Worcester
The Worcester Greenstar 25 i ErP is a 25 kW gas combi boiler, introduced in 2015, offering 94% seasonal efficiency and an A-rated ErP for both heating and hot water.
The Worcester Greenstar 25 i ErP is a wall-hung condensing combi boiler designed for domestic heating and hot water in UK properties. Introduced in 2015, this natural gas and LPG compatible appliance provides a maximum central heating output of 24 kW and a domestic hot water output of 25 kW. It achieves a seasonal efficiency of 94% and holds an A-rating for both heating and hot water under the ErP directive.
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Full technical specifications extracted from the manufacturer brochure. Empty sections are hidden.
Vertical pipe route behind the appliance
Artificially softened water must not be used to fill the central heating system. The pH value of the system water must be less than 8.
The Greenstar 25 i ErP operates with a central heating output range of 8.2 kW to 24 kW, providing modulated performance. Domestic hot water is delivered at a maximum output of 25 kW, with a minimum activation flow rate of 2.9 lpm and a temperature range of 40-60°C. The appliance features a preheat function for rapid hot water availability. Physical dimensions are 700 mm (H) x 400 mm (W) x 330 mm (D), with a dry weight of 29 kg. Installation requires clearances of 20 mm front, 5 mm sides, 170 mm top, and 200 mm bottom. The boiler is compatible with various flue types, including horizontal and vertical, with maximum lengths of 4.6 m and 6.4 m respectively for 60/100 mm flues. Electrical requirements are 230V, 50Hz, with a maximum power consumption of 110W. The primary heat exchanger is aluminium-silicon, and the secondary is a plate type. System water pH must be less than 8, and artificially softened water is not to be used for filling the central heating system.
Every fault code listed in the manufacturer brochure, with likely causes and engineer actions. Each code has a permalink — paste a URL like https://www.boilertag.com/boilers/worcester/greenstar-25i-erp#fault-h-- to jump straight to the entry.
| Code | Meaning | Details |
|---|---|---|
| H-- | No service request | — |
| H03 | Planned maintenance required Show causes & actionsThe number of operating hours set for service interval has expired. This will appear on the appliance display screen. Can also be accessed in the maintenance menu. Engineer action This message will only be available if burner hours service option has been enabled in intelligent controller. Reset maintenance message, (press reset button). Carry out a service and reset the service reminder. Reset procedure Reset maintenance message, (press reset button). | Details |
| h03 | burner hours set Show causes & actionsThe number of operating hours set for service interval has not been reached at the time the maintenance menu messages are accessed. Engineer action This message will only be available if burner hours service option has been enabled in intelligent controller. Reset maintenance message, press reset button. If a service has been carried out at visit, reset the service reminder. Reset procedure Reset maintenance message, press reset button. | Details |
| H08 | The set interview date has expired. Maintenance required. Show causes & actionsThis will appear on the appliance display screen. Can also be accessed in the maintenance menu. Engineer action This message will only be available if burner hours service option has been enabled in intelligent controller. Reset maintenance message, (press reset button). Carry out a service and reset the service reminder. Reset procedure Reset maintenance message, (press reset button). | Details |
| h08 | Confirmation of service date. Show causes & actionsEngineer action This message will only be available if burner hours service option has been enabled in intelligent controller. Reset maintenance message, (press reset button). Reset procedure Reset maintenance message, (press reset button). | Details |
| H09 | Communications to the pump has failed. Show causes & actionsLikely causes
Engineer action Check: Electrical connections are fitted correctly. Correct pump has been fitted. Once checked, re power the appliance for test of communications. | Details |
| H11 | DHW temperature sensor defect. Show causes & actionsLikely causes
Engineer action Check: Sensor harness and connector. Operation, replace if necessary. | Details |
| H13 | The maximum maintenance interval set (in months), has exceeded or after the appliance has been placed into commissioning mode. Show causes & actionsThis will appear on the appliance display screen. Can also be accessed in the maintenance menu. Engineer action Reset maintenance message, (press reset button). Carry out a service and reset the service reminder. Service reminder is set in boiler setting 2.5F (→section 6.5.13, page 43). Service reminder function details (→ section 6.5.10, page 42). Reset procedure Reset maintenance message, (press reset button). | Details |
| h13 | The maximum maintenance interval set (in months), has not been reached or after the appliance has been placed into commissioning mode. Show causes & actionsEngineer action Reset maintenance message, (press reset button). If a service has been carried out at visit, reset the service reminder. Service reminder is set in boiler setting 2.5F (→section 6.5.13, page 43). Service reminder function details (→ section 6.5.10, page 42). Reset procedure Reset maintenance message, (press reset button). | Details |
| H29 | Outdoor sensor defect (available when accessory outdoor sensor is connected) Show causes & actionsLikely causes
Engineer action Check: Sensor harness and connector. Operation, replace if necessary. | Details |
