Furnace runs but radiators stay cold or only lukewarm

Safety first: Allow the system to cool before bleeding radiators.

• Check system pressure and top up to the recommended level.
• Bleed all radiators starting from the lowest floor to the highest to remove trapped air.
• Clean or replace the system filter on the return line if fitted.
• Check the pump speed setting on the ATAG pump module (if adjustable) and set it according to the installation manual.
• If some radiators heat and others do not, balancing of the system may be required by adjusting lockshield valves.