Worcester Bosch Boiler Fault Code Troubleshooter

Worcester Bosch boilers error code categories:

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.

 

Worcester Bosch CDI Classic Combi Boiler Error Codes

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 is 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
The Greenstar i combi boiler is the 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
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.

 

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	Common fault, caused by an electrical fault, requires a call out from a Worcester Bosch engineer.
Worcester Bosch 4000	224	Software issue. Arrange a visit from a Worcester Bosch engineer to reset the boiler/PCB.