How to Reset a Worcester Boiler
26 August 2026
How to Reset a Worcester Boiler
Resetting a Worcester Bosch boiler takes between five and thirty seconds depending on the model. The reset button is in a different location on every major Greenstar series, and that is why most people searching for this are standing in front of their boiler unable to find it rather than unsure what the reset process itself involves.
There is also a more important step before pressing anything: read the fault code on the display. Resetting a boiler without understanding the fault code it is showing is the equivalent of turning a warning light off without checking what triggered it. Most Worcester Bosch fault codes resolve cleanly with a reset. Some indicate a fault that will return within minutes. A small number indicate something that should not be reset without an engineer's assessment.
Find the Fault Code First
Worcester Bosch boilers display fault codes as either a letter-number combination (EA 229, E9 110, C6 and similar) or as a flashing symbol on the display. The code tells you what triggered the lockout and whether a reset is the correct response.
Codes that are safe to reset:
EA 229 / 2970 -- low water pressure. Top up the pressure to 1 to 1.5 bar first, then reset. Resetting without topping up pressure produces a second lockout within minutes.
E9 110 -- flow temperature too high. Usually a temporary overheat that clears on reset. If it recurs, call an engineer.
C6 -- fan speed fault. Often clears on reset. Recurrence means a fan or PCB fault requiring an engineer.
EA 338 -- flame loss. Can be caused by a momentary gas supply interruption. Reset once. If it recurs, call an engineer and do not attempt further resets.
Codes that should not be reset without an engineer:
E5 132 / E5 133 -- heat exchanger thermistor fault. Reset will not hold. Engineer required.
E3 110 -- flue temperature sensor fault. Safety-critical lockout. Engineer required.
2971 -- pressure switch fault. May indicate a component failure. Engineer required if reset does not hold.
If the display shows no fault code but the boiler has stopped working, check the power supply, the programmer or thermostat, and whether the boiler is in standby rather than lockout before attempting a reset.
Reset Button Location by Model
Worcester Bosch Greenstar 2000 and 4000 series (most common current models): The reset is performed by pressing and holding the central dial or mode button for three to five seconds. The button is on the front control panel. A flame symbol with a line through it or the fault code clears when the reset is accepted. Release the button when the display changes.
Worcester Bosch Greenstar 8000 series: The 8000 has a touchscreen display. The reset option appears on screen when a fault is active -- tap the flame or fault symbol on the display and follow the on-screen prompt. There is no physical reset button to press and hold.
Worcester Bosch Greenstar i and Si series (older, pre-2015): These models have a dedicated reset button, usually a small red or orange button marked with a flame symbol, located on the front of the boiler behind the drop-down facia panel. Open the facia by pressing the clips on either side and lowering it. The reset button is visible on the right-hand side of the control board. Press and hold for three seconds.
Worcester Bosch Greenstar CDi and CDi Classic: The reset button is on the front control panel, marked with a flame symbol. Press and hold for three to five seconds until the display clears.
Worcester Bosch Junior and Highflow series (older models): These older models have a reset button on the gas valve or on a separate overheat thermostat, accessed through the front casing. If the front panel controls have not responded, locate the overheat thermostat button -- a small white or grey button typically visible through the lower vent grille -- and press it once with a thin implement such as a pen.
If you are unsure which model you have, the model name is printed on a label inside the front casing of the boiler, visible when the facia panel is open or the lower access door is removed.
Step-by-Step Reset Process
Note the fault code on the display. Photograph it on your phone so you have a record.
Address the underlying cause first where the fault code indicates one. Low pressure (EA 229 / 2970) means top up to 1 to 1.5 bar before resetting. A pressure top-up guide is in the related article below.
Locate the reset button for your model using the guide above.
Press and hold for three to five seconds until the display clears or changes. On touchscreen models, follow the on-screen prompt.
Wait for the boiler to restart. Worcester Bosch boilers run through a startup sequence of approximately 30 to 60 seconds before firing. The display may show a rotating symbol or a status code during this period -- this is normal.
