Complete List of Worcester Boiler Fault Codes & Error

If you are facing problems with your Worcester boilers, it will probably turn off. This is called a “lockout,” and it keeps you and your home safe from more harm.

This is often where you’ll see a problem code or an error code that shows up on the screen. These error codes are meant to make it easier for you or the tech to find the problem and fix it faster.

In this guide, we’ve put together a full list of the brand’s most common boiler problem numbers. This should help you figure out what’s wrong with your boiler and maybe how much it will cost to fix.

Note: Your boiler should only be fixed by a trained Gas Safe Engineer. You should never try to open it or mess with it yourself.

Worcester Bosch Boiler Error Codes

There are many Worcester Bosch trouble codes, and the ones you need depend on the type you have. The company that made the product has put its error codes into the following groups to make the process easier:

Locking an Error

If your boiler can’t lock, it will flash a trouble code and show a triangle. There will also be a static cause code shown. To get rid of the code, you will need to reset the boiler. However, you should only do this after you have fixed the problem.

Error in Blocking

When the boiler turns off and stops working, there won’t be a fault code shown. To see the code, press the “Return” key. The error will go away once the problem is fixed.

In this case, if the boiler’s condenser line is clogged, the blockage needs to be taken care of before the error goes away.

Error in Fault

If something is wrong with your boiler, a trouble code will show up. This error code will have letters and numbers in it.

How to Do Maintenance

If a code starts with an H, it’s a repair code. The boiler will still work even though there is a problem, but it needs to be fixed by a professional.

Cause Error Code

A three-digit number that shows up on your screen when you look for the block code. In the event of a stopping error, the back button can be used to get to it. When there is a problem with locking, the reason error code should flash on the screen every once in a while.

Worcester Boiler Fault Codes by Different Models

Worcester Bosch Greenstar i System/Combi Boiler Error Codes

The Worcester Bosch Greenstar I was the brand’s best-selling combi boiler type, with more than a million units put in homes across the UK. Both models use the same problem numbers. Both were also sold as system boilers.

The Greenstar I boiler, which has won awards, comes in two sizes. The 25i, which can handle 25 kilowatts, is great for small homes and apartments, while the 30i, which can handle 30 kilowatts, is better for a typical three-bedroom house with one bathroom.

The Greenstar 4000 type has replaced the Greenstar I, which was just taken off the market.

Fault code	Description
FD	No electricity
C7	Fan won’t turn on.
C6	Fan speed: too fast or too slow
C1	The fan turns off when it’s being used
C4	Fan is still going
E2	Problem with temperature flow
E9	The temperature of the main flow is above 95°
FA	Finding ionisation after the gas valve is closed
EA	Ionisation is undetected after ignition
F7	Ionisation was found before the burner started
9U	Defective or not so tight control box
C4	Defective control box or heat control module
F0	Gas valve or control box error
A8	Heat control module is not valid.
CC	Outdoor camera not working right
A7	Domestic hot water sensor defect
A1	Pump not working or stuck
E9	Activated flue or high limit thermostat
D4	Main flow temperature rising too fast

Worcester Bosch Greenstar Si Compact Error Codes

The Worcester Bosch Greenstar Si is good for small to medium-sized homes because it has many of the same features as the Worcester Bosch Greenstar I.

The main difference is that the Greenstar Si Compact is made to fit into smaller spaces, like kitchen drawers.

Fault code	Description
T1	Test of Ignition
T2	Fan examination
T3	Pump examination
T4	Three-way valve examination
T6	Test of Ionization Oscillator
9A 362 error	Erroneously fitted HCM
9U 233 Heat Control Module (HCM) error	Issue with the code plug
B7 257 Internal error	Possible issue with the control board
C6 215 Fan problem	Fan runs too fast
C7 214 Fan problem	The fan is not operating
D1 240 Return sensor error	The sensor can be broken or wet.
E2 222	An error of a short circuit in the flow sensor
E5 218	Excessive flow temperature
E9 219 Safety sensor fault	Overheated temperature, shorted or open circuit sensor
EA 227	During operation, no flame was seen or the flame indication was lost.
F0 237	Internal error
F7 228 Flame error	False flame or flame observed prior to burner activation
FA 306 False flame fault	Following burner cutoff, flame was found
FD 231 Mains power fault	Interruptions in electrical power
FA 364 Gas valve EV2 leak test failed	Gas Valve Leak
FB 365	Gas valve EV1 leak test failed.
A1 281	Pump not operating or stuck in the system
C1 264	During operation, the airflow halted.
C4 273	Airflow was present during the previous day.
D4 271	Temperature differential between safety sensor and flow exceeds threshold
D1 240	Short circuit of the return sensor
E9 224 Max thermostat activated	Overheated flue gas thermostat
EA 227	After ignition, no ionisation was seen
EF 349 Central heating boil detected	Boiler running at minimal burner load with a temperature differential between the flow and return of more than 18°C
NO CODE 212	Safety or too high flow temperature

Worcester Bosch CDi Classic Regular Boiler

There is now a very stylish new Worcester Bosch boiler line called Greenstar 8000 Style. The old Worcester Bosch CDi Classic boiler line has been replaced.

