How are fans controlled in greenhouses in the United States

3 minutes reading - published on July 7, 2021

Depending on the area and the crop, the desired fan performance in greenhouses may vary throughout the cultivation process. These kind of adjustments ask for a certain level of control over fans. We talked to our greenhouse specialist John Juhler and asked him some questions concerning the use of fan control equipment in greenhouses in the USA.

As the name indicates, control equipment allows the control of fan functions such as rotation speed or on and off functions depending on the needs of the user. While consistency in fan performance is usually desirable in greenhouses to benefit a uniform climate, certain growers make use of controllers for a few reasons.

Why controllers are used in greenhouses

• Adjusting airflow
• Noise reduction
• Reduction of energy consumption

1. Adjusting airflow to plant growth

John: “Some growers desire different levels of airflow at different stages of plant growth. In the case of cannabis greenhouses, one may want smaller plants in propagation rooms to receive less airflow than mature plants. As the plants mature, the airflow and air speed in the greenhouse can then be adjusted to the size of the plants.” In order to keep track of airflow, sensors are placed and connected to controllers. This way, fans can be turned on and off to control air speed and humidity or temperature as desired.

2. Noise reduction

Besides flexibility in terms of airflow, reduction of the sound output of fans can also be a reason to invest in control equipment. This does mean sacrificing fan performance for sound reduction. This can be beneficial in cases where users do not require 100% rpm. By reducing rpm with a variable speed controller, sound output is reduced.

3. Reduction of energy consumption

Fans are subject to some mechanical laws, which we cover further in our article on the fan laws. One of these laws is that the power consumption of a fan reduces to the 3rd power as speed is lowered with a frequency controller. This allows for significant energy savings. Additionally, triac and transformer controllers can save some energy albeit less than frequency controllers. The downside here is that the airflow also decreases and therefore more fans are required. Some growers choose to invest in additional frequency controlled fans to reduce their long-term operational costs.

What types of controllers are commonly used in greenhouses?

John explains: “Our most prominent controller is the manual variable speed controller. With this standard level of control, the user can adjust the fan manually to suit the needs of the crop or their situation. The next level of control equipment is the integration with a customer’s master control system. For the American market, this would be our VSD1MC Series. These controllers will take a 0 to 10 signal from someone’s master system and tell that control what rpm to use. Other than that, more intricate control options exist. Depending on the situation and the size of the operation, the cost of these systems will need to be weighed off against the benefits. Small operations will often opt for more basic means of control.”

Are there specific things to pay attention to when installing control equipment in greenhouses?

“Keep in mind what your end goal with the controller is and base your choice on those needs. What are the specific needs in your cultivation process? Additionally, while it may be obvious to some, make sure you connect the correct power source. With various power sources in the US such as 120V and 230V, it is important to note the power source in your facility and that it corresponds with your equipment.”

Are there differences per region or per country in the use of controllers in greenhouses?

Certain geographical locations are more beneficial for greenhouses in general. In locations with temperate climates and little fluctuation in temperature throughout the year, control may not be required as often as in regions with varying seasons, temperatures and thus crop requirements.

What is the effect on the crop?

With proper control, desired adjustments in temperature and air speed inside the greenhouse can help maintain a uniform microclimate and prevent issues in cultivation. If you would like to read more about the benefits of ventilation and circulation in greenhouses, read this blog concerning the topic.

Are controllers compatible with all fans?

Not all fans are controllable or controllable in all aspects. This is why it is important to double-check the capabilities of fans before investing in controllers. While many fans are sold with the promise of being speed variable, they may in fact not be. Varying the speed of these kinds of fans will in turn greatly reduce the lifetime. While nearly all of our fans are built for varying speed we advise not to use variable speed control with the Multifan V-Flo Fan, as this negatively affects the ability of the fan to generate a uniform climate.

Would you like to learn more about the effects of control equipment on the fans in your greenhouse or are you simply exploring the possibilities to improve your greenhouse climate? Feel free to get in touch with a specialist using our contact form. We’ll be glad to help!

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published on July 7, 2021

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