“How does it know when to run my fans?”

It’s the most common question we get. And honestly, it’s a fair one—handing over control of your aeration to a computer feels like a leap of faith.

So let’s pull back the curtain.

The basic principle

At its core, our fan control algorithm is answering one question: Will running the fan right now move moisture out of the grain?

That depends on the relationship between the air inside the bin and the air outside. Specifically:

  • The temperature and relative humidity inside
  • The temperature and relative humidity outside
  • The equilibrium moisture content of the grain

If the outside air can absorb moisture from the grain, we run. If it can’t—or would actually add moisture—we don’t.

Equilibrium moisture content (EMC)

This is the key concept. Every combination of temperature and humidity produces an “equilibrium” point where grain neither gains nor loses moisture.

For example, 15°C air at 65% relative humidity is roughly in equilibrium with wheat at 14% moisture content. Put that grain in contact with drier air, and it loses moisture. Wetter air, and it gains.

Our algorithm calculates EMC continuously for both the bin air and the outside air, then compares them.

The decision tree

Here’s a simplified version of what happens every few minutes:

  1. Read sensors: Get current temp and humidity from inside the bin and from weather data
  2. Calculate EMC: What moisture level would grain reach at these conditions?
  3. Compare: Is outside EMC lower than inside? By how much?
  4. Check constraints: Is it too cold? Too humid? Raining?
  5. Decide: If conditions are favorable, run the fan. Otherwise, wait.

Why not just run 24/7?

Some farmers ask why we don’t just run fans continuously. A few reasons:

  • Wasted energy: Running when conditions aren’t favorable doesn’t help—it just costs money
  • Potential harm: In some conditions, you can actually add moisture or cause condensation
  • Wear and tear: Motors last longer when they’re not running nonstop

Our goal is to dry as effectively as manual management—but without requiring you to check weather forecasts at 2am.

Manual override

Of course, you’re still in control. Any time you want to take over, you can. Turn fans on, turn them off, set schedules—the automation is there to help, not to replace your judgment.

Got questions about how this works on your specific setup? Drop us a line. We nerd out about this stuff.