Boiler indicates a flow/return temperature differential fault; temperature difference is outside normal range.

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

Blocked heat exchanger or system, Pump running too slowly or failed, Incorrectly balanced heating system, Faulty flow or return NTC sensor

Safety: Isolate power and allow the system to cool.

Steps:

Check that all radiator valves are open and that thermostatic radiator valves are not all closed.
Bleed radiators to remove air.
Verify system pressure is correct.
Listen for pump operation; if silent or excessively noisy, it may be failing.

If the problem persists, a professional should check NTC sensors, pump performance, and system balancing.

Medium 3/5

Circulation Pump

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