Biasi Poor Central Heating Circulation

Boiler runs but radiators remain cold or only lukewarm, hot water may still work.

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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

Seized or weak circulation pump, Stuck diverter valve in DHW position, Sludge in radiators and pipework, Closed radiator or isolation valves

How to Fix / Troubleshooting

Safety: Turn off power before touching the pump or internal valves.

  • Check radiator valves: Ensure all TRVs and lockshield valves are open, especially on problem radiators.
  • Feel flow and return pipes: At the boiler, the flow should be hot and the return warm. If both are only slightly warm, circulation may be poor.
  • Verify pump operation: Place a screwdriver tip on the pump body and your ear on the handle to listen for rotation. If silent or just humming, the pump may be seized.
  • Engineer service: A technician can free or replace the pump, check the diverter valve, and flush the system if sludge is present.
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Repair Difficulty

Hard 4/5

Required Part

Circulation Pump
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