Check that the boiler fires and reaches operating temperature. Run the heating for 10 minutes and confirm the radiators are warming. Check the pressure gauge has remained stable at 1 to 1.5 bar.
If the same fault code returns within 30 minutes, do not reset again. Call a Gas Safe registered engineer.
When One Reset Is Enough
The one-reset rule is the most important thing to take from this guide. Worcester Bosch's own guidance, and HSE guidance on gas appliances generally, is that a boiler which locks out repeatedly on the same fault code has a fault that a reset cannot fix.
The specific risk of repeated resets is greatest on flame-loss codes (EA 338 and similar). A boiler that relights and then loses flame repeatedly may be doing so because of an unsafe combustion condition -- a blocked flue, a gas pressure issue, or a failed flame detection component -- and a reset in these circumstances restores apparent operation without resolving the underlying safety issue.
Reset once. If the same fault recurs within 30 minutes, stop resetting and call an engineer.
What a Reset Does and Does Not Fix
A reset clears the lockout condition and restarts the boiler's startup sequence. It does not repair a component, clean a heat exchanger, restore gas pressure at the meter, clear a blocked condensate pipe, or service the boiler in any way.
The faults that reset cleanly and stay clear are those caused by a momentary external condition: a brief gas supply interruption, a temporary overpressure, or a power supply fluctuation that caused the boiler to register a false safety lockout. These are genuine use cases for a user reset.
The faults that reset and then return are those caused by a failing or failed component: a degraded ignition electrode, a failing gas valve, a blocked heat exchanger, or a sensor that is reading incorrectly. Repeated resets in these cases produce an intermittent heating supply and mask a fault that will eventually result in a non-recoverable lockout at the worst possible time.
A boiler that has required more than three resets in a single heating season, regardless of fault code, is telling you something. A service visit that investigates the pattern rather than clearing individual faults is the correct response.
A Note on the Condensate Pipe in Winter
A specific seasonal fault worth knowing: during freezing weather, the condensate discharge pipe that runs outside the boiler and exits through an external wall can freeze, blocking condensate flow and causing the boiler to lock out. This shows as an EA fault code with a gurgling sound from the boiler in the period before lockout.
Thawing the condensate pipe with warm (not boiling) water poured over the external section clears the blockage. Reset the boiler after the pipe has been thawed. This is one of the few situations where a reset will hold immediately and cleanly without further investigation, because the fault is external rather than internal.
If the condensate pipe freezes repeatedly each winter, lagging the external section with pipe insulation prevents the problem recurring. This is a five-minute job with materials costing under £10.
If your Worcester Bosch boiler is locking out regularly -- multiple times per season, on different codes, or with decreasing intervals between lockouts -- the reset process is not the answer. That pattern typically indicates a boiler that is approaching the end of its reliable service life or has a component that needs replacement. According to InstantCost 2026 UK boiler pricing data, a new Worcester Bosch Greenstar combi boiler costs £1,800 to £3,500 supplied and fitted depending on size and output, and a service and repair diagnostic visit runs £80 to £150. The InstantCost boiler cost guide has a full 2026 breakdown of replacement costs, service costs, and the repair-versus-replace decision framework so you can assess the options before a heating engineer visit.
Low pressure is the most common cause of Worcester Bosch lockouts and is often what brings people to the reset process when the real fix is a pressure top-up. Our related guide on how to increase pressure on a Worcester boiler without a key covers the three filling loop types across the Greenstar range, why most modern Worcester Bosch models need no key to repressurise, and when a recurring pressure drop means a system leak rather than a simple top-up job.
Common Mistakes and What to Do Instead
Mistake: pressing reset without noting the fault code. The fault code is the information that tells you whether a reset is appropriate, whether a pre-reset action is needed, and whether to call an engineer. Photograph it before doing anything else.
Mistake: resetting a low-pressure fault without topping up first. The boiler will relock within minutes. Top up to 1 to 1.5 bar on a cold system, then reset.
Mistake: resetting more than once on the same fault code. A fault that returns within 30 minutes needs an engineer, not another reset. Repeated resets on flame-loss codes carry a specific safety risk.
