If your boiler encounters an error, it will ‘lockout’ to protect itself and display an error code to give you information on what the problem could be. We have created a list of error codes for all models of Worcester boilers.
Our Worcester Bosch boiler error code list is meant as a guide to help you understand what the issue is and assess how much it would be likely to cost to fix it. You should never attempt to fix an issue within your boiler if you aren’t a Gas Safe registered engineer.
However, if you’ve got to the end of your tether with the same error code popping up on your boilers display screen or just simply fancy a new boiler, then you could try out our Boiler Comparison tool that lets you compare up to three boiler models or brands in one go, to help you find the best new boiler for your home.
Before looking at the individual boiler models, Worcester Bosch boilers categorise their error codes into the following:
| FAULT DESCRIPTION | CODES THAT WILL APPEAR ON YOUR BOILER |
| Blocking Error | The boiler will stop operating but no fault code will appear. You can access the cause code by pressing the spanner/return button. The condition will clear once the fault clears. For instance, if the boiler is waiting for an area to cool, the error will clear automatically once the associated area has cooled down. |
| Locking Error | The boiler will flash a warning triangle and a fault code. It will also show a static cause code. You’ll need to press the boiler reset button to clear the code, but only after the boiler has been fixed. |
| Fault Error | The boiler will display an alphanumeric fault code to indicate the fault group. |
| Cause Error | A three-digit number that can be accessed via the info menu by pressing the spanner/return button during a blocking error or when in normal operating status. The cause code should flash on the display during a locking error. |
| Maintenance Code | A maintenance code is displayed with the letter H followed by a number. The fault won’t stop the boiler from working but it tells you that the boiler needs to be looked at by a qualified engineer. |
Generally speaking, if you see these signs on your boiler, this is what they mean;
1. Siphon fill mode
The boiler will run at a low burn for about 15 minutes to fill the condense trap. This happens after the boiler has been turned off, if it hasn’t been used for a day or so, and if the control knob has been turned down and back up. This is perfectly normal – it is a safety feature of the boiler. It will last about 15 minutes, the boiler will then go back to normal. If the boiler does this for more than half an hour, please ring Worcester Bosch on 0330 123 9559.
2. Key Lock (child lock)
Key Lock (child lock) – the front panel has been locked (New Greenstar 24/28 only)
3. One key
One key has been pressed
4. Two keys
Two keys have been pressed at once
5. The boiler is operating in maximum mode.
This should not last any longer than 15 minutes. Leave the boiler alone for 15 minutes, if the symbol is still showing after 15 minutes, please call Worcester Bosch on 0330 123 9559 to arrange an appointment
6. Service function 1A
The boiler is operating within a set range (service function 1A). Please ring the technical department on 0330 123 3366.
7. The boiler is operating in minimum mode
This should not last any longer than 15 minutes. Leave the boiler alone for 15 minutes, if the symbol is still showing after 15 minutes, please ring Worcester Bosch on 0330 123 9559 to arrange an appointment.
8. Air purge mode
The boiler will not fire, but will pulse the pump on and off. This should only happen when the boiler is first switched on after installation, or if a circuit board is changed. It will last about 15 minutes, then the boiler will go back to normal operation. If the boiler does this for more than half an hour, please ring to arrange an appointment on 0330 123 9559.
9. Save function
This is only seen when an adjustment is made in the menus and then saved. Does not appear in normal operation.
10. Temperature blocking mode
Temperature blocking mode (‘Gradient limitation’). The boiler is programmed to increase its flow temperature by a certain number of degrees per minute. If it exceeds that rate, then this symbol will appear, the burner will stop for two minutes, and will restart afterwards. It means that the flow temperature is increasing too quickly – not really an overheat as such, but it can mean there is a circulation issue. It can also happen on initial installation, especially with the CDi Conventionals. If continues, please ring 0330 123 9559 to arrange an engineer appointment.
11. Boiler due a service
The display will flash between this symbol and the flow temperature. On this model of boiler, it means the service is due.
12. The heating circuit pump is blocked
The display will flash between this symbol and the flow temperature. The heating circuit pump is blocked, please ring 0330 123 9559 to arrange an engineer appointment.
