Suggestions for determining horizontal air flow fans

March 1998

During the past several years growers are beginning to realize the importance of proper air flow in the greenhouse particularly when the greenhouse is not in a cooling or ventilating mode is very important for maintaining the greenhouse environment during these times of the year.

The installation of adequately sized horizontal air flow fans can greatly increase crop productivity and quality. Temperature differentials caused by stratification are reduced. Humidification and carbon dioxide levels within the greenhouse are evened out. Condensation drip can be controlled and plant foliage can remain drier. Cold water standing on plant foliage is an invitation for a host of infestations.
Also, during these past few years we have seen growers steadily changing over from the blower type unit heaters with jet tubing and replacing them with propeller fan unit heaters and horizontal air flow fans. There are several reasons for this, these being:

• Capital cost of equipment is less expensive.
  
• On a bay per bay basis the net brake horsepower propeller fan unit heater and horizontal air flow fan(s) verses the blower fan type unit heater is less. So significant power savings are realized by the grower.
  
  • As an example a greenhouse bay 24' wide X 100 ' long, has a blower unit heater with a 1 1/2 hp motor, at 5,700 CFM air flow and is poly tube ducted. The unit is drawing 7.5 amps at 230 volts. The power consumed every hour of operation would be 1.725 Kwatts. Power costs are $0.08 / KwHr. Therefor the cost per hour of operation would be $0.138 / HR. If operated on continuous air circulation, the cost per day = $3.312, the cost per month = $99.36.
  • Now if in the above example, the blower fan unit heater was replaced with a propeller fan unit heater and say a GCS2423DDTA HAF fan. The following would occur. Air flow in greenhouse would increase from 5,700 CFM to 9,400 CFM. The total power consumed would be 1.180 Kwatts ( based on 1/2 hp motor on unit heater and 1/3 hp on HAF fan). The cost of power would drop $0.0436/ hour, or $1.0464/day or $31.39 per month during the winter heating months. Interesting more air flow at less power costs. Now consider that greenhouse has 10 bays of the old blower fan unit heaters; it becomes the utility companies favorite client.
    
• The amount of air ( CFM ) is greatly increased with the use of horizontal air flow fans verses the use of a blower or jet fan with poly tubing.
  

The following illustration provides a general rule for laying out a horizontal air flow system in various greenhouse configurations. Also, we have furnished basic information on the various horizontal air flow fans that we manufacturer. Our GCSTA series fans are of tube axial design. They operate at 1075 rpm and generally throw the air 60 to 70 feet when installed 8 feet off grade or bench. When we designed our fans we selected 1075 rpm motors for noise considerations. The result is a fairly quiet fan. Much much quieter than fans operating at 1600 to 1700 RPM. For specifications on our GCSTA HAF fans.

If you require further information, assistance in sizing and selection or would wish a quotation please contact our office.

 

 

< Back to In the News