This document provides a comprehensive list of Worcester Greenstar 8000 fault codes for the following models in the range:

• Worcester Bosch Greenstar 8000 Life GR8300iW 30 C NG | Part Number: 7 738 100 800 | GC Number: 47-800-18
• Worcester Bosch Greenstar 8000 Life GR8300iW 35 C NG | Part Number: 7 738 100 801 | GC Number: 47-800-17
• Worcester Bosch Greenstar 8000 Life GR8300iW 40 C NG | Part Number: 7 738 100 802 | GC Number: 47-800-16
• Worcester Bosch Greenstar 8000 Life GR8300iW 45 C NG | Part Number: 7 738 100 803 | GC Number: 47-800-15
• Worcester Bosch Greenstar 8000 Life GR8300iW 50 C NG | Part Number: 7 738 100 804 | GC Number: 47-800-14
• Worcester Bosch Greenstar 8000 Life GR8300iW 30 C LPG | Part Number: 7 738 100 849 | GC Number: 47-800-23
• Worcester Bosch Greenstar 8000 Life GR8300iW 35 C LPG | Part Number: 7 738 100 850 | GC Number: 47-800-22
• Worcester Bosch Greenstar 8000 Life GR8300iW 40 C LPG | Part Number: 7 738 100 851 | GC Number: 47-800-21
• Worcester Bosch Greenstar 8000 Life GR8300iW 45 C LPG | Part Number: 7 738 100 852 | GC Number: 47-800-20
• Worcester Bosch Greenstar 8000 Life GR8300iW 50 C LPG | Part Number: 7 738 100 853 | GC Number: 47-800-19

Information Before Proceeding

This fault finding and diagnosis guide is for competent gas engineers only. This information assumes the appliance has been operating normally until the time of failure and is not an installation error.
Before proceeding with fault finding, a gas engineer should perform basic checks.

1. Ensure a 230V power supply with correct polarity is present.
2. Verify that appliance settings are correct and that external controls like programmers, room thermostats, and cylinder thermostats are functioning.
3. Confirm the mains water is on, the primary heating system has adequate pressure, and there is a gas supply to the appliance.
   Upon completion of any service or repair task involving electrical connections, it is essential to check for earth continuity, short circuits, correct polarity, and resistance to earth for safety and compliance.

Fault Categories and Reset Procedures

The Worcester 2000 boiler uses different categories to classify faults, each requiring a different response:

Indicators (Fault Category O)

Indicators are not faults but signal normal operating conditions. These can be viewed using service function 1-A1.

Non-blocking Faults (Fault Category R)

With non-blocking faults, the heating system continues to operate. The triangle symbol is shown on the display. To reset a non-blocking fault, press the OK button until the triangle symbol and spanner symbol are displayed. Use the up arrow button or down arrow button to select a fault code and press the OK button to delete it.

Blocking Faults (Fault Category B)

Blocking faults cause a temporary shutdown of the heating system. The boiler will restart automatically once the fault is rectified. The fault code can be read using service function 1-A2.

Locking Faults (Fault Category V)

Locking faults result in a complete system shutdown and require a manual reset to restart. The fault code will flash on the display along with the triangle symbol. To reset a locking fault, turn the boiler’s power off and on again, or press the up arrow button and down arrow button simultaneously until the symbols disappear. If a fault persists, the main PCB may require inspection and replacement.

Fault Finding & Diagnostics : Displayed on Screen Fault Codes

Fault Code : 200

Fault Category: 0
Description: Boiler in heating mode.
Possible Causes and Diagnostic Procedures: None

Fault Code : 201

Fault Category: 0
Description: Boiler in hot water mode.
Possible Causes and Diagnostic Procedures: None

Fault Code : 202

Fault Category: 0
Description: Boiler in anti-cycle mode.
Possible Causes and Diagnostic Procedures: None

Fault Code : 203

Fault Category: 0
Description: Boiler in standby, no heat energy demand.
Possible Causes and Diagnostic Procedures: None

Fault Code : 204

Fault Category: 0
Description: Current primary water temperature higher than set value.
Possible Causes and Diagnostic Procedures: None

Fault Code : 208

Fault Category: 0
Description: Chimney sweep demand.
Possible Causes and Diagnostic Procedures: None

Fault Code : 224

Fault Category: V
Description: Safety temperature limiter has tripped.
Possible Causes and Diagnostic Procedures:

1. Open the closed valve in the heating circuit.
2. Top up water until the preset pressure is reached.
3. Connect the plug correctly to the safety temperature limiter.
4. Replace the safety temperature limiter.

Fault Code : 227

Fault Category: V
Description: No flame signal after ignition.
Possible Causes and Diagnostic Procedures:

1. Open the gas isolator.
2. Change the gas installation.
3. Replace the control unit/burner control unit.
4. Replace the ignition electrode.
5. Replace the monitoring electrode.
6. Replace the ignition cable.
7. Replace the ionisation cable.
8. Replace the air/gas ratio control valve.
9. Correct the burner setting.

Fault Code : 228

Fault Category: V
Description: Flame signal without flame present.
Possible Causes and Diagnostic Procedures:

1. Replace the air/gas ratio control valve.
2. Replace the ionisation cable.
3. Replace the control unit/burner control unit.

Fault Code : 305

Fault Category: 0
Description: Boiler in hot water anti-cycle mode.
Possible Causes and Diagnostic Procedures: None

Fault Code : 306

Fault Category: V
Description: Flame signal after closing the fuel supply.
Possible Causes and Diagnostic Procedures:

1. Replace the air/gas ratio control valve.
2. Replace the ionisation cable.
3. Replace the control unit/burner control unit.

Fault Code : 360

Fault Category: V
Description: Incompatible code plug.
Possible Causes and Diagnostic Procedures:

1. Check if a correct code plug is installed.
2. Exchange or reconnect code plug.

Fault Code : 815

Fault Category: W
Description: Low loss header temp. sensor faulty.
Possible Causes and Diagnostic Procedures:

1. Check the sensor port.
2. Check the differential sensor for incorrect installation position or breakage.

Fault Code : 1010

Fault Category: O
Description: No BUS communication. Cable for EMS-Bus is not correctly connected or damaged.
Possible Causes and Diagnostic Procedures:

1. Connect the cable for the EMS-Bus correctly or replace the damaged cable.
2. Exchange fuse.

Fault Code : 1017

Fault Category: W
Description: Water pressure too low.
Possible Causes and Diagnostic Procedures:

1. Top up water and vent the system.
2. Replace the pressure sensor.

Fault Code : 1021

Fault Category: B
Description: Hot water temperature sensor is defective.
Possible Causes and Diagnostic Procedures:

1. Connect the plug to the hot water temperature sensor correctly.
2. Mount the hot water temperature sensor correctly.
3. Replace the hot water temperature sensor.
4. Replace the connecting lead to the hot water temperature sensor.

Fault Code : 1037

Fault Category: W
Description: Outside temperature sensor defective. The control panel is receiving unrealistic values from the outside sensor. Effect: The minimum outside temperature is used.
Possible Causes and Diagnostic Procedures: None

Fault Code : 1065

Fault Category: B
Description: Pressure sensor defective or not connected.
Possible Causes and Diagnostic Procedures:

1. Connect the plug to the pressure sensor correctly.
2. Replace the connecting lead to the pressure sensor.
3. Replace the pressure sensor.
4. Replace the control unit.

Fault Code : 1068

Fault Category: W
Description: Outside temperature sensor defective.
Possible Causes and Diagnostic Procedures:

1. Outdoor temperature sensor is defective.

Fault Code : 1073

Fault Category: W
Description: Short circuit of the flow temperature sensor.
Possible Causes and Diagnostic Procedures:

1. Replace the temperature sensor.
2. Replace the connecting lead to the temperature sensor.
3. Replace the control unit.

