Boiler shows E9 and locks out; may indicate condensate or drain-related issue on condensing models.

Safety first: Turn off power to the boiler. Condensate is mildly acidic; wear gloves and eye protection when handling.

• Step 1 – Inspect condensate trap: Locate the condensate trap at the base of the heat exchanger. Check for sludge, debris, or algae buildup. Remove and flush the trap with clean water. Refill the trap with water before reinstalling to maintain the seal.
• Step 2 – Check drain line: Follow the condensate line to its termination. Ensure it is not kinked, sagging, or blocked. Clear any obstructions and verify proper slope for drainage.
• Step 3 – Look for freezing: In cold climates, condensate lines routed outdoors can freeze. Thaw the line carefully and insulate or reroute to prevent recurrence.
• Step 4 – Test condensate float switch: If equipped, inspect the condensate pump or reservoir float switch. Make sure it moves freely and is not stuck. Clean or replace the pump or switch if it fails to activate.
• Step 5 – Reset boiler: After restoring proper drainage, reset the boiler and observe operation. If E9 returns, have a technician verify internal condensate passages and trap configuration.

Warning: Do not operate the boiler with the condensate trap removed; flue gases can leak into the space.