Nibe Imbalanced or Sludged Heating Circuit

Radiators upstairs are hot but downstairs are cold

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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

Sludge build-up in lower circuit, Incorrect balancing of radiators, Weak Nibe circulation pump, Air trapped in downstairs pipework

How to Fix / Troubleshooting

Safety first: Allow radiators to cool slightly before working on valves.

  • Bleed downstairs radiators: Remove air from the affected radiators and re-check system pressure.
  • Balance system: Slightly close lockshield valves on the hottest radiators upstairs to force more flow to cooler downstairs radiators.
  • Check pump setting: Ensure the Nibe pump is set to an appropriate speed or mode for the system size.
  • Professional cleaning: If downstairs radiators remain cold, a system powerflush and possible pump upgrade may be required.
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Repair Difficulty

Medium 3/5
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