The unit has failed to prove main burner ignition after four attempts on the 399 model or one attempt on the 500
The No Flame Ign error code on Lochinvar boilers indicates the unit has failed to prove main burner ignition after four attempts on the 399 model or one attempt on the 500.
Lochinvar No Flame Ign means: the unit has failed to prove main burner ignition after four attempts on the 399 model or one attempt on the 500. The usual causes are no gas reaching the burner, or the gas supply is shut off, flue or air intake blocked or restricted or ignition or detection electrode dirty, worn or out of position. You can safely reset the boiler once — if No Flame Ign returns, do not keep resetting. A qualified heating engineer should diagnose the root cause.
What Does No Flame Ign Mean
800 models It will require a manual reset before attempting to fire again. It will require a manual reset before attempting to fire again
The No Flame Ign code is shown by the boiler’s control board when it detects the unit has failed to prove main burner ignition after four attempts on the 399 model or one attempt on the 500. The boiler then stops instead of continuing to run in that condition: the code is the appliance reporting a problem, not proof that the boiler is broken.
| What you see on the boiler |
|---|
| The display shows No Flame Ign and the boiler stops until the fault is cleared |
Common Causes
Causes documented in the Lochinvar service literature published by lochinvar.com, cross-checked against the manufacturer’s fault-code table.
| Cause |
|---|
| No gas reaching the burner, or the gas supply is shut off |
| Flue or air intake blocked or restricted |
| Ignition or detection electrode dirty, worn or out of position |
| Faulty gas valve, or its wiring and connector |
| Control board (PCB) faulty |
Safety Warning
No Flame Ign involves electrical or pressure-related components. Do not attempt repairs without proper qualifications. Ensure the boiler is electrically isolated before any inspection. If you notice water leaks, unusual sounds, or pressure anomalies, contact a qualified heating engineer immediately.
Parts & Prices
Prices shown are indicative. Actual prices and availability vary by region.
How to Fix It
Inspect spark electrode and associated wiring for damage and connection. Reference page 26 of this manual for removal and cleaning procedures. Replace if necessary
Check for proper electrical grounding of the unit
Check incoming supply gas pressure. Natural gas pressures should be between 4 - 14 inches w.c. and LP gas pressures should be between 8 - 14 inches w.c. Refer to Section 7 - Gas Connections of the Knight Boiler Installation and Operation Manual for detailed information concerning the gas supply
Verify that the plastic hose from the gas valve to the air inlet is connected and
Check that the gas service valve is open and that other gas appliances in the property work. If they do not, the problem is the gas supply, not the boiler.
Inspect the flue and air intake along their whole length, including the outside terminal, and clear any obstruction or debris.
Refer to the Lochinvar service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
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Affected Models
Lochinvar models that can display fault code No Flame Ign:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Lochinvar models | — | Possible |
Frequently Asked Questions
Inspect spark electrode and associated wiring for damage and connection. Reference page 26 of this manual for removal and cleaning procedures. Replace if necessary. According to the technical documentation, this is the first check on the list for No Flame Ign.
No Flame Ign is not classified as a high-severity fault, so the boiler can be reset once. If No Flame Ign comes back, stop resetting: the underlying cause is still there and needs a qualified heating engineer.