13. SE Code
The SE Code is not a fault, it is a function that is displayed when the boiler has run for 2324 hours, which is average for a 12 month period. And therefore is due for a Service. Please ring 0330 123 9559 to arrange a Service.
Common Worcester Bosch Boiler Fault Codes
| FAULT DESCRIPTION | SYSTEM BEHAVIOUR |
| EA338 | A leak somewhere, either within your boiler or around the system. |
| A281 | A leak somewhere, either within your boiler or around the system. |
| A41 | Boiler making loud noises – likely due to a faulty pump or heat exchanger. |
| EA227 | Boiler has locked out. This will be to prevent any further damage occurring and to remove potential danger. |
| E5218 | Boiler has overheated. |
| E5332 | Boiler has overheated. |
| E9219 | Boiler has overheated. |
| E9224 | Boiler has overheated. |
| D1286 | Boiler has overheated. |
| EA225 | Condensate pipe is blocked. |
| D5 | Condensate pipe is blocked. |
| U9 | The boiler flow temperature is too high, which means it will shut down until it has cooled down. |
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Worcester Bosch CDI Classic Combi Boiler Error Codes
The Worcester Bosch CDi Classic are a range of combi boilers available in 29 CDi, 34 CDi, 38CDi and 42CDi. As a combi boiler, they heat water on demand without the need for any storage tanks.
They offer the highest hot water flow rate of the Greenstar combi wall mounted range, ideal for larger properties with high water demands. Two bathroom plus properties can be serviced by the higher spec CDi models.
| Boiler | Flow Rate |
| 29CDi | 12.3 litres per minute |
| 34CDi | 14.3 litres per minute |
| 38CDi | 16.4 litres per minute |
| 42CDi | 17.2 litres per minute |
This boiler was manufactured in 2012 and is currently in production.
Download the CDi Classic Brochure
| Fault Description | System Behaviour |
| A1 | Water is leaking or the pump needs replacing or freeing due to the pump running dry. |
| A7 | The hot water negative thermistor coefficient (NTC) sensor is defective – the hot water sensor or connecting leads need checking. |
| A8 | Break communication to FX sensor controls electrical connections need checking. |
| B1 | Code plug not detected. |
| C6 | Fan speed too low – the fan lead and connector need checking and may need replacing. |
| E2 | Central heating (CH) water flow negative thermistor coefficient (NTC) sensor defective check CH flow NTC sensor and connection leads. |
| E9 | Safety temperature limiter in central heating (CH) flow has tripped the system pressure or safety temperature limiter needs checking. |
| EA | Flame not detected due to a gas issue – the gas supply, power supply or igniter, electrode and lead need checking – contact a Gas Safe installer. |
| F0 | Internal error – electrical connector contacts or programmer interface module – check ignition leads are not loose. |
| F7 | Flame detected even though the appliance is switched off – check the electrode assembly is dry and the pcb and flue are clear. |
| FA | Flame detected after gas shut off – the gas valve needs checking – hire a Gas Safe installer. |
| FD | Reset button pressed by mistake – press reset button again. |
Worcester Bosch CDI Highflow Combi Boiler Error Codes
The Greenstar CDi Highflow is a powerful floor-standing Combi boiler that provides a high flow rate which is ideal for homes with high water demands.
The Greenstar CDi Highflow provides up to 25 litres a minute and can fit underneath a standard kitchen worktop.
The Highflow is available in two models – the Greenstar Highflow 440CDi and the Greenstar Highflow 550CDi.