| Fd 231Lockout | Electrical interruption fault Show causes & actionsThe power has been interrupted during a lockout Likely causes
Engineer action Check locking error history Reset procedure Reset the appliance | Details |
| C7 214 | Fan does not run during the start up phase Show causes & actionsLikely causes
Engineer action Check: Fan harness and connector. 230 Vac across brown and blue wires. Fan operation, replace if necessary. Connections of the control box. Replace control box if necessary. | Details |
| C6 215 | Fan speed too high Show causes & actionsLikely causes
Engineer action Check: Fan harness and connector. Fan operation, replace if necessary. Connections of the control box. Replace control box if necessary. | Details |
| C6 216 | Fan speed too low Show causes & actionsLikely causes
Engineer action Check: Fan harness and connector. Fan operation, replace if necessary. Connections of the control box. Replace control box if necessary. | Details |
| C7 217 | Fan has stopped during appliance operation Show causes & actionsLikely causes
Engineer action Check: Fan harness and connector. 230 Vac across brown and blue wires. Fan operation, replace if necessary. Connections of the control box. Replace control box if necessary. | Details |
| C1 264 | Fan stopped during operation Show causes & actionsLikely causes
Engineer action Check: Fan harness and connector. 230 Vac across brown and blue wires. Operation, replace if necessary. | Details |
| C4 273 | Continuous fan operation for the last 24 hours (appliance temporary blocked) Show causes & actionsLikely causes
Engineer action Check if demand has been calling for the 24 hours. Appliance has been blocked from firing for a minimum of 2 minutes as it has been operated continuously for 24 hours. | Details |
| E2 222 | Flow temperature sensor shorted Show causes & actionsLikely causes
Engineer action Check: Sensor harness and connector. Operation, replace if necessary. | Details |
| E2 223 | Flow temperature sensor disconnected Show causes & actionsLikely causes
Engineer action Check: Sensor harness and connector. Operation, replace if necessary. | Details |
| E9 276 | Primary Flow temperature exceeded 95 °C Show causes & actionsLikely causes
Engineer action Check: Primary system water pressure. For air in the system Circulation within heating system. Wiring and operation of the pump and flow temperature sensor, replace part/s if necessary. | Details |
| E2 350 | Flow temperature sensor shorted Show causes & actionsLikely causes
Engineer action Check: Sensor harness and connector. Operation, replace if necessary. | Details |
| E2 351 | Flow temperature sensor disconnected Show causes & actionsLikely causes
Engineer action Check: Sensor harness and connector. Operation, replace if necessary. | Details |
| FA 306 | Gas valve fault Show causes & actionsIonisation detected after the gas valve closed. Likely causes
Engineer action Inspect the ionization probe, replace if necessary. Check that the condensate is discharging. Check 230Vac across blue & orange wires to the coils. Replace gas valve if no voltage. Replace control box if there is voltage. | Details |
| EA 227 | No ionisation detected after ignition Show causes & actionsLikely causes
Engineer action Check: The dynamic gas pressure. The flue system for restrictions. The gas-air ratio (if possible). Connectors of the ignition unit. Ignition and ionisation current. Ignition unit for damage or wear, replace if necessary. Gas valve operation. Appliance for contamination. | Details |
| F7 228 | Ionisation current detected before burner-start Show causes & actionsLikely causes
Engineer action Check: Condition of the ionisation probe. Connection of the ionisation probe. Condensate is discharging correctly. Replace parts if necessary. | Details |
| EA 229 | Loss of ionisation signal during operation Show causes & actionsLikely causes
Engineer action Check: The gas-air ratio. The dynamic gas. Wiring and connection of flame probe. Replace flame probe necessary. | Details |
| EA 261 | HCM potentially defective Show causes & actionsLikely causes
Engineer action Reset the appliance. If continues to go to this error Check: HCM is inserted properly. HCM number. Contact technical helpline. Reset procedure Reset the appliance. | Details |
| 9U 233 | Control box or HCM is defective or loose Show causes & actionsLikely causes
Engineer action Check: HCM is inserted properly. Replace HCM if necessary. Connections of the control box. Replace control box if necessary. | Details |
| C4 237 | Control box or the HCM is defective. Show causes & actionsLikely causes
Engineer action Check: HCM is inserted properly. Replace HCM if necessary. Connections of the control box. Replace control box if necessary. | Details |
| F0 238 | Gas valve or control box error Show causes & actionsLikely causes
Engineer action Check: Gas valve coils: 230V ac across blue & orange wires. Replace gas valve if necessary. Connections of the control box. Replace control box if necessary. | Details |
| F0 239 | Control box or the HCM is defective. Show causes & actionsLikely causes
Engineer action Check: HCM is inserted properly. Replace HCM if necessary. Connections of the control box. Replace control box if necessary. | Details |
| F0 242-256 | Control box or the HCM is defective. Show causes & actionsLikely causes
Engineer action Check: HCM is inserted properly. Connections of the control box. Contact technical helpline. | Details |
| b7 257 | Control box or the HCM is defective. Show causes & actionsLikely causes
Engineer action Check: HCM is inserted properly. Connections of the control box. Contact technical helpline. | Details |
| F0 258 EH 258 | Control box or the HCM is defective. Show causes & actionsLikely causes
