Boiler displays E1 256, often with no response to thermostat calls.

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-circuit room thermostat, Faulty wiring to controls, Incorrect control configuration, Faulty external programmer

Safety first: Isolate power before working on control wiring.

Check programmer and thermostat: Ensure the programmer is set to ON and the room thermostat is turned up above room temperature.
Bypass test (engineer level): A competent person can temporarily link the boiler's room stat terminals to see if it fires, indicating a control circuit fault.
Engineer tasks: A technician should test continuity of control wiring, verify correct configuration of the boiler for the type of controls used, and replace faulty thermostats or programmers.

Medium 3/5

Room Thermostat / External Controls

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