Error 07; unit overheats and shuts down, sometimes with loud boiling noises from inside the heater.

Safety: Turn off power and allow the unit to cool completely before working on it.

• Bleed air: Open the automatic air vent cap slightly (if fitted) on the primary circuit. Use manual bleed valves on nearby radiators or high points if the heater is part of a combined system.
• Check circulation pump: With power restored, call for hot water and listen/feel for the pump running. If it hums but does not turn, the impeller may be seized. Some pumps have a front screw that can be opened to manually free the shaft (follow manufacturer instructions).
• Inspect primary filter/strainer: Many Immergas units have a filter on the return line. Close isolation valves, remove and clean the filter mesh of sludge and debris.
• Reset overheat thermostat: Some models have a manual reset button on the overheat thermostat. Press it once the unit is cool. If it trips repeatedly, do not keep resetting—find and fix the root cause.
• Descale heat exchanger: If overheating persists, the primary heat exchanger may be scaled or blocked and should be chemically cleaned or replaced by a technician.

Warning: Persistent overheating is dangerous and can damage the appliance. If you cannot restore normal circulation, contact an authorized Immergas service center.