Alpha E27 Fault Code: Causes, Fixes & Repair Costs
What does the Alpha E27 fault code mean?
The Alpha E27 fault code signals that the boiler has detected a problem with flame establishment or flame recognition. In plain terms, the boiler either failed to ignite a flame when it tried, or it lit briefly and then lost the flame before it could be confirmed as stable. Either way, the boiler locks out as a safety measure, leaving you without heating or hot water. The most widely accepted interpretation across UK heating trade sources is that E27 is a flame detection fault — covering everything from a weak spark at the electrodes through to the boiler cutting out shortly after ignition. A small number of secondary sources have described E27 as a primary flow fault, but this is not consistent with the majority of dedicated Alpha fault code references and should be treated with caution.
General guidance only — not a substitute for professional advice. 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 supply interrupted or insufficient Common
If the mains gas supply to the property has been disrupted — for example, a meter cock that has been partially or fully closed, recent works on the supply line, or low mains pressure affecting the street — the boiler cannot receive enough gas to establish a flame. Testing another gas appliance such as a hob is the quickest way to rule this out.
- Dirty or degraded flame sensor (ionisation probe) Common
The flame sensor detects whether a flame is actually present by measuring a small electrical current through it. Over time, carbon deposits from combustion build up on the probe tip, insulating it and preventing it from reading the flame accurately. This is one of the most frequent hands-on causes of E27 and is easily rectified by a Gas Safe engineer during a service visit.
- Worn, dirty, or misaligned ignition electrodes Common
The ignition electrodes produce the spark that lights the gas. If the ceramic insulation is cracked, the tips are worn or coated with deposits, or the gap between the electrodes has shifted, the spark will be weak or absent. This is common in older boilers or those that have not been serviced regularly.
- Faulty gas valve Sometimes
If the boiler attempts to fire — you hear the igniter clicking and perhaps a brief flame — but then cuts out within a few seconds, the gas valve may not be opening correctly or is delivering inconsistent gas flow. A faulty gas valve is a moderately common cause of persistent flame detection faults after other simpler causes have been ruled out.
- Diverter valve or flow sensor fault Sometimes
In some cases a stuck or failing diverter valve, or a faulty flow sensor, can interfere with the conditions the boiler needs to attempt ignition. This is a less typical cause of E27 but worth investigating if electrode and sensor checks come back clear.
- PCB (printed circuit board) fault Rare
The PCB manages the ignition sequence and processes the signal from the flame sensor. If it is misreading the sensor signal or failing to trigger the ignition sequence correctly, an E27 code can appear even when all the physical components are in good condition. PCB faults are relatively uncommon but should be considered if everything else has been checked.
How to fix it
- Check your gas supply is live DIY safe
Before doing anything else, check that the gas meter cock is fully open (handle parallel to the pipe). Then try lighting a gas hob or another gas appliance in the property. If that also fails to light, the problem lies with your gas supply rather than the boiler — contact your gas supplier or call the National Gas Emergency Service on 0800 111 999.
- Reset the boiler DIY safe
On most Alpha models, rotate the front selector switch to the RESET position, hold it for around 30 seconds, then return it to your normal heating or hot water setting. The boiler will attempt to re-ignite. If it fires successfully and stays running, monitor it over the next few hours. If E27 returns, do not keep resetting — repeated resets without identifying the root cause can mask a more serious fault.
- Check system pressure DIY safe
While not a direct cause of E27, low system pressure (below around 0.8 bar on the pressure gauge) can prevent the boiler from operating correctly. If the gauge reads low, top up via the filling loop until it reads between 1.0 and 1.5 bar, then attempt a reset. If pressure drops repeatedly, there may be a leak that needs a Gas Safe engineer to trace.
- Call a Gas Safe registered engineer to inspect the flame sensor and ignition electrodes Gas Safe engineer
A qualified engineer will remove the boiler casing (which must not be opened by an unqualified person), inspect and clean the ionisation probe, check the electrode gap and condition, and replace any worn parts. This is the most common hands-on repair for E27 and is typically straightforward at a service visit.
- Have the engineer test the gas valve Gas Safe engineer
If cleaning the flame sensor and electrodes does not resolve the fault, the engineer will carry out gas rate and gas valve function checks. A faulty gas valve must only be tested and replaced by a Gas Safe registered engineer — it is a gas-carrying component and illegal for an unregistered person to work on.
- Have the PCB and wiring loom inspected if the fault persists Gas Safe engineer
If flame detection components are in good order and gas supply is confirmed, the engineer may test the PCB's output signals and inspect the wiring between the PCB, electrodes, and flame sensor for damage or loose connections. A replacement PCB is a last resort but occasionally necessary.
Parts you may need
- Ionisation / flame sensor probe · from £25
- Ignition electrode assembly · from £35
- Gas valve · from £120
- Diverter valve · from £65
- 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 £120–£350, depending on the underlying cause.
Frequently asked questions
Is the Alpha E27 fault code dangerous?
E27 itself is not a gas-leak fault — the boiler has locked out precisely because it could not confirm a stable flame, which is the safe thing to do. However, you should never attempt to open the boiler casing or interfere with any gas components yourself. If you smell gas at any point, do not reset the boiler, leave the property, and call the National Gas Emergency Service on 0800 111 999 immediately.
How much does it typically cost to fix an Alpha E27 fault?
For the most common repairs — cleaning or replacing the flame sensor probe or ignition electrodes — you would typically expect to pay between £120 and £350 including callout, labour, parts, and VAT. If the fault turns out to be a gas valve replacement, costs are likely to sit towards the top of that range or slightly above. A PCB replacement is less common but can push costs to £400–£500 or more; if your boiler is already several years old and facing that kind of bill, it is worth getting a new boiler quote for comparison.
Can I keep resetting the boiler to clear the E27 code?
You can try one or two resets to see whether a one-off glitch has cleared, but repeatedly resetting the boiler without fixing the underlying cause is not recommended. It will not resolve a faulty flame sensor, worn electrode, or gas valve problem, and continued failed ignition attempts can put additional stress on components. If E27 returns after two resets, book a Gas Safe engineer.
My Alpha boiler is still under warranty — does E27 affect my warranty claim?
If your Alpha boiler is still within its warranty period and you have kept up with annual services by a Gas Safe registered engineer (a typical warranty condition), you should contact Alpha directly before booking an independent engineer. Alpha may be able to arrange a warranty repair at no cost. Booking your own engineer first could affect your warranty position, so check your documentation or call Alpha's customer support line first.