When Should Aeration Fans Run? Reading Outside Temperature and Humidity
The best time to run silo fans is when outside air will cool the grain without wetting it. Here's how to read the weather for aeration.
SiloSense IQ ·
Aeration is only as good as the air you choose. The same fan can cool and protect grain on a crisp night, and quietly dry it out — or re-wet it — on the wrong afternoon or evening. Here’s how to pick your hours.
What you want from the air
For stored grain, good aeration air is:
- Cooler than the grain — so it takes heat out.
- Not too humid — so it doesn’t add moisture.
- Not too dry or hot — so it doesn’t strip moisture you’ll be paid for.
How the day usually plays out
On a typical Australian day:
- Afternoon: warmest and driest. Little cooling value, and drying power you may not want.
- Evening into night: temperature falls; humidity rises. Often the best cooling window — until humidity climbs too high.
- Early morning: coolest, but often the most humid. Can be ideal cooling air or too damp, depending on the night.
That’s why fixed timers struggle. “Run 8pm to 6am” is right on some nights and wrong on others.
Use limits, not clock times
A better approach is to decide what air you’ll accept, and let the fans run whenever the outside air meets it:
- A minimum temperature — for example, don’t run on frosty air that won’t help.
- A maximum temperature — don’t push hot air into cool grain.
- A maximum humidity — don’t run on damp air that adds moisture.
- A minimum humidity — optionally, avoid very dry air that over-dries.
Limits differ between winter and summer. In summer you can accept warmer air because the grain is warmer too; in winter you can be choosier.
Check the forecast, act on the measurement
A 7-day forecast helps you plan — for example, knowing a cool, dry spell is coming. But fan decisions should use the live reading from a weather station on site, because the forecast for the nearest town isn’t the air at your fan intakes.
How SiloSense helps
Aeration Manager lets you set winter dates and, for winter and summer, a minimum and maximum outside temperature and humidity for every silo. In Automatic and Auto Protect, fans only run when the live air is within those limits, and the dashboard tells you which limit is holding a fan off. You also get the 7-day forecast alongside.
With SiloSense IQ+, decisions go one step further: the air is compared with the grain inside the silo, not just with fixed limits.
Request a demo to see the limits on a live site.