| Boiler | Flow Rate |
| 440CDi | 20 litres per minute |
| 550CDi | 25 litres per minute |
Download the CDi Highflow Brochure
| Fault Description | System Behaviour |
| A1 | Pump dry run detection or pump is running in air the system pressure needs checking |
| A5 | Tank negative thermistor coefficient (NTC) defect |
| A7 | Domestic hot water (DHW) negative thermistor coefficient (NTC) defect |
| A8 | Energy Management System (EMS) communication error |
| B1 | Code plug not detected |
| B2, B3, B4, B5, B6 | Data error |
| B7 | Burner control error |
| C6 | Fan defect |
| D3 | External temperature limiter |
| D5 | Condensate pump failure |
| D6 | Internal heat bank overflow |
| EA | Flame not detected |
| E2 | Primary negative thermistor coefficient (NTC) defect |
| E9 | Safety temperature limiter in central heating (CH) flow stat tripped |
| F0 | Internal error |
| F1 | ROM fault |
| F7 | Flame detected after appliance has been shut off |
| FA | Flame detected after gas shut off |
| FD | Reset button pressed – try pressing the reset button again |
Worcester Bosch CDi Compact Boiler Error Codes
The Greenstar CDi Compact combi boiler is suitable for small, medium and large-sized properties with one or two bathrooms.
This boiler is designed to fit within a standard kitchen cupboard. Despite its compact size, the high outputs make it suitable for homes with more than one bathroom.
| Boiler | Flow Rate |
| 28CDi | 11.4 litres per minute |
| 32CDi | 13.1 litres per minute |
| 36CDi | 14.7 litres per minute |
Download the CDi Compact Brochure
| Fault Description | System Behaviour |
| T1 | Ignition test – checking the igniter spark |
| T2 | Fan test – checking the basic fan |
| T3 | Pump test – checking the basic pump |
| T4 | Three way valve test |
| T6 | Ionisation oscillator test |
| 9A 362 | error – incorrect HCM fitted |
| 9U 233 | Heat Control Module (HCM) error – problem with code plug |
| B7 257 | Internal error – possible control board problem |
| C6 215 | Fan problem – fan running too fast |
| C7 214 | Fan problem – fan not running |
| D1 240 | Return sensor error – sensor may be wet or damaged |
| E2 222 | Flow sensor short circuit error |
| E5 218 | Flow temperature too high |
| E9 219 | Safety sensor fault – temperature too high, sensor short circuit or open circuit |
| EA 227 | No flame detected or flame signal loss during operation |
| F0 237 | Internal error |
| F7 228 | Flame error – false flame or flame detected before burner started |
| FA 306 | False flame fault – flame detected after burner stop |
| FD 231 | Mains power fault – electrical power interruption |
| FA 364 | Gas valve EV2 leak test failed – gas valve leak |
| FB 365 | Gas valve EV1 leak test failed |
| A1 281 | Pump stuck or running with air in the system |
| C1 264 | Airflow stopped during operation |
| C4 273 | Airflow present during last 24 hour |
| D1 240 | Return sensor short circuit |
| D4 271 | Temperature difference between flow and safety sensor exceeds limit |
| E9 224 | Max thermostat activated – flue gas thermostat overheat |
| EA 227 | No ionisation detected after ignition |
| EF 349 | Central heating boil detected – boiler operating at minimum burner load with temperature difference greater than 18°C between Flow & Return. |
| NO CODE 212 | Safety or flow temperature rising too fast |
Worcester Bosch Greenstar 25/30 Si Combi Boiler Error Codes
The Greenstar Si Compact combi boiler is suitable for small to medium sized homes with one bathroom.
This boiler is designed to fit within a standard kitchen cupboard and has an easy to use control that allows you to fine tune your comfort.
