E10
CTC
Circulation Fault / No Flow Detected
Boiler shows E10; no heating or hot water; pump may run briefly.
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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, Airlock in primary circuit, Closed isolation valves, Blocked system filter or heat exchanger
How to Fix / Troubleshooting
Safety: Isolate power and allow the boiler to cool. Some components may still be hot.
- Check isolation valves: Confirm that the flow and return valves beneath the CTC boiler are fully open.
- Bleed air: Bleed radiators and any high-point air vents. On some CTC pumps, loosen the pump vent screw slightly to release trapped air until water appears.
- Check pump operation: With power restored and a heat demand, place a hand on the pump body. It should vibrate and get warm. If it hums but does not turn, the rotor may be seized.
- Freeing a stuck pump (technician): Isolate power and close valves. Remove the pump head and gently turn the rotor with a screwdriver to free it. If it repeatedly seizes, replace the pump.
- Inspect system filter: If a magnetic or mesh filter is installed on the return to the boiler, isolate and clean it. Sludge can restrict flow and trigger E10.
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Repair Difficulty
Medium
3/5
Required Part
Primary Circulation Pump
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