This fault can involve incomplete combustion and carbon monoxide.
If anyone in the property feels sick, dizzy or drowsy, or you can smell gas: open the windows, leave the building, and do not switch anything on or off. Then call the National Gas Emergency Service.
0800 111 999Worcester Bosch F7 228 fault codewhat it means and how to fix it
A flame is being detected before the burner has started. Switch the appliance off and get a Gas Safe engineer rather than resetting.
Stop — this needs an engineer
Get a Gas Safe registered engineer to look at your Worcester Bosch F7 228
We do not pass enquiries to a repair firm, so there is no form here. Find a Gas Safe registered engineer through the Gas Safe Register, and ask to see their registration card when they arrive — it is the register, not the van, that tells you they are qualified.
What F7 228 means
Worcester describe F7 as a flame detected even though the appliance is switched off, with the 228 sub-code specifying ionisation detected before burner start. There are two possible explanations and they carry very different weight. The likely one is that the sensing circuit is at fault and reporting a flame that does not exist — contamination on the ionisation electrode, moisture across a connector, or a degraded flame amplifier on the control board. The serious one is that the reading is correct and gas is reaching a burner that should be shut off, which means the gas valve is passing.
Worcester's own literature is unambiguous that F7 is an engineer's job and instructs householders not to attempt to rectify it. Since neither you nor the appliance can distinguish the two without test equipment, the right response is to treat it as the serious one until proved otherwise. This is one of the few codes where the correct first action is to isolate rather than reset.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Ionisation electrode contaminated or shorting | Deposit or moisture creating a conduction path that mimics a flame signal. The most common cause and the benign one. | Common |
| Gas valve passing | The valve not sealing fully when closed. Less common, and the entire reason this code is treated as urgent. | Occasional |
| Moisture in the electrode lead or connector | Water tracking after an internal leak, or condensation in a cold garage or loft installation. | Occasional |
| Control board flame amplifier fault | The board misreading its own input. Diagnosed once the gas side has been proved sound. | Rare |
Can you fix it yourself?
Stop — this needs an engineer
What it costs to fix
Typical repair cost
£120–£450
An electrode is £120 to £200 fitted. A gas valve is £300 to £450. Expect a diagnostic charge on top, since separating the two needs a flue gas analyser.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Parts you may need
We may earn a commission if you buy a part through one of these links. It does not change what you pay, and it does not affect which parts we list.
Worcester Bosch Greenstar electrode set
87161431020£22–£52Authorised Worcester parts distributor
Price checked 28 September 2026
Own this appliance and had this code? . Nothing is published until a person has read it.
Related Worcester Bosch fault codes
- EA 227Stop — call an engineerThe boiler tried to light and never detected a flame, so it has shut the gas off and locked out. This is the most common Worcester fault code.Related: ignition and gas supply
- EA 229Get it checkedThe burner lit and then the flame was lost during operation. That is a different fault from failing to light in the first place.Related: ignition and gas supply
- FA 306Stop — call an engineerThe boiler detected a flame after it had closed the gas valve. That points to a valve letting gas past when it should be shut, and it must not be reset.Related: ignition and gas supply
- 2951Stop — call an engineerThe flame has been lost too many times in a row and the boiler has locked out. Each loss was a 229; Worcester's instruction is to read the history and find what put it out.Related: ignition and gas supply
- EA 261Stop — call an engineerAn ignition fault that Worcester define two ways: on the Greenstar i it points at the heat control module, on the Compact range it means the flame was not established inside the four-second ignition window.Related: ignition and gas supply
- EA 234Get it checkedThe control board cannot see the gas valve coil, so it will not attempt to light. Worcester call it a gas valve error, coil disconnected. No gas is released, but it is a gas job.Related: ignition and gas supply
Own a Worcester Bosch boiler? Save it and its codes come first next time.
Related guides
Common questions about Worcester Bosch F7 228
Is there anything I can try myself first?
No, and unusually the manufacturer says so directly. Worcester put it in writing in their own user literature: do not attempt to rectify F7 yourself. Manufacturers rarely word things that plainly, and it is worth heeding. Turn it off at the fused spur and leave it off.
Should I call Worcester or a local engineer?
Check the guarantee first. Greenstar guarantees run long — considerably longer than people assume — so an appliance you think is out of cover often is not. If it is still covered, book through Worcester directly, because an independent engineer opening the case can end the remaining cover.
How does F7 differ from FA?
F7 is a flame detected before the burner should start; FA is a flame detected after the gas valve has closed. Both concern flame where there should be none. FA is generally treated as the more safety-critical of the two, but neither is a householder repair.
What is the 228 part telling me?
It pins down the moment the ionisation current was measured — 228 is before burner start, whereas 328 relates to a different point in the sequence. Two appliances both showing F7 can need different investigations depending on the suffix, so quote it in full.
Could this just be a damp electrode after the cold snap?
It could, and on a garage or outbuilding installation that is a real possibility. But damp and a passing gas valve produce the same code, and only test equipment can separate them. Worcester's own instruction not to attempt a fix applies either way.
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
- Manufacturer support portal
- Trade body guidance
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.