347 error code
Return temperature exceeds flow temperature
What does Worcester Bosch Greenstar 1000 gas boiler 347 mean?
Worcester Bosch documents code 347 on the Greenstar 1000 as “Return temperature exceeds flow temperature”. This is a diagnostic condition that may interrupt heating or hot-water operation. The code meaning is model-specific, so it should not be applied to a different Worcester Bosch range without checking that product's manual.
The code identifies the condition detected by the product; it does not always identify the failed component on its own. Confirm the full code and exact model before ordering parts or attempting a reset.
The Worcester Bosch Greenstar 1000 gas boiler 347 error code indicates worcester Bosch documents code 347 on the Greenstar 1000 as “Return temperature exceeds flow temperature”. This is a diagnostic condition that may interrupt heating or hot-water operation. The code meaning is model-specific, so it should not be applied to a different Worcester Bosch range without checking that product's manual. This guide explains what the code means, the symptoms and likely causes, the checks that are safe to make, and when to stop and arrange an authorised repair.
Symptoms you may notice
- The Greenstar 1000 display shows code 347.
- Heating, hot water or burner operation may pause, lock out or become intermittent.
- The display behaviour and any accompanying symbols depend on the fault category and appliance state.
- The same numeric code can have a different application on another Worcester Bosch product, so confirm the model label first.
Common causes
- Return temperature exceeds flow temperature
- A condition detected by the boiler's control and safety electronics.
- The precise cause cannot be confirmed from the display code alone; wiring, sensors, circulation, combustion and control components require model-specific diagnosis.
Before you start troubleshooting
Use the display, rating label or product menu to confirm the exact model. Similar-looking codes can have different meanings across product generations and regions.
- Record the complete code before switching the equipment off.
- Check only user-accessible controls, filters and external connections described in the manual.
- Do not open gas, refrigerant, combustion or electrical compartments.
Troubleshooting steps
- Record code 347, any accompanying symbol and whether the boiler was heating, producing hot water or starting up.
- Confirm the appliance is a Worcester Bosch Greenstar 1000 and read the fault history where the user instructions permit.
- Check only external items described in the operating instructions, including the system pressure display and whether power and gas supplies are available.
- Do not remove the casing or test internal gas, combustion, electrical, fan, pump or sensor components.
- If code 347 returns after one permitted reset, stop resetting and arrange diagnosis by a Gas Safe registered engineer.
Can you fix this error code yourself?
This fault is not intended for user repair. Do not remove covers or test internal components; record the code and contact an authorised technician.
A successful reset is not proof that the underlying issue is fixed. If 347 reappears, note when it happens and give that information to the service engineer.
Reset instructions
Use only the reset procedure in the Greenstar 1000 operating instructions. Reset once after completing any permitted external check. Repeatedly resetting code 347 can hide a returning fault without correcting its cause.
Applicable products and models
Greenstar 1000 gas boilerGreenstar 10002023 onwardsWhen to contact a professional
Arrange a Gas Safe registered engineer if code 347 returns, the boiler remains locked out, system pressure will not remain stable, or any check requires internal access. Provide the exact Greenstar 1000 model, serial number, full code and the operating stage at which it appeared.
Frequently asked questions
What does Worcester Bosch Greenstar 1000 gas boiler 347 mean?
Worcester Bosch documents code 347 on the Greenstar 1000 as “Return temperature exceeds flow temperature”. This is a diagnostic condition that may interrupt heating or hot-water operation. The code meaning is model-specific, so it should not be applied to a different Worcester Bosch range without checking that product's manual.
Can I fix Worcester Bosch Greenstar 1000 gas boiler 347 myself?
This code is not classed as user-fixable. Record it and arrange authorised diagnosis rather than opening the product.
Should I reset the product after code 347?
Use only the reset procedure in the Greenstar 1000 operating instructions. Reset once after completing any permitted external check. Repeatedly resetting code 347 can hide a returning fault without correcting its cause.
When should I arrange a repair?
Arrange a Gas Safe registered engineer if code 347 returns, the boiler remains locked out, system pressure will not remain stable, or any check requires internal access. Provide the exact Greenstar 1000 model, serial number, full code and the operating stage at which it appeared.