Ariston
Central Heating Circuit Flow Problem
Radiators not heating properly while hot water works fine
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Stuck diverter valve in DHW position, Sludged radiators and pipework, Airlocks in CH circuit, Incorrectly balanced radiators
How to Fix / Troubleshooting
Safety: Turn off power before working on valves. Radiators may be hot.
- Check boiler mode: Ensure the boiler is set to heating + hot water mode, not hot water only.
- Bleed radiators: Bleed all radiators to remove air. Top up system pressure afterwards.
- Feel pipes at boiler: When CH is demanded, the CH flow pipe should get hot. If it stays cool while DHW works, the diverter valve may be stuck and needs an engineer to replace the motor head or cartridge.
- Balance system: Partially close lockshield valves on radiators that heat quickly to force more flow to colder radiators.
- System cleaning: If some radiators remain cold or only warm at the top, a power flush and addition of inhibitor may be required.
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Repair Difficulty
Medium
3/5
Required Part
Diverter Valve Assembly
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