Furnace locks out with E13, indicating a condensate drain or condensate level fault (for condensing furnaces with Danfoss controls)

Safety first: Turn off power. Condensate may contain acidic water; wear gloves and eye protection.

Steps:

• Inspect condensate trap: Locate the plastic condensate trap at the base of the heat exchanger. Remove and flush it with clean water to remove slime and debris.
• Clear drain line: Disconnect the drain tubing and blow through it or use a wet/dry vacuum at the outlet to clear blockages. Ensure the line slopes continuously downward to the drain.
• Check float switch: If equipped, inspect the condensate pump or pan float switch. Clean any buildup that may prevent it from moving freely. Verify the switch returns to the normal (non-tripped) position when water is removed.
• Reassemble and test: Reconnect all tubing securely to prevent leaks. Restore power, reset the controller, and run the furnace to confirm proper condensate flow.