain bin that holds about 5500 bu of corn. It never had a fan or a floor as we have a batch dryer. We always dry and cool our corn before filling. I want to put a floor and unload system in the bin so that I can use a sweep and save on shoveling. This year I think that we might be harvesting 15-16% moisture corn if we wait a few more weeks. I would like to add a fan to this bin before installing the used floor we bought. How big of a fan should I have? This bin also has an electric grain spreader. I have a used bin fan that is 18 inches in diameter. Is this enough? We will grind some out of the bin all winter and sell the rest in June or July. I did one small bin (1800 bu) last year and it was fine.We are southern Wi. Thanks Tom

 

[coonie minnie]

How many HP is the fan? And how many rings high is the bin? More depth requires more oomph.

There are two approaches to this, too... Do you want the fan you have to be "good enough?" Or do you want the correct fan? Either can be an acceptable answer.

One last thing for you to think about. I know you have been growing cover crop seed. Small grains require a bigger fan to get the same amount of air through, because the kernels (and voids between) are small. Is it possible you could have this thing 3/4 full of rye seed in two years? If so, go for a big fan.

Fan sizing has some engineering behind it. There may be some sizing charts online somewhere.

 

[NY 986]

I would go in excess of "good enough" when it comes to fans and vents.

 

[Fritz Maurer]

Whatever size fan you get, I'd recommend a squirrel cage fan as opposed to an axial-flow. The efficiency is as good or better, and it makes less racket. Downside? Price. As to what size, find a bin-raiser and I'm sure he would know.

 

[coonie minnie]

http://webapps.bbe.umn.edu/fans/

Try this link. Pretty nice calculator from University of Minnesota.

 

[andy r]

I dry outside of the bin and then dump warm corn into the bin. Corn has been cooled some in the drier. I have 3/4 to 1 horsepower motors running 12 inch fans cooling and aerating six bins totaling about 30,000 bushels. Works well, but it takes a while to cool the corn and blow the last moisture out. Bins are all 7 rings high. Originally I was short on electricity at the bin site and could only support the smaller fans. I have now upgraded to 100 amp service. Secondly, 12 inch fans and transitions cost less at the initial construction. I have even taken some 17 and 18% corn down to 15 with the smaller fans if I had good weather in the fall. The smaller fans have to run along time because it takes a lot of cfm to blow the moisture out. There are tables online that show the how TIME and CFM will dry certain percentage moisture corn. If I was to replace everything I would now run larger motors and fans. That way I could actually air dry relatively dry corn out of the field. Many guys around the neighborhood have maybe 5 or 7 horsepower fans on something like an 18 inch fan with no burner. Allows them the chance to air dry if the corn moisture and weather allows. Just depends on if you want the opportunity to air dry or eventually would want to add a burner.

 

[hydro70guy]

If you cool the corn before putting in bin that 18" dia. is big enough it is probably a 1.5 HP. In a 5500 21' bin that is plenty. If putting it in warm with spreader running it would still be plenty. That is the size we have in our bin that we drop corn in hot right out of continuous flow dryer and its fine. I am in NC Iowa so weather is comparable.

Joe

 

[brutus49DC]

I have a 24 footer that used to be a drying bin before I moved it to my farm. A guy who sells bins and equipment told me a 14" would be adequate for aeration. I want to dump my drying bin hot and cool it in the other bin. I forgot to ask him if that would be enough for cooling.

 

[ss55]

Will you be adding heat to the air or will this be strictly an aeration fan? How many bushels do you need to dry and what is your harvest capacity per day? You already have a substantial investment in the drying floor, sweep auger and unloading auger, the fan won't change that investment significantly. Consider installing a larger fan with heat and replace some or all of your batch drying with bin drying. Your drying costs per bushel might be much lower. A 24 inch fan with a 5 HP or 7.5 HP motor was common on a drying bin that size and worked well. In all but the dampest weather, a 36 inch fan with a 10 HP motor would let you dry with no heat during most days and only 10 degrees F heat rise at night. Using electricity to move air through a bin can dry grain at lower cost per bushel than a high temperature batch dryer. The grain quality is better too.

 

[JD Seller]

Well I have several older 21 foot bins. They had 18 inch 5 HP fans on them when they were new. That was enough just for aeration. When I wanted to air dry corn later on I replaced the 18 inch fans with 24 inch fans with 7 HP motors on them.

So if your just wanting to drop in 15-16% corn and feed all winter then sell it before the heat of spring you would be fine with your 18 inch fan.

IF your going to be grinding feed all winter I would NOT use the grain spreader. All of the fines will be dropped directly on the center sump. After you grind 3-4 times you will have just about all the fines out of the center of the bin.