Boiler does not respond to the room thermostat; heating stays off even when the thermostat is calling for heat.

Safety: Isolate the power before working on control wiring.

• Check thermostat: Replace batteries in wireless thermostats and ensure the set temperature is above room temperature.
• Check programmer: Confirm heating schedules are active and that the programmer is not set to OFF or HOLIDAY mode.
• Boiler demand light: On many Alpha boilers, a demand indicator shows when there is a call for heat. If this is off despite the thermostat calling, the issue is likely external to the boiler.
• Wiring test (qualified person): At the boiler terminal block, link the room thermostat terminals to simulate a call for heat. If the boiler starts, the external controls or wiring are faulty.