Boiler shows F24, rapid temperature rise on display, then shutdown

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.

Possible Causes

Seized pump, air lock, closed valves, blocked filter/strainer, incorrect bypass setting

Safety: Isolate power before working on the pump.

Check valves: Confirm all isolation valves around the pump and boiler are open.
Bleed pump: If accessible, open the pump vent screw briefly to release trapped air (have a towel ready).
Clean filter: Many Viessmann systems have a dirt separator or Y-strainer on the return. Isolate, remove, and clean the filter mesh.
Pump replacement (technician): If the pump does not run or is very noisy, it may need replacement with a compatible Viessmann pump module.

Hard 4/5

Circulation Pump

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