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

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

User checks:

• Bleed all radiators starting from the top floor; top up system pressure afterwards.
• Ensure all lockshield and TRV valves are open.
• Check that the room thermostat is set high enough and that the programmer is on.

Engineer checks:

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

Improving circulation and balancing will restore radiator performance.