Keeping Cows and Calves Cool Through Ventilation System Maintenance

Jason Hartschuh, Extension Educator, Crawford County, Ohio State University Extension

Spring is in the air, with the tulips and daffodils starting to bloom, and alfalfa fields coming back to life. It is also the time when our barn ventilation systems roar back to life to keep our cows and calves cool. While an inefficient system may not create problems now, it is wasting energy, and by summer, it will be creating problems when your livestock are experiencing heat stress. Ventilation systems often consume between 20 to 25% of the total energy used on the farm.

Fan maintenance is critical to keeping your cows cool and saving energy. Lack of cleaning can reduce a fan efficiency by as much as 40%. This means that your electric bill stays the same, but less air is moving through the barn. Monthly maintenance through the summer is critical to keep fans clean. Even a thin layer of dirt on the fan blades, shutters, and protective shrouds decreases air movement and increases the power requirements from the fan. Heavy cleaners and a pressure washer work well to remove dirt from the fans.

Dirty fans in need of cleaning.

Be sure to disconnect the power supply before washing the fan and be extra cautious of water entering unsealed motors. After washing, allow fans to dry and grease bearings before turning the power back on. During washing, inspect the fans closely using the following maintenance checklist:

  • Do all shafts turn smooth and are bearings showing wear?
  • Inspect impellers for cracks.
  • Are belts worn?
  • Are pulleys still aligned?
  • Are bolts and set-screws tight?

While monitoring fan performance and wear can be challenging, there are a few tools that can help you. Fans should be monitored on a routine basis, such as every month in the summer or on the manufacturers recommended grease internal.

Logbook- If you assign a number to each fan on the farm, it will help you to track the maintenance cost of each individual fan. The logbook allows you to monitor when a fan is having increased belt wear or motors that are not lasting as long as they should, which is a sign of greater problems occurring. Recording air velocity also helps to notice wear issues before they become major problems.

Digital Anemometer-This is used to measure the air velocity to determine if fans are operating properly. Be sure to record these values in your logbook so that you can find changes in fan performance. Lower air velocity is often caused by either dirt build up or improper belt tension which allows for slippage.

Digital Tachometer-This is used to help determine why your fan may not be producing enough air velocity. This can be used to help determine the revolutions per minute (RPM) of both your fan and the motor. When the motor is running at the correct RPM, but the blades are not, it may be due to poor belt tension, damaged or worn pulleys, or poor belt alignment.

Groove Gage- This is used to identify pulleys that are worn and need replaced. Worn pulleys increase belt wear and slippage and decrease fan RPM. Belts should ride at the top of a pulley and not sunken into the pulley. The gage should fit tightly; if more than 1/32 inches of wear can be seen, poor belt life can be expected. If the gauge hits the bottom of the pulley, it is worn out.

Source: Dayton motor

Belt Tension Tester- This is used to measure the force required to move a belt 1/64inch per inch of span. It helps to trouble shoot fans that are turning slower than they should. If tension is correct but fans are turning too slow, pulleys or belts maybe worn out. If belts with spring tensioners cannot be tensioned correctly, it may be a sign that the spring tensioner is weak or that belts are stretched or improperly sized. 

Multi-Meter-This instrument allows you to check the amp draw of the fan motor; high amp draw wastes electricity and can lead to premature motor failure. This can be caused by too high of belt tension, dirt build-up on blades and housing, or bearings that are binding and need replaced.

When adding new or replacing ventilation fans, it important to look at more than the price. Many motors have electric efficiency ratings, but the higher efficiency motors have more copper windings which increases their cost. Often high efficiency motors pay for themselves with decreased electric consumption within one to three years. When adding or replacing fans, it is important to not buy the cheapest one but also consider the fans efficiency rating. For tunnel ventilation fans, look for a minimum efficiency rating of 20 cfm/watt at 0.05-inches static pressure. Tunnel ventilation and exhaust fans are rated under static pressure because they create a pressure difference from one side to the other, with the higher the rating the better. Circulation fans, on the other hand, have efficiency ratings based on thrust measured as pounds of force per kilowatt (Lbf/kW). The ideal minimum efficiency rating for circulation fans is 21 Lbf /kW. Similar to tunnel ventilation fans, the higher the rating the better. Larger fans often have better efficiency ratings and sometimes when paired with a variable rate controller and ran slower are more cost effective due to the increased efficiency than smaller fans.

Through proper fan maintenance, we can keep our ventilation system working at maximum efficiency, keeping cows cool and comfortable. The ideal ventilation system will provide between 40 and 60 air changes per hour.