Furnace displays F30; no heating, potentially associated with room thermostat input.

Safety first: Turn off power before working on control wiring.

• Check thermostat settings: Ensure the room thermostat or programmer is calling for heat and not set to OFF or low temperature.
• Inspect wiring: At the furnace control terminals, verify that the thermostat wires are correctly connected and secure.
• Bypass test (qualified): Temporarily link the thermostat terminals at the furnace (if permitted by the manual). If the furnace starts, the thermostat or its wiring is faulty and should be repaired or replaced.
• Replace control: Fit a compatible Saunier Duval-approved room thermostat or controller if the existing one is defective.