Worcester Bosch EC Fault Code: Causes, Fixes & Repair Costs
What does the Worcester Bosch EC fault code mean?
If your Worcester Bosch boiler is showing what looks like an 'EC' fault code, it is almost certainly displaying 'EA' — the segment display on many Greenstar models can make an 'A' look like a 'C' depending on viewing angle or screen font. The EA fault code means the boiler's PCB has failed to confirm a stable flame after multiple ignition attempts and has locked the boiler out as a safety precaution. In plain terms: your boiler tried to light the burner, could not verify a flame was present, and shut itself down to prevent any risk. Both heating and hot water will be unavailable until the underlying cause is resolved and the boiler is reset. Many Worcester Bosch models show a numeric sub-code alongside EA to give a more precise diagnosis — for example, EA 227 (ignition electrode or lead fault), EA 229 (flame sensor or ionisation signal issue), and EA 234 (gas valve or gas supply fault). If you can see a number after the EA on your display, note it down before calling an engineer, as it will help them identify the faulty component faster.
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 supply interruption Common
If no gas is reaching the boiler, no flame can form regardless of how the ignition components are performing. This could be a prepayment meter running out of credit, a closed isolation valve at the meter, or a wider street-level supply disruption affecting neighbouring properties too. Sub-code EA 234 often points toward a gas supply or gas valve issue.
- Faulty or contaminated flame sensor (ionisation probe) Common
The flame sensor passes a tiny electrical current through the burner flame to confirm ignition. If the sensor is coated in combustion deposits or has deteriorated, it may fail to detect a flame that is actually present, causing the PCB to lock out. EA 229 is the sub-code most closely associated with ionisation or flame-sensing signal problems.
- Worn or mispositioned ignition electrode Common
The ignition electrode generates the spark that lights the burner. If the electrode tip is worn, cracked, or positioned incorrectly, the spark may be too weak or miss the gas stream entirely. EA 227 is the sub-code most often linked to electrode or ignition lead faults.
- Frozen condensate pipe Sometimes
The white plastic condensate pipe carries acidic water from the boiler to an external drain. In cold weather it can freeze at bends or at the point it exits the building, causing the boiler to lock out. While this typically triggers a separate condensate-specific code, in some models and conditions it can contribute to or be misread alongside an EA fault.
- Low system pressure Sometimes
Worcester Bosch boilers require a system pressure of roughly 1–1.5 bar when cold. If the gauge on the front of the boiler reads below 1 bar, the ignition sequence can be disrupted and the boiler may fail to fire correctly.
- Faulty gas valve Sometimes
The gas valve meters the precise amount of gas delivered to the burner. A valve that is sticking, has failed electrically, or is delivering incorrect gas pressure will prevent stable ignition. This is a Gas Safe-only repair. EA 234 can also appear when the valve itself is at fault rather than the supply.
- Blocked or restricted flue Rare
The flue must be clear for combustion products to escape and fresh air to enter. A partial blockage — caused by debris, bird nesting material, or a damaged terminal — can disrupt the air-to-gas ratio enough to prevent a stable flame from forming.
- PCB failure Rare
The printed circuit board controls every stage of the ignition sequence. If the PCB itself is faulty, it may fail to trigger the spark, misread sensor signals, or lock out incorrectly. This is an uncommon cause but becomes more likely on older boilers that have experienced repeated lockouts or moisture ingress.
How to fix it
- Check that other gas appliances are working DIY safe
Go to your gas hob or another gas appliance and see whether it lights normally. If nothing gas-powered is working in your home, the issue is likely with your gas supply rather than the boiler itself. If you are on a prepayment meter, check that it has sufficient credit before proceeding.
- Check the system pressure gauge DIY safe
Look at the pressure gauge on the front of the boiler — it is usually a small dial or digital reading. When the system is cold it should sit between 1 and 1.5 bar. If it reads below 1 bar, you can top it up using the filling loop (the small braided hose or lever beneath the boiler). Open the valves slowly, watch the gauge, and close them once you reach around 1.2 bar. Do not overpressure the system above 2 bar.
- Check and thaw the condensate pipe if the weather is freezing DIY safe
Locate the white plastic pipe (typically 21.5 mm or 32 mm diameter) that exits through an external wall, usually at low level. If temperatures are below zero and the pipe feels solid or has visible ice at bends or the open end, thaw it by pouring warm — not boiling — water gently over the frozen section. Boiling water can split plastic pipework. Once thawed, reset the boiler.
- Reset the boiler once DIY safe
Press and hold the reset button (on most Worcester Greenstar models this is a button marked with a flame and a line through it, or a dedicated reset key) for around three seconds. Release it and allow the boiler a full minute to attempt ignition. Watch and listen for the burner firing. If the boiler lights and stays on, monitor it over the next hour. If it locks out again with the same EA code, do not reset repeatedly — this adds wear to the ignition components and PCB.
- Note the full fault code including any sub-code number DIY safe
Before calling an engineer, look at the display again and note down the complete code — for example EA 227, EA 229, or EA 234. Write it down along with how often the fault has occurred and whether it only happens when calling for heating, hot water, or both. This information significantly speeds up diagnosis.
- Call a Gas Safe registered engineer to inspect ignition components Gas Safe engineer
If the boiler has locked out again after a single reset, a Gas Safe engineer needs to attend. They will check spark and ionisation readings, inspect the electrode and flame sensor, test gas pressure at the inlet and burner, and verify the gas valve is operating correctly. Parts such as the electrode, ignition lead, and flame sensor are relatively straightforward replacements; a gas valve or PCB is more involved but still a routine job for a qualified engineer.
- If you suspect a gas leak, act immediately — do not reset the boiler Gas Safe engineer
If you can smell gas at any point, do not attempt to reset the boiler or operate any electrical switches. Leave the property, leaving doors open as you go, and call the National Gas Emergency Service on 0800 111 999. This line is free and available 24 hours a day. Only return when the service has confirmed it is safe to do so.
Parts you may need
- Ignition electrode and lead assembly · from £35
- Flame sensor / ionisation probe · from £25
- Gas valve (model-specific) · from £120
- PCB (printed circuit board) · from £200
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 'EC' actually a Worcester Bosch fault code, or have I misread the display?
Worcester Bosch does not use 'EC' as a fault code in its Greenstar range. The correct code is 'EA', but the seven-segment display on many models renders the letter 'A' in a way that can look very much like a 'C', particularly when viewed at an angle or in bright light. If your boiler is showing this code, treat it as EA and follow the EA guidance. The numeric sub-codes that appear alongside it — such as EA 227, EA 229, or EA 234 — will help your engineer identify the specific component involved.
What do the numbers after EA mean — for example EA 227, EA 229, EA 234?
These sub-codes give a more specific pointer to the fault location. EA 227 typically relates to the ignition electrode or ignition lead — the component that creates the spark. EA 229 points toward the flame sensor or ionisation circuit, meaning the boiler may actually be sparking but cannot confirm the flame. EA 234 is generally linked to the gas valve or a gas supply pressure issue. Whichever sub-code you see, note it down before your engineer arrives — it can save diagnostic time and reduce your call-out cost.
How much does it cost to fix a Worcester Bosch EA fault in the UK?
For the most common causes — ignition electrode, flame sensor, or ignition lead — you should expect to pay roughly £120 to £250 all-in including labour and parts. A gas valve replacement typically costs £200 to £350 depending on the model. A PCB is less common and can cost considerably more; if your engineer recommends a PCB on a boiler that is already over ten years old, it is worth asking for a like-for-like quote on a new boiler as well, since the economics of repairing older boilers can tip the other way.
Can I keep resetting my boiler to get it working while I wait for an engineer?
You can attempt a single reset to see whether the fault clears — sometimes a momentary issue such as a temporary gas supply fluctuation will not reappear. However, if the boiler locks out again with the same EA code, repeated resetting is not helpful and can cause additional wear to the ignition electrode, PCB, and gas valve. Reset it once, observe whether it holds, and if it locks out again leave it in that state until an engineer can attend.