Biasi E22 Fault Code: Causes, Fixes & Repair Costs
What does the Biasi E22 fault code mean?
E22 is a safety lockout triggered when the Biasi control board detects a flame signal still present after it has sent the command to close the gas valve (known as the EVG — electronically controlled gas valve group). In normal operation, once the boiler shuts down, the flame should extinguish immediately as the valve closes. If the control board continues to see a flame signal beyond that point, it treats this as a potentially dangerous condition and locks the boiler out to prevent uncontrolled burning. E22 sits in a family of related EVG lockout codes (E20, E21, E22, E23), each of which requires a manual reset and points to a fault within the gas valve control circuit. A single successful reset may clear it if the fault was a brief glitch, but if the code returns, a Gas Safe registered engineer must investigate before the boiler is used again.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Gas valve (EVG) sticking or failing to close fully Common
The EVG gas valve may be worn, mechanically stuck, or electrically unresponsive, meaning a small amount of gas continues to pass through after the close command is issued. This sustains a residual flame that the ionisation circuit detects, triggering the E22 lockout. This is the most common root cause of this specific code.
- Faulty flame detection electrode producing a ghost signal Common
A contaminated, cracked, or misaligned detection electrode can generate a spurious ionisation current even when no real flame is present. The control board interprets this as a persistent flame after valve closure and locks out. The electrode lead or its insulation may also be damaged, causing leakage current to mimic a flame signal.
- Wiring or relay fault in the gas valve circuit Sometimes
Loose, corroded, or damaged wiring between the PCB relay and the gas valve can cause the valve to receive incomplete close signals, or cause the relay to remain partially energised. Intermittent connector faults are a common reason this code reappears shortly after a reset or a first engineer visit.
- PCB relay or control board fault Sometimes
If the PCB relay that drives the gas valve is failing, it may not fully de-energise when the boiler shuts down, keeping the valve partially open or sending confusing signals to the flame detection circuit. A PCB fault is typically suspected only after the valve, electrode, and wiring have been checked and found to be in good order.
How to fix it
- Reset the boiler once (twice at most) DIY safe
Locate the reset button on the front panel of your Biasi boiler. Press and hold it for approximately 5–10 seconds until the display changes or the boiler attempts to restart. Allow up to 10 minutes for the full ignition sequence to complete. Do not reset more than twice in succession — repeated failed ignition attempts can introduce unburnt gas into the combustion chamber, which is dangerous. A reset is not a repair; if E22 returns, move on to the next steps.
- Check your gas supply is active DIY safe
Confirm that other gas appliances in your home (such as a gas hob) are working normally. If they are not, contact your gas supplier, as a supply interruption can cause unusual boiler behaviour. If the gas supply is fine and E22 persists after reset, the fault is internal to the boiler.
- Do not attempt any further DIY — contact a Gas Safe registered engineer Gas Safe engineer
E22 involves the gas valve control circuit, flame detection components, and potentially the PCB. All of these require Gas Safe registration to work on legally and safely. Do not open the boiler casing, touch any wiring, or attempt to clean or adjust the gas valve or electrode yourself.
- Engineer checks the flame detection electrode Gas Safe engineer
A Gas Safe engineer will remove and inspect the ionisation or detection electrode for contamination (such as carbon deposits), cracks in the ceramic insulation, or misalignment relative to the burner. They will also check the electrode lead for damage or current leakage. A faulty electrode is cleaned or replaced as required.
- Engineer tests the gas valve (EVG) operation Gas Safe engineer
The engineer will verify that the EVG valve responds correctly to open and close commands from the PCB, closes completely with no residual gas flow, and shows correct electrical resistance across its coil terminals. A valve that is slow to close, sticking, or failing electrically will be replaced.
- Engineer inspects wiring and PCB relay Gas Safe engineer
All wiring connections to the gas valve and flame detection circuit will be checked for looseness, corrosion, or heat damage. If the valve and electrode are both serviceable, the PCB relay will be tested. A faulty PCB relay — or the PCB as a whole — will be replaced if confirmed as the cause.
Parts you may need
- Biasi EVG gas valve · from £120
- Flame detection / ionisation electrode · from £25
- Electrode lead and insulation · from £15
- PCB (printed circuit board) · from £180
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £150–£380, depending on the underlying cause.
Frequently asked questions
Can I keep resetting my Biasi boiler to clear E22?
You can try one or two resets — occasionally a transient glitch will clear with a single reset and the code will not return. However, if E22 comes back, resetting again will not fix the underlying fault. Repeatedly forcing the boiler through ignition attempts when the gas valve circuit is faulty is not safe practice and can mask a worsening problem. If the code returns after two resets, call a Gas Safe engineer.
What is the difference between Biasi fault codes E20, E21, E22, and E23?
All four are EVG gas valve group lockouts, meaning they relate to the electronically controlled gas valve circuit. E20 is typically triggered by a flame detected before the valve has been commanded to open (a spurious pre-ignition signal), E21 relates to a flame signal fault during the ignition sequence, E22 specifically flags a flame or flame signal persisting after the valve has been told to close, and E23 indicates a further valve-group fault variant. All four require a manual reset and investigation by a Gas Safe engineer — the diagnostic approach for each overlaps significantly, focusing on the gas valve, detection electrode, wiring, and PCB.
How much does it cost to fix a Biasi E22 fault in the UK?
Most homeowners pay between £150 and £380 including parts and labour. Replacing a faulty flame detection electrode is at the lower end (roughly £100–£180 all in), while a gas valve replacement typically costs £180–£280 including labour. A PCB replacement tends to be the most expensive common repair, usually £200–£380 depending on the specific Biasi model. If the PCB quote comes in significantly higher than this, it is worth getting a new boiler quotation for comparison — on an older Biasi, repair costs approaching or exceeding £500 may not represent good value.
Will E22 be covered under my Biasi warranty?
Biasi boilers typically carry a manufacturer's warranty of between 5 and 7 years depending on the model. If your boiler is still within this period and has been serviced annually by a Gas Safe engineer as required by the warranty terms, contact Biasi directly to arrange an assessment under warranty before paying for independent repairs. Resetting the boiler and checking system pressure are considered normal user actions and do not affect warranty validity.