BoilerFaultCodesFerroli F43 Fault Code
The Ferroli F43 fault code means: your boiler has shut down to prevent the heat exchanger from overheating, often because the water isn't flowing through the system correctly.. It appears on 13 Ferroli models in our database.
Technical description: Exchanger protection intervention
What causes the Ferroli F43 fault?
This fault occurs when the boiler's internal sensors detect that the heat exchanger is getting too hot too quickly, which usually indicates that water isn't moving through the unit fast enough to carry the heat away. The most common reason is a failing internal pump or a build-up of sludge and debris that is restricting the flow of water through the system. In some cases, it can also be caused by air trapped in the heat exchanger or a faulty temperature sensor giving an incorrect reading.
This fault is more common during the first few cold spells of autumn or winter when the heating is turned on after a long summer break, as pumps can seize up during periods of inactivity.
DIY fix possible
Check that your home heating system pressure is between 1.0 and 1.5 barEnsure all radiator valves and isolation valves are fully openTry resetting the boiler using the 'R' button once the unit has cooled down
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Ferroli models that show the F43 fault code
Click a model for the full fault code list and model-specific repair notes.
- Arena 30 C Repair: £150-300
- Arena 30A Repair: £150-300
- Bluehelix Pro RRT Repair: £150-350
- Bluehelix Tech Repair: £120-£450
- Bluehelix Tech RRT Repair: £100-350
- Bluehelix Tech RRT 24C Repair: £150-300
- Domiproject Repair: £120-350
- Force W Repair: £150-350
- Maxima 35 S Repair: £120-220
- Modena HE Repair: £100-£350
- Optima 201 Repair: £120-220
- Optimax Repair: £90-160
- Optimax 25 C Repair: £120-200
Source
Ferroli F43 fault code information on this page is sourced and cross-checked against the official Ferroli service / installation manuals for each affected model.
- Ferroli Arena 30 C manual (PDF)
- Ferroli Arena 30A manual (PDF)
- Ferroli Bluehelix Pro RRT manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026