Environmental Greenhouse Controls

May 8, 2008

By Amanda Sylvie

Garden & Greenhouse Magazine

Greenhouse controls!

Do you ever wish your greenhouse or indoor garden was higher in humidity during the day, fifteen degrees cooler at night, or higher in CO2 levels? Sometimes controlling the atmosphere in a greenhouse can seem like an unattainable dream! However, as long as you are trying to manage the environment of an enclosed area, atmospheric controls can make life a lot easier. Good greenhouse will be reliable, accurate, economical and resistant to corrosive damage in humid enclosures.

Greenhouse or atmospheric controls can manage humidity, temperature, irrigation, ventilation, lighting and CO2 levels. These controls are ideal for greenhouse environments, indoor gardens and atriums, herbariums, reptariums, vivariums, aviaries, solariums as well as many other environments. Depending on the environment you are trying to manage, certain elements will be more important to control than others. When growing orchids, as well as many other types of plants, temperature, humidity, lighting and air circulation are essential. If you are utilizing a hydroponic growing environment, CO2 production and monitoring will yield improved results. Automated controls are the only way to ensure a productive and dependable environment.

Humidity

Humidity controls manage the amount of moisture in the air and are ideal for greenhouses or for indoor gardens that use a fogger, such as an Aquafog 400 or similar product. These controls easily switch between humidifying and dehumidifying. Humidity control models like Green Air Product’s RHC-1 or THC manage either relative humidity or total humidity and may be built with a deluxe piggy-back plug and cord set to attach to a power source and either a humidifier or a dehumidifier.

A humidistat, such as the Jaybird humidistat, offers excellent control when humidity requirements are 85% or lower. Once humidity levels drop about 7% below the set-point, the humidistat will activate to increase the humidity. We connect a humidistat to a solenoid valve that opens to activate the misters when additional humidity is needed. Swamp coolers or evaporative coolers also help to cool the air in climates that typically have low humidity.

A wireless thermometer/hydrometer with a remote sensor, such as the LaCrosse Weather Station, provides an ideal method for monitoring conditions in your growing area. This system allows you to set alarms for temperature highs and lows, while recording high and low levels throughout the day and night. You can monitor your greenhouse from the comfort of your home and check the recorded levels to ensure your plants were comfortable during the heat of the day or the cold of the night.

Temperature

Temperature controls can manage exhaust fans, air conditioning, evaporative coolers, or heaters to maintain the ideal temperature range in your garden area. Controllers such as the Green Air TEMP-H/C models allow easy switching between heating and cooling systems while keeping the temperature within a range around the ideal programmed temperature. One of my favorite controllers, the CT-CT-P maintains different cooling settings for day and night to produce at least a 15-degree differential by utilizing a photosensor. The Green Air HT-HT-P maintains different heating settings for day and night. Achieving at least a 15-degree differential is needed by many orchids and other plants to encourage blooming.

Timers – Cycle & Lighting

Timers are indispensable for setting up your ideal growing area for plants. A variety of timers are available and can introduce cycles of day-night, temperature differentials based on the time of day, misting or irrigation, as well as lighting management.

Cycle timers, like the Green Air Cyclestat 4P, repeat a selected cycle anywhere from every 5 minutes to every 8 hours. Misting, lighting, air circulation or irrigation can last 5 seconds to 30 minutes, repeating as frequently as needed. Just like the misters at the grocery store, you can have your misting system spray your plants every five minutes for 15 seconds. Now if I could just locate a source for the thunderstorm sound to accompany the misters!

The Green Air Product’s 24-hour cycle timers offer two options. The first being a 24-hour clock timer with a built-in cooling thermostat (24-CT-1) to activate the cooling/exhaust equipment when temperature exceeds your set point. The second type offers dual 24-hour clock timers to control lighting, CO2, pumps or other timed equipment. For hydroponic systems using CO2 enrichment, the 24-DT-1 can coordinate the functions of the exhaust fan and the CO2 cycles within a 24-hour period to ensure CO2 enrichment does not occur during exhaust periods.

Sequential timers are very exciting due to the options they offer. These timers feature adjustable frequency and duration that can be impacted by photosensors. As a result, the timer can turn systems off during dark periods but maintain a lighting, misting or CO2 schedule during daylight hours. For example, the Green Air CST-1SP (Sequential Timer with Solenoid and Photo Sensor), in combination with a humidistat, can turn on a misting system when humidity drops below 70% in an orchid greenhouse during daylight hours only. This would provide orchids with the humidity they require, but not increase their risk of fungal infection or rot by misting them in the evening/night hours.

Lighting timers are programmable with multiple outlets and high load capacity to accommodate 120 or 240 volt requirements often needed by high-intensity lighting. To ensure a lighting timer will meet your needs, options such as latching relay, temperature override, and high amperage relay are available on lighting timers made by Green Air Products. Latching relays minimize the effects of photo-period interruptions in power outages. The temperature override feature suspends the operation of lighting equipment during periods when the room temperature exceeds your maximum allowable level. Operation resumes when the temperature drops to acceptable limits. This feature helps to keep lighting-related heat from damaging sensitive plants or crops.

Carbon Dioxide Systems

Researchers have been showing that an increased level of carbon dioxide can improve the growth, quality and yield of crops as long as the plants have adequate light, nutrients and water. Many hydroponics and greenhouse growers have been incorporating CO2 generators or emitters and CO2 monitoring controls into their growing environments. To achieve ideal results, though, certain conditions need to be met. Ideally, the indoor garden area or greenhouse needs to reach 1000 ppm (parts per minute) CO2 within 10 minutes. This allows the greenhouse to achieve ideal CO2 levels after exhausting or venting the area hourly.

Venting or exhausting the area should occur just before enriching the room with CO2. The Green Air model CT-DH-4P can coordinate cooling with the CO2 generator (such as model CD-12) so your system will vent the room and then generate the CO2 needed. The photosensor on the CT-DH-4P ensures your system will not generate CO2 at night while the plants are resting. The simplest and least expensive way to monitor CO2 levels is with Green Air Product’s new Set Point Controller (SPC-1). The SPC-1 samples the air and maintains the desired CO2 levels.

Multi-Function Systems

It is not necessary to have six different controllers. Multi-function controllers such as Green Air’s Micro Climate Controller (MCC-1) can automate all of the major functions in your greenhouse to include: lighting, heating and humidifying, cooling and dehumidifying, irrigation and CO2 enrichment. The built-in photosensor, 24-hour timer and cycle timer help to ensure and maintain an ideal growing atmosphere.

With all of the time and effort growers invest in nurturing healthy crops and plants, it is reassuring to know you can indeed manage the environment of your greenhouse or growing area. By optimizing the temperature, humidity, light, water and nutrients you can reap abundant crops of healthy, beautiful plants.

Amanda Sylvie is the owner of Lone Star Orchids and may be contacted by calling 866.433.8256 or emailing info@lonestarorchids.com. You can visit her website at www.lonestarorchids.com.

This article was originally published in Garden & Greenhouse Magazine. Garden & Greenhouse is written for small commercial growers, hobby greenhouse owners and indoor/outdoor gardeners and is free to qualified readers. For more information visit http://www.GardenAndGreenhouse.net.

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