Medium
EF 349 on Worcester Bosch Junior 24i

Your boiler has slowed down because it is struggling to circulate water quickly enough through the system, often caused by a blockage or a pump issue.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description

Central heating boil detected – boiler operating at minimum burner load with temperature difference greater than 18°C between Flow & Return.

DIY fix possible

Check that all radiator valves are fully openEnsure the central heating pressure is topped up to 1.5 barBleed all radiators to remove trapped air

Find a Gas Safe engineer
Search the official register →

Related fault codes

E9View →

Related guides you might find useful

Banging / kettling / whistling noise

Each noise points to a different fault.

Read →

Radiators cold at the bottom

Sludge build-up — needs flushing, not bleeding.

Read →

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →