The unit was running and lost the flame signal This condition occurred four straight times on the 399 model or twice on the 500 800 models This condition occurred four straight times on the 399 model or twice on the 500 - 800 models
The No Flame Running error code on Lochinvar boilers indicates the unit was running and lost the flame signal this condition occurred four straight times on the 399 model or twice on the 500 800 models this condition occurred four straight times on the 399 model or twice on the 500 - 800 models.
Lochinvar No Flame Running means: the unit was running and lost the flame signal this condition occurred four straight times on the 399 model or twice on the 500 800 models this condition occurred four straight times on the 399 model or twice on the 500 - 800 models. On this component the documented failure modes are no gas reaching the burner, or the gas supply is shut off, ignition or detection electrode dirty, worn or out of position or flue or air intake blocked or restricted. You can safely reset the boiler once — if No Flame Running returns, do not keep resetting. A qualified heating engineer should diagnose the root cause.
What Does No Flame Running Mean
The No Flame Running code is shown by the boiler’s control board when it detects the unit was running and lost the flame signal this condition occurred four straight times on the 399 model or twice on the 500 800 models this condition occurred four straight times on the 399 model or twice on the 500 - 800 models. 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 Running and the boiler stops until the fault is cleared |
Common Causes
The manufacturer does not publish a cause list for this specific code. The causes below are the failure modes documented for the same component on other boilers, confirmed by the service literature of 11 different manufacturers.
| Cause |
|---|
| No gas reaching the burner, or the gas supply is shut off |
| Ignition or detection electrode dirty, worn or out of position |
| Flue or air intake blocked or restricted |
| Mains gas pressure too low |
| Faulty gas valve, or its wiring and connector |
Safety Warning
No Flame Running 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 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 is not
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 ignition and detection electrode: clean off any deposits, check the gap and position against the manual, and replace it if it is worn.
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 Running:
| 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 Running.
No Flame Running is not classified as a high-severity fault, so the boiler can be reset once. If No Flame Running comes back, stop resetting: the underlying cause is still there and needs a qualified heating engineer.