| Boiler | Flow Rate |
| 25Si | 8.9 litres per minute |
| 30Si | 10.7 litres per minute |
Download the 25/30 Si Combi Brochure
| Fault Description | System Behaviour |
| T1 | Ignition test – checking the igniter spark |
| T2 | Fan test – checking the basic fan |
| T3 | Pump test – checking the basic pump |
| T4 | Three way valve test |
| T6 | Ionisation oscillator test |
| 9A 362 | error – incorrect HCM fitted |
| 9U 233 | Heat Control Module (HCM) error – problem with code plug |
| B7 257 | Internal error – possible control board problem |
| C6 215 | Fan problem – fan running too fast |
| C7 214 | Fan problem – fan not running |
| D1 240 | Return sensor error – sensor may be wet or damaged |
| E2 222 | Flow sensor short circuit error |
| E5 218 | Flow temperature too high |
| E9 219 | Safety sensor fault – temperature too high, sensor short circuit or open circuit |
| EA 227 | No flame detected or flame signal loss during operation |
| F0 237 | Internal error |
| F7 228 | Flame error – false flame or flame detected before burner started |
| FA 306 | False flame fault – flame detected after burner stop |
| FD 231 | Mains power fault – electrical power interruption |
| FA 364 | Gas valve EV2 leak test failed – gas valve leak |
| FB 365 | Gas valve EV1 leak test failed |
| A1 281 | Pump stuck or running with air in the system |
| C1 264 | Airflow stopped during operation |
| C4 273 | Airflow present during last 24 hour |
| D1 240 | Return sensor short circuit |
| D4 271 | Temperature difference between flow and safety sensor exceeds limit |
| E9 224 | Max thermostat activated – flue gas thermostat overheat |
| EA 227 | No ionisation detected after ignition |
| EF 349 | Central heating boil detected – boiler operating at minimum burner load with temperature difference greater than 18°C between Flow & Return. |
| NO CODE 212 | Safety or flow temperature rising too fast |
Worcester Bosch Greenstar 27/30 I System Boiler Error Codes
The higher output Greenstar i System boiler was part of that latest generation of smaller and lighter boilers.
Suitable for small, medium and large homes, the boiler can also be fitted in a standard kitchen cupboard.
Download the 27/30i System Brochure
| Fault Description | System Behaviour |
| T1 | Ignition test – checking the igniter spark |
| T2 | Fan test – checking the basic fan |
| T3 | Pump test – checking the basic pump |
| T4 | Three way valve test |
| T6 | Ionisation oscillator test |
| 9A 362 | error – incorrect HCM fitted |
| 9U 233 | Heat Control Module (HCM) error – problem with code plug |
| B7 257 | Internal error – possible control board problem |
| C6 215 | Fan problem – fan running too fast |
| C7 214 | Fan problem – fan not running |
| D1 240 | Return sensor error – sensor may be wet or damaged |
| E2 222 | Flow sensor short circuit error |
| E5 218 | Flow temperature too high |
| E9 219 | Safety sensor fault – temperature too high, sensor short circuit or open circuit |
| EA 227 | No flame detected or flame signal loss during operation |
| F0 237 | Internal error |
| F7 228 | Flame error – false flame or flame detected before burner started |
| FA 306 | False flame fault – flame detected after burner stop |
| FD 231 | Mains power fault – electrical power interruption |
| FA 364 | Gas valve EV2 leak test failed – gas valve leak |
| FB 365 | Gas valve EV1 leak test failed |
| A1 281 | Pump stuck or running with air in the system |
| C1 264 | Airflow stopped during operation |
| C4 273 | Airflow present during last 24 hour |
| D1 240 | Return sensor short circuit |
| D4 271 | Temperature difference between flow and safety sensor exceeds limit |
| E9 224 | Max thermostat activated – flue gas thermostat overheat |
| EA 227 | No ionisation detected after ignition |
| EF 349 | Central heating boil detected – boiler operating at minimum burner load with temperature difference greater than 18°C between Flow & Return. |
| NO CODE 212 | Safety or flow temperature rising too fast |
Worcester Bosch CDi Classic Regular Boiler Error Codes
The Worcester CDi Classic range is discontinued, having been replaced by the Worcester Greenstar 8000 Style Regular boiler.
Regular boilers, also known as conventional or heat only boilers, heat your central heating system directly and produce hot water for a cylinder. As you need a hot water cylinder, often fed by a cold water storage cistern located in the attic, this boiler type isn’t suitable for smaller properties where space is limited.
This boiler is suited to homes with high water demand with multiple bathrooms requiring hot water at the same time.
Download the CDi Classic Regular Boiler Brochure
| Fault Description | System Behaviour |
| B1 | Code plug not detected |
| C6 | Fan speed too low |
| E2 | Central heating (CH) flow negative thermistor coefficient (NTC) sensor defective |
| E9 | Safety temperature limiter in central heating (CH) flow has tripped |
| EA | Flame not detected |
| F0 | Internal error |
| F7 | Flame detected even though appliance switched off |
| FA | Flame detected after gas shut off |
| FD | Reset button pressed by mistake |
Worcester Bosch Greenstar i System/Combi Boiler Error Codes
Combi Boiler
The Greenstar i combi boiler range was discontinued in 2021. The Greenstar i combi boiler range was a replacement for the well-established award-winning Greenstar i Junior, which has been installed in over 1 million homes across the UK.