Engineer action Check: HCM is inserted properly. Connections of the control box. Contact technical helpline. | Details |
| F1 259 | Control box or the HCM is defective. Show causes & actionsLikely causes
Engineer action Check: HCM is inserted properly. Connections of the control box. Contact technical helpline. | Details |
| F0 262 | Control box or the HCM is defective. Show causes & actionsLikely causes
Engineer action Check: HCM is inserted properly. Connections of the control box. Contact technical helpline. | Details |
| F1 263 | Control box or the HCM is defective. Show causes & actionsLikely causes
Engineer action Check: HCM is inserted properly. Connections of the control box. Contact technical helpline. | Details |
| F0 272 | Control box or the HCM is defective. Show causes & actionsLikely causes
Engineer action Check: HCM is inserted properly. Replace HCM if necessary. Connections of the control box. Replace control box if necessary. | Details |
| F0 280 | Control box is defective. Show causes & actionsLikely causes
Engineer action Check: HCM is inserted properly. Connections of the control box. Replace control box if necessary. | Details |
| F0 290 | Control box is defective, (Analogue / Digital converter reference error). Show causes & actionsLikely causes
Engineer action Check: HCM is inserted properly. Connections of the burner control. Replace burner control if necessary. Check the voltage and frequency. | Details |
| 328 | Internal error (Mains voltage / frequency may be inconsistent) Show causes & actionsEngineer action Check the voltage and frequency. | Details |
| 235 | Incompatible HCM software version Show causes & actionsLikely causes
Engineer action Revised HCM software requires latest version of control box to operate correctly Replace the control box with the latest software. On the barcode label of the burner control the software version is indicated. | Details |
| 356 | Low mains voltage, (the voltage may be interrupted or inconsistent). Show causes & actionsEngineer action Check mains voltage. | Details |
| 360 | HCM invalid Show causes & actionsLikely causes
Engineer action The inserted HCM does not correspond with the control box. HCM must be within the same appliance type. Check the correct HCM is fitted. HCM identification number found in Technical data table. | Details |
| A8 361 | HCM invalid Show causes & actionsLikely causes
Engineer action The inserted HCM does not correspond with the control box or HMI type. Contact technical helpline. | Details |
| 363 | Ionisation measuring fault Show causes & actionsEngineer action Check heat cell earth wire continuity. | Details |
| 356 | Low mains voltage, (the voltage may be interrupted or inconsistent). Show causes & actionsEngineer action Check mains voltage. | Details |
| CC 800 | Outdoor sensor defect (available when accessory outdoor sensor is connected) Show causes & actionsLikely causes
Engineer action Check: Sensor harness and connector. Operation, replace if necessary. | Details |
| A7 808 | DHW sensor fault Show causes & actionsDomestic hot water sensor defect Likely causes
Engineer action Check: Sensor harness and connector. Operation, replace if necessary. | Details |
| A1 281 | Pump error Show causes & actionsPump stuck or running dry Likely causes
Engineer action Check: Primary system water pressure. For air in the system. Circulation within heating system. Wiring and operation of the pump, replace if necessary. | Details |
| E9 224 | Temperature fault Show causes & actionsFlue or high limit thermostat activated (safety circuit) Likely causes
Engineer action Check: Flue & high limit thermostat harness and connector. Operation, replace if necessary. Circulation within heating system. Burner gasket for leakage of flue gasses, replace if necessary. Heat exchanger for debris. Air-gas ratio. | Details |
| D4 341 | Temperature fault Show causes & actionsPrimary flow temperatures rising too fast Likely causes
Engineer action Check: Primary system water pressure. For air in the system. Circulation within heating system. Wiring and operation of the pump and the respective sensors, replace if necessary. | Details |
Patterns that group across the manufacturer's fault-code table. Each entry links to the full code listing further down the page.
Engineer: Check locking error history
Triggered by fault code Fd 231.
Triggered by fault code H--.
Engineer: This message will only be available if burner hours service option has been enabled in intelligent controller. Reset maintenance message, (press reset button). Carry out a service and reset the service reminder.
Triggered by fault code H03.
Engineer: This message will only be available if burner hours service option has been enabled in intelligent controller. Reset maintenance message, press reset button. If a service has been carried out at visit, reset the service reminder.
Triggered by fault code h03.
Engineer: This message will only be available if burner hours service option has been enabled in intelligent controller. Reset maintenance message, (press reset button). Carry out a service and reset the service reminder.
Triggered by fault code H08.
Diagnostic checklists from engineer-submitted Worcester faults, with step-by-step checks and safety notes.
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The Worcester Greenstar 12i System displaying an 'Ignition lockout' fault indicates that the boiler has attempted to ignite but failed to…
Common questions from engineers and homeowners about the Worcester Greenstar 25i ErP.
Parts referenced in the manufacturer brochure for routine service and repair.
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Specifications on this page are extracted from the manufacturer brochure. Always cross-check against the latest datasheet before commissioning or quoting. Last updated 28 June 2026.