Fault Code : 1074

Fault Category: W
Description: No signal from the flow temperature sensor available.
Possible Causes and Diagnostic Procedures:

1. Connect the plug to the flow temperature sensor correctly.
2. Replace the flow temperature sensor.
3. Replace the connecting lead to the flow temperature sensor.
4. Replace the control unit.

Fault Code : 1075

Fault Category: W
Description: Short circuit of the temperature sensor at the heating block.
Possible Causes and Diagnostic Procedures:

1. Replace the temperature sensor.
2. Replace the connecting lead to the temperature sensor.
3. Replace the control appliance.

Fault Code : 1076

Fault Category: W
Description: No signal from the temperature sensor at the heating block available.
Possible Causes and Diagnostic Procedures:

1. Replace the temperature sensor.
2. Replace the connecting lead to the temperature sensor.
3. Replace the control unit.

Fault Code : 2920

Fault Category: VDescription: Fault in flame monitoring. Igniter on for too long after flame detected.
Possible Causes and Diagnostic Procedures:

1. Check cabling.
2. Check igniter.
3. Check burner module.

Fault Code : 2924

Fault Category: V
Description: No feedback from the modulating gas valve. Gas valve relay defect.
Possible Causes and Diagnostic Procedures:

1. Press Reset button and apply burner start. Wait to see if fault reoccurs.
2. Replace the gas valve.

Fault Code : 2925

Fault Category: V
Description: Too low feedback from the modulating gas valve.
Possible Causes and Diagnostic Procedures:

1. Too low feedback from the modulating/current controlled gas valve.

Fault Code : 2927

Fault Category: B
Description: Flame failed during burner operation.
Possible Causes and Diagnostic Procedures:

1. Open the main shut-off valve.
2. Open the appliance shut-off valve.
3. Shut down the appliance and check the gas line.
4. Signal evaluation on printed circuit board defective.
5. Replace the ionisation electrode.
6. Establish protective conductor connection (PE) in the control unit.
7. Replace the ignition cable.
8. Replace the connecting lead to the ionisation electrode.
9. Replace the air/gas ratio control valve.
10. Set the burner correctly.
11. Set the burner at minimum rated load.
12. Check the integrity of the flue system.
13. The interconnected room air supply is too small or the size of the ventilation opening is too small.
14. Clean the heating block on the flue gas side.
15. Replace the control unit/burner control unit.

Fault Code : 2946

Fault Category: V
Description: Incorrect code plug detected.
Possible Causes and Diagnostic Procedures:

1. Replace the code plug.

Fault Code : 2948

Fault Category: B
Description: No flame signal with low output. The burner starts automatically after cleaning.
Possible Causes and Diagnostic Procedures:

1. If the fault occurs repeatedly: check the settings of the CO2 values.

Fault Code : 2950

Fault Category: B
Description: No flame signal following starting procedure. The burner starts automatically after cleaning.
Possible Causes and Diagnostic Procedures:

1. Set the correct gas/air ratio correctly.

Fault Code : 2963

Fault Category: B
Description: Signal from flow and heat exchanger temperature sensor outside the permissible range.
Possible Causes and Diagnostic Procedures:

1. Connect the connecting lead correctly.

Fault Code : 2964

Fault Category: B
Description: Flow rate in heat exchanger too low.
Possible Causes and Diagnostic Procedures:

1. Supply sensor is not assembled on the supply pipe.
2. Supply sensor does not make proper contact with the supply pipe.
3. System is not filled with water.
4. No water flow, because the CH system is closed.
5. No water flow, because the pump is not operating correctly.

Fault Code : 2965

Fault Category: B
Description: Flow temperature too high.
Possible Causes and Diagnostic Procedures:

1. System is not filled with water.
2. No water flow, because the CH system is closed.
3. No water flow, because the pump is not operating correctly.

