Boiler runs but radiators do not get hot or are only partially warm

Safety first: Allow radiators to cool slightly before bleeding to prevent burns.

User checks:

• Bleed all radiators, starting from the top floor; top up system pressure afterwards.
• Ensure all lockshield and TRV (Thermostatic Radiator Valve) valves are open.
• Check that the room thermostat is set high enough and that the programmer is active.

Engineer checks:

• Check pump operation and increase its speed if necessary.
• Balance the system by adjusting lockshield valves to ensure even heat distribution.
• Powerflush or chemically clean the system if sludge is detected.

Improving circulation and balancing will restore radiator performance.