Perfect for small to medium sized homes with one bathroom, the boilers’ new features have been designed based on installer feedback.
System Boiler
The Greenstar i System is a popular wall-mounted system boiler with outputs between 9kW up to 24kW.
Suitable for a wide range of homes, this boiler comes with a steel wall-mounting jig that not only allows pipes to go behind the boiler but also the ability to pre-pipe all of the pipework before the boiler is placed on the wall.
| Boiler | Flow Rate |
| 25i | 9 litres per minute |
| 30i | 10.8 litres per minute |
Download the 25/30 i Combi Brochure
Download the i System Brochure
| Fault Description | System Behaviour |
| 226 | Service tool has been connected in the blocking error history menu |
| FD 231 | The power has been interrupted during a lockout |
| C7 214 | Fan does not run during the start up phase – fan harness connector needs checking |
| C6 215 | Fan speed too high – check the fan harness and connector |
| C7 216 | Fan speed too low – check the fan harness and connector |
| C7 217 | Fan has stopped during appliance operation |
| C1 264 | Fan stopped during operation |
| C4 273 | Continuous fan operation for the last 24 hours – appliance temporarily blocked |
| E2 222 | Flow temperature sensor shorted |
| E2 233 | Flow temperature sensor disconnected |
| E9 276 | Primary flow temperature exceeded 95°c |
| E2 350 | Flow temperature sensor shorted |
| E2 351 | Flow temperature sensor disconnected |
| FA 306 | Ionisation detected after the gas valve closed |
| EA 227 | No ionisation detected after ignition |
| F7 228 | Isioniation current detected before burner start |
| EA 229 | Loss of ionisation signal during operation |
| EA 261 | Heat control module (HCM) potentially defective – reset the appliance |
| 9U 233 | Control box or heat control module (HCM) is defective or loose, the HCM needs to be checked |
| C4 237 | Control box or heat control module (HCM) is defective |
| F0 238 | Gas valve or control box error – gas valve coils need checking |
| F0 239 | Control box or the heat control module (HCM) is defective – the control box connections need checking |
| F0 242 | Control box or the heat control module (HCM) is defective – the HCM and control box connections need to be checked |
| B7 257 | Control box or the heat control module HCM) is defective- the HCM and control box connections need to be checked |
| F0 258 | Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked |
| EH 258 | Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked |
| F1 259 | Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked |
| F0 262 | Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked |
| F1 263 | Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked |
| F0 272 | Control box or the heat control module (HCM) is defective – control box and connections need checking or HCM might not be inserted properly and need replacing |
| F0 280 | Control box or the heat control module (HCM) is defective – control box and connections need checking or HCM might not be inserted properly and need replacing |
| F0 290 | Control box is defective – HCM needs checking as it might not be inserted properly or need replacing |
| 328 | Internal error with the mains voltage – frequency may be inconsistent |
| 235 | Incompatible heat control module (HCM) software versions – control box needs latest software |
| 356 | Low mains voltage – the voltage may be interrupted or inconsistent and needs checking |
| 360 | Heat control module (HCM) invalid – the inserted HCM does not correspond with the control box |
| A8 362 | Low mains voltage – the voltage may be interrupted, inconsistent or heat control module (HCM) invalid |
| CC 800 | Outdoor sensor defect available when accessory outdoor sensor is connected |
| A1 281 | Pump stock or running dry |
| E9 224 | Flue or high limit thermostat activated |
| D4 341 | Primary flow temperature rising too fast |
Worcester Bosch Greenstar Ri Boiler Error Codes
The Greenstar Ri is a compact regular boiler with outputs between 9kW to 30kW.The 9-24kW range is suitable for small and medium-sized homes, with the 27 & 30kW models catering for medium and large sized homes. This boiler can be installed in a standard kitchen cupboard.
