| At the plant
propagation unit seeds are germinated in small pots on plinths raised just off the floor
of the building. The propagation is in two phases typically taking 6 days each, giving a
total time of 12 days.
The key problems occur when
ambient temperatures exceed 30 degrees centigrade which results in slow propagation and
weak plants. This leads to excessive wastage when potting and inability to supply the
product on time.
Two units connected to fabric ducts were
installed for this 56m x 9m propagation unit. These were specified for ease of
installation and maintenance.
Fabric duct air distribution is used to
provide draught free conditions for the plants. Installed at a height of 1.5m these
also give evenly distributed cover throughout the building
Temperature and humidity functions are
controlled by a hygro-thermostat. This is directly connected to the evaporative
cooler which then regulates the air flow and water distribution to maintain the set
points.
There is the facility to run the coolers in
manual mode allowing 5 speed air flow control in addition to cool or ventilation mode.
The two coolers give a maximum duty of
15 air changes per hour in the building.
The temperature set point is set to 25C and
the target humidity level is 80%. Without the evaporative cooling system the temperature
would exceed 35C.The installation resulted in reducing the time of phase one by 2 days and
phase two by 4 days thus reducing the total propagation time by half. There is the added
commercial benefit of plant prices being at a premium during hot weather.
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