Exhaust fan use rises along with drying trend

Bin-top exhaust fans help expel hot, moist air before it cools and causes grain-spoiling condensation. | Blaine Krahn/Corr Grain Systems photo

Ed Radcliffe is witnessing a bit of a new trend in grain storage in Western Canada.

“We’re starting to see a lot of roof exhaust fans being put in so we can pull moisture out of the top of the bin if need be,” said the manager of grain conditioning and dryers with CORR Grain Systems.

He estimates the number of bins with exhaust fans in the prairie region is still well under five percent but the add-on product is definitely gaining traction.

“It’s just starting to become more and more popular,” said Radcliffe.

A primary reason is that more growers are drying grain. When warm grain from the dryer goes into the bin, the heated and moist air moves out through the vents at the top of the bin.

An exhaust fan can help expel that air before it cools and causes grain-spoiling condensation.

Blaine Krahn, Manitoba territory sales manager for CORR Grain, said he first encountered roof exhaust fans in the United States, where farmers realized there was a condensation problem when conducting secondary cooling of grain in bins.

“If there was cold air outside, the moisture would deadhead at the fill and then the moisture would freeze and land back on top of the grain and create crusting,” he said.

The same scenario occurs when farmers install in-line heaters for supplemental heating of grain inside a bin.

Krahn said he even recommends roof exhaust fans for farmers who use natural air drying because on a hot day, that process can also create condensation.

“I really like them in all applications,” he said.

Exhaust fans can help keep grain at the top of the bin in proper condition. Crops like lentils and chickpeas tend to spoil or develop mould at the top if conditions are too moist.

Radcliffe said proper fans allow farmers to keep their grain longer so they can take advantage of market conditions.

The fans sell in the range of $3,500 to $5,000 depending on the type of power supply. They can be installed at the time of construction or retrofitted into any type of bin after the fact.

Radcliffe hasn’t seen them on smaller bins. The fans instead tend to be used on larger, flat-bottomed bins that store 30,000 bushels or more. Really large bins may require more than one exhaust fan.

He added that the term exhaust fan is a bit of a misnomer because some of them draw air from the outside, forcing moist air out the bin vents at the top.

“There is two different schools of thought,” said Radcliffe. “Some guys say they should blow into the bin and some guys say they should suck out.”

Krahn is definitely in the camp of blowing air out of the bin. When outside air is sucked in, it pushes a mixture of condensation and fine dust particles out the vents, which can cause the vents to freeze over.

“I really don’t like that. I stay away from that,” he said.

Krahn also advises farmers to install the roof vents on the peak of the bin rather than the eaves because moisture tends to collect in the peak.

Many roof exhaust fans are wired to turn on when the bottom fan is on. They can also be used in conjunction with a humidistat installed at the top of the bin, which triggers the fan whenever humidity gets too high.

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