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GNA-2538 R0
8. Appendix
8.1. General Drying Operation Information
The drying of grain involves two primary components:
• heat - as measured in British Thermal Units (BTU)
• airflow - as measured in cubic feet per minute (CFM)
Airflow
The proper amount of airflow is as crucial to the drying process as is the amount of heat generated.
• LP and NG-Fired Heaters are sized according to the fan’s power source and the motor HP rating.
• The burner is fueled by either Liquid Propane (LP) or Natural Gas (NG).
Proper combustion requires an ideal fuel-to-air ratio. As static pressure under the drying floor increases the
airflow encounters resistance and is diminished. As airflow decreases, the amount of fuel being delivered to the
burner should be decreased accordingly.
Note
Airflow may decrease due to factors such as a greater bed depth, compactness of the grain being dried,
and the amount of foreign material in the grain. If the amount of fuel being delivered is not reduced
accordingly, the excessive fuel-to-air ratio will cause the flame to get long and yellow indicating an
inefficient burn.
A good flame should not extend past the heater housing, with a blue center and yellow ends.
Regulator Setting
• The regulator setting determines the amount of heat generated by the burner.
• Heaters typically operate between 2 and 20 psi (14 and 138 kPa) and should not be allowed to exceed 20 psi
(138 kPa) on propane gas.
Important
Do not exceed 8 psi (55 kpa) natural gas.
Drying Temperature Setting
• All heater models include an ON/OFF switch and thermostat to control on-off cycling of heater.
• AGI recommends that a thermometer be mounted near the burner control probe under the bin to ensure
that the burner controls are operating at the desired setting.
• Heaters control the plenum temperature by cycling on and off. The ideal cycle time should last between 1.5
- 3 minutes. Avoid temperature settings that allow the heater to cycle on and off too frequently. Cycle times
will vary somewhat with each installation depending on factors such as bin size, grain depth, fan size, and
type of grain being dried.
• The following conditions determine the drying temperature:
–
type of crop
–
type of drying system
–
target moisture
AXIAL FAN HEATER – LP AND NG-FIRED HEATER