Thermostat powers on but does not call for heat even when room temperature is well below the setpoint.

Safety: Turn off power before touching wiring; menu changes can be done with power on.

Steps:

• Check mode and setpoint: Ensure the thermostat is in HEAT mode and the set temperature is above the current room temperature. Disable any vacation/away mode.
• Override schedule: Temporarily set the thermostat to manual/hold mode with a high setpoint to force a heat call.
• Verify output indicator: Look for a flame or heat icon on the display when calling for heat. If the icon appears but the boiler or heater does not start, suspect wiring or relay issues.
• Check control wiring: With power off, verify that the control output terminals are wired correctly to the boiler or valve according to the Meross diagram.

Resolution: If the thermostat indicates a heat call but no voltage or contact change is present at the output terminals, the internal relay/triac is faulty and the thermostat should be replaced.