Bottled CO₂ System

A bottled CO₂ system offers the benefits of low cost of acquisition and does not add heat and humidity to the indoor garden or hobby greenhouse. There are still some disadvantages. The regulator or solenoid valve may "freeze" and get jammed in the open position and leak unnecessary and costly CO₂ to the atmosphere. The frequent need to replace empty CO₂ bottles may become an inconvenience. Also, the bottled CO₂ system requires regular supervision. When a CO₂ bottle is empty, the CO₂ controller may still activate the system demanding to raise the CO₂ concentration. Then, the solenoid valve may be continuously activated without the cooling of the passing thru evaporating CO₂: often, a weak solenoid valve will overheat and burn or some other part of the system is damaged.

The regulator or solenoid valve "freezes"

This situation arises even if the power to the valve is turned off from the CO₂ ppm controller or timer. The problem is partly due to the very low temperature of the evaporating CO₂ thru the regulator product weak components. Plug'N'Grow's regulator iGS-REG has been designed to alleviate this problem and last for years of service.

There is also a physical limit to the CO₂ evaporation in the bottle:

• A 20 lbs CO₂ bottle can only deliver 14 cubic feet of gas per hour;

• A 50 lbs CO₂ cylinder can only deliver 50 cubic feet of gas per hour;

If one tries to draw more than 14 cubic feet of gas per hour from a 20 lbs bottle, the gas temperature drops well below 0 degrees at the outlet and in the bottle. Drawing a high flow of CO₂ from the bottle may cause the regulator and solenoid valve to freeze and ultimately the content of the bottle to freeze to carbonic ice thus stopping all flow. The same situation tested in our laboratory arose from a 50 lbs CO₂ cylinder while drawing a high flow.

If a flow rate higher than 14 cubic feet per hour of CO₂ is needed with 20 lbs bottles, it is better to use multiple regulators set at 14 cu. ft. an hour or less or use a high flow regulator like the iGS-REG and multiple 20 lbs CO₂ bottles so as never withdrawing more than 14 cu. ft. an hour of CO₂ per bottle.

CO₂ bottle replacement

A gardener may also consider a CO₂ gas combustion generator to avoid another major inconvenience associated with a bottled CO₂ system: transportation. Most countries law relative to dangerous materials forbid transportation of high pressure gas bottle in a passenger vehicle. A valve leak is always possible. In the worst case of a valve breaking off, the bottle transforms into a rocket or explodes causing both damages and injuries. Some large indoor garden or hobby greenhouse may require frequent replacement of empty CO₂ bottles.

• 20 lbs Compressed CO₂ Bottle contains 175 cubic feet of gas at atmospheric pressure and 68°F (standard conditions)

• 20 lbs CO₂ bottle may last from 5 to 7 days in the garden to enrich at 1200 ppm CO₂ concentration a 1500 cubic feet garden also depending on the lighting duration set in the garden (14 to 18 hours).

Relative to the indoor garden or hobby greenhouse volume (length x width x height), the following table suggest the flow meter adjustment in standard  cubic feet per hour (SCFH) to raise the CO₂ concentration from 450 to 1500 ppm in 10 minutes.

* We recommend using two 20 lbs compressed bottles in parallel or one 50 lbs bottle for flow rates higher than 16 SCFH.

Plug'N'Grow CO₂ Controllers Comparison

* CO2 concentration varies in outside air depending on location, time, surroundings and altitude. It is recommended to calibrate the CO2 sensor with a certified concentration calibration gas.

** CO2 NDIR sensors loose their precision with time and "drift away" from calibration. Drifts of 100 to 200 ppm below the real value over 3 months use have been observed. It is recommended to calibrate the CO2 sensor at the beginning of each cultivation.

*** The marked CO2 controller has only one output and can only serve one purpose at a time, enrichment OR ventilation.