- Boilers
- Tankless gas water heater
F05
Saunier Duval F05 on a gas water heater: air or flue fault
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
F05 on the Saunier Duval Opalia F points to a fault in the air intake and flue system or the fan, detected by the air pressure sensor. The user manual says a professional must fix it; switch the heater off and call one.
Safety first
Stop and check this first
- If you smell gas while the Opalia F shows F05, do not operate switches, plugs, doorbells or phones, avoid any flame, open doors and windows if you can, close the meter or main gas valve and the appliance gas tap if possible, warn neighbours without ringing, leave the building, keep others out and call the emergency services and the gas supplier emergency line from outside.
- With F05 on the Opalia F, if you smell fumes, a CO alarm sounds or anyone has a headache, dizziness or nausea, open doors and windows on your way out, switch the appliance off only if it is on your path, get into fresh air and call for urgent help from outside, because carbon monoxide has no smell.
Safe checks you can perform
- Ventilate and switch off if you smell fumes
- Keep the Opalia off until the visit
- Describe what the fan does
Leave these tasks to a qualified professional
- Do not attempt this professional task: Test pressure sensor, tube and fan
- Do not attempt this professional task: Check final operation
- Do not attempt this professional task: Check duct slope and blockages
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.
Test pressure sensor, tube and fan
What they doThey verify the air pressure sensor, its connecting tube and the fan, replacing whichever part does not respond.
They must show youthe sensor and fan test while running.
In writingwhich sensor or fan part was changed and why.
Check final operation
What they doBefore handing back the Opalia, they run it, check operation and tightness and record the work.
They must show youseveral consecutive ignitions without F05.
In writingthe final check and recorded work.
Check duct slope and blockages
What they doThe gas technician checks that the flue pipe is not blocked and its slope does not exceed 3 degrees, along with its tightness and fixing.
They must show youthe flue duct condition and slope.
In writingwhat was found in the duct and corrected.
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.
Ventilate and switch off if you smell fumes
If you smell fumes while F05 shows, the user manual says to open doors and windows fully, switch the appliance off and call an authorised professional. Do not run the hot water again.
Evidence: Saunier Duval Opalia F 12/1 LR y F 14/1 LR, instrucciones de funcionamiento 0020265481_04
Keep the Opalia off until the visit
The user manual refers F05 to a professional, with no user reset. Turn the on and off switch anticlockwise to the stop; the display goes out and the heater will not try to light.
Evidence: Saunier Duval Opalia F 12/1 LR y F 14/1 LR, instrucciones de funcionamiento 0020265481_04
Describe what the fan does
- If you already heard it, note whether the fan ran briefly and then stopped:
- that is the symptom the manufacturer links to F05. Also mention any recent work or change near the flue outlet.
Evidence: Saunier Duval Opalia F 12/1 LR y F 14/1 LR, instrucciones de funcionamiento 0020265481_04
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
- Tankless gas water heater
Known code variants
- Anomalía F05 Ferroli
- calentador Cointra F05
- Cointra F05
- Cointra water heater F05
- CPE T F05
- Error F05 Ferroli
- error F05 lavadora Hotpoint
- error F05 lavadora Indesit
- error F05 lavadora Whirlpool
- F-05
- F5
- Ferroli error F05
- Ferroli F05
- Ferroli F05 boiler
- Ferroli F05 caldera
- Hotpoint F05 error washer
- Hotpoint F05 lavadora
- Hotpoint washer F05 not draining
- Hotpoint washing machine F05
- Indesit F05 error washer
- Indesit F05 lavadora
- Indesit washer F05 not draining
- Indesit washing machine F05
- lavadora Hotpoint F05 no desagua
- lavadora Indesit F05 no desagua
- lavadora Whirlpool F05 no desagua
- Opalia F.05
- Opalia F05
- Saunier Duval F05
- Supreme E TS F05
- Whirlpool F05 lavadora
- Whirlpool F05 washing machine
- Whirlpool washer F05 not draining
- Whirlpool washing machine error F05
What it means
The Opalia F 12/1 LR and F 14/1 LR is room-sealed and uses a fan monitored by an air pressure sensor. F05 appears when that pressure controller stays open for 25 seconds while the fan runs. The installation manual attributes it to a fault in the air intake and flue system or in the fan, and describes the symptom of a fan that starts briefly and then stops. It calls for checking the flue pipe slope, 3 degrees at most, and that it is not blocked. The user manual gives no reset for F05.
Warnings and stop conditions
- Criticaleditorial warning
If you smell gas while the Opalia F shows F05, do not operate switches, plugs, doorbells or phones, avoid any flame, open doors and windows if you can, close the meter or main gas valve and the appliance gas tap if possible, warn neighbours without ringing, leave the building, keep others out and call the emergency services and the gas supplier emergency line from outside.
Evidence: Saunier Duval Opalia F 12/1 LR y F 14/1 LR, instrucciones de funcionamiento 0020265481_04
- Criticaleditorial warning
With F05 on the Opalia F, if you smell fumes, a CO alarm sounds or anyone has a headache, dizziness or nausea, open doors and windows on your way out, switch the appliance off only if it is on your path, get into fresh air and call for urgent help from outside, because carbon monoxide has no smell.
Evidence: Saunier Duval Opalia F 12/1 LR y F 14/1 LR, instrucciones de funcionamiento 0020265481_04
Symptoms and causes
Probable causes · in order
- Blocked or badly sloped air or flue ductCommon
A blockage in the air intake or flue, or a flue pipe slope above 3 degrees, stops the sensor seeing the correct draught.
Evidence: Saunier Duval Opalia F 12/1 LR y F 14/1 LR, instrucciones de instalación y mantenimiento 0020265480_08
- Fan failurePossible
If the fan does not create the expected pressure the controller stays open, and the table lists fan failure as a cause of F05.
Evidence: Saunier Duval Opalia F 12/1 LR y F 14/1 LR, instrucciones de instalación y mantenimiento 0020265480_08
- Air pressure sensor or its tubePossible
The code is named faulty air pressure sensor; the appliance has the sensor and a connecting tube that the technician has to inspect.
Evidence: Saunier Duval Opalia F 12/1 LR y F 14/1 LR, instrucciones de instalación y mantenimiento 0020265480_08
Virtual technician
Does F05 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 · 2025 · manual
- 2
Saunier Duval Opalia F 12/1 LR y F 14/1 LR, instrucciones de funcionamiento 0020265481_04
Saunier Duval · 2020 · manual
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