Boiler runs but radiators stay cold or only lukewarm

Safety: Allow system to cool before touching pipework. Isolate power before opening the boiler.

• 1. Check boiler status: Confirm that the Buderus boiler is firing and that the flow pipe leaving the boiler is hot.
• 2. Feel pump and pipes: The circulation pump should vibrate slightly when running. If hot but not circulating, it may be seized.
• 3. Vent pump: If the pump has a vent screw, carefully loosen it to release trapped air (have a cloth ready). Retighten once water flows steadily.
• 4. Open valves: Ensure all isolation valves near the boiler and any zone valves are open. Check that motorized valves move when there is a call for heat.
• 5. Clean filters: Clean any magnetic or mesh filters on the return line.
• 6. System balancing: If only some radiators heat, balance the system by partially closing lockshield valves on the hottest radiators.