Heater shows H6 and shuts down; may occur during very hot operation.

Safety first: Turn off power and gas. Overheated exhaust can damage the heater and pose a fire risk.

• Inspect flue path: Check that the AstralPool flue kit is installed per manufacturer specs and is not blocked or reduced in diameter. Remove any visible obstructions at the terminal.
• Check for soot: Remove the front panel and inspect the heat exchanger and burners for black soot deposits. Heavy soot indicates improper combustion and requires professional cleaning.
• Verify adequate ventilation: For indoor installations, ensure the equipment room has proper combustion air openings and is not sealed.
• Inspect flue temperature sensor: Locate the sensor on the flue collector. Check wiring for damage and ensure it is firmly attached to the flue surface.

If H6 persists, a technician should check combustion, gas pressure, and replace the flue temperature sensor if defective.