Glow-worm Circulation failure / valve issue

Furnace runs but no heat to radiators, pipes near furnace are hot but radiators stay 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

Seized circulation pump, Stuck 3-port or 2-port motorised valve, Airlock in heating circuit, Blocked system filter on Glow-worm return

How to Fix / Troubleshooting

Safety: System water can be hot. Allow to cool before bleeding radiators.

User steps:

  • Check that room thermostat is turned up and calling for heat.
  • Bleed radiators starting from the top floor to remove trapped air.
  • Ensure radiator valves are open.

Technician steps:

  • Check operation of the circulation pump; free the rotor if seized or replace the pump.
  • Inspect motorised valves for correct movement and replace actuator heads if stuck.
  • Clean or replace any magnetic filter on the return to the furnace.
  • Balance the system by adjusting lockshield valves.
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Repair Difficulty

Medium 3/5

Required Part

Circulation Pump or Motorised Valve
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