PRINCIPLES OF Carbon Dioxide Enrichment
Carbon Dioxide Enrichment will dramatically increase the growth of green plants. Green plants use carbon dioxide ( CO2 ) and water in the presence of light to synthesize organic compounds. The plant then converts these organic compounds into elements that it can use (food). This process is called photosynthesis. If any of these ingredients ( CO2, water or light ) are at levels below what the plant can use for maximum efficiency, it will only be able to perform at that level and no greater. Adding carbon dioxide to a growing environment that is not receiving proper nutrients or is low on light will not produce the desired results. Similarly, plants that are receiving plenty of sunshine and nutrients will only perform as well as the ambient level of CO2 will allow. The ambient level of CO2 in the earth's atmosphere is generally between 300 and 600 ppm. Most plants receive far more water and energy in the form of sunshine than they can use. Increasing the CO2 in the growing area will let the plant use the excess water and energy that is stored in the leaves. The result is a substantial increase in the growth rate of any plant that uses chlorophyll in the process of photosynthesis. Enrichment should commence at sunrise or when photoperiod begins and refrain during darkness hours. The average CO2 level that is recommended is 1000 to 2000 parts per million (PPM). The object is to maintain a constant level in the atmosphere. You can run a small unit continuously during photoperiods or you can use a larger unit and time it to function periodically. Where exhaust requirements are frequent, the latter method is preferable. After the exhaust function the generator can be cycled to replenish CO2 quickly to maintain rapid plant photosynthesis. Use the operation time charts to determine the size of generator and the number of minutes of operation required for the level of CO2 desired. Frequency of recharge depends on the rate of consumption. For the greatest fuel economy and accuracy of recharge it is recommended that the Green Air Products CO2 Monitor Controller (CDMC) be used with all generator and emitter systems. Carbon dioxide generators operate by burning carbonaceous fuels such as propane or natural gas. The burners used in Green Air Products CO2 generators are specially designed to maximize the production of CO2 and minimize heat as a by-product. Green Air Products generators provide CO2 far more economically than any other means of enrichment. A constant burning pilot is used to ignite the gas when the generator is turned on. A thermocouple is used to monitor the pilot flame. If the pilot flame is lost, a safety valve will close so that unburned fuel will not be released into the enclosure. CO2 Generator operations may be automatically functioned according to actual ambient values when installed in conjunction with the CDMC. This control device continually samples the level of carbon dioxide in the growing area and functions the generator whenever CO2 levels do not meet your predetermined values. Generators are easily installed, dependable and efficient. Transformer included. Operates on 110 VAC.
Choosing the right size Generator
CD-3 through CD-36 Carbon dioxide enrichment equipment and methods have improved as experience and the understanding of atmospheric control and plant physiology has advanced. Plant metabolism and growth rate are dependent on the available atmospheric CO2. Plants are keenly sensitive to CO2 variations and optimum values must be constant and precisely controlled. The method, timing, and size of equipment must be properly determined to provide maximum benefits and economy. Carefully follow the operation charts to choose the proper size generator for the cubic foot area. Keep the recharge times to a minimum for best results. Do not undersize the generator or optimum results may never be achieved.
Size and Timing Charts
CO2 GENERATORS OPERATION TIME CHARTS
CO2 Charge Time
ROOM DIMENSIONS (FT.)
CO2 GENERATOR MODEL
Total minutes =
(minutes generator must be on to
reach the CO2 level you chose)
This chart will give you minutes of operation required for areas and models shown. Top row of the chart represents the cu. ft. of area (Length x Width x Height) in the enclosure. Left column is model size. Model numbers represent maximum CO2 output per hour in cubic feet (CD-3 = 3 cu ft/hr). Example: A CD-6 will take 10 minutes to produce a CO2 level of 1000 ppm in a 1000 cu. ft. enclosure.
Large greenhouses logically require longer charge times and multiple units may be necessary. The CD-36 takes 1.66 min. per 1000 cu. ft. area. Therefore a 20,000 cu. ft. area would be 20 X 1.66 = 33.2 min. to charge to 1000 ppm. For this application this may be an acceptable charge time. The area should be charged as quickly as possible for maximum advantage. Charging the atmosphere quickly insures that the rapid photosynthesis process will not be interrupted and the plants growth rate reduced Five to ten minutes is a good charge time. Try not to exceed twenty minutes when possible although this is not always practical in very large spaces. Your microclimate will need to be recharged every one to four hours depending on how much atmosphere is lost due to natural convection or plant usage.
This chart is used to decide how long a tank
of propane will last. This chart is fairly self explanatory
first you will look in the left column to pick a model,
then follow it across to the propane tank size you have.
The number that corresponds with the two selections will be
the number of hours that you can operate the Co2 Generator.
wall mount screw holes must be 10 inches center to center.
Mount brackets to wall and housing will slip over screw
heads and fit snug into slotted holes in housing back. This
allows for easy removal of housing from wall brackets. Make
certain bracket screws are secure in wall and use good
judgment when choosing mounting location.
eyebolts and ceiling hooks found in hardware pack. Hang unit
from sturdy location at least 18 inches from ceiling. The
unit must operate in level upright position. "CAUTION"
Should unit fall during operation fire may result.
screws holding bottom plate on housing. Locate holes on
bracket to match and replace screws .
