GAS BOILER ERROR CODES
Identify Boiler Faults
Consumer groups in the UK rate Worcester Bosch gas boilers highly in terms of reliability and quality. No matter how good a boiler is though, it’s a complex appliance that at some point will develop a fault, have a part wear out or stop operating properly for numerous different reasons.
If you’re wondering what’s wrong with your boiler you can get a clue or two from the error code that your boiler will probably display when things go wrong and it effectively locks down. A faulty boiler turns itself off automatically for safety’s sake, but the interface will in most cases display an error code to help diagnose the problem.
Please be aware though that even if you can identify the problem by way of an error code or any other means, it’s extremely dangerous to open up your boiler or attempt to investigate it in any way – the inner workings of a gas boiler should only be accessed by a qualified Gas Safe registered boiler engineer.
Worcester Bosch gas boilers do not have standardised error codes across different models in their range of boilers.
We’ll list some of the main alphanumeric error codes for the most popular Worcester Bosch boilers later on, but the first thing to be aware of is that there are different ways that error codes are categorised:
The safest thing to do in the event of seeing any type of error code on your gas boiler is to call an engineer straight away – it helps if you can identify the model of your boiler and the code that is being displayed when you make the call.
There are different error codes for different models of Worcester Bosch boilers, but we can’t possibly list them all. The Greenstar 8000 range of boilers is currently the most popular boiler from Worcester Bosch, installed in hundreds of thousands of UK homes, so we have chosen to feature the error codes from this model. These codes apply to both Greenstar combi and system boilers.
Boiler in heating mode
Fan failing to start running
Boiler in anti-cycle mode
Current primary water temperature higher than set value
Chimney sweep demand
Safety temperature limiter has tripped – top up water until the reset pressure is reached
No flame signal after ignition – burner control unit might need replacing
Flame signal without flame present – air/gas ratio control valve or ionisation cable may need replacing
Boiler in hot water anti-cycle mode
Flame signal after closing the fuel supply – the air/gas ratio control valve might need replacing
Incompatible code plug – check if a correct code plug is installed and exchange or reconnect code plug
Low loss header temperature sensor faulty – check the sensor port or check the differential sensor for incorrect installation position or breakage
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
Water pressure too low – the water needs topping up and the vent system or pressure sensor may need replacing
The hot water temperature sensor is defective – the plug to the hot water temperature sensor may not be connected
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
The outside temperature sensor is defective – check the connecting lead
Pressure sensor defective or not connected – check pressure sensor connection as it may need replacing
Outside temperature sensor defective – check the connecting lead
Short circuit of the flow temperature sensor – the temperature sensor may need replacing
No signal from the flow temperature sensor available – connect the plug to the flow temperature sensor correctly or temperature sensor could need replacing
Short circuit of the temperature sensor at the heating block – temperature sensor may need replacing
No signal from the temperature sensor at the heating block available – replace the temperature sensor, the connecting lead, or the control unit
Error with flame monitoring
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
Feedback from the modulating gas valve is too low
Flame failed during burner operation. Open the main shut off valve, shut down the appliance and check the 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
Incorrect code plug detected – the code plug needs replacing
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
No flame signal. Following starting the procedure the burner starts automatically. After cleaning set the correct gas/air ratio correctly
The signal from the flow and heat exchanger temperature sensor is outside the permissible range – the connecting lead needs to connect correctly
The flow rate in the heat exchanger is too low
The flow temperature is too high
The flow/heat exchanger temperature sensor differential is to great
The pressure drop in the heating system is too rapid
The system pressure is 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
There are still many other older Worcester Bosch boilers doing sterling duty out there – each with their own set of error codes. If you have a Worcester Bosch Greenstar I system or combi boiler; a Greenstar Si Compact; a Worcester Bosch CDi Classic Regular or Combi Boiler; a CDi Highflow; or a Greenstar 4000 Boiler you’ll find they all display their own set of error codes.
If you book your boiler in for repairs with Prestige Heating & Electrical, let us know the make, model and error code – if any – that you are seeing so we can make sure we identify the problem area. We’re happy to help.
If you want to keep your gas boiler in tip-top condition and avoid seeing those error codes make sure you have it regularly serviced and maintained by our experts.
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