CPS: Continuous Production Systems Part IV
Most infrared CO2 monitors will require
calibration every year or two to ensure
accuracy. Some models you can calibrate
yourself, but most require a shipment
back to the manufacturer or your place of
purchase to have the service performed.
For smaller installations bottled CO2 is
a great option, because it is easy to install
and relatively safe to use. However, even
in smaller areas, the tanks will require
frequent replacement; especially if not
running sealed or “perfect” rooms where
exhaust is infrequent or does not occur
at all. For a lot of growers, gas fired CO2
generators are the way to go. They are
available for propane (LP) or natural gas
(NG). DO NOT hook up propane to
a NG burner or natural gas to an LP
burner or the results could be disastrous
and potentially fatal! Having a gas fired
CO2 generator requires a level of care
and diligence. While in theory it is very
similar to a BBQ, the fact that it is being
1000W HPS
400 - 1000W MH
Stage I: 0-3 weeks
Water-cooled CO2 Generator
AREA OF HIGHER CO2
Infra-red CO2 probe/monitor (to controller)
AREA OF LOWER CO2
Stage II: 3-6 weeks
Stage III: 6-9 weeks
Overview of CO2 boost system
Desired CO2 Drift Schematic - Note the placement
of the water-cooled CO2 generator and infrared
monitor. This allows for slightly higher CO2 levels
where desired.
38
MAXIMUM YIELD USA - March 2009
“Most AC units blow the heat away, which
can be ducted away from the growing area
or water cooled air-conditioners can capture
any heat and drain it away very efficiently.”
used in an indoor environment requires
very careful consideration and care.
For safety, never bring a propane tank
directly into the growing area, or even
inside the building. Long hoses are
available for propane tanks, so keep
them outside, and carefully run the hose
to the generator inside of the growing
area. Carefully inspect the hose and any
connections for leaks with a solution of
soapy water. NEVER use a damaged tank,
supply hose or regulator; you are literally
playing with fire. If you have a natural gas
supply, have a qualified technician install
a hose/supply with an on/off valve that
meets or exceeds your local code.
Make sure the CO2 generator is securely
mounted (chains and hooks are great) and
the CO2 distribution openings are several
feet away from ceilings. And always make
sure that there is no possibility that the
burner can come into contact with
any flammable materials. Areas that are
prone to earthquakes may require special
considerations.
For the ultimate in safety and high
efficiency CO2 generation, look for water
cooled CO2 generators, such as the unit
featured in this series of articles. The unit
is compact and runs so cool that it can
be safely wall mounted, provided that
it is a safe distance from ceilings. This is
excellent, because it keeps the unit out
of harms way, and there is much less of
a chance of whacking your head on it as
you intently observe your garden.
Remember, maximize the amount of
usable space in your growing area, as you
will get bigger yields and make the most
of your expenses associated with the
inputs required per square foot of area.
Most gas fired CO2 burners produce a
lot of heat while generating CO2. This
heat winds up in the growing area. In
an in/out situation, the exhaust system
will be activated, defeating the CO2
supplementation. In sealed or “perfect”
rooms it will cause the air-conditioning
system to cycle more frequently,
increasing your electrical consumption.
Water cooled units use a heat exchanger
in the combustion area of the unit that
captures the heat in the water supplied
to it. Here it is drained away to waste for
cooling, or for other purposes. In this way,
most of the heat is captured and never
enters the growing area at all. Even at the
maximum CO2 output, which is a big 45
cubic feet, you can hold your hand over
the discharge. Try this with a conventional
model, and you might be on a trip for
medical attention.
The output of the water cooled CO2
generator is totally controllable from 15 to
45 cubic feet, so it can be adapted to just
about any sized growing area. Some of the
safety features include a tip-over shut off,
low flow shut off and the use of electronic
ignition, so there is no standing pilot light.
For the greenhouse grower or indoor
grower in cold climates, the heat that
the unit captures is a dream come true.
The water heated and captured during
the light cycle can be circulated through
hydronic heaters in the growing area
or directly in the root zone to radiate
warm heat during the dark cycle,
when temperatures may need to be
supplemented to stay optimal for growth
or flowering. It could also be used to
reduce the heating costs of residences or
institutions in cooler climates.
The CPS model featured in this
series of articles demonstrates an in/
out ventilation/cooling system with
air-cooled lighting for temperature
control. It is very reliable and extremely
accurate when using the automatic day/
night centrifugal fan speed controller
featured. However, in hot climates, it may
not be enough to keep the temperature
between 72 to 82°F in the flowering