- Boilers
- Gas boiler
F27
Glow-worm F27 on a gas boiler: flame signal with burner off
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
On Glow-worm boilers, F.27 means a flame signal was detected while the burner is off. Glow-worm calls this a case for an expert: do not try to solve it yourself. Reset at most once as your manual shows and 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
- Smell of gas
- One reset at most
- Boiler left off until the visit
- Gas valve and PCB test
Leave these tasks to a qualified professional
- Do not attempt this professional task: Flame signal and PCB test
- Do not attempt this professional task: Gas valve closure and tightness test
- Do not attempt this professional task: Combustion analysis after repair
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.
Flame signal and PCB test
What they doThe engineer measures the flame signal with the burner off and tests the PCB.
They must show youthe readings.
In writingthe values and the part replaced and why.
Gas valve closure and tightness test
What they doThe engineer checks the gas valve shuts fully and carries out a gas tightness test.
They must show youthe tightness test result.
In writingthe result and any valve replaced with its reference.
Combustion analysis after repair
What they doAfter the repair, the engineer measures combustion with a flue gas analyser.
They must show youthe analyser printout.
In writingthe readings against the manufacturer's figures.
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.
Smell of gas
- Who:
- you.
- How:
- notice, without opening anything, whether there is any gas smell near the boiler.
- Result that matters:
- whether gas may be escaping.
- If you smell gas:
- follow the gas emergency advice; do not reset.
- If not:
- go to the next step.
- Evidence to keep:
- a note of what you noticed.
Evidence: Glow-worm boiler fault codes: what they mean and how to fix them
One reset at most
- Who:
- you.
- How:
- reset once as your user manual describes; Glow-worm says resetting can sometimes get a boiler working again.
- Result that matters:
- whether F.27 returns.
- If it returns:
- switch the boiler off and call a Glow-worm engineer.
- If it clears:
- still report it; F.27 is an expert case.
- Evidence to keep:
- a photo of the display and the time.
Evidence: Glow-worm boiler fault codes: what they mean and how to fix them
Boiler left off until the visit
- Who:
- you.
- How:
- switch the boiler off at its electrical switch and leave it off if F.27 comes back.
- Result that matters:
- that it cannot keep trying.
- If you need heat:
- use another safe heater meanwhile.
- If the engineer is booked:
- tell them how often it appeared.
- Evidence to keep:
- dates and times of each F.27.
Evidence: Glow-worm boiler fault codes: what they mean and how to fix them
Gas valve and PCB test
- Who:
- a Glow-worm or Gas Safe registered engineer.
- How:
- checks whether the gas valve closes fully and tests the flame signal and PCB.
- Result that matters:
- whether the flame is real or a false signal.
- If the valve leaks through:
- it is replaced and gas tightness tested.
- If the signal is false:
- the PCB is replaced.
- Evidence to keep:
- a job sheet with test results.
Glow-worm says F.27 is a case for an expert and can be dangerous; only a Gas Safe registered engineer works on the gas valve.
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
- 27
- cocina LG error F27
- code erreur F27 chaudière Vaillant
- code erreur F27 lave-linge Siemens
- codice E27 Siemens
- codice F27 Vaillant
- código E27 Siemens
- código F27 Vaillant
- E00-27
- erreur E27 Siemens
- error F27 caldera Vaillant
- error F27 lavadora Siemens
- Error F27 Saunier Duval
- errore F27 caldaia Vaillant
- errore F27 lavatrice Siemens
- F 27
- F27 Siemens
- Fehlercode F27 Vaillant
- Glow worm boiler F27
- Glow worm F27
- Glow-worm F.27
- Glow-worm F27
- Glow-worm F27 flame signal
- LG F27 cooling fan self clean
- LG F27 ventilador autolimpieza
- LG horno F27
- LG oven error F27
- LG range F27
- panne F27 Vaillant
- Saunier Duval F.27
- Siemens E27
- Siemens F27
- Siemens Fehlercode E27
- Siemens Waschmaschine Fehler F27
- Siemens washer F27
- Siemens washing machine E27
- ThemaFast Condens F.27
- Vaillant boiler F27 fault
- Vaillant F.27
- Vaillant F27
- Vaillant Fehler F27
What it means
Glow-worm's fault code page gives F.27 as a flame signal detected while the burner is off. The two possible causes it lists are a gas valve not fully closed and a defective PCB. Either a real flame is present when gas should be shut, or the board reports a flame that is not there. Glow-worm says this is a case for an expert and that you should not try to solve it yourself, because separating the two needs gas valve and flame signal tests.
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 valve not fully closedPossible
Fits if a real flame remains after shut down; this is a gas safety fault for an engineer at once.
Evidence: Glow-worm boiler fault codes: what they mean and how to fix them
- Defective PCBPossible
Fits if no flame is present but the board still reports one; the board is tested and replaced.
Evidence: Glow-worm boiler fault codes: what they mean and how to fix them
Virtual technician
Does F27 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
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