. Plug the
transformer into a grounded 110 V timer and
2. Depress the
RED button located on the inside of the
generator for 90 seconds to clear the air from
3. Once gas is
present at the pilot let up button and wait 60
seconds for excess gas to clear from the
housing. Now depress the RED button again and
light the pilot burner. Maintain holding the
button down for an additional 30 seconds to
allow the thermocouple to heat to operating
4. Push the front on-off switch to the "ON
position. If your timer is also in the on
position fuel will pass through the solenoid
valve and the main burner will be ignited by the
pilot flame. As your timer cycles on and off so
will the main burner flame.
5. For the
CD-18 and CD-36 , the brass needle valve may be
used to adjust the flame size. This will
increase the time that the unit needs to charge
the space with CO2.FUEL
Replacement LPG regulator and hose: GAP propane CO2
generators use a standard small appliance type propane
regulator such as might be used with a small heater or
barbecue. It can be obtained at most hardware or home
improvement stores. Original equipment comes with a Marshall
Brass model 140 LPG tank mount regulator. The outlet uses a
1/4 inch male pipe thread to 1/4 male hose fitting to
facilitate a flexible hose connection between the regulator
and the generator. The regulator inlet uses a standard LP
tank POL fitting to connect to the LP tank. The fuel hose is
a typical flammable gas type welding hose such as might be
used with an acetylene welding torch. These parts are
available at a welding supply store.
propane applications use a propane tank that
has been filled to only 80% of it’s
capacity. This is very important for all
propane burning mechanisms. Failure to
observe this common rule will make your
generator hard to ignite and will not stay
lit (refer to troubleshooting).
thread the regulator flange nut in the tank
valve counterclockwise with your fingers
until you feel the flange seat. Tighten
firmly with adjustable end wrench. DO NOT
USE PLIERS! Fasten hose between regulator
and generator gas inlet in same fashion.
- Turn the
propane tank valve to wide open "ON"
- Check for
gas leaks. A solution of 25% hand dish soap
and 75% water in a spray bottle will work
well for detecting gas leaks. Apply solution
to all previously connected fittings.
Bubbles will occur around loose connections.
Always use two wrenches when tightening
Turn gas supply off before you begin work. Now
connect a gas shut off valve (not included) onto
your incoming gas supply line. If needed reduce
to 1/2 male nipple to accept enclosed regulator.
Note gas flow direction indicator arrow. Use gas
compatible pipe compound on all pipe thread
fittings and tighten securely.
Connect regulator to shut off valve nipple with
compound and tighten.
Check for gas leaks. A solution of 25% hand dish
soap and 75% water in a spray bottle will work
well detecting gas leaks. Apply solution to all
previously connected fittings. Bubbles will
occur around loose connections. Always use two
wrenches when tightening gas fittings.
Replacement NG regulator and hose:
GAP natural gas CO2 generators use a standard
small appliance type NG regulator such as might be used with
a residential stove or water heater. It can be obtained at
most hardware or home improvement stores. Original equipment
comes with a Harper-Wyman
second stage small appliance
regulator. It is 1/2 P.S.I.G. (with inlet pressure
spring setting is 7.0" W.C).
The outlet uses a 1/4 inch male pipe thread to 1/4 male hose
fitting to facilitate a flexible hose connection between the
regulator and the generator. The regulator inlet uses a
standard 1/2 pipe fitting to connect to the NG supply line.
The fuel hose is a typical flammable gas type welding hose
such as might be used with an acetylene welding torch. These
parts are available at a welding supply store.
a CO2 generator from propane to natural gas or vice-versa
involves changing the pilot and burner orifices and the gas
regulator. This involves a conversion kit and partial
disassembly of the unit. We strongly recommend that you have
this service performed by the manufacturer or one of its
authorized repair stations. Should you decide to undertake
this modification yourself be advised that you are tampering
with flammable gas connections and the manufacturer or its
representatives will not be liable and warranty obligations
by the manufacturer may be void. Contact your dealer or the
manufacturer at 1-800-669-2113 to arrange for conversion
This example shows the simplest method of CO2
generator control. Set timer for short intervals
during light hours only.
This diagram demonstrates an
exhaust synchronized system where the CO2
equipment is disabled during exhaust functions
and immediately replenished when exhaust is
completed. The CT-DH-3P
temperature and humidity controller activates
the exhaust fan and shuts off the CO2
during the exhaust cycle. It has a built in
photo sensor to limit CO2
enrichment to photoperiods only. Enrichment
will only occur when exhaust fan
is off and light is present.The CO2 "On" cycles
are timed by the Cyclestat
repeat cycle timer which cycles the CO2
equipment according to your preset periods. An
example might be that the timer is set for 5
minutes every hour. The CO2 generator
would be operated according to that hour
schedule. In the event that there is an exhaust
function at any time the CO2 will come on for 5
minutes immediately after the exhaust cycle is
completed. It will repeat again one hour after
that point. Replenishment of CO2 will always
follow an exhaust cycle to maintain a constant
and continuous enrichment level.
This system is the
ultimate in precise automated CO2 control. The
CDM-7001 sensor continuously determines
atmospheric CO2 values. The CDDS-2 controller
interprets these values and provides flexible
set point adjustments to sequence CO2 equipment
functions. The CDDS-2 has a built in photo
sensor for night time defeat and is disabled
during exhaust functions when plugged into
CT-DH-3 Atmospheric controller.
The LPCV-1 liquid
propane crossover valve will automatically
switch from the empty tank to the full one. This
will enable you to fill the empty tank at your
convenience and suffer no downtime.