How to Fix / Troubleshooting

Safety: Radiators and pipes may be hot; use caution when bleeding.

Bleed radiators: Starting from the lowest floor, bleed each radiator until water flows without air. Re-pressurise the system as needed.
Check pump setting: Increase pump speed if adjustable, following Immergas guidelines.
Balance system: Partially close lockshield valves on radiators that heat quickly to force more flow to colder radiators.
Diverter valve check (combi): If hot water works but heating does not, the diverter valve may be stuck in DHW position. A technician should inspect and clean or replace the diverter valve.
System flush (engineer): If radiators are cold at the bottom and hot at the top, sludge may require professional flushing.

Boiler runs but radiators do not get hot or only partially heat up.

Possible Causes