If you’re in the habit of switching off low-volume grainstore fans during wet weather for fear of dampening grain, then think again, consultant Ken Wildey said at a recent HGCA grain storage workshop in Essex.

“Make use of all ‘cooling’ hours you can and don’t switch off fans because you think it’s a little damp. Any cool air going through grain is a benefit, providing you’ve got enough of a temperature differential.”

Generally, that differential – the difference between ambient and grain temperature – should be around 5C, he said.

Even if air going into the fans had a high relative humidity (rh), fans generally heated air by 2-5C, which dropped the rh by nearly 10%, he explained. “As the cold air meets warm grain, it heats up and the rh drops further because warm air carries more moisture.”

But where high volume systems were used, he said there was a risk of adding moisture during wet weather, so operators should consider using rh control. “Bigger fans introduce a significant temperature rise on ambient air (5-7C) so you need a bigger temperature difference.”

Cooling tips

• Cool grain quickly to reduce pest risk
• Use low volume ventilation
• Air must always be cooler than the grain
• Temperature differential is key
• Make use of all available cooling hours – use a differential thermostat