BoilerFaultCodesFerroli F34 Fault Code
The Ferroli F34 fault code means: your boiler has stopped working because the electrical power supply coming into your home is currently too low for the system to operate safely.. It appears on 17 Ferroli models in our database.
Technical description: Supply voltage under 170V
What causes the Ferroli F34 fault?
This fault occurs when the electrical supply entering the boiler drops to a level that is too weak to power the internal components safely. The most common reason is an external issue with the local power grid, but it can also be triggered by a faulty control board inside the boiler that is misreading the incoming voltage.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Ferroli models that show the F34 fault code
Click a model for the full fault code list and model-specific repair notes.
- Arena 30 C Repair: £120-250
- Arena 30A Repair: £100-200
- Atlas D Repair: £120-250
- Bluehelix HiTech RRT Repair: £100-350
- Bluehelix Pro RRT Repair: £120-250
- Bluehelix Tech Repair: £100-350
- Bluehelix Tech RRT Repair: £100-£350
- Bluehelix Tech RRT 24C Repair: £120-250
- Domiproject Repair: £100-£350
- Energy Top B Repair: £120-250
- Extrema C Repair: £120-250
- Force W Repair: £100-250
- Maxima 35 S Repair: £120-250
- Modena HE Repair: £100-350
- Optima 201 Repair: £120-250
- Optimax Repair: £100-250
- Optimax 25 C Repair: £120-250
Source
Ferroli F34 fault code information on this page is sourced and cross-checked against the official Ferroli service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026