Download the Greenstar Ri 9-24kW Regular Boiler Brochure
Download the Greenstar Ri 27 & 30kW Regular Boiler Brochure
| Fault Description | System Behaviour |
| No light | No power at control board |
| Light on | Appliance on but not operating during demand |
| Slow flash (mostly off flashes on) | Ignition lockout |
| Slow flash (mostly on flashes off) | Flue overheat or heat exchanger overheat |
| Fast flash | Volatile lockout sensor fan or code plug |
| 2 pulses | Check service mode switch is in minimum position |
| 5 pulses | Check service mode switch is in max position |
Worcester Bosch Greenstar 8000 Boiler Error Code
Available as a system, combi or regular boiler (Life only) the Life and Style boilers are the updated versions of the much-loved CDi Classic.
The Life offers outputs of up to 50kW for combi and regular, and outputs up to 35kW for system, the next generation boiler also benefits from the same pipe connections, flue and fixing points as the CDi Classic for a ‘simple switch’.
The Greenstar 8000 Style is available in combi up to 50kW and system 30-35kW, with a unique design and a pioneering full colour touchscreen display. It features a detailed text display and an intuitive menu structure for rapid diagnosis, fault-finding and commissioning, with no need to search through manuals and fault codes.
Download the Greenstar 8000 Life Combi Boiler Brochure
Download the Greenstar 8000 Style Combi Boiler Brochure
Download the Greenstar 8000 Life System Boiler Brochure
Download the Greenstar 8000 Style System Boiler Brochure
Download the Greenstar 8000 Life Regular Boiler Brochure
| Fault Description | System Behaviour |
| 200 O | Boiler in heating mode |
| 201 O | Boiler in hot water mode |
| 202 O | Boiler in anti-cycle mode |
| 203 0 | Boiler in standby – no heat energy demand |
| 204 O | Current primary water temperature higher than set value |
| 208 0 | Chimney sweep demand |
| 224 V | Safety temperature limiter has tripped – top-up water until the reset pressure is reached |
| 227 V | No flame signal after ignition burner control unit could need replacing |
| 228 V | Flame signal without flame present – air/gas ratio control valve may need replacing as might the ionisation cable |
| 305 0 | Boiler in hot water anti-cycle mode |
| 306 V | Flame signal after closing the fuel supply – the air/gas ratio control valve might need replacing |
| 360 V | Incompatible code plug – check if a correct code plug is installed and exchange or reconnect code plug |
| 815 W/B | Low loss header temperature sensor faulty – check the sensor port or check the differential sensor for incorrect installation position or breakage |
| 1010 O | No BUS communication cable, EMS-Bus isn’t connected or damaged – connect the cable for the EMS-Bus or replace the damaged cable exchange fuse |
| 1017 W | Water pressure too low – the water needs topping up and the vent system or pressure sensor may need replacing |
| 1021 B | Hot water temperature sensor is defective – the plug to the hot water temperature sensor may not be connected |
| 1022 B | Hot water storage temperature sensor is defective – connect the plug to the hot water temperature sensor correctly, mount the hot water temperature sensor correctly or replace the hot water temperature sensor |
| 1037 W | Outside temperature sensor is defective – check the connecting lead |
| 1065 B | Pressure sensor defective or not connected – check pressure sensor connection as it may need replacing |
| 1068 W | Outside temperature sensor defective – check the connecting lead |
| 1073 W | Short circuit of the flow temperature sensor – the temperature sensor may need replacing |
| 1074 W | No signal from the flow temperature sensor available – connect the plug to the flow temperature sensor correctly or temperature sensor could need replacing |
| 1075 W | Short circuit of the temperature sensor at the heating block – temperature sensor may need replacing |
| 1076 W | No signal from the temperature sensor at the heating block available – replace the temperature sensor, the connecting lead or the control unit |
| 2920 V | Error with the flame monitoring |
| 2924 V | No feedback from the modulating gas valve. The gas valve relay is defective – press the reset button and apply burner start, wait to see if fault reoccurs, if it does the gas valve needs replacing |
| 2925 V | Feedback from the modulating gas valve is too low |
