Precimet - Circulation Fans

The stillness of air in a greenhouse causes the deterioration of its microclimate and has an adverse effect on plants. In order to even out the temperature and optimize the humidity, ventilation is needed. Opened ventilators may serve as a poor substitute. A much better solution is a fan designed especially for greenhouse horticulture.

Circulation fans of N series are designed for use in humid environment characteristic for greenhouse buildings and in the general ventilation systems of industrial buildings. The fans feature compact design, high efficiency and reliable operation. The rotor is powered by an electric engine. The rotor is mounted directly at the tip of the engine`s spindle. The fan`s housing is made of steel sheet and protected against corrosion by zinc galvanizing and then powder coated. In order to ensure the precise directioning of an air stream, which is particularly important in greenhouses, special air fins are placed inside an oblong hosing which at the same time serve as a mounting construction for the engine. Access to the rotor is blocked by a protective grid made of steel wire, mounted to the housing. The fans are adapted to be suspended in the room in which they are used. Accessories include an analogue (voltage) speed regulators.

PARALLEL VENTILATION  is achieved by arranging the fans in two rows with the back parts of the fans from one row turned to the back parts of the fans from the other row, e.g. along the middle path of the greenhouse. The air is blown over the crops, towards the gable walls of the greenhouse, from which it rebounds and moves back through the lower part of the greenhouse among the plants and along the adjacent naves. Nevertheless, in some cases, due to the sensitivity of the plants to the air movement achieved through the abovementioned arrangement of the fans, it is better to use a linear ventilation.

LINEAR VENTILATION here, the fans are suspended above the plants in a row. As a result, the air blown out by one fan is sucked by another fan and blown out once more. Consequently, the air movement takes place mostly above the harvest. 

The number of fans:
It is recommended to install a number of fans sufficient for intermixing the whole air in the greenhouse in one hour`s time.

How should they be suspended?  
Minimum 0.5-1 m below the gutter. If the distribution of the temperatures inside the greenhouse is uneven, i.e. the temperature near one gable is higher than near the other gable, the fans should blow the hot air towards the colder part. The use of fans helps to level off the temperatures or to reduce the difference between them by 3-4 ºC.

When to turn on the fans?

• When the difference of temperature in various places inside the greenhouse exceeds 0.5 ºC.
• When the windows are closed, till the moment when they are opened 2-5 %.
• When there is no wind.
• When in tight, modern greenhouses, with the temperature difference of 15 ºC between the inside and the outside of the greenhouse, the windows are opened in a few percents in order to prevent the humidity of the air inside the greenhouse from dropping suddenly.

NOTE!

Fans are necessary in tight greenhouses and when the foil is stretched. Large temperature differences have to be levelled off by insulating the pipes. The use of fans increases electricity and heating consumption, but it also helps to grow better plants of similar sizes.