F40
Ferroli High System Pressure

Boiler displays F40; usually indicates high system pressure on Ferroli boilers.

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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

Overfilled system, Faulty filling loop letting by, Failed expansion vessel, Blocked expansion pipework

How to Fix / Troubleshooting

Safety first: Hot water under pressure can cause scalding. Allow the system to cool before relieving pressure.

  • Check pressure gauge: If above 2.5–3.0 bar when cold, the system is over-pressurised.
  • Reduce pressure: Bleed a radiator or use a drain point to lower pressure to around 1.2 bar (cold).
  • Ensure filling loop is closed: Both valves on the filling loop must be fully shut and the hose removed if detachable.
  • Engineer checks:
    • Test expansion vessel charge; recharge or replace if waterlogged.
    • Inspect filling loop for passing and replace if necessary.
    • Check pressure relief valve (PRV) for damage from frequent lifting.
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Repair Difficulty

Medium 3/5

Required Part

Expansion Vessel
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