Boiler display shows A07; unit may shut down shortly after ignition, often associated with flue or vent temperature issues.

Safety first: High flue temperatures can damage the boiler and venting and may indicate unsafe combustion. Turn OFF power and gas before inspecting.

Steps:

• 1. Inspect venting: Check the entire vent run for sags, disconnections, or restrictions. From outside, ensure the vent termination is clear of obstructions and meets Raypak clearance requirements.
• 2. Check for flue gas recirculation: Make sure the combustion air intake is not too close to the exhaust outlet. Look for staining or melting around the vent termination that indicates hot gases are being drawn back in.
• 3. Inspect flue temperature sensor: Locate the flue sensor on the vent outlet or heat exchanger. Ensure it is firmly mounted and wiring is intact. If the sensor is loose or corroded, secure or replace it.
• 4. Verify combustion air supply: Ensure combustion air openings or intake piping are not blocked. In tight mechanical rooms, inadequate air can cause overheating.

Technician tasks: A qualified technician should verify gas input, combustion settings, and flue temperature readings. If A07 persists, the flue sensor or control board may require replacement.