The CDi Classic came as a normal or heat-only combi boiler and in a range of power levels, such as 29kW, 34kW, 38kW, and 42kW.

The range’s wide range of options made it suitable for both normal-sized homes and bigger homes with higher-than-average hot water needs.

Fault code	Description
B1	There was no code plug found.
C6	Too fast or too slow of a fan speed
E2	Poor quality sensor for central heating (CH) flow with a negative temperature coefficient (NTC).
E9	The safety temperature limit for the central heating (CH) flow has been reached.
EA	There was no light.
F0	Mistake on the Inside
F7	A spark was seen even when the device was turned off.
FA	There was a flame when the gas was turned off
FD	Hit the stop button by accident.

Worcester Bosch CDi Compact Error Codes

While the CDi Compact is another popular Worcester combi boiler, it only comes in three power levels: 28 kW, 32 kW, and 34 kW. This makes it great for small to average-sized houses.

This boiler is great for people who want to hide it because it is small enough to fit in a normal kitchen cupboard–hence the name.

Fault code	Description
T1	Test of Ignition
T2	Fan examination
T3	Pump examination
T4	Three-way valve examination
T6	Test of Ionization Oscillator
9A 362 error	Erroneously fitted HCM
9U 233 Heat Control Module (HCM) error	Issue with the code plug
B7 257 Internal error	Possible issue with the control board
C6 215 Fan problem	Fan runs too fast
C7 214 Fan problem	The fan is not operating
D1 240 Return sensor error	The sensor can be broken or wet.
E2 222	An error of a short circuit in the flow sensor
E5 218	Excessive flow temperature
E9 219 Safety sensor fault	Overheated temperature, shorted or open circuit sensor
EA 227	During operation, no flame was seen or the flame indication was lost.
F0 237	Internal error
F7 228 Flame error	False flame or flame observed prior to burner activation
FA 306 False flame fault	Following burner cutoff, flame was found
FD 231 Mains power fault	Interruptions in electrical power
FA 364 Gas valve EV2 leak test failed	Gas Valve Leak
FB 365	Gas valve EV1 leak test failed.
A1 281	Pump not operating or stuck in the system
C1 264	During operation, the airflow halted.
C4 273	Airflow was present during the previous day.
D4 271	Temperature differential between safety sensor and flow exceeds threshold
D1 240	Short circuit of the return sensor
E9 224 Max thermostat activated	Overheated flue gas thermostat
EA 227	After ignition, no ionisation was seen
EF 349 Central heating boil detected	Boiler running at minimal burner load with a temperature differential between the flow and return of more than 18°C
NO CODE 212	Safety or too high flow temperature

Worcester Bosch CDi Classic Combi Boiler Error Codes

Since it came out in 2012, the Worcester Bosch CDi Classic combination boiler was the brand’s top model. It has been replaced by the Worcester Bosch 8000.

The CDi Classic was the brand’s most powerful combi boiler, with power levels of 29, 34, 38, and 42kW. It was perfect for homes that used a lot of hot water.

Fault code	Description
A1	The pump is empty and needs to be fixed or there is a water leak.
A7	The connecting lines or the hot water sensor need to be checked because the NTC sensor for the hot water is broken.
A8	The electrical lines between the Break and the FX sensor need to be checked.
B1	There was no code plug found.
C6	The fan speed is too low; check the fan lead and link and maybe replace it.
E2	NTC stands for negative thermistor coefficient. If this sensor isn’t working right, check the flow of CH water. Connecting the NTC sensor and wires.
E9	The safety temperature control for the central heating (CH) system has set off or needs to be checked.
EA	If there is no spark, there may be a problem with the gas. Check the gas source, power supply, igniter, electrode, and lead. Talk to a technician who is Gas Safe.
FO	Make sure that the starting leads on a module for an electrical link or programming interface are tight.
F7	A flame is found even when the gadget is turned off. Make sure the PCB and flue are clean and that the electrode assembly is dry.
FA	There was a flame even after the gas was turned off. Call a Gas Safe installation to check the gas valve.
FD	If you pressed the reset button by chance, do it again.

Worcester Bosch CDi Highflow Error Codes

The Worcester Bosch CDi Highflow is a strong floor standing combi boiler with the fastest hot water flow rates in its class.

The CDi Highflow would work great in big homes with lots of bathrooms that don’t want to add another water tank.

It has a great reputation for being the best combination boiler for big homes. The best part? It can be put in place under the kitchen counter.

