- Boilers
- Gas boiler
F29
Glow-worm F29 on a gas boiler: flame lost, failed to reignite
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
On Glow-worm boilers, F.29 means the flame went out and the boiler failed to reignite. Check other gas appliances work, top up a prepayment meter if needed and, in cold weather, look for an iced condensate pipe outside. Then reset; otherwise call a Glow-worm engineer.
Safety first
Stop and check this first
- This code involves the flame or the flue, so check that a working carbon monoxide alarm is fitted, as HSE strongly recommends. If it sounds, switch the boiler off, open windows, get everyone outside and call 0800 111 999.
- If you smell gas, Glow-worm says to leave the property immediately and call the National Gas Emergency Service on 0800 111 999. Do not operate switches on the way out and make the call from outside.
Safe checks you can perform
- Other gas appliances and credit
- Condensate pipe in cold weather
- One reset
- Gas pressure, flue and electrode check
Leave these tasks to a qualified professional
- Do not attempt this professional task: Gas pressure measurement
- Do not attempt this professional task: Flue integrity and recirculation check
- Do not attempt this professional task: Electrode, earth and combustion check
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Gas pressure measurement
What they doThe engineer measures the gas pressure at the boiler with it firing.
They must show youthe pressure reading.
In writingthe measured value against the manufacturer's figure.
Flue integrity and recirculation check
What they doThe engineer inspects the flue for blockage, damage and flue gas recirculation into the air intake.
They must show youthe flue inspection.
In writingthe flue condition and any repair.
Electrode, earth and combustion check
What they doThe engineer checks the control electrode position, the electrical earth and measures combustion with an analyser.
They must show youthe electrode condition and analyser printout.
In writingthe readings and the reference of any part replaced.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Other gas appliances and credit
- Who:
- you.
- How:
- check another gas appliance lights and, with a prepayment meter, that there is credit.
- Result that matters:
- whether gas reaches the home.
- If not:
- restore the supply or credit, then reset.
- If gas is present:
- check the condensate pipe.
- Evidence to keep:
- a photo of the meter credit.
Evidence: Glow-worm boiler fault codes: what they mean and how to fix them
Condensate pipe in cold weather
- Who:
- you, at ground level only.
- How:
- during cold weather, check the outside condensate pipe for ice; thaw with warm, not boiling, water as Glow-worm's video shows.
- Result that matters:
- whether the pipe was frozen.
- If it was frozen:
- thaw it and reset; the code should clear.
- If it was clear:
- the boiler side needs an engineer.
- Evidence to keep:
- a photo of the pipe before and after.
Evidence: Glow-worm boiler fault codes: what they mean and how to fix them · Glow-worm winter weather advice: boiler fault codes and what to do if they occur
One reset
- Who:
- you.
- How:
- reset the boiler as your user manual describes.
- Result that matters:
- whether it relights and stays lit.
- If F.29 returns:
- call a Glow-worm engineer.
- If it runs:
- note the time and the weather.
- Evidence to keep:
- a note of each reset.
Evidence: Glow-worm boiler fault codes: what they mean and how to fix them
Gas pressure, flue and electrode check
- Who:
- a Glow-worm or Gas Safe registered engineer.
- How:
- measures gas pressure, checks the flue for recirculation or blockage, the earthing and the control electrode.
- Result that matters:
- why the flame went out.
- If gas pressure is low:
- the supply is investigated.
- If pressure is right:
- flue, earth and electrode are corrected.
- Evidence to keep:
- a job sheet with the readings.
Gas, flue and electrode work is for Gas Safe registered engineers only; Glow-worm advises against opening the boiler.
Evidence: HSE gas safety for homeowners · Glow-worm boiler fault codes: what they mean and how to fix them
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Boilers
- Brand
- Glow-worm
- Product type
- Gas boiler
Known code variants
- 29
- code erreur F29 chaudière Vaillant
- codice F29 Vaillant
- código F29 Vaillant
- error F29 caldera Vaillant
- Error F29 Saunier Duval
- errore F29 caldaia Vaillant
- F 29
- Fehlercode F29 Vaillant
- Glow worm boiler F29
- Glow worm F29
- Glow-worm F.29
- Glow-worm F29
- Glow-worm F29 flame loss
- panne F29 Vaillant
- Saunier Duval F29
- Thema NOx F29
- Vaillant boiler F29
- Vaillant F.29
- Vaillant F29
- Vaillant Fehler F29
What it means
Glow-worm's fault code page lists F.29 as the flame having gone out and the boiler failing to reignite. Possible causes it gives are an interrupted gas supply or insufficient gas pressure, a fault in the flue gas route from recirculation or blockage, poor electrical earthing, a blocked condensate discharge pipe and the control electrode touching the burner. Glow-worm's winter advice says older appliances show this kind of fault as F1. The code does not say which cause put the flame out.
Warnings and stop conditions
- Higheditorial warning
This code involves the flame or the flue, so check that a working carbon monoxide alarm is fitted, as HSE strongly recommends. If it sounds, switch the boiler off, open windows, get everyone outside and call 0800 111 999.
Evidence: HSE gas safety for homeowners · Glow-worm boiler fault codes: what they mean and how to fix them
- Criticaleditorial warning
If you smell gas, Glow-worm says to leave the property immediately and call the National Gas Emergency Service on 0800 111 999. Do not operate switches on the way out and make the call from outside.
Evidence: HSE gas safety for homeowners · Glow-worm boiler fault codes: what they mean and how to fix them
Symptoms and causes
Probable causes · in order
- Gas supply or creditCommon
Fits if other gas appliances also fail or the prepayment meter is out of credit.
Evidence: Glow-worm boiler fault codes: what they mean and how to fix them · Glow-worm winter weather advice: boiler fault codes and what to do if they occur
- Frozen or blocked condensate pipeCommon
Fits in cold weather when the outside condensate pipe is iced; thawing it and resetting clears the code.
Evidence: Glow-worm boiler fault codes: what they mean and how to fix them · Glow-worm winter weather advice: boiler fault codes and what to do if they occur
- Flue, earthing or electrode faultPossible
Fits when supply and condensate are fine and F.29 repeats; Glow-worm lists flue recirculation or blockage, poor earthing and the electrode touching the burner.
Evidence: Glow-worm boiler fault codes: what they mean and how to fix them
Virtual technician
Does F29 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Health and Safety Executive · official_doc
- 2
Glow-worm boiler fault codes: what they mean and how to fix them
Glow-worm · official_doc
- 3
Glow-worm winter weather advice: boiler fault codes and what to do if they occur
Glow-worm · official_doc
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