Glow-worm- f1 and f28 errors

Overview of the Issue

Because Glow-worm and Vaillant are part of the same manufacturing family, they share many internal components and diagnostic codes. One of the most frustrating issues homeowners face is a boiler that refuses to ignite or stay lit.
When this happens, your boiler will display an error code. The most common ignition-related error codes for Glow-worm and Vaillant boilers are F1, F28, and F29.
Understanding what these codes mean can save you time and money, and in some cases, you might be able to resolve the issue yourself without needing to call an engineer.
In other situations, knowing the code will help you explain the problem clearly to a

Common Ignition Fault Codes: F1, F28, and F29

F1 and F28: Ignition Failure

The F28 code (and F1 on some Glow-worm models) indicates that your boiler has attempted to ignite but failed to detect a flame. For your safety, the boiler shuts down and locks out to prevent unburned gas from accumulating.

Common causes and what you can do:

Frozen Condensate Pipe: In freezing weather, the plastic pipe outside your home that carries condensation can freeze and block. This forces gases back into the boiler, causing it to shut down. Gently thaw the pipe using warm water or a hot water bottle. Check the Gas Supply: Ensure your gas meter is turned on. Test other gas appliances, such as a stove, to verify your home has an active gas supply. Reset the Boiler: Sometimes a temporary glitch causes an ignition failure. Press the reset button on your boiler once. If it fails to ignite again, do not continue resetting it.

If basic checks do not clear the F28 or F1 code, the issue may involve worn ignition electrodes, a faulty gas valve, or a broken spark generator, which requires professional attention.

F29: Flame Extinguished During Operation

While F28 means the boiler couldn’t start at all, the F29 fault code means the boiler successfully ignited, but the flame went out unexpectedly while it was running, and subsequent attempts to relight it failed.

What this means:

Interrupted Gas Supply: The gas pressure may be dropping intermittently, causing the flame to die out. Flue Recirculation or Blockage: Exhaust gases might be getting pulled back into the air intake, literally choking the flame out. Faulty Flame Sensor: The sensor responsible for detecting the flame may be dirty or damaged, mistakenly thinking the flame has gone out.

Because an F29 error involves a running boiler losing its flame, it almost always points to a gas or combustion issue. You must not attempt to fix this yourself. A Gas Safe registered engineer is required to test the gas pressure, flue integrity, and sensors.

When to Call a Professional

Safety Considerations

While basic checks like thawing a condensate pipe can be done safely, you should never remove the boiler casing. Here is when to contact a Response Gas Safe registered engineer:

Internal Component Faults: Errors like F28 and F29 often require testing and replacing gas valves, electrodes, or the printed circuit board (PCB). Suspected Gas Leaks: If you smell gas at any point, turn off your gas supply at the meter, open windows, and immediately call an emergency Gas Safe engineer. Persistent Issues: If you have reset the boiler and checked the condensate pipe but the ignition codes keep returning, there is a deeper combustion or electrical failure that needs expert repair.