F22
Saunier Duval Dry Fire / Low Water Content Protection

Furnace shows F22, no heating, may occur after draining or bleeding the system

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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

Insufficient water in primary circuit,Airlocks in heat exchanger,Faulty water pressure sensor,Recently drained system not properly refilled

How to Fix / Troubleshooting

Safety first: Allow the appliance to cool. Do not attempt to run the furnace with no water; this can damage the heat exchanger.

  • Refill system: Use the filling loop to bring system pressure up to the recommended level. Bleed radiators and the pump, then recheck pressure.
  • Bleed heat exchanger: Some Saunier Duval models have manual air vents on the heat exchanger or hydraulic block. Carefully vent trapped air until water appears.
  • Check for leaks: Inspect the system for visible leaks that could be causing water loss.
  • Sensor verification: If pressure is correct and air removed but F22 persists, the water pressure sensor may be faulty and should be tested and replaced if necessary.
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Repair Difficulty

Medium 3/5

Required Part

Water Pressure Sensor
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