in control: the perfect indoor climate
usually result in reduced nutrient uptake.
Gardens by their nature are generally
humid environments, so the addition
of humidity is usually only necessary in
exceptionally dry environments—high
humidity is a much more common problem. When venting or air cooling, the
humidity outside is going to have a direct
effect on the humidity inside the garden.
If you’re striving to maintain a humidity
level of 50 per cent and you introduce
air that’s 90 per cent humidity, you have
to offset that somehow. Gardeners in
moderate or humid environments nearly
always have to use a dehumidifier in the
garden. Dehumidifiers are also a source
of heat (usually anywhere from 1,000
BTU to 5,000 BTU per hour, depending
on the size of the dehumidifier and the
amount of time it’s running), so this will
need to be considered when the cooling system is being sized. Liquid cooled
dehumidifiers are available as well.
All air conditioning and chiller systems
will dehumidify to some extent, but if
you’re able to maintain the humidity
where you want it with lights on using
only the a/c or chiller, during the lights
off cycle the humidity will build quickly,
because the cooling system doesn’t
need to operate as frequently and less
dehumidification will occur as a result.
For gardeners who prefer not to use a
separate dehumidifier, some air conditioning systems are available with a 24
hour dehumidification option, which
utilizes a heater in conjunction with
the a/c system to achieve dehumidification without adding cooling. These
same options are also usually available in
chiller systems, as well as an ‘extended’
192
Maximum Yield USA | March 2012
dehumidification option, which utilizes
a thermostat in conjunction with a humidistat for tighter control.
Nutrients
In hydroponic applications maintaining
the correct nutrient temperature is abso-
"Chiller systems are extremely
energy-efficient alternatives for
climate control."
lutely vital. A certain amount of dissolved
oxygen is necessary to maintain the
health of your plant’s roots and its ability to uptake nutrients—if the nutrient
temperatures get too warm, the level of
dissolved oxygen in the nutrient solution
goes down, which results in slower nutrient uptake by the plant. Compounding
this problem is the fact that the warmer
the nutrient water temperature, the more
dissolved oxygen the plants need for
proper nutrient uptake—so they require
more dissolved oxygen in this circumstance, but they’re actually getting less.
If the problem continues, the dreaded
pathogen pythium is the usual result.
If the garden is warmer than the
recommended nutrient solution temperatures for your application, a nutrient chiller will need to be employed. If
you’re using a standard a/c, the chiller is
a separate piece of equipment that must
be accounted for as part of the heat load
when sizing the a/c
system—unless you’re
able to kee