Fault Code : 2966

Fault Category: B
Description: Flow temperature rise in heat exchanger too rapid.
Possible Causes and Diagnostic Procedures:

1. System is not filled with water.
2. No water flow, because the CH system is closed.
3. No water flow, because the pump is not operating correctly.

Fault Code : 2967

Fault Category: B
Description: Flow/heat exchanger temperature sensor differential too great.
Possible Causes and Diagnostic Procedures:

1. Supply sensor is not assembled on the supply pipe.
2. Supply sensor does not make proper contact with the supply pipe.
3. System is not filled with water.
4. No water flow, because the CH system is closed.
5. No water flow, because the pump is not operating correctly.

Fault Code : 2970

Fault Category: B
Description: Pressure drop in heating system too rapid.
Possible Causes and Diagnostic Procedures: None

Fault Code : 2971

Fault Category: B
Description: System pressure too low.
Possible Causes and Diagnostic Procedures:

1. Vent the heating system.
2. Top up water until the preset pressure is reached.
3. Replace the cable to the pressure sensor.
4. Replace the pressure sensor.

Fault Finding and Diagnosis: Faults Not Displayed

Not all faults will cause a fault code to be displayed, some issues will cause audible symptoms, whilst others will produce physical differences like having a lower hot water flow rate.

Fault : Combustion noises too loud; rumbling noises

Description: The appliance is making loud combustion or rumbling noises.
Possible Causes and Diagnostic Procedures:

1. Check the gas type.
2. Check the gas supply pressure.
3. Check the flue system; clean or repair if required.
4. Check the gas/air ratio.
5. Check the air/gas ratio control valve; replace if required.

Fault : Flow noises

Description: The appliance is making noises related to water flow.
Possible Causes and Diagnostic Procedures:

1. Set the pump rate or pump characteristic map correctly and match to the maximum output.

Fault : Heat-up takes too long

Description: The system is taking too long to reach the desired temperature.
Possible Causes and Diagnostic Procedures:

1. Set the pump rate or pump characteristic map correctly and match to the maximum output.

Fault : Flue gas values incorrect; CO content too high

Description: The flue gas analysis shows incorrect values, specifically the Carbon Monoxide (CO) content is too high.
Possible Causes and Diagnostic Procedures:

1. Check the gas type.
2. Check the gas supply pressure.
3. Check the flue system; clean or repair if required.
4. Check the gas/air ratio.
5. Check the air/gas ratio control valve; replace if required.

Fault : Violent ignition, poor ignition

Description: The burner ignition is harsh, violent, or fails.
Possible Causes and Diagnostic Procedures:

1. Check the ignition transformer with service function t01 for misfiring, replace if required.
2. Check the gas type.
3. Check the gas supply pressure.
4. Check the power supply.
5. Check the electrodes with cable; replace if required.
6. Check the flue system; clean or repair if required.
7. Check the gas/air ratio.
8. For natural gas: check the external gas flow monitor, replace if required.
9. Check the burner, replace if required.
10. Check the air/gas ratio control valve; replace if required.

Fault : Condensate in air box

Description: There is a presence of condensate within the air box.
Possible Causes and Diagnostic Procedures:

1. Check the non-return valve in the air gas manifold, replace if required.

Fault : Combi boilers: hot water outlet temperature is not reached

Description: The Domestic Hot Water (DHW) is not reaching the set temperature.
Possible Causes and Diagnostic Procedures:

1. Check the turbine, replace if required.
2. Check the gas/air ratio.

Fault : Combi boilers: DHW volume is not reached

Description: The volume or flow rate of Domestic Hot Water (DHW) is insufficient.
Possible Causes and Diagnostic Procedures:

1. Check the plate heat exchanger.

Fault : No function, the display remains dark

Description: The appliance has no power and the user display is blank.
Possible Causes and Diagnostic Procedures:

1. Check the electrical wiring for damage.
2. Replace defective cables.
3. Check the fuse, replace if required.

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