Boiler runs continuously and overheats the house even when room thermostat is turned down

Safety first: Overheating can be uncomfortable but usually not immediately dangerous. However, components may be stressed.

• Check thermostat settings: Ensure the thermostat is set to a reasonable temperature and not in a permanent override mode.
• Observe boiler display: See if the boiler believes there is a continuous heat demand (heating symbol active).
• Check zone valves: Feel the pipes around motorised valves; if hot when there should be no demand, the valve may be stuck open.
• Temporary isolation: You can turn off the heating circuit using the programmer or by lowering the setpoint until a technician attends.
• Professional repair: A Nibe technician may need to replace the room thermostat, repair wiring, or replace the Nibe main control PCB or stuck zone valve.