Grain starts to spoil the moment it is harvested. The deterioration can be slowed down to almost nothing by cooling and drying the grain. Grain can be cooled in a matter of hours with natural aeration, especially with cool night air. Drying may take a little bit longer, but our data has shown that if grain is cooled by 15 deg C on the first day, that it will lower the moisture content (MC) by one percentage point. So we see that cooling is drying if done with aeration. Leaving the grain cool by itself in the bin does not result in any drying. Even if your grain is dry, it is important to get it cooled as soon as possible, to put a halt to the deterioration process. The fan should be run as soon as the grain covers the screen and left on until 9:00 the next morning.
At one time it was suggested that grain should be left hot to sweat out the moisture. This is not a good idea; the grain is starting its deterioration process, it is spoiling and losing quality. Get it cooled down with aeration as soon as possible. Once it is cool, it is safe from spoilage. Then getting it dry is secondary. You can take your time and use the calculator to figure out when to run the fan.
The take home is this: If you have aeration fans, use them, especially the first day the freshly harvested grain is stored; don’t wait.