| 2927 B | Flame failed during burner operation. Open the main shut off valve, shut down the appliance and check gas line, replace the ionisation electrode, set burner correctly and minimum rated load, check the integrity flue system and if the interconnected room air supply is too small, or the size of the ventilation opening is too small, clean the heating block on the flue gas side or replace the control unit/burner control unit |
| 2946 V | Incorrect code plug detected – the code plug needs replacing |
| 2948 B | No flame signal. With low output the burner starts automatically after cleaning. If the fault occurs repeatedly, the setting of the CO2 valves need checking |
| 2950 B | No flame signal. Following starting procedure the burner starts automatically. After cleaning set the correct gas / air ratio correctly |
| 2963 B | Signal from flow and heat exchanger temperature sensor outside the permissible range – the connecting lead needs connecting correctly |
| 2964 B | Flow rate in heat exchanger is too low |
| 2965 B | Flow temperature too high |
| 2966 B | Flow temperature rise in heat exchanger too rapid |
| 2967 B | Flow / heat exchanger temperature sensor differential too great |
| 2970 B | Pressure drop in heating system too rapid |
| 2971 B | System pressure too low – the heating system needs venting or water needs topping up until the preset pressure is reached. Replace the cable to the pressure sensor replace the pressure sensor |
Worcester Bosch Error Code EA 229 or D5
If you are experiencing a Worcester Bosch EA 229 or D5 fault code then you are experiencing a frozen condensate pipe.
This is usually an issue you can fix yourself with some warm (not boiling) water poured over your condensate pipe wherever it has frozen.
You can read our frozen condensate pipe guide that explains the process fully.
Worcester Bosch Greenstar 2000 Boiler Error Code
The warning symbol indicates that a fault has occurred. The cause of the fault is displayed in code (e.g. fault code 214).
Some faults lead to a shutdown of the appliance, which only starts again after a reset:
▶ Switch off the appliance and switch it on again.
-or-
▶ Press the up and down arrows simultaneously, until the symbols warning and spanner icons are no longer be displayed. The appliance starts up again. The flow temperature is displayed.
If a fault can not be eliminated:
▶ Contact an Installer/Service Engineer or Worcester, Bosch Group appointments team on 0330 123 9339.
▶ You will need to provide them with the displayed fault code and the following appliance data.
– Appliance type and serial number.
– Commissioning date.
Worcester Bosch Greenstar 4000 Boiler Error Code
Download the Greenstar 4000 Boiler Brochure
Download the Greenstar 4000 Installation Manual
| Boiler Model | Fault Description / Code | Reason |
| Worcester Bosch Greenstar 4000 30 | 1021 | Cylinder charging or hot water temperature sensor faulty. Turn the appliance off and back on again. The hot water sensor has been changed if an open or short circuit or refitted to the pipe if it has fallen off. |
| Worcester Bosch 4000 | 224 | Software issue. Arrange a visit from a Worcester Bosch engineer to reset the boiler/PCB. |
How to know if my Worcester Bosch boiler is faulty?
All Worcester Bosch boilers installed in the last decade have been designed with a clearly displaying fault code control panel. When you experience a fault, the EA should appear on your control panel. This helps to pinpoint the error with your boiler, which you should be able to find in the error codes above.
It is important to do regular checks on your boiler to help you identify any errors. Here are a few checks you should complete to ensure that any issues do not develop and cause serious damage further down the line.
- Check if your thermostat timer and temperature gauge are set correctly
- Is your boiler pressure at a normal level?
- Are all the appliances around your home receiving a gas supply?
- Is there a blue light showing on the front of your boiler? If so, there will be an error to investigate.
- Are there any Worcester boiler error codes being displayed? The code will allow you to identify the issue easily.
Have you noticed a fault with your Worcester Bosch boiler?
It’s not very often that your Worcester Bosch boiler should occur an issue, thanks to their quality components, however, as with everything, the longer you have it the more issues start to show.
If you are experiencing an issue with your Worcester Bosch boiler, you should be able to find the issue by using our error code tables above.
