Air Pressure Switch

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.

Setpoint Check

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.

1. After the dryer has been filled with grain and before the burner is ignited, the operation of each air pressure switch must be checked.

2. All of the fans must be running (including the cooling fans) before the air pressure switches can be accurately adjusted.

3. 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.

4. 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.

Switch Adjustment

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:

1. 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.

2. 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.