Furnace attempts to start but locks out with E1, no flame is established

Safety first: Switch off electrical power and close the fuel shutoff valve (gas cock or oil isolation valve). Allow the furnace to cool before working near the burner.

Steps:

• Check fuel supply: Ensure the main gas valve is open or the oil tank has fuel and the oil isolation valve is open. Verify any manual shutoff valves near the burner are fully open.
• Inspect ignition electrodes: Remove the burner access cover. Locate the ignition electrodes near the burner head. Clean carbon deposits with fine emery cloth and check the electrode gap and position against the Danfoss burner diagram. Adjust so the spark is in the fuel stream.
• Check ignition transformer/spark generator: With power off, inspect the high-voltage leads from the Danfoss ignition transformer for cracks or loose connections. Tighten terminals. If safe and per manual, observe for spark during a start attempt (through the inspection port). No visible spark indicates a failed ignition transformer or control.
• Inspect burner nozzle/orifice: For oil burners using Danfoss nozzles, remove the nozzle assembly and check for clogging. Replace the nozzle with the exact type and capacity specified on the furnace rating plate. For gas burners, ensure the main orifice is not blocked by debris.
• Reset and test: Restore fuel and power, then reset the Danfoss burner control (usually by pressing the reset button until the LED changes state). Observe the ignition sequence. If E1 returns repeatedly, stop resetting and call a qualified technician.