Reminder! Please do not attempt to fix any issues you experience yourself. It is always best to help identify the issue and inform your Gas Safe Engineer.
Here are some boiler issues that may begin to happen after time. If any of these problems happen, this will help you understand why so that there is no need to panic.
No hot water
If you are experiencing lukewarm or cold water coming through your taps, or are your radiators not reaching optimum temperature? This could be a sign of a fault or blockage in your heating system.
A faulty diverter valve
Although a diverter valve may seem like a small part, it’s responsible for controlling both the hot water that flows to your taps and showers as well as the hot water for your central heating.
As your boiler gets older, your diverter valve may start to stick whilst opening and closing. Sadly, having a faulty diverter valve is not good news. The valves are not always the cheapest item to replace. This will of course have to be carried out by a Gas Safety Registered Engineer. If you add up the cost of a valve, the tools needed to do the job, and the hourly rate of a skilled engineer will be expensive. Therefore, if your diverter starts to stick, it’s probably time to get yourself a new boiler.
As mentioned above, if you are looking to get a new or replacement boiler but you’re unsure which boiler brand or model to choose from, then why not try our Boiler Comparison tool. This new tool allows you to compare up to three boiler models or brands at one time, to help you find the best boiler for your home.
No heating
If your boiler’s simply not turning on or functioning at all, this is referred to as a boiler locking out. There are many potential causes for this. It could be that your boiler has gained or lost too much pressure, or perhaps completely lost power.
If a boiler lockout occurs, then the error code 227 will display on your control board. If you get this error code, contact your Gas Safe Engineer immediately.
A blocked condensate pipe
All modern combi boilers by law must have a condensate pipe that vents any harmful flue gases from your home. As a result of the condensate pipe being outside, they can become blocked by debris or freeze during the winter. This can cause issues like your boiler overheating and eventually locking out.
If you are experiencing this, you can simply use warm water to defrost the pipe if necessary or remove any blockages to allow flue gas to escape freely. Most issues are identifiable by a Worcester Bosch boiler EA fault – in this case, look out for the code EA225.
Boiler pressure issues
When it comes to the issue of pressure within your boiler, the problem can be simple and easy to solve, or a lot more serious.
If you have noticed that your pressure rises or drops gradually over time, this is normal. However, if you witness sudden or dramatic drops in boiler pressure, this could be a more serious matter. In this case, make sure you call an engineer.
Problems with your central heating pump
If you do experience a sudden drop in boiler pressure, your central heating pump may be the problem. Naturally, the valve seal on the pump wears down over time, especially if too much pressure is being placed on it or there is a sudden increase in water flow.
Another issue you may experience is that if your pump gets too hot as a result of an error, it will seize up. affecting the overall temperature of your boiler.
Whilst replacing your central heating pump is an option, if your boiler has reached a certain age, it won’t be worthwhile. Here at WarmZilla, we offer the Best Price Guarantee, if you’re looking to replace your boiler. This means that we will beat any competitors in price, by £50!
Loud noises coming from your boiler
Occasionally with a Worcester Bosch boiler or any boiler for that matter, faults may be noticeable due to loud or unusual noises being produced. If you do hear some strange noises, look for Worcester boiler error codes to identify why this may be happening.
Code A41 is a common code that presents itself when a boiler is making loud noises.
This could be a result of a faulty water pump or an airlock in the pump. Or, there could be an issue with your boiler heat exchanger, in this case your boiler is ‘kettling’.
This noise occurs due to a build up of limescale or sludge on the heat exchanger, which restricts the water flow, causing the kettle-like noise. You don’t need to worry when this happens, as your boiler will use its built-in safeguards to lockout and remove any further risk. However, once you do identify that this is the issue, you should call your Gas Safe Engineer to come and take a look.
No boiler power
In an instance of your boiler power cutting off: check your sockets in case they have tripped, your Printed Circuit Board (PCB), or your Residual Current Device (RCD) for any faults.
If you think there is a fault with any of these components, it’s essential that you call out an engineer to look closer. Again, it’s likely that power failures are a result of a more serious issue around your boiler that would be best solved by replacing your unit – and can be affordable.
