TL;DR

High plenum temperature risks grain scorching and bin fire. Immediately reduce burner output, increase airflow, and check for obstructed airflow paths before resuming normal operation.

What you might see

plenum temperature alarm on control panel
plenum temperature trending above the setpoint limit
grain discharge showing burned or scorched appearance
airflow alarm associated with high temperature event

Likely causes

Tap to mark as ruled out

Grain column airflow obstruction reducing heat removal from the plenum
Burner modulation fault holding burner at high fire when demand is lower
Grain flow through the dryer stopped or reduced while burner continues at setpoint
Faulty plenum temperature sensor giving a false high reading

Required tools

IR thermometer for plenum spot check
Dryer control panel access

Safety first

Grain dryer fire risk. If smoke is visible, stop the dryer and call the fire response team. Do not re-enter the dryer structure.
Grain dust in the dryer plenum reaches explosive concentration. No ignition sources during cleaning or inspection.

Procedure

7 steps · ~30 min

1
Immediately reduce burner to low fire or pilot from the control panel if the plenum temperature alarm activates.
Warning: High plenum temperature can ignite grain dust in the dryer column. If smoke or fire is observed, activate the emergency stop and call the fire response team.
2
Confirm that grain is flowing through the dryer at the correct discharge rate. A stalled dryer with the burner on will rapidly overheat.[1]
3
Check all airflow paths for blockage. Inspect the plenum inlet screens for grain or debris accumulation restricting airflow.
4
Verify the airflow fans are running at correct speed and direction. A fan running backwards provides no cooling to the plenum.[1]
5
If grain flow is normal and airflow is clear, compare the plenum thermocouple reading to an independent IR measurement at the plenum access port to check sensor accuracy.
6
After resolving the root cause, restore burner output gradually while monitoring plenum temperature.
7
Inspect a sample of grain from the dryer discharge for scorching before returning to production.

Sources

GSI (AGCO) GSI X-Stream / Topdry Grain Dryer general technical documentation, GSI (AGCO)
Grain dryer plenum temperature control and safety response, general grain drying practice (general)

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