Navien Error Code E012

What Does E012 Mean?

Error code E012 indicates flame loss - the boiler successfully ignited but then lost the flame during operation.

This is different from E003 (ignition failure) - E012 means the boiler did light, but couldn't maintain the flame.

Common Causes

Gas Supply Issues

1. Insufficient gas pressure to the boiler
2. Air in gas lines (especially after recent work)
3. Gas valve partially closed or faulty
4. Gas meter issue not supplying enough pressure

Boiler Component Faults

1. Dirty or faulty flame sensor can't detect the flame properly
2. Blocked burner preventing stable combustion
3. Faulty fan not providing enough combustion air
4. Flue blockage preventing proper exhaust
5. Condensate trap blockage affecting airflow

Environmental Factors

1. Windy conditions blowing down the flue
2. Flue termination issues - incorrectly positioned
3. Insufficient ventilation in the boiler room

What You Can Do

Immediate Checks

1. Check other gas appliances - do they work normally?
2. Listen to the boiler - does it ignite then cut out quickly?
3. Check the weather - is it particularly windy?
4. Inspect the flue terminal - is it blocked or damaged?

Simple Fixes

1. Check the condensate pipe - ensure it's not frozen or blocked
2. Verify gas isolation valve is fully open
3. Clear any obvious flue obstructions (leaves, debris)
4. Ensure adequate ventilation if boiler is in a cupboard

When to Call an Engineer

Contact a Gas Safe registered engineer if:

• E012 persists in normal conditions
• The boiler ignites but cuts out after 5-10 seconds
• You hear unusual noises before flame loss
• Other gas appliances also have issues
• The error occurs repeatedly throughout the day

What the Engineer Will Check

Gas Supply

• Gas pressure at the meter and boiler
• Gas valve operation and flow
• Pipework sizing and condition

Combustion System

• Burner cleanliness and condition
• Flame sensor position and cleanliness
• Electrode gap and condition
• Combustion chamber seals

Air and Flue

• Fan operation and speed
• Flue integrity and termination
• Air pressure switches
• Condensate drainage

Likely Solutions

• Clean the flame sensor and burner
• Adjust gas pressure if needed
• Clear condensate trap blockage
• Repair or relocate flue terminal
• Replace faulty fan or air pressure switch
• Service the gas valve

Prevention Tips

• Annual service including burner cleaning
• Check condensate pipe doesn't freeze in winter
• Maintain clear flue - check terminal regularly
• Ensure proper gas pressure during service
• Keep ventilation clear around the boiler

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Applicable Models: NCB-CE, NCB300, NCB500, NCB700, LCB700, and NPE series.

Note: If flame loss occurs during windy weather only, the flue terminal may need a wind deflector or repositioning.