- Boilers
- Gas boiler
F27
Saunier Duval F.27 on a gas boiler: incorrect flame detection
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
Saunier Duval F.27 is a safety shutdown for incorrect flame detection: the boiler sees a flame when it should not. One possible cause is a leaking gas solenoid valve. Do not chain resets and call the official service centre.
Safety first
Stop and check this first
- F.27 can come from a gas valve that does not close: do not chain resets. If it returns after one, leave the boiler off until the official service centre checks it.
- If you smell gas: Saunier Duval says to keep away from the area, open doors and windows, light no flames and do not smoke, do not touch switches, sockets, doorbells or phones, close the meter and appliance gas valves, leave the building and call the gas company from a phone outside.
Safe checks you can perform
- Smell of gas
- Water or damp near the boiler
- One reset with the fault clearance key
- Valve and flame control check by the technician
Leave these tasks to a qualified professional
- Do not attempt this professional task: Gas valve tightness test
- Do not attempt this professional task: Flame control and electronics check
- Do not attempt this professional task: CO2 check after the 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.
Gas valve tightness test
What they doThe technician checks whether the solenoid valve closes fully, with a tightness test of the gas pipe and valve assembly.
They must show youthe test carried out.
In writingthe result and the valve reference, if replaced.
Flame control and electronics check
What they doThe technician checks the board and flame control for humidity or damage and reads the fault memory.
They must show youthe fault memory and the board's condition.
In writingwhat was checked and any part replaced.
CO2 check after the repair
What they doIf the valve assembly is replaced, the technician measures CO2 at the test point and compares it with Saunier Duval's table.
They must show youthe analyser printout.
In writingthe CO2 measured and whether it was adjusted.
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 whether there is a smell of gas near the boiler or in the home.
- Result that matters:
- whether there is a smell.
- If there is a smell:
- do not reset; follow the gas warning and leave the home.
- If there is no smell:
- carry on with the checks.
- Evidence to keep:
- a note of the time.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de funcionamiento 0020238204_00
Water or damp near the boiler
- Who:
- you.
- How:
- look for water under the boiler or visible damp around it, without opening the casing.
- Result that matters:
- whether there is water or damp.
- If there is water:
- shut off the cold water to the appliance and tell the official service centre, as Saunier Duval asks.
- If it is dry:
- humidity is less likely.
- Evidence to keep:
- photos of the area.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de funcionamiento 0020238204_00
One reset with the fault clearance key
- Who:
- you.
- How:
- press the fault clearance (reset) key and wait five seconds, as Saunier Duval describes when the display shows an error message. Do it once.
- Result that matters:
- whether F.27 clears and the boiler works again.
- If it clears and stays away:
- note the date and time.
- If it stays or returns:
- Saunier Duval says to inform the official service centre; do not keep trying.
- Evidence to keep:
- a photo of the display and a note of each reset.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de funcionamiento 0020238204_00
Valve and flame control check by the technician
- Who:
- official service centre gas technician.
- How:
- checks the gas solenoid valve for tightness, humidity in the electronics and the flame control.
- Result that matters:
- whether there is a real flame with gas shut off or a false signal.
- If the valve does not close properly:
- it is replaced.
- If it closes properly:
- humidity and electronics are checked.
- Evidence to keep:
- a report with the tightness test and what was replaced.
Only a gas technician checks the gas solenoid valve: Saunier Duval reserves gas settings for the specialist installer.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de instalación y mantenimiento 0020238203_00
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
- Saunier Duval
- 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
In the ThemaFast Condens table, F.27 is safety shutdown: incorrect flame detection. Saunier Duval gives three causes: humidity in the electronics, faulty electronics (flame control) or a leaking gas solenoid valve. The flame control detects a flame signal at a moment when gas should be shut off; it may be a real flame from a valve that does not fully close or a false signal from the electronics. The code does not say which.
Warnings and stop conditions
- Higheditorial warning
F.27 can come from a gas valve that does not close: do not chain resets. If it returns after one, leave the boiler off until the official service centre checks it.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de instalación y mantenimiento 0020238203_00
- Criticalsource verified
If you smell gas: Saunier Duval says to keep away from the area, open doors and windows, light no flames and do not smoke, do not touch switches, sockets, doorbells or phones, close the meter and appliance gas valves, leave the building and call the gas company from a phone outside.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de funcionamiento 0020238204_00
Symptoms and causes
Probable causes · in order
- Leaking gas solenoid valvePossible
If the valve does not fully close, gas keeps flowing and there is a real flame with the burner off; it is the most serious cause and the technician confirms it with a tightness test.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de instalación y mantenimiento 0020238203_00
- Humidity in the electronicsPossible
If F.27 appears after damp or water near the boiler and clears when it dries, it fits this cause.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de instalación y mantenimiento 0020238203_00
- Faulty flame controlPossible
If the valve closes properly and there is no humidity, the board sees a flame that does not exist.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de instalación y mantenimiento 0020238203_00
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
Saunier Duval ThemaFast Condens, instrucciones de instalación y mantenimiento 0020238203_00
Saunier Duval · 2016 · manual
- 2
Saunier Duval ThemaFast Condens, instrucciones de funcionamiento 0020238204_00
Saunier Duval · 2016 · manual
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