Aeration

[cilknderby]

The question. Do you run your aeration fan constantly or do you turn it off at night or when it is raining. Who knows?

[mhartman]

The following answer if from our Alberta Agriculture free publication 'Movement of Natural Air Through Grain' (Agdex 736-11). Aeration is NOT a grain drying system... the purpose of an aeration system is to maintain the lowest practical temperature and the least temperature variation within the stored grain. ..It is essential that the fan should be operated long enough to equalize the temperature in the entire bin... Inadequate fan time is the major source of problems when aerating stored grain. Shutting the fan off too soon may increase temperature variations within the bin, rather than reduce them. ...During the fall, grain must be cooled as quickly as possible. Cooling can be accomplished whenever the exhaust air temperature from the grain is at least 5 degree C above the maximum daily outside temperature. Run the fan day and night as long as this condition exists, regardless of relative humidity. A day or two of fan operation during rainy weather or other high relative humidity periods does no harm if the fan operates for a day or two of fair weather afterwards. Avoid extensive fan operation during rain or wet weather after the grain has cooled to within 5 degrees C of the average outside air temperature. ...Cool the entire volume of grain to -5 to 0 degrees C for the winter holding period. Make sure you run the fan long enough to cool the top center of the grain in the bin or you will increase your risk of spoilage!

[lorne]

My experience is not to turn the fan off. I leave it on even when it rains and snows. I place a piece of plywood over the fan so that it does not suck rain or snow directly into the fan.

The first year I used airation, I turned it off at night. I lost a bin of barley due to that mistake. I talked to an agroligist and was told that gain in a bin released moisture about 5 times faster than it abosorbs it.

When grain is airated there is a wet front moving up in the grain just above the dry zone and that is the reason to leave the fan on, because that wet front will swell up and form a tight layer that will not let air pass through evenly next time you turn the fan on. So even if it is raining that wet front is moving up, which is what you want. I have taken a humidistat and put it by the fan during rain,and checked the humidity after an hour, then moved it to the top of the bin in the air moving out and checked the humidity after an hour, and have always found that the humidity at the top of the bin was higher than the air going in. So now when I turn the fan on it stays on until the grain is dry or frozen.

I welcome your comments.
Lorne