De Dietrich Control Input / Safety Chain Open

Boiler display works but no response to heating or hot water demand

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

Open safety thermostat, open flue safety device, external interlock open, wiring fault on safety loop

Safety: Do not bypass safety devices. They protect against overheating and flue gas hazards.

Check lockout indicators: Some De Dietrich models show symbols for open safety devices. Refer to the manual.
External interlocks: If an external safety device (e.g., low-water cut-off) is fitted, ensure it has not tripped.
Technician tasks: A heating engineer should test continuity through the safety chain, reset or replace the overheat thermostat or flue safety device, and repair wiring faults.

Hard 4/5

Safety Overheat Thermostat

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