- Boilers
- Gas boiler
F28
Glow-worm F28 fault: ignition unsuccessful
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
On the documented Easicom3 open-vent range F28 means ignition was unsuccessful when starting. The code describes the ignition outcome and does not identify one failed part.
Safety first
Stop and check this first
- If you smell gas or suspect a leak turn the appliance off do not touch it call 0800 111 999 open doors and windows and follow HSE emergency guidance.
- F28 does not prove that the gas valve ignition electrode or electronics have failed. Internal testing and gas work require a competent Gas Safe registered engineer.
Safe checks you can perform
- Record the exact Glow-worm model and F.28 code
- Separate a supply outage from appliance diagnosis
- Stop after the model-specific reset fails
Leave these tasks to a qualified professional
- Do not attempt this professional task: Verify gas inlet and ignition conditions
- Do not attempt this professional task: Diagnose the gas valve harness earthing and electronics
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.
Verify gas inlet and ignition conditions
What they doA Gas Safe registered engineer should test meter and inlet conditions gas flow pressure and the complete ignition and ionisation paths using the exact Glow-worm service procedure.
Diagnose the gas valve harness earthing and electronics
What they doA competent engineer should inspect the correct gas-valve assembly connectors cable harness product earthing and control electronics before replacing any component.
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.
Record the exact Glow-worm model and F.28 code
Photograph the display and identification label without removing the casing. Confirm that the boiler is in the documented Easicom3 family or use the instructions for its actual product.
This evidence does not make F28 universal across every Glow-worm product family.
Evidence: Glow-worm Easicom3 open-vent installation and maintenance instructions
Separate a supply outage from appliance diagnosis
If there is no smell of gas and the appliance is not suspected unsafe note whether the household gas supply is unavailable and contact the supplier. Do not test pressure switches flow pressure or the gas valve yourself.
Gas smell or a suspected unsafe appliance overrides ordinary F28 checks and requires the HSE safety response.
Evidence: HSE gas safety for homeowners · Glow-worm Easicom3 open-vent installation and maintenance instructions
Stop after the model-specific reset fails
Use only the reset method in the exact operating instructions. If F28 returns or the boiler does not resume normal operation arrange qualified service rather than repeating resets.
Resetting cannot establish whether gas pressure ignition ionisation valve wiring or electronics are safe.
Evidence: HSE gas safety for homeowners · Glow-worm Easicom3 open-vent installation and maintenance instructions
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
- caldera Glow-worm F28
- erreur F28 chaudière
- Error F28 Saunier Duval
- Error F28 Vaillant
- errore F28 caldaia
- F28
- Fallo F28 Thema NOx
- Glow worm boiler F28 fault
- Glow worm F28
- Glow-worm F.28
- Glow-worm F28
- Saunier Duval boiler F28
- Saunier Duval F28
- Saunier Duval Thema NOx F28
- Vaillant F.28
- Vaillant F28
- Vaillant F28 fault
- Vaillant Fehler F28
What it means
Glow-worm lists gas supply and pressure conditions together with ignition ionisation wiring gas-valve and electronic causes. Appliance gas and internal electrical work require a Gas Safe registered engineer.
Warnings and stop conditions
- Criticalsource verified
If you smell gas or suspect a leak turn the appliance off do not touch it call 0800 111 999 open doors and windows and follow HSE emergency guidance.
Evidence: HSE gas safety for homeowners
- Highsource verified
F28 does not prove that the gas valve ignition electrode or electronics have failed. Internal testing and gas work require a competent Gas Safe registered engineer.
Evidence: HSE gas safety for homeowners · Glow-worm Easicom3 open-vent installation and maintenance instructions
Symptoms and causes
Probable causes · in order
- Ignition unsuccessful when starting on Easicom3Confirmed
Glow-worm defines F.28 on the documented Easicom3 open-vent range as ignition unsuccessful when starting up.
Evidence: Glow-worm Easicom3 open-vent installation and maintenance instructions
- Gas supply pressure switch or flow-pressure conditionPossible
The Easicom3 instructions list a defective meter a triggered gas-pressure switch air in the gas or gas flow pressure that is too low as possible branches.
Evidence: Glow-worm Easicom3 open-vent installation and maintenance instructions
- Ignition or ionisation circuit faultPossible
Glow-worm also lists the ignition transformer cable plug and electrode plus an interrupted ionisation path or incorrect product earthing.
Evidence: Glow-worm Easicom3 open-vent installation and maintenance instructions
- Gas-valve wiring or electronic faultPossible
An incorrect or faulty gas-valve assembly a connector or cable-harness fault and defective electronics remain professional diagnostic branches.
Evidence: Glow-worm Easicom3 open-vent installation and maintenance instructions
Virtual technician
Does F28 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 Easicom3 open-vent installation and maintenance instructions
Glow-worm · 2020 · manual
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