Mistake: not waiting for the startup sequence to complete. Worcester Bosch boilers take 30 to 60 seconds to run through ignition checks after a reset. The display showing a status code during this period is normal -- it is not a second fault.
Mistake: searching for a reset button on the 8000 series. The 8000 uses a touchscreen interface. The reset is on-screen, not a physical button.
Mistake: treating repeated lockouts as a reset problem. A boiler that locks out three or more times in a season is indicating a component fault or end-of-life condition. A service visit is the correct response, not a better reset technique.
What It Costs in the UK
Item | Typical UK cost (2026) |
|---|---|
User reset | Free |
Condensate pipe lagging (DIY) | Under £10 |
Gas Safe engineer diagnostic visit | £80 to £150 |
Boiler service (annual) | £80 to £150 |
Common repair (ignition, sensor, valve) | £150 to £400 |
New Worcester Bosch Greenstar combi (supplied and fitted) | £1,800 to £3,500 |
Figures based on InstantCost.co.uk's 2026 UK boiler pricing data and vary by model, region, and installer.
Staying Safe
Resetting a boiler restarts its gas combustion cycle. The safety systems built into Worcester Bosch boilers are designed to prevent unsafe operation, and a lockout is those systems working correctly. Overriding them repeatedly by resetting is working against the safety design of the appliance.
If at any point during or after a reset attempt you can smell gas, stop immediately. Do not press any switches. Leave the property, turn off the gas at the meter if it is safe to do so on the way out, and call the National Gas Emergency Service on 0800 111 999. This is a free 24-hour line.
Do not attempt to access the internal components of the boiler beyond the front facia panel. The gas valve, heat exchanger, burner, and associated components carry hazardous pressures and temperatures and must only be accessed by a Gas Safe registered engineer.
If the boiler is in a property with vulnerable occupants -- elderly residents, young children, or anyone with a respiratory condition -- and the heating has failed in cold weather, contact your energy supplier's priority services register if you are already registered, or call the Warm and Well line for your region. Most UK energy suppliers offer emergency support for vulnerable households with heating failures.
All work on the gas components of a Worcester Bosch boiler, including repair, component replacement, and flue inspection, must be carried out by a Gas Safe registered engineer. Verify registration at gassaferegister.co.uk before allowing any gas work to proceed. A user reset via the front panel controls does not constitute gas work and does not require Gas Safe registration.
FAQ
Where is the reset button on a Worcester Bosch boiler? It varies by model. On Greenstar 2000 and 4000 series, press and hold the central mode dial for three to five seconds. On the 8000 series, the reset is on the touchscreen display. On older i and Si series models, the reset button is behind the drop-down facia panel. The model name is on a label inside the front casing.
What do I do if my Worcester boiler keeps locking out? Note the fault code each time. If the same code recurs within 30 minutes of a reset, stop resetting and call a Gas Safe registered engineer. A boiler that locks out repeatedly has a component fault a reset cannot fix.
What is the most common reason a Worcester Bosch boiler locks out? Low water pressure, showing as fault code EA 229 or 2970. Top up the system pressure to 1 to 1.5 bar using the filling loop before resetting. The boiler will relock immediately if the pressure is still below the minimum when reset is attempted.
Can I reset my Worcester boiler myself? Yes, for a user reset via the front panel controls. This does not constitute gas work. Do not attempt to access or reset any internal gas components. If the reset does not hold or if you smell gas at any point, call a Gas Safe registered engineer.
How long does a Worcester boiler take to restart after a reset? Thirty to sixty seconds for the startup and ignition check sequence. The display may show a rotating symbol or a status code during this period, which is normal. Wait for the sequence to complete before concluding the reset has not worked.
My Worcester boiler reset button is not working. What should I do? Confirm you have the correct button for your model -- the location differs across Greenstar generations. On the 8000 series there is no physical button; the reset is on the touchscreen. If the correct button is unresponsive, the boiler may have a control board fault requiring an engineer.