Fault code	Description
A1	Pump dry run detection, check the system pressure if the pump is running in the air.
A5	The tank has a problem with a negative thermistor coefficient (NTC).
A7	A negative thermistor coefficient (NTC) that doesn’t work right in home hot water.
A8	The Energy Management System (EMS) has a damage in communication.
B1	There was no code plug found.
B2, B3, B4, B5, B6	Data error
B7	Error in the burner control
C6	Fan problem
D3	Limiter on temperature outside
D5	The condensation pump stopped working
D6	The heat bank inside overflows
EA	There was no flame
E2	The main fault was caused by the negative thermistor coefficient (NTC).
E9	The safety temperature limit on the central heating (CH) flow tripped.
F0	Internal error
F1	ROM fault
F7	Flame detected after the device was turned off.
FA	Flames were found when the gas was turned off.
FD	You pressed the “reset” button. Please press it again.

Worcester Bosch 8000 Style Error Codes

The Worcester Bosch 8000 Life is one of the newest models in the company’s Greenstar line, and it is thought to be their best model.

It is officially known as the most powerful type of boiler the company sells. With power levels between 30kW and 45kW, it’s perfect for large homes or people who use a lot of hot water.

Check out our comparison of Viessmann and Worcester Bosch boilers if you need help choosing between these two well-known brands.

The front of the boiler is also a first of its kind, giving homes a boiler that looks good and works well. It might be the first wall-hung boiler that looks really great, and you can get it in both black and white.

This is the best choice for people who want an award-winning boiler that is at the top of its field and has all the newest features.

Fault code	Description
200 O	The boiler is in heating mode.
201 O	The fan won’t turn on.
202 O	When the boiler is in anti-cycle mode.
203 O	The boiler is in stand-by mode
204 O	The temperature of the main water is higher than the set limit.
208 O	Need for chimney sweeps
224 V	Safety temperature regulator tripped; add water until the pressure is back to normal.
227 V	There is no light after the spark is lit; the hob control unit may need to be changed.
228 V	There is a flame signal but there is no flame. The ionisation wire and the air/gas ratio control valve may need to be changed.
305 O	The boiler’s hot water anti-cycle setting.
306 V	The flame turns off when the fuel is cut off; the air/gas ratio control valve may need to be replaced.
360 V	The code plug is not suitable. Make sure the correct code plug is attached, then either swap it out or reconnect it.
815 W/B	The low loss header temperature sensor isn’t working right; check the sensor port or differential sensor to see if it’s broken or put wrong.
1010 O	There is no BUS transmission cable and the EMS-Bus cable is either broken or unplugged. Either connect the EMS-Bus cable or fix the damaged cable exchange fuse.
1017 W	The water pressure is too low. Fix the pressure sensor or air system and add more water.
1021 B	The switch that checks the temperature of the hot water is broken; the plug might not be connected.
1022 B	The indicator for the temperature of the hot water tank is broken. Either replace the hot water temperature sensor or make sure it is installed correctly. Also, make sure the plug is properly connected to the hot water temperature sensor.
1037 W	The outside temperature sensor is broken, and the link line needs to be checked.
1065 B	Check the connection to the pressure sensor. If it’s broken or not there, you may need to replace it.
1068 W	Check the link lead because the monitor for the outside temperature is broken.
1073 W	The flow temperature sensor fried; the temperature sensor might need to be changed.
1074 W	The flow temperature sensor isn’t sending a signal. Check that the plug is in correctly, or the temperature sensor may need to be changed.
1075 W	There was a short circuit in the temperature sensor at the heating block. This sensor might need to be changed.
1076 W	There is no information from the boiler block temperature sensor. Change the temperature sensor, the wire that connects it to the control unit, or both.
2920 V	Flame monitoring error
2924 V	The gas valve that changes its shape is not working. The gas valve circuit is broken. Press the reset button on the hob to turn it back on. Change the gas valve if the problem doesn’t go away.
2925 V	The adjustable gas valve doesn’t have enough input.
2927 B	The cooker lost its light while it was working. As a safety measure, turn off the appliance, open the main shut-off valve, check the gas line, replace the ionisation electrode, make sure the burner is set correctly and at the lowest load, check the flue system for damage, clean the heating block on the flue gas side or replace the control unit/burner control unit if needed.
2946 V	A wrong code plug was found and needs to be changed.
2948 B	There is no sign of a flame. The hob turns on automatically with low power after being cleaned. If it keeps happening, you need to check the settings on the CO2 valve.
2963 B	The output from the flow and heat exchanger temperature monitor is not within the allowed range; the connecting line needs to be properly linked.
2964 B	The flow rate of the heat exchanger is not enough
2965 B	Flow temperature too high
2966 B	The flow temperature in the heat exchanger is rising too quickly.
2967 B	The flow and heat transfer sensors are too far apart in terms of temperature
2970 B	The pressure in the heating system drops too quickly.
2971 B	The system pressure is too low. Either add more water or let air out of the heating system until the pressure is right. Change the wire that connects to the pressure monitor and the sensor itself.

The Bottom Line

You can keep your home safe and warm by learning how to read Worcester boiler faults and error codes. Our complete guide gives you the tools you need to quickly fix problems with your heating system and keep it running smoothly. Don’t let problems get in the way of your comfort—stay aware and sure of how to handle any problems that might come up. With the information and answers you have access to, you can enjoy a cosy home all year long.