State-of-the-Art CO2 Injection and
Environmental Controls
Recently several
manufacturers have introduced equipment that allows extremely fine
control over most of the environmental factors in the high-tech indoor
growing environment. These systems that automatically monitor the
temperature and humidity, and turn on the exhaust fan or an airconditioner or dehumidifier any time the temperature or humidity rises
above pre-set levels.
After the exhaust cycle is completed, the fan stops and the necessary amount of CO2 is injected into the air. The injection is facilitated by a small timer that opens the solenoid valve and releases CO2 for a predetermined number of seconds.
The equipment remains off until one of three things happens:
Periodic CO2 Injection
The CO2 injection system pictured on
page 24 contains an integrated fan system. The fan is necessary to remove
the stale air
and replace it with clean, fresh air from outside before
additional CO2 is injected into the room. Here is how the system
works:
Evacuation! Injection
Cycles
There are a number of reasons that growers choose different
lengths of time between cycles for the evacuation/injection process. The
exhaust fan does a lot more than just change the air to eliminate CO2
depletion. Artificial lighting often causes a heat build-up. Periodically
replacing the hot, stale air with cool, fresh air helps keep the heat
within acceptable limits. Also, plants transpire water through their
leaves into the air during the growth process. This raises the humidity,
which can also make the environment prone to mold and rot, as well as
cause loose, stringy plant growth.
Depending on the location, season,
placement of the chamber in the house, and other factors, the temperature
and humidity changes from day to day. In many cases, simply changing the
air and re-injecting CO2 can cure a problem with temperature or humidity
build-up. This is because the heat and moisture-laden air that builds up
in the room is replaced with cool, fresh, drier air from the outside.
Seasonal changes in the weather often result in alterations
to the time between evacuation/injection cycles. For example, as the
temperature heats up in the summer, more frequent cycles are necessary
because the air being drawn into the chamber is considerably warmer to
begin with, and therefore rises more quickly to the point where the
temperature is unduly high. In some locales, more cycles may be warranted
in the winter rainy season, because the air being drawn into the room
contains more moisture.
Tubing and CO2
Dispersion
CO2 must be
introduced into the grow room in the proper manner for it to do its job
correctly. Some equipment manufacturers recommend a perforated tube
strung around the ceiling with small holes to let the cool CO2 fall down
over the plants. This is a must in a grow room with inadequate internal
circulation, but the CO2 probably won’t do much in these circumstances.
It quickly falls to the floor and escapes through cracks in the baseboards
in a room with improper internal circulation.
Large, heavy duty, oscillating fans are
the solution. You just can’t get too much air blowing around in the
growth chamber, both above and below the green canopy. (See drawing.)
CO2 Tanks
A CO2 tank can be a monster. Even
the little ones can be little monsters! Why? Because they weigh far more
than most people estimate.., especially half way up a few flights of
stairs.
The smaller tanks are referred to as twenty pound CO2
cylinders. That is because they hold 20 pounds of CO2 gas. But don’t let
the nomenclature fool you. A twenty pound steel tank weighs about 50
pounds when full. A full fifty pound tank weighs about 170 pounds.
Tanks are
available for sale or rental at welding supply companies. This is where a
tank is re-filled. (Usually the empty tank is swapped for a full one.)
CO2 tanks are regularly used by welders, bars, and people
with home beer tappers.
Always protect the valve from being knocked off or damaged
in an industrial accident. Always chain the tank to the wall in an upright
position to prevent accidental tip-over.
Regulator Freeze -
Up
Gas is extremely cold when it
escapes from the tank. A quick blast can do damage to skin tissue or eyes.
Be careful!
CO2 can also freeze and ruin a regulator. In haste to supply
CO2 to the waiting plants, many growers crank the regulator up to a
flow-rate that can cause cause regulator freeze-up. This can occur at
anything above 20 CFH (cubic feet per hour). Special heated regulators are
available for those with a large area, or a shortage of
patience.
Determining CO2 Release
Time
At 20 CFH, each minute of CO2 release yields one-third of a
cubic foot of CO2 released. A 10 X 10 X 8 foot room would require a little
over 3 minutes of CO2 release.
Advantages of Injection
Disadvantages of Injection
The author of this book was nearly asphyxiated while running
a machine that was activated by CO2 release, causing a slow but steady
build-up of CO2 in the room, gradually displacing all the oxygen.
Asphyxiation symptoms come on slowly. They begin with a
sleepy and lethargic feeling, and can be followed by a desire to lay down
for a nap. There are no ”danger sign” feelings in the lungs. If you feel
this way when in your growing chamber, get out quickly! Check your
equipment for signs of malfunction
later.
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