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The variable frequency drive (VFD) controls the speed of the dryer's metering/sweep discha. The VFD's parameters depend on the type of dryer and the machine's voltage. Select from the options below:
The variable frequency drive (VFD) controls the speed of the dryer's metering/sweep discharge. The VFD's parameters depend on the type of dryer and the machine's voltage. Select from the options on the following pages:
The sections that follow provides details needed to properly operate the different components of the dryer and to make any adjustments necessary. The components included do not comprise of everything that can be adjusted on the dryer, but rather the components that need to be adjusted based on normal operation.
The purpose of the High Limit Switch is to provide a safety shutdown in the event that the temperature in any of the plenums has exceeded the high limit setpoint. The high limit switch senses the temperature in the plenum that it is monitoring by means of a capillary bulb temperature sensing device.
Depending on the number of burners, this will determine the number of high limit switches, with one installed per burner. The high limit switch is adjustable and should be set once at the start of a drying season or for a given grain. Adjustment of the switch is done in the ignition box for tower dryers and in the burner control cabinet for all other dryers. Note that when a high limit setpoint is exceeded, the high limit for the applicable fan/burner will become tripped as well as all other high limit switches above it because the wiring of the switches are in series. For example, if the high limit switch in plenum #1 is exceeded, the high limit for plenum 2 will no longer show to be in good status.
The safety features associated with the high limit switch(es) are for your safety and for the protection of the dryer. They should be checked for correct operation at the start of the drying season and periodically during the season as they are designed to protect the dryer from a fire that may result from fan (air flow) failure while the burner is ignited and a flame is present.
The following procedure shall be utilized to properly check the high limit switch(es) setpoint. Note that the high limit switch for each fan/burner must be checked and set independently. Once the high limit setpoint has been reached, the switch will need to be reset by pressing the small reset button on the top of the device. After the dryer has been filled with grain and after the burner is ignited, the operation of each high limit switch must be checked.
Start the fan, ignite the burner and establish a stable temperature in the plenum.
Inside the ignition box for tower dryers and burner control cabinet(s) for all other dryers, adjust the high limit switch setpoint by turning the small dial counterclockwise to a temperature below the current temperature in the plenum.
Once the high limit switch determines that the temperature in the plenum has exceeded the high limit setpoint, the switch will cause the dryer to shutdown.
If the high limit switch does not shut down the dryer, it is defective and must be replaced. Once the switch is replaced, check its operation and make adjustments as previously outlined.
If the setpoint is exceeded and properly shuts down the dryer, the setpoint can be adjusted to a value that is approximately 40 deg F above the desired plenum temperature.
The purpose of the Air Pressure Switch is to prove airflow from the fan for safe operation of the burner. Once the pressure switch has been satisfied, operation of the burner and its ignition system are permitted. In the event that air pressure is lost as indicated by a non-illuminated air pressure light, the burner will extinguish.
Depending on the number of burners, this will determine the number of air pressure switches, with one installed per burner. The air pressure switch is adjustable and should be set once the dryer is full of grain. Adjustment of the switch is done in the High Voltage cabinet for tower dryers and in the burner control cabinet(s) for all other dryers. Reaching the air pressure switch's setpoint is indicated by the green air pressure light on the outside of the cabinet housing the air pressure switch.
The safety features associated with the air pressure switch(es) are for your safety and for the protection of the dryer. They should be checked for correct operation at the start of the drying season and periodically during the season as they are designed to protect the dryer from a fire that may result from fan (air flow) failure while the burner is ignited and a flame is present.
The following procedure shall be utilized to properly check the air pressure switch(es) setpoint. Note that the air pressure switch for each fan/burner must be checked and set independently.
After the dryer has been filled with grain and before the burner is ignited, the operation of each air pressure switch must be checked.
All of the fans must be running (including the cooling fans) before the air pressure switches can be accurately adjusted.
Start all fans and determine if the air pressure switch light (for the switch that is being verified) on the burner control cabinet illuminates once the respective fan has reached its normal operating speed.
If the indicator light does not illuminate or comes on too soon (before the fan reaches operating speed), the air pressure switch must be adjusted.
In the event that the indicator light does not illuminate or comes on too soon (before the fan reaches operating speed), the following procedure shall be used to properly set the air pressure switch:
Remove the cap on the air pressure switch. Inside the air pressure switch use the slotted screw to make adjustments by turning clockwise or counter-clockwise.
Turn the adjusting screw counter-clockwise until the air pressure light comes on. After the air pressure light comes on, turn the adjusting screw counter-clockwise an additional ¼ to ½ turn to allow for normal changes in static pressure.
If all air pressure switch adjustment is used and the air pressure light does not illuminate, the air pressure switch is defective and must be replaced. Once the switch is replaced, check its operation and make adjustments as previously outlined.
The Operating Procedures section of this manual will explain the operation of the primary components of the dryer and provide procedures to properly start-up and shut-down the machine.