C02 Emitter Systems

Compressed CO, systems are virtually risk-free, producing no toxic gases, heat, or water. These systems are also precise, metering an exact amount of CO, into the room. Carbon dioxide is metered out of a cylinder of the compressed gas using a regulator, flow meter, a solenoid valve, and a short-range timer. Two types of systems are: continuous flow and short range. Metal carbon dioxide cylinders which hold the gas under 1000 to 2200 pounds of pressure per square inch (psi) (depending upon temperature) can be purchased from welding or beverage supply stores. The cylinders are often available at

When open, the red on/off valve on top supplies compressed CO, via the regulator and How meter. An electric solenoid valve controls the timed bursts of COgas.

hydroponic stores. In North America, cylinders come in three sizes: 20, 35, and 50 pounds (9, 16, and 23 kg), and average between $100 and S200 (with refills costing about $30). Tanks must be inspected annually and registered with a nationwide safety agency. Welding suppliers and beverage suppliers often require identification such as a driver's license. Most suppliers exchange tanks and refill them. Fire extinguisher companies and beverage supply companies normally fill CO, tanks on the spot. If you purchase a lighter and stronger aluminum tank, make sure to request an aluminum tank exchange. Remember, the tank you buy is not necessarily the one you keep. To experiment before purchasing equipment, rent a 50-pound (23 kg) tank, A large 50-pound (23 kg) cylinder is heavier but saves you the time of returning to the store to have it refilled. When full, a 50-pound steel tank weighs 170 pounds (77 kg). A full 20-pound (9 kg) steel tank weighs 70 pounds (32 kg) and might be too heavy to carry up and down stairs. A full 20-pound (9 kg) aluminum tank weighs about 50 pounds (23 kg), and a full 35-pound (16 kg) tank weights 75 pounds (34 kg). Make sure CO, tanks have a protective collar on top to shield the valve, if the valve is knocked off by an accidental fall, there is

A set-up consists of a tank of CO, gas, regulator, solenoid valve, and a flow meter.

enough pressure to send the top (regulator, flow meter, valve, etc) straight through a parked car.

Buying a complete CO, emitter system at a hydroponic store is the best option for most closet growers. These systems offer a good value for small indoor growers. You can make your own system as described below, but these systems often cost more than the pre-manufac-tured models.

Welding suppliers also carry regulators, and flow meters. Flow meters reduce and control the cubic feet per hour (cfh). The regulator controls the psi. Models with smaller flow rates, 10 to 60 cfh, are preferable for gardening purposes, Buy a quality regulator-flow meter. Buy all components at the same time, and make sure they are compatible.

Carbon dioxide is very cold when released from a bottle where it has been kept under pressure. Even a quick blast can do damage to skin or eyes. If the flow rate is above 20 cfh, your regulator might freeze.

A regulator and flow valve is essential, but the solenoid valve and the timer are optional. However, growers wh do not use a solenoid valve and timer waste CO ,. The solenoid valve and timer regulate the flow of CO,. A solenoid valve is electrically operated and is used to start and stop the gas flow from the regulator and flow meter. The least expensive timer is plastic and is commonly used for automatic sprinkler systems, but 240-, 115-, 24- and 12-volt systems are available. They cost about the same, but the lower voltages offer added safety from electrical shock.

To automate the system, you need a "short range" digital timer to open the solenoid valve for brief periods several times a day.

Control the exact amount of CO, released into the garden room by altering the flow and duration of CO,, To determine how long the valve should remain open, divide the number of cubic feet of gas required by the flow rate. If the flow meter is set at 10 cfh, the valve will need to be open for 0.1 hours (1 divided by 10) or 6 minutes (0.1 hour x 60 minutes) to bring the room up to 1500 ppm. Remember, CO, leaks out of the grow room. On average, the CO, level of the room returns to 300 ppm in about three hours due to plant usage and room leakage, To maintain a steady level of CO,, split the amount of CO, released per hour into two or four smaller increments dispersed more frequently.

Distribute the CO., from the tank to the grow room by using a tube or fan. Suspend lightweight perforated plastic from the ceiling to disperse the CO,. The tubing carries CO, from the supply lank to the center of the grow room. The main supply line is attached to several smaller branches that extend throughout the garden. CO, is heavier and cooler than air and cascades onto the plants below.

To make sure the CO, is dispersed from the tubing evenly, submerge the lightweight plastic tubing in water and punch the emission holes under water while the CO, is being piped into the line. This way you know the proper diameter holes to punch and where to punch them to create the ideal CO, flow over the garden.

Overhead fans help distribute CO, evenly throughout the room. The CO., is released directly below the fan into its airflow. This evenly mixes the CO, throughout the air and keeps it recirculating across the plants.

Compressed CO, is expensive, especially in large grow shows. At roughly £0.50 per pound (450 gin), compressed gas is much more expensive than fuels used in generators. Cost of equipment and fuel make compressed CO, enrichment systems less economical than generators,

Growing Soilless

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