The furnace frequently starts and stops (short cycling) without maintaining a stable temperature.

Safety first: Short cycling reduces efficiency and component life but is not usually an immediate safety risk.

• Lower flow temperature: Reduce the central heating flow temperature setpoint to lengthen burner run times.
• Relocate thermostat: Ensure the room thermostat is not near heat sources, drafts, or in direct sunlight.
• Enable modulation: Use a Remeha modulating (OpenTherm) controller if supported to better match output to demand.
• Limit maximum output: In the installer menu, reduce the maximum CH output to better suit the system size.