Boiler shows E18, flame present when there should be no flame

Safety: Turn off power and gas immediately. A false flame condition can indicate a serious safety issue.

• Step 1 – Inspect flame sensor: Remove the flame sensor from the burner on the Triangle Tube boiler. Check for moisture, soot, or damage. Clean and dry thoroughly.
• Step 2 – Check wiring: Inspect the flame sensor wire for shorts to ground or contact with metal surfaces. Reroute or replace if damaged.
• Step 3 – Dry combustion area: If there is visible condensation inside the combustion chamber, allow it to dry and verify condensate drainage is working.
• Step 4 – Do not operate if issue persists: If E18 returns after cleaning and drying, leave the boiler off.
• Professional service required: A licensed technician must test the gas valve for leakage, verify flame circuit operation, and replace the gas valve or control board if necessary.