Radiators on upper floors remain cold while lower ones heat normally

Safety first: Turn off the furnace and allow the system to cool slightly before bleeding radiators.

• Bleed upper radiators: Starting at the top floor, bleed each radiator until water flows steadily. Keep an eye on system pressure and top up as needed.
• Check pump setting: Increase pump speed or select a higher head mode if available.
• Open valves fully: Ensure lockshield and thermostatic radiator valves on upper floors are fully open during troubleshooting.
• Professional flushing: If some risers remain cold, sludge or blockage may require power flushing by a heating engineer.

Warning: Do not overpressurize the system while topping up; stay within the gauge limits.