Controller shows E07; flue gas temperature alarm or lockout.

Safety: Isolate power and allow boiler and flue to cool. Hot flue surfaces can cause burns.

• Check flue gas sensor: Locate the flue gas temperature sensor in the flue outlet. Inspect wiring and connections to the Danstoker controller. Replace the sensor if readings are clearly unrealistic.
• Inspect heat exchanger: Open the boiler access doors or hatches. Examine the Danstoker boiler tubes or smoke passes for soot, ash, or scale buildup. Brush and vacuum the surfaces as per maintenance manual.
• Verify burner firing rate: Ensure the burner is not set above the boiler’s rated capacity. Check the modulation settings and that the fan and fuel valves are correctly adjusted.
• Check flue gas path: Inspect the chimney or stack for obstructions, collapsed liners, or dampers that are partially closed.

After cleaning and checks, reset the alarm and monitor flue gas temperature. Persistent E07 requires a combustion specialist to optimize burner settings.