Is a fan without a wire guard more energy efficient?

Since energy costs have increased, we increasingly get asked whether a wire guard on a fan is necessary. The reasoning that a fan without a wire guard experiences less resistance and thus becomes more energy efficient is true. Yet it is not always allowed or advisable to remove a wire guard. Vostermans Ventilations explains more in this article, so you can make your own informed choice.

Regulation
In some cases, it is mandatory to protect the fan impeller with a wire guard. This is stipulated in various regulations and legislation, such as ISO, CE (Europe), and OSHA (USA). Thus, local regulations may differ from the International Standard set forth in the ISO standard. However, we see a trend of gradually adopting the ISO standard worldwide. This stipulates that fans below 2.7 meters (Service Level) must have a wire guard. The service level is determined by regular operations. Harvesting the crop in a horticultural greenhouse which is usually done on an aerial work platform, increases the working height to the level at which harvesting takes place. Incidental maintenance with a ladder is not considered regular work and therefore does not increase the working height.

What kind of wire guards are used depends on local laws and regulations. We supply both OSHA and CE wire guards. OSHA wire guards use a fixed mesh size of 0.5 inches. CE wire guards have a variable mesh size determined by the distance between the wire guard and the fan impeller. The further away the wire guard is from the fan, the coarser the wire guard is allowed to be. However, there is one exception. When a fan is not freely accessible, such as because it is installed deep in a pipe, a wire guard is not required.

Protection of both animals and fans
There are also cases where a wire guard is not required but is still desirable. Consider situations where there is a high probability that animals can reach the fan. To protect both the animals and the fan, a wire guard is recommended in these cases. Should it occasionally happen that something passes the fan, it is good to know that in such a case, the blades of the fan can break off, protecting the fan motor from imbalance. This is an important advantage of plastic impellers over metal impellers because they bend, resulting in imbalance. New blades or complete impellers can be ordered through our customer service at a low cost. Depending on the position of the fan, these can often be replaced within minutes.

Energy savings and more air
Finally, the reason to remove the wire guards: Energy savings. Because a fan without a wire guard encounters less resistance, it will absorb less power AND move more air. This can make a fan up to 20% more efficient. Usually, this is 5 to 10%, which is highly dependent on a number of factors:

  • A wire guard on the blower side of the fan creates more resistance than a wire guard on the suction side.
  • A wire guard close to the impeller creates more resistance than a wire guard far from the impeller.
  • A fine-mesh wire guard creates more resistance than a coarse-mesh wire guard.
  • The greater the pressure difference between inside and outside the room, the more "trouble" a fan has with the wire guards.

Two examples
We explain using two examples. A Horizontal Circulation Fan is often used in the horticultural sector, and a Panel Fan is often used for ventilation in industrial halls and stables.

Horizontal Circulation Fan (T4E45BAM81100 vs. T4E45BAM80100)
The fan is used for circulation applications. Because of this, we assume a static pressure of 0 Pa in this example.

With wire guards on two sides.

  • Airflow rate: 6,434 m3/h
  • Power consumption: 264 W
  • Efficiency: 41 W/1000m3/h

Without wire guards

  • Airflow rate: 6,931 m3/h
  • Power consumption: 247 W
  • Efficiency: 35.6 W/1000m3/h

Removing the wire guards makes the Horizontal Circulation Fan 15.1% more efficient in this case.

Panel fan (V6E50AAM11100 vs V6E50AAM10100)
The fan is typically used for ventilation applications. Because of this, we keep a static pressure of 30 Pa in this example.

With wire guards on the suction side.

  • Airflow rate: 4,644 m3/h
  • Power consumption: 185 W
  • Efficiency: 39.8 W/1000m3/h

Without wire guards

  • Airflow rate: 4,799 m3/h
  • Power consumption: 182 W
  • Efficiency: 37.9 W/1000m3/h

Removing the wire guard makes the Panel Fan 5.0% more efficient in this case.

Final conclusion
If possible, install fans without wire guards. This improves the efficiency of the fan and can provide a benefit of up to 20%. Do check that safety is not compromised, however, and that you comply with local regulations in doing so.

For more information:
Vostermans Ventilation bv
+31 77 389 32 32
www.vostermans.com


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