F15
Saunier Duval
Primary Heat Exchanger Overheat / Flow Restriction
Boiler shows F15 and stops, sometimes with noisy operation beforehand
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Severely scaled primary heat exchanger, Blocked system filter or strainers, Pump running at too low speed, Sludge in central heating circuit
How to Fix / Troubleshooting
Safety first: Turn off power and allow the boiler to cool. Overheated components can cause burns and damage.
Steps to check:
- Check system pressure and top up if low.
- Bleed radiators and any high points to remove trapped air.
- Clean or check any magnetic filter or dirt separator installed on the return to the boiler.
- Ensure the pump speed setting (if adjustable) is appropriate for the system.
- If F15 persists, a professional chemical flush or replacement of the primary heat exchanger may be required.
Warning: Do not ignore repeated overheat faults; they can lead to heat exchanger damage and unsafe operation.
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Repair Difficulty
Hard
4/5
Required Part